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Volume 12
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Minerals, Volume 12, Issue 2 (February 2022) – 168 articles

Cover Story (view full-size image): Excessive phosphorus will cause the eutrophication of a water body, which brings many environmental problems. It is of both fundamental and practical importance to develop effective adsorbents for the continuous removal of phosphate from wastewater. In this paper, magnetic amorphous lanthanum silicate alginate hydrogel beads (MALS-Bs) were synthesized through the hydrogel embedding method. MALS-Bs exhibited a preferable adsorption capacity of 40.14 mg P/g for phosphorus compared to other hydrogel beads, and showed a treatment volume of 480 BV when the effluent phosphorus concentration was below 0.5 mg/L in continuous column runs. Finally, the underlying mechanisms of phosphate removal by MALS-Bs were revealed. Our work demonstrates that MALS-Bs can serve as a promising filling adsorbent candidate for the continuous removal of phosphate from wastewater. View this paper
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24 pages, 12410 KiB  
Article
Effects of Magmatic Fluids in Coals of São Pedro da Cova Coalfield, Douro Carboniferous Basin, Portugal: Insights from Inorganic Geochemistry
by Mariana Costa, Helena Moura, Ary Pinto de Jesus, Isabel Suárez-Ruiz and Deolinda Flores
Minerals 2022, 12(2), 275; https://doi.org/10.3390/min12020275 - 21 Feb 2022
Cited by 4 | Viewed by 2276
Abstract
The Douro Carboniferous Basin (DCB), aged from Gzhelian, is an important coal-bearing basin occurring in Northern Portugal. While the coals and the sedimentary sequence of the DCB have been deeply studied, the inorganic geochemical data are scarce. This study intends to provide major [...] Read more.
The Douro Carboniferous Basin (DCB), aged from Gzhelian, is an important coal-bearing basin occurring in Northern Portugal. While the coals and the sedimentary sequence of the DCB have been deeply studied, the inorganic geochemical data are scarce. This study intends to provide major and trace element contents and discuss their modes of occurrence and origins using a set of twenty-four coal samples from the São Pedro da Cova Coalfield taken from different sectors/outcrops. Thus, an integrated approach using petrographic, geochemical, both organic and inorganic, and mineralogical data was used to achieve these purposes. The main results demonstrated that these coals are anthracite A and vitrinite is the main organic component. Most of the elements have inorganic affinities and are associated with aluminosilicates, while the other elements have affinities with sulfides. Illite and muscovite are the main phyllosilicates occurring in these coals and pyrite is the most common sulfide. However, cinnabar, together with phosphates (fluorapatite, monazite, xenotime and gorceixite), were also identified. The enrichment of most elements as well as a heterogenous rare earth elements (REE) distribution pattern in the tectono-sedimentary unit (TSU) samples are related to magmatic fluids. On the other hand, on the Eastern Outcrop (EO), a tectonic slice, the subparallel trend of the REE distribution patterns, and a depletion of all the elements are related to the sedimentary contribution. The occurrence of cinnabar and gorceixite epigenetic mineralizations is interpreted as the action of a porphyry intrusion identified in this area of the DCB, between the TSU B1 and TSU D1. Full article
(This article belongs to the Special Issue Organic Matter in Sedimentary Systems: Insights from Organic Petrology and Organic Geochemistry)
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Figure 1

Figure 1
<p>Simplified geological setting of DCB: (<b>a</b>) location of DCB in the CIZ of the Iberian Massif; (<b>b</b>) main geological setting of São Pedro da Cova Coalfield in the DCB and relation with DBSZ (modified with permission from ref. [<a href="#B5-minerals-12-00275" class="html-bibr">5</a>], Copyright 2019 Springer Nature Switzerland AG).</p> Full article ">Figure 2
<p>Synthetic lithological succession of the Germunde Formation of the DCB [<a href="#B5-minerals-12-00275" class="html-bibr">5</a>]. TSU A—Debris-flow dominated alluvial fan characterized by matrix-supported breccia; TSU B—Lacustrine/palustrine system marked by fossiliferous shales and coal seams; TSU C—Braided fluvial complex developing multi-story/multichannel architecture with predominant SE to NW paleocurrent flow and minor lateral flows from tributaries; TSU D—Lacustrine or palustrine system formed by fossiliferous shale beds and coal seams with intercalations of sandy-conglomeratic beds of deltaic lobes whose main flows had its source in the NE margin, the rock clasts being mainly composed by quartzite, schist, and lyddite (black chert) with provenance from Ordovician and Silurian terranes. The succession is repeated by a thrust fault, the reason by which the unit’s symbols are marked by the numbers 1 and 2 (modified with permission from ref. [<a href="#B5-minerals-12-00275" class="html-bibr">5</a>], Copyright 2019 Springer Nature Switzerland AG).</p> Full article ">Figure 3
<p>Synthetic tectonic structure of the DCB at São Pedro da Cova Coalfield (after [<a href="#B3-minerals-12-00275" class="html-bibr">3</a>]).</p> Full article ">Figure 4
<p>Location of the studied samples (see also <a href="#minerals-12-00275-f001" class="html-fig">Figure 1</a> for more details in the geographical localization).</p> Full article ">Figure 5
<p>Photomicrographs of the studied coals. (<b>A</b>) Collotelinite (Ct) and framboidal pyrite (Py); (<b>B</b>) collotelinite (Ct), collodetrinite (Cd) and semifusinite (Sf); (<b>C</b>) collotelinite (Ct), fusinite (F) and epigenetic pyrite filling a fracture in the collotelinite; (<b>D</b>) collotelinite (Ct) mylonitized. Photomicrographs taken under reflected white light (<b>A</b>–<b>C</b> sample 95 from TSU B1; <b>D</b> sample 77 from EO).</p> Full article ">Figure 6
<p>Photomicrographs of the studied coals. (<b>A</b>) Collodetrinite (Cd) and clay minerals (clay); (<b>B</b>) epigenetic pyrite (Py) filling a fracture in the collotelinite (Ct); (<b>C</b>) carbonates in the collotelinite (Ct); (<b>D</b>) carbonates in the collotelinite (Ct) mylonitized. Photomicrographs taken under reflected white light (<b>A</b>–<b>C</b> sample 15 from TSU B1; <b>D</b> sample 77 from EO).</p> Full article ">Figure 7
<p>SEM (BSE images) and EDS spectrum of the mineral phases in the coals: illite and xenotime (sample 215/218 from TSU D2).</p> Full article ">Figure 8
<p>SEM (BSE images) and EDS spectrum of the mineral phases in the coals: illite and monazite (sample 42/48 from TSU B2).</p> Full article ">Figure 9
<p>SEM (BSE images) and EDS spectrum of the mineral phases in the coals: muscovite and fluorapatite (sample 215/218 from TSU D2).</p> Full article ">Figure 10
<p>SEM (BSE images) and EDS spectrum of the mineral phases in the coals: galena, sphalerite and chalcopyrite (sample 204/211 from TSU B1).</p> Full article ">Figure 11
<p>SEM (BSE images) and EDS spectrum of the fluorapatite in the coals. Barite and quartz were also identified (sample 204/211 from TSU B1).</p> Full article ">Figure 12
<p>SEM (BSE images) and EDS spectrum of the mineral phases in the coals: gorceixite and illite. Fluorapatite was also identified (sample 42/48 from TSU B2).</p> Full article ">Figure 13
<p>Concentration coefficients (CC) of trace elements for the studied samples from TSU and EO, normalized by average trace element concentrations in the world hard coals [<a href="#B77-minerals-12-00275" class="html-bibr">77</a>].</p> Full article ">Figure 14
<p>Concentration coefficients (CC) of REE for the studied samples from TSU and EO, normalized by average trace element concentrations in the world hard coals [<a href="#B77-minerals-12-00275" class="html-bibr">77</a>].</p> Full article ">Figure 15
<p>SEM (BSE images) and EDS spectrum of the cinnabar identified in the studied coals (sample 15 from TSU B1).</p> Full article ">Figure 16
<p>Dendrograms showing hierarchical cluster analysis of studied coals from TSUs (<b>A</b>–<b>D</b>) and EO (<b>E</b>).</p> Full article ">Figure 16 Cont.
<p>Dendrograms showing hierarchical cluster analysis of studied coals from TSUs (<b>A</b>–<b>D</b>) and EO (<b>E</b>).</p> Full article ">Figure 17
<p>Distribution patterns of REE in the coal samples from TSU and EO. REE are normalized to the Upper Continental Crust (UCC; [<a href="#B84-minerals-12-00275" class="html-bibr">84</a>]).</p> Full article ">
12 pages, 3141 KiB  
Article
Columnar Structure of Claw Denticles in the Coconut Crab, Birgus latro
by Tadanobu Inoue, Shin-ichiro Oka, Koji Nakazato and Toru Hara
Minerals 2022, 12(2), 274; https://doi.org/10.3390/min12020274 - 21 Feb 2022
Cited by 6 | Viewed by 2678
Abstract
Some decapod crustaceans have tooth-like white denticles that exist only on the pinching side of claws. We revealed the denticle microstructure in the coconut crab, Birgus latro, using optical and scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and a focused [...] Read more.
Some decapod crustaceans have tooth-like white denticles that exist only on the pinching side of claws. We revealed the denticle microstructure in the coconut crab, Birgus latro, using optical and scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), and a focused ion beam (FIB)-SEM. Three-dimensional analysis and fracture surface observation were performed in order to clarify the microstructural differences in two mineralized layers—the exocuticle and the endocuticle. The denticles consist of a columnar structure normal to the surface and are covered with a very thin epicuticle and an exocuticle with a twisted plywood pattern structure. Due to abrasion, the exocuticle layer was lost in the wide area above the large denticles; conversely, these layers remained on the surface of the relatively small denticles and on the base of the denticle. The results showed that the mineralized exoskeleton of the crab’s claw is classified into three structures: a twisted plywood pattern structure stacked parallel to the surface for the exocuticle, a porous structure with many regularly arranged pores vertical to the surface for the endocuticle, and a columnar structure vertical to the surface for the denticle. Full article
(This article belongs to the Special Issue Biominerals and Bio-Inspired Materials)
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Figure 1

Figure 1
<p>(<b>a</b>) Photographs of the left claw of the coconut crab used in the present study. Here, the movable finger was broken from the claw through the joint, and the fixed finger was cut by a saw. (<b>b</b>) Optical micrographs of a cross section of the fixed finger after polishing [<a href="#B20-minerals-12-00274" class="html-bibr">20</a>]. (<b>c</b>) Scanning electron microscope (SEM) image of the exoskeleton with the denticle on the pinching side and (<b>d</b>) a high-magnification SEM image of the denticle top.</p> Full article ">Figure 2
<p>Three-dimensional (3D) microstructure in (<b>a</b>,<b>b</b>) surface and (<b>c</b>,<b>d</b>) <span class="html-italic">x</span> = 1 mm of the denticle. Each image was recorded with a slice pitch of 15 nm in the <span class="html-italic">z</span>-direction <span class="html-italic">via</span> a focused ion beam–SEM system, and 3D images were reconstructed using visualization software from serial-sectioning images in the <span class="html-italic">x</span>-<span class="html-italic">y</span> plane. (<b>a</b>,<b>c</b>) 3D images reconstructed through the software without any special image processing and (<b>b</b>,<b>d</b>) 3D images were reconstructed by coloring the edges of the high-brightness part with gold through the software.</p> Full article ">Figure 3
<p>SEM micrograph of (<b>a</b>) a fracture surface of the denticle. Enlarged SEM micrographs of the area enclosed by rectangles in (<b>a</b>); (<b>b</b>,<b>c</b>) inside the denticle and (<b>d</b>–<b>f</b>) the exocuticle layer. Here, pct denotes pore canal tubules.</p> Full article ">Figure 4
<p>SEM micrograph near the valley of the (<b>a</b>) fracture surface of the denticle; (<b>b</b>) enlarged SEM micrographs of the area enclosed by rectangles in (<b>a</b>); SEM micrographs of (<b>c</b>,<b>d</b>) the endocuticle layer; and (<b>e</b>) the exocuticle layer. Here, pc denotes pore canal, and pct denotes pore canal tubules.</p> Full article ">Figure 5
<p>(<b>a</b>) Appearance of a sample after osmium coating and (<b>b</b>,<b>c</b>) SEM micrograph of the surface observed from the denticle top; (<b>d</b>–<b>f</b>) enlarged SEM micrographs of the area enclosed by yellow rectangles in (<b>c</b>); (<b>g</b>,<b>h</b>) enlarged SEM micrographs of the area enclosed by the blue rectangle in (<b>b</b>).</p> Full article ">Figure 6
<p>SEM micrographs of the denticle surface on the pinching side of the fixed finger of the left claw in coconut crabs of different sizes: (<b>a</b>) 1070 g, (<b>b</b>) 610 g, and (<b>c</b>) 300 g. Here, <span class="html-italic">Sh</span> denotes the stacking height of the twisted plywood structure, and pct denotes pore canal tubules.</p> Full article ">Figure 7
<p>(<b>a</b>) Optical micrographs of a cross section of the fixed finger after polishing [<a href="#B20-minerals-12-00274" class="html-bibr">20</a>] and the cutting positions; (<b>b</b>) optical micrographs of the entire surface part of the pinching side. (<b>c</b>–<b>f</b>) SEM micrographs of the denticle surface with and without the exocuticle layer. Here, the white arrow denotes the position where the exocuticle disappeared on the denticle surface.</p> Full article ">
21 pages, 6356 KiB  
Article
Implications for Metallogenesis and Tectonic Evolution of Ore-Hosting Granodiorite Porphyry in the Tongkuangyu Cu Deposit, North China Craton: Evidence from Geochemistry, Zircon U-Pb Chronology, and Hf Isotopes
by Jungang Sun, Ting Liang, Hongying Li, Kun Yan, Yinyin Chao and Zhanbin Wang
Minerals 2022, 12(2), 273; https://doi.org/10.3390/min12020273 - 21 Feb 2022
Cited by 1 | Viewed by 1937
Abstract
The Tongkuangyu copper deposit in Zhongtiaoshan at the southern margin of the North China Craton is one of the oldest porphyry Cu deposits in the world and its metallogenesis and tectonic evolution have been debated. Here, porphyritic intrusion geochemical and geochronological data are [...] Read more.
The Tongkuangyu copper deposit in Zhongtiaoshan at the southern margin of the North China Craton is one of the oldest porphyry Cu deposits in the world and its metallogenesis and tectonic evolution have been debated. Here, porphyritic intrusion geochemical and geochronological data are reported to identify the diagenetic age, mineralization, tectonic setting, and evolution of the deposit. Geochemical data show that granodiorite porphyry is a peraluminous rock, with low concentrations of Fe (~3.99%) and Ti (~0.29%) and high concentrations of alkali (~6.13%) and high Al (~15.42%) and Mg numbers (~51). The rocks show comparative enrichment of Na, K, and Mg; higher La/Yb ratios, no significant Eu anomaly, and obvious Nb–Ta–Ti negative anomaly, showing similar geochemical characteristics to Archean TTG and sanukitoid. ΣREE vary greatly, ranging from 33.47 × 10−6 to 277.81 × 10−6 (average 137.09 × 10−6). The characteristics of REE show obvious fractionation of LREE and HREE, enrichment of LREE, and depletion of HREE. Some of the LREE (La and Ce) and LILE (K, Rb, and Ba) are enriched, but some of the LILE (Th and U) are depleted. In addition, some of the HFSE (Nb, Ta, P, and Ti) are depleted while some (Zr and Hf) are enriched. High precision LA–MC–ICP MS zircon U–Pb dating yield concordant ages of 2159 ± 19 Ma, which is broadly coeval with ore formation (~2.1 Ga) in the area. Zircon εHf(t) values range from −3.8 to 1.13, with a model age of 2778 to 2959 Ma, indicating that the formation of porphyry is related to the partial melting of Archean crust (~2.7 Ga) with a minor amount of mantle material added. Tongkuangyu granodiorite porphyry formed in the tectonic setting of the post-orogenic extension in the Paleoproterozoic, and Tongkuangyu Cu deposit may be related to the extension of the North China Craton in the Paleoproterozoic. Full article
(This article belongs to the Special Issue Genesis of Porphyry Cu–Mo Deposits: Geochemistry, Mineralogy and Geochronology)
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Figure 1

Figure 1
<p>Simplified geotectonic map of study area (<b>A</b>) and Regional geological map of Zhongtiaoshan (<b>B</b>) (modified after CGGCDZM, 1978 [<a href="#B1-minerals-12-00273" class="html-bibr">1</a>]).</p> Full article ">Figure 2
<p>Simplified geologic map of the Tongkuangyu Cu deposit (modified after 214 Geological Group in Zhongtiaoshan in Shanxi Province, unpub. report, 1956; Meng et al., 2020 [<a href="#B8-minerals-12-00273" class="html-bibr">8</a>]).</p> Full article ">Figure 3
<p>Geological section of the main ore veins (modified after 214 Geological Group in Zhongtiaoshan in Shanxi Province, unpub. report, 1956; Meng et al., 2020 [<a href="#B8-minerals-12-00273" class="html-bibr">8</a>]).</p> Full article ">Figure 4
<p>Different alteration types in the Tongkuangyu deposit. (<b>A</b>) Chloritization, biotitization, silication, and carbonatization in biotite schist (Sample 1381, No. 5147 tunnel of No. V orebody on 690-m level). (<b>B</b>) Chloritization and quartz–sericitization in quartz–sericite schist (Sample 1569, No. 4143 tunnel of No. IV orebody on 530-m level). (<b>C</b>) Chloritization and biotitization in biotite schist (Sample 1604, No. 4143 tunnel of No. IV orebody on 530-m level). (<b>D</b>) K–feldsparization and chloritization crosscut by quartz–calcite–chalcopyrite vein. Quartz–calcite–chalcopyrite vein cut by calcite–chalcopyrite vein within chloritization zone (Sample 2599, No. 5147 tunnel of No. V orebody on 690-m level). (<b>E</b>) Chloritization, biotitization and K feldspathization in biotite schist (Sample 2603, No.5147 tunnel of No. V orebody on 690-m level). (<b>F</b>) Quartz–sericitization along biotitization zone (Sample 2633, No. 4143 tunnel of No. IV orebody on 530-m level). (<b>G</b>) Quartz–sericitization and kaolinizitation in the contact zone between granodiorite porphyry and quartz–sericite schist (Sample 2643, No. 4143 tunnel of No. IV orebody on 530-m level). (<b>H</b>) Biotite schist (sample 5147–3–2); cross-polarized light. (<b>I</b>) Quartz–sericite schist (sample 5147–20); cross-polarized light. Abbreviations: Qtz: quartz; Bt: biotite; Ser: sericite; and Bn: bornite.</p> Full article ">Figure 5
<p>Vein types and their relationships in Tongkuangyu deposit. (<b>A</b>) Quartz–chalcopyrite–pyrite vein cutting quartz–K feldspar–chalcopyrite–pyrite vein, all crosscut by later calcite–chalcopyrite–pyrite vein (Sample 263–14, No. 263 drilling of No. V orebody). (<b>B</b>) Late quartz–magnetite vein cutting barren quartz vein (Sample 256–10, No. 256 drilling of No. V orebody). (<b>C</b>) Quartz–chalcopyrite–pyrite vein cutting veinlet-disseminated chalcopyrite ± pyrite in granodiorite porphyry (Sample 0629, No. 041 drilling of No. IV orebody). (<b>D</b>) Quartz–chalcopyrite–pyrite vein crosscut by quartz–calcite–chalcopyrite–pyrite–specularite vein (Sample 4s’–19, No. 041 drilling of No. IV orebody). (<b>E</b>) Quartz–chalcopyrite–pyrite vein crosscut by quartz–calcite–chalcopyrite–pyrite vein (Sample 0653, No. 041 drilling of No. IV orebody). (<b>F</b>) Quartz–calcite–chalcopyrite–bornite vein cutting quartz–chalcopyrite–pyrite vein (Sample 1387, No. 5147 tunnel of No. V orebody on 690-m level). (<b>G</b>) Calcite–chalcopyrite–pyrite vein cutting quartz–calcite–chalcopyrite–bornite (Sample 1484, No. 5147 tunnel of No. V orebody on 690-m level). (<b>H</b>) Late calcite vein cutting K–feldsparization, biotitization and silication (Sample 2884, No. 263 drilling of No. V orebody). (<b>I</b>) K–feldsparization, biotitization, sericitization, and silication beside quartz–chalcopyrite vein (Sample 2871, No. 263 drilling of No. V orebody). Abbreviations: Qtz: quartz; Cp: chalcopyrite; Py: pyrite; Kfs: K–feldspar; Cal: calcite; Mt: magnetite; Pl: plagioclase; Spe: specularite; Bn: bornite; Bt: biotite; and Ser: sericite.</p> Full article ">Figure 6
<p>Representative photographs and photomicrographs of granodiorite porphyry from Tongkuangyu. (<b>A</b>) Biotite schist intruded by granodiorite porphyry (Sample 2596, No. 5147 tunnel of No. V orebody on 690-m level). (<b>B</b>) The granodiorite porphyry is cross-cut by quartz– chalcopyrite–pyrite vein (Sample D1, No. 5141 tunnel of No. V orebody on 540-m level). (<b>C</b>) Quartz–chalcopyrite–pyrite vein cutting veinlet-disseminated chalcopyrite–pyrite in granodiorite porphyry (Sample 263–3, No. 263 drilling of No. V orebody). (<b>D</b>–<b>F</b>) Granodiorite porphyry (sample D4, D5, and D6); cross–polarized light; No. 5141 tunnel of No. V orebody on 540-m level. (<b>G</b>) Apatite intergrown with pyrite in granodiorite porphyry (sample 5s–1); baskscattered electron (BSE) image. (<b>H</b>) Crystals of feldspar in granodiorite porphyry (sample 5s–13); BSE. (<b>I</b>) Apatite, biotite, and chlorite in granodiorite porphyry (sample 5s–26); BSE. Abbreviations: Qtz: quartz; Cp: chalcopyrite; Py: pyrite; Kfs: K–feldspar; Bt: biotite; Zrn: zircon; Ap: apatite; and Chl: chlorite.</p> Full article ">Figure 7
<p>Zircon cathodoluminescence (CL) images of Tongkuangyu granodiorite porphyry.</p> Full article ">Figure 8
<p>U-Pb Concordant diagram (<b>A</b>) and weighted average diagram (<b>B</b>) for Tongkuangyu granodiorite porphyry.</p> Full article ">Figure 9
<p>Nb/Y vs. Zr/TiO<sub>2</sub> (<b>A</b>) and SiO<sub>2</sub> vs. K<sub>2</sub>O (<b>B</b>) diagrams for the major rock types from the Tongkuangyu district (after Winchester and Floyd,1977 [<a href="#B48-minerals-12-00273" class="html-bibr">48</a>]; Middlemost, 1985, 1994 [<a href="#B49-minerals-12-00273" class="html-bibr">49</a>,<a href="#B50-minerals-12-00273" class="html-bibr">50</a>]; Peccerillo et al., 1976 [<a href="#B51-minerals-12-00273" class="html-bibr">51</a>]; andregional rock data from Yang et al., 2015 [<a href="#B52-minerals-12-00273" class="html-bibr">52</a>]).</p> Full article ">Figure 10
<p>Chondrite-normalized REE patterns diagram (<b>A</b>) and primitive mantle normalized trace element spider diagram (<b>B</b>) for Tongkuangyu granodiorite porphyry (normalization data after Sun and McDonough, 1989 [<a href="#B53-minerals-12-00273" class="html-bibr">53</a>]; regional rock data source as same as <a href="#minerals-12-00273-f009" class="html-fig">Figure 9</a>).</p> Full article ">Figure 11
<p>Diagram of zircon ε<sub>Hf</sub>(t) values vs. U-Pb ages for granodiorite porphyries at Tongkuangyu Cu deposit (2.7 Ga and 3.8 Ga crust lines were constructed through 2.7 Ga diorite [<a href="#B25-minerals-12-00273" class="html-bibr">25</a>] and Songjiashan Formation (detrital zircon) [<a href="#B28-minerals-12-00273" class="html-bibr">28</a>] assuming a <sup>176</sup>Lu/<sup>177</sup>Hf ratio of 0.01).</p> Full article ">Figure 12
<p>Y vs. Nb (<b>A</b>) and Yb vs. Ta (<b>B</b>) diagrams of Tongkuangyu granodiorite porphyry (after Pearce et al., 1984 [<a href="#B72-minerals-12-00273" class="html-bibr">72</a>]; regional rock data source as same as <a href="#minerals-12-00273-f009" class="html-fig">Figure 9</a>).</p> Full article ">
24 pages, 8892 KiB  
Article
Passive Structural Control on Skarn Mineralization Localization: A Case Study from the Variscan Rosas Shear Zone (SW Sardinia, Italy)
by Fabrizio Cocco, Antonio Attardi, Matteo Luca Deidda, Dario Fancello, Antonio Funedda and Stefano Naitza
Minerals 2022, 12(2), 272; https://doi.org/10.3390/min12020272 - 21 Feb 2022
Cited by 8 | Viewed by 3843
Abstract
The case study presented here deals with the Pb-Zn-Cu skarn ores hosted in the Rosas Shear Zone (RSZ), a highly strained domain located in the external zone of the Sardinian Variscan chain. The RSZ is characterized by several tectonic slices of Cambrian limestones [...] Read more.
The case study presented here deals with the Pb-Zn-Cu skarn ores hosted in the Rosas Shear Zone (RSZ), a highly strained domain located in the external zone of the Sardinian Variscan chain. The RSZ is characterized by several tectonic slices of Cambrian limestones within a strongly folded and foliated Cambrian-Ordovician siliciclastic succession, intruded by late Variscan granites and mafic dykes. Based on geological mapping, structural and microscope analyses, our results show that the skarn ores in the RSZ are an example of passive structurally controlled mineralization. The RSZ was structured close to the brittle–ductile transition and, once exhumed to shallower crustal levels, acted as plumbing system favoring a large-scale granite-related fluid circulation. The paragenesis and the mineralization style of the skarn vary slightly according to the peculiarity of the local structural setting: a tectonic slice adjacent to the mafic dyke; an intensely sheared zone or a discrete thrust surface. Full article
(This article belongs to the Special Issue Application of Structural Analysis in Studies on Genesis and Exploration of Ore Deposits)
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Figure 1

Figure 1
<p>(<b>a</b>) Tectonic sketch map of the Variscan basement of Sardinia (after [<a href="#B26-minerals-12-00272" class="html-bibr">26</a>]); (<b>b</b>) geological sketch map of the central sector of the external zone. Location in <a href="#minerals-12-00272-f001" class="html-fig">Figure 1</a>a. RSZ: Rosas Shear Zone. The grey box shows the location of Figure 2. (<b>c</b>) Geological cross-section across the Rosas Shear Zone (after [<a href="#B25-minerals-12-00272" class="html-bibr">25</a>]).</p> Full article ">Figure 2
<p>Geological sketch map (after [<a href="#B58-minerals-12-00272" class="html-bibr">58</a>]) and main mineworks in the Rosas district (after [<a href="#B54-minerals-12-00272" class="html-bibr">54</a>,<a href="#B59-minerals-12-00272" class="html-bibr">59</a>], modified). Location in <a href="#minerals-12-00272-f001" class="html-fig">Figure 1</a>. The grey box shows the location of the study area in Figure 3.</p> Full article ">Figure 3
<p>Geological map of the Rosas Shear Zone and geological cross-section. Location in <a href="#minerals-12-00272-f002" class="html-fig">Figure 2</a>. Note that the limestone slices in the Barisonis and Mitza Sermentus mines are very small and have not been drawn at the scale of this map.</p> Full article ">Figure 4
<p>Lens-shaped skarn at the Barisonis mine embedded within the siliciclastic Monte Orri Fm. (MRI) and the gabbro dyke. The mineral zoning pattern is also shown.</p> Full article ">Figure 5
<p>Lens-shaped skarn lenses at the Mitza Sermentus mine embedded in the shales of the Monte Argentu Fm; red dashed line: Variscan thrust with tectonic transport direction the-top-to-the-SW (view from SW).</p> Full article ">Figure 6
<p>Relationships between the tectonic contact and the skarn mineralization at the S’Ega Su Forru locality. (<b>a</b>) thin skarn band (20 cm) located along the contact between a slice of recrystallized Cambrian limestone of the Gonnesa Fm. (GNN) and Ordovician phyllites of the Monte Orri Fm. (MRI); (<b>b</b>) same contact of (<b>a</b>) in a lower stratigraphic position between phyllites and a more magnesian facies of the GNN, where no skarn ore has been detected.</p> Full article ">Figure 7
<p>Photomicrographs of the Barisonis orebody. The mineral assemblages include (<b>a</b>) garnets with birefringent rims; (<b>b</b>) epidote, chlorite and calcite pseudomorphs with interstitial sphalerite; (<b>c</b>) interstitial sulfides in the amphibole-quartz matrix; (<b>d</b>) magnetite with subordinate cassiterite in fluorite-quartz veins; (<b>e</b>) chalcopyrite-magnetite zones with thin rims of covellite and Ag-sulfides (acanthite-argentite); (<b>f</b>) Ag-sulfides and covellite veinlets cross-cutting pyrite. Grt = garnet; Amp = amphibole; Wo = wollastonite; Chl = chlorite; Ep = epidote; Qz = quartz; Cal = calcite; Mag = magnetite; Cst = cassiterite; Sp = sphalerite; Ccp = chalcopyrite; Gn = galena; Py = pyrite; Cv = covellite; Ag-Sulf = acanthite-argentite.</p> Full article ">Figure 8
<p>(<b>a</b>) Photomicrographs of the Mitza Sermentus orebody in the proximity of the black-phyllite host rock. Black domains are the mylonitic foliation. Mineral assemblages include (<b>b</b>) calcite-quartz replacing wollastonite; (<b>c</b>) chalcopyrite veinlets in a pyroxene-epidote-quartz-calcite gangue with subordinate pumpellyte, armenite, titanite and apatite; (<b>d</b>) Ag-sulfantimonides (tetrahedrite) grains associated with chalcopyrite; (<b>e</b>) galena, chalcopyrite and sphalerite in the armenite-rich zones; (<b>f</b>) native Au grains in the titanite, armenite, chlorite, epidote matrix. Mn-Cal = manganocalcite; Arm = armenite; Pmp = pumpellyte; Fe-Sp = Fe-rich sphalerite; Ag-Sb-Sulf = Ag-sulfantimonides (tetrahedrite); Au = native gold.</p> Full article ">Figure 9
<p>Photomicrographs of the S’Ega Su Forru vein: (<b>a</b>) a clinopyroxene-quartz-calcite matrix with base metal sulfides and Ni-Co-Fe sulfarsenides; (<b>b</b>) galena and Fe-oxides (goethite-hematite) enveloping Ni-Co sulfarsenide crystals; (<b>c</b>) Ni-Co sulfarsenides enclosed in pyrite with sphalerite, chalcopyrite and galena. Cpx = clinopyroxene; Ni-Co-Sulf-Ars = Ni-Co sulfarsenides; Fe-Ox = Fe-oxides (goethite-hematite).</p> Full article ">Figure 10
<p>Cartoon showing the tectonic evolution and the passive structural control on the skarn ore mineralization in the Barisonis (1), Mitza Sermentus (2) and S’Ega Su Forru (3) mines. The plumbing system is inherited from the structuring of the Rosas Shear Zone at deep structural levels. Once exhumed at shallow structural levels, the Rosas Shear Zone acted as weakness and permeable zone favorable for the intrusion of mafic dyke and, soon after, for extensive granite-related fluid circulation. The ages of each step are supposed taking into account the available dating in the Sardinian basement of the regional metamorphism (~350 Ma, [<a href="#B68-minerals-12-00272" class="html-bibr">68</a>], mafic dyke intrusion (~300 Ma, [<a href="#B41-minerals-12-00272" class="html-bibr">41</a>,<a href="#B69-minerals-12-00272" class="html-bibr">69</a>,<a href="#B70-minerals-12-00272" class="html-bibr">70</a>]) and granite intrusion (~289 Ma [<a href="#B17-minerals-12-00272" class="html-bibr">17</a>,<a href="#B42-minerals-12-00272" class="html-bibr">42</a>]).</p> Full article ">
16 pages, 4596 KiB  
Article
Stability Evaluation of Layered Backfill Considering Filling Interval, Backfill Strength and Creep Behavior
by Chongchong Qi, Li Guo, Yu Wu, Qinli Zhang and Qiusong Chen
Minerals 2022, 12(2), 271; https://doi.org/10.3390/min12020271 - 21 Feb 2022
Cited by 16 | Viewed by 2380
Abstract
Cemented paste backfill (CPB) is the primary solution to improving the safety of continuous mining. The interaction between rock mass and backfill is an important indicator of backfill stability. The creep behavior of weak rock mass is an essential factor, which causes the [...] Read more.
Cemented paste backfill (CPB) is the primary solution to improving the safety of continuous mining. The interaction between rock mass and backfill is an important indicator of backfill stability. The creep behavior of weak rock mass is an essential factor, which causes the evolution of stresses and displacements in the backfill stope. In this paper, numerical models were constructed to analyze the interactions between rock mass and backfill by considering the creep behavior of the rock mass, filling interval, and backfill strength. The numerical simulation results showed the effects of different parameters, including the number of backfilling layers, filling interval time (FIT), and backfill strength under creep behavior on stress, displacements, and plastic deformation. The horizontal displacement near the mid-height and vertical displacement at the top of the backfilled stope is the largest compared to layered backfilling. The stress within the backfilled stope is smallest when the stope is filled in a single layer. With increasing FIT, stress in the backfilled stope decreases. FIT mainly affected the horizontal displacement of the stope. The stresses on the stope bottom decrease when the strength of the middle-backfilled stope decreases. Overall, this study provides important insights for understanding the creep behavior of rock mass in underground backfilling practices. Full article
(This article belongs to the Special Issue Backfilling Materials for Underground Mining, Volume II)
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Figure 1
<p>Schematic view of a typical vertical backfilled stope built with FLAC<sup>2D</sup>.</p> Full article ">Figure 2
<p>Schematic diagram of grid density division.</p> Full article ">Figure 3
<p>Time-dependent response in the reference case: (<b>a</b>) horizontal, (<b>b</b>) vertical stress versus time, (<b>c</b>) horizontal, and (<b>d</b>) vertical displacement versus time.</p> Full article ">Figure 4
<p>Different layers of cemented paste backfill case: (<b>a</b>) Case 1 (backfilled in a single step); (<b>b</b>) Case 2 (backfill in two steps); (<b>c</b>) Case 3 (backfill in three steps).</p> Full article ">Figure 5
<p>The influence of backfill layers on the (<b>a</b>) horizontal stresses, (<b>b</b>) vertical stresses, (<b>c</b>) horizontal displacement, and (<b>d</b>) vertical displacements evolution on the monitoring point (see the red dot in <a href="#minerals-12-00271-f005" class="html-fig">Figure 5</a>).</p> Full article ">Figure 6
<p>Stress distribution at 32 days with different backfill layers.</p> Full article ">Figure 7
<p>Elastic and plastic region within the backfilled stope at 32 days with different backfill layers: (<b>a</b>) Case 1, (<b>b</b>) Case 2, and (<b>c</b>) Case 3.</p> Full article ">Figure 8
<p>The stress difference between (<b>a</b>) MC and (<b>b</b>) CVISC constitutive models of the rock mass.</p> Full article ">Figure 9
<p>Stresses and displacements evolution with different FIT values (24 h, 36 h, and 48 h): (<b>a</b>) horizontal stresses, (<b>b</b>) vertical stresses, (<b>c</b>) horizontal displacement, and (<b>d</b>) vertical displacements, on the monitoring point (see the red dot in <a href="#minerals-12-00271-f009" class="html-fig">Figure 9</a>).</p> Full article ">Figure 10
<p>Elastic and plastic region within the backfilled stope at 32 days with different FIT values; (<b>a</b>) the FIT is 24 h, (<b>b</b>) 36 h, and (<b>c</b>) 48 h.</p> Full article ">Figure 11
<p>Effect of backfill strength on the stress and displacement distribution: (<b>a</b>) horizontal stresses, (<b>b</b>) vertical stresses, (<b>c</b>) horizontal displacements, and (<b>d</b>) vertical displacements.</p> Full article ">Figure 12
<p>Plastic strain distribution in the backfilled stope at 32 days with different strength (<b>a</b>) 0.5, (<b>b</b>) 0.7, and (<b>c</b>) 0.9 of the middle-backfilled stope (coefficient in <a href="#minerals-12-00271-f011" class="html-fig">Figure 11</a> is the strength in the middle backfill accounts for the strength in the top and bottom).</p> Full article ">
12 pages, 1192 KiB  
Article
Study on the Grinding Law of Ball Media for Cassiterite–Polymetallic Sulfide Ore
by Jinlin Yang, Xingjian Deng, Wenzhe Xu, Hengjun Li and Shaojian Ma
Minerals 2022, 12(2), 270; https://doi.org/10.3390/min12020270 - 21 Feb 2022
Cited by 1 | Viewed by 1742
Abstract
To solve the problem involved in the grinding of cassiterite–polymetallic sulfide ore in which fine grinding causes the cassiterite to be overground or coarse grinding leads to inadequate liberation of sulfide minerals, the influences of the ball grinding medium on the size distribution [...] Read more.
To solve the problem involved in the grinding of cassiterite–polymetallic sulfide ore in which fine grinding causes the cassiterite to be overground or coarse grinding leads to inadequate liberation of sulfide minerals, the influences of the ball grinding medium on the size distribution of the grinding product were investigated. Two types of ball filling patterns, namely, single-sized and multi-sized ball grinding media, were adopted in wet batch grinding tests. The results show that increasing the grinding time resulted in a rapid increase in minus 0.038 mm particles and a slight increase in the Sn grade in this fine size fraction. The smaller the ball filling fraction was, the more obviously the ball size affected the size distribution of the grinding product, the variation of which with the ball size became complicated with the increase in the ball filling fraction. Obvious jumping phenomena in the plotting of the percentages of the discussed size fractions against the ball size were observed when the balling filling fraction was larger than 30%; the most obvious jumping phenomena took place at a 35% ball filling fraction. The results of the grinding tests with the multi-sized media show that the size distribution of the grinding product was closely related to that of the mixed ball sizes and their composition percentages. Full article
(This article belongs to the Special Issue Experimental and Numerical Studies of Mineral Comminution)
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<p>Particle size distribution of the test samples.</p> Full article ">Figure 2
<p>Plots of the yields of the product size fractions against the ball size at ball filling fractions of (<b>a</b>) 30%, (<b>b</b>) 35%, (<b>c</b>) 40%, and (<b>d</b>) 45%.</p> Full article ">Figure 3
<p>Plot of the yields of the size fractions of the grinding product against the ball filling fraction for balls that were (<b>a</b>) 40, (<b>b</b>) 30, (<b>c</b>) 25, (<b>d</b>) 20, (<b>e</b>) 18, and (<b>f</b>) 16 mm in diameter.</p> Full article ">Figure 4
<p>Grinding results with different ball mixture patterns: (<b>a</b>) 40 plus 16 mm balls, (<b>b</b>) 40 plus 25 mm balls, (<b>c</b>) 30 plus 20 mm balls, (<b>d</b>) 40 plus 18 mm balls, (<b>e</b>) 30 plus 25 mm balls, and (<b>f</b>) 20 plus 16 mm balls.</p> Full article ">Figure 4 Cont.
<p>Grinding results with different ball mixture patterns: (<b>a</b>) 40 plus 16 mm balls, (<b>b</b>) 40 plus 25 mm balls, (<b>c</b>) 30 plus 20 mm balls, (<b>d</b>) 40 plus 18 mm balls, (<b>e</b>) 30 plus 25 mm balls, and (<b>f</b>) 20 plus 16 mm balls.</p> Full article ">Figure 5
<p>Relationship of the yields of the size fractions in grinding products with the total surface area of the grinding media.</p> Full article ">
18 pages, 7387 KiB  
Article
Microplastic Extraction from the Sediment Using Potassium Formate Water Solution (H2O/KCOOH)
by Kinga Jarosz, Piotr Natkański and Marek Michalik
Minerals 2022, 12(2), 269; https://doi.org/10.3390/min12020269 - 20 Feb 2022
Cited by 2 | Viewed by 3142
Abstract
Microplastics (MPs) are considered an important stratigraphic indicator, or ‘technofossils’, of the Anthropocene. Research on MP abundance in the environment has gained much attention but the lack of a standardized procedure has hindered the comparability of the results. The development of an effective [...] Read more.
Microplastics (MPs) are considered an important stratigraphic indicator, or ‘technofossils’, of the Anthropocene. Research on MP abundance in the environment has gained much attention but the lack of a standardized procedure has hindered the comparability of the results. The development of an effective and efficient method of MP extraction from the matrix is crucial for the proper identification and quantifying analysis of MPs in environmental samples. The procedures of density separation used currently have various limitations: high cost of reagents, limited solution density range, hazardous reagents, or a combination of the above. In this research, a procedure based on density separation with the use of potassium formate water solution (H2O/KCOOH) in controlled conditions was performed. Experimental sediment mixtures, spiked with polyethylene (PE), polystyrene (PS), polyurethane (PUR) and polyethylene terephthalate (PET) particles were prepared and an extraction procedure was tested in the context of a weight-based quantitative analysis of MPs. This article discusses the effectiveness and safety of the method. It additionally provides new information on the interactions between MP particles and the mineral matter of the sediment. Results were acquired with the use of instrumental methods, namely thermogravimetry (TG), Fourier Transform Infrared (FTIR) spectroscopy, Field Emission Scanning Electron microscopy and Energy Dispersive spectrometry (SEM/EDS), as well as X-ray fluorescence (XRF) analysis. Full article
(This article belongs to the Section Mineral Processing and Extractive Metallurgy)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Grain size distribution of the sediment used for the experiment.</p> Full article ">Figure 2
<p>XRD pattern of the pure sediment used to prepare the experimental mixtures (Qz-quartz, Kfs-potassium feldspar, Pl-plagioclase, Mic-mica).</p> Full article ">Figure 3
<p>The ATR-FTIR spectra of polyethylene (PE): Extracted from sediment with water, the potassium formate water solution and clean PE and potassium formate as references.</p> Full article ">Figure 4
<p>The ATR-FTIR spectra of PUR, PS, PET, PE and residuum from the blank sample.</p> Full article ">Figure 5
<p>TG-DTG-DTA curves recorded for the initial and extracted MP samples: (<b>a</b>) PUR, (<b>b</b>) PS, (<b>c</b>) PE, (<b>d</b>) PET.</p> Full article ">Figure 6
<p>SEM images of the sediment without polymers after mixing (<b>A</b>); SEM image and EDS analysis of pure sediment surface after mixing (<b>B</b>).</p> Full article ">Figure 7
<p>SEM images of polyethylene terephthalate particles before they were added to the sediment (PET) and extracted from the sediment (extracted PET).</p> Full article ">Figure 8
<p>SEM images of polyethylene particles before they were added to the sediment (PE) and extracted from the sediment (extracted PE).</p> Full article ">Figure 9
<p>SEM images of polystyrene particles before they were added to the sediment (PS) and extracted from the sediment (extracted PS).</p> Full article ">Figure 10
<p>SEM images of polyurethane particles before they were added to the sediment (PUR) and extracted from the sediment (extracted PUR).</p> Full article ">Figure 11
<p>SEM images of the surface of the PET particle extracted from the sediment (with positions and the results of the EDS analysis).</p> Full article ">
19 pages, 9479 KiB  
Article
Spectral Angle Mapping and AI Methods Applied in Automatic Identification of Placer Deposit Magnetite Using Multispectral Camera Mounted on UAV
by Brian Bino Sinaice, Narihiro Owada, Hajime Ikeda, Hisatoshi Toriya, Zibisani Bagai, Elisha Shemang, Tsuyoshi Adachi and Youhei Kawamura
Minerals 2022, 12(2), 268; https://doi.org/10.3390/min12020268 - 20 Feb 2022
Cited by 10 | Viewed by 3524
Abstract
The use of drones in mining environments is one way in which data pertaining to the state of a site in various industries can be remotely collected. This paper proposes a combined system that employs a 6-bands multispectral image capturing camera mounted on [...] Read more.
The use of drones in mining environments is one way in which data pertaining to the state of a site in various industries can be remotely collected. This paper proposes a combined system that employs a 6-bands multispectral image capturing camera mounted on an Unmanned Aerial Vehicle (UAV) drone, Spectral Angle Mapping (SAM), as well as Artificial Intelligence (AI). Depth possessing multispectral data were captured at different flight elevations. This was in an attempt to find the best elevation where remote identification of magnetite iron sands via the UAV drone specialized in collecting spectral information at a minimum accuracy of +/− 16 nm was possible. Data were analyzed via SAM to deduce the cosine similarity thresholds at each elevation. Using these thresholds, AI algorithms specialized in classifying imagery data were trained and tested to find the best performing model at classifying magnetite iron sand. Considering the post flight logs, the spatial area coverage of 338 m2, a global classification accuracy of 99.7%, as well the per-class precision of 99.4%, the 20 m flight elevation outputs presented the best performance ratios overall. Thus, the positive outputs of this study suggest viability in a variety of mining and mineral engineering practices. Full article
(This article belongs to the Special Issue Application of Deep Learning Approaches in Rocks Hyperspectral Imaging)
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<p>Study area map showing Kamaiso magnetite iron sand placer deposits. Red polygon denotes the 30 m by 90 m study area within which the UAV drone shown was flown. Map acquired from: Google maps (2021).</p> Full article ">Figure 2
<p>The 6-bands multispectral sensor with a 62.7° field of view; (<b>1</b>) Blue: 450 nm ± 16 nm, (<b>2</b>) Green: 560 nm ± 16 nm, (<b>3</b>) Red: 650 nm ± 16 nm, (<b>4</b>) Red Edge: 730 nm ± 16 nm, (<b>5</b>) Near Infrared: 840 nm ± 26 nm and (<b>6</b>) RGB camera: 400–700 nm represent the multispectral sensor capabilities. Images captured are corrected for parallax error via an edge detection method. The red point is the reference area from which magnetite iron sands are known to exist.</p> Full article ">Figure 3
<p>Schematic diagram showing the principle of spectral angle mapping via cosine similarity. Reference spectrum is the sought after target. Angle a is the cosine similarity threshold between a reference and a true spectrum.</p> Full article ">Figure 4
<p>Illustration of the difference spatial resolutions of each image, attained from capturing multispectral images at 2 m, 10 m, and 20 m flight elevations.</p> Full article ">Figure 5
<p>SAM analysis at 2 m, 10 m and 20 m UAV drone elevations at different reference spectral thresholds. The red points represent the user-selected reference point known to be magnetite (pre-SAM), whilst the blue overlay represent areas within the threshold limit thought to be magnetite (post SAM cosine similarity). The best threshold cosine similarities are 0.12, 0.13 and 0.17 at 2 m, 10 m and 20 m, respectively. The x and y axis represent the size of each captured multispectral image. The bar on the right of each first image represents the variation in spectral intensities present in each captured image. Reprinted with permission from ref. [<a href="#B1-minerals-12-00268" class="html-bibr">1</a>]. 2021 AusIMM [<a href="#B1-minerals-12-00268" class="html-bibr">1</a>] (p. 38).</p> Full article ">Figure 6
<p>Extraction of 6-bands deep segmentation maps (binazized for easier visual representation) used to create a magnetite iron sand database. Noise refers to non-magnetite pixels. Segmentation maps at each UAV flight elevation are based on the 0.12, 0.13 and 0.17 cosine similarity thresholds at 2 m, 10 m and 20 m. This process is summarized in step ② of <a href="#minerals-12-00268-f007" class="html-fig">Figure 7</a>, as well as <a href="#app1-minerals-12-00268" class="html-app">Appendix A</a>.</p> Full article ">Figure 7
<p>Proposed process overview with emphasis on how data extracted from spectral angle mapping cosine similarities is segmented, assigned ground truths, and used in training artificially intelligent algorithms in the classification of magnetite iron sand. <a href="#app1-minerals-12-00268" class="html-app">Appendix A</a> has extended explanations on this procedure.</p> Full article ">Figure 8
<p>Input dataset sizes used to train the machine learning and deep learning algorithms as well as selection of the best performing model at each UAV flight elevation.</p> Full article ">Figure 9
<p>Machine learning confusion matrices from Ensemble (RUS Boosted Trees) at 2 m UAV drone elevation, Tree (Course-tree) at 10 m UAV drone elevation, and Tree (Course-tree) at 20 m UAV drone. Reprinted with permission from ref. [<a href="#B1-minerals-12-00268" class="html-bibr">1</a>]. 2021 AusIMM [<a href="#B1-minerals-12-00268" class="html-bibr">1</a>] (p. 40).</p> Full article ">Figure 10
<p>Deep learning one dimensional convolution neural network confusion matrices at 2 m, 10 m and 20 m UAV drone elevation.</p> Full article ">Figure 11
<p>Best performing machine learning vs. deep learning classification models based on 0.12, 0.13 and 0.17 SAM cosine similarity thresholds at 2 m, 10 m and 20 m, respectively: (<b>a</b>) Comparisons based on global accuracy and pre-class precision; (<b>b</b>) Comparisons based on model training durations.</p> Full article ">
30 pages, 40960 KiB  
Article
Contrasting Modes of Carbonate Precipitation in a Hypersaline Microbial Mat and Their Influence on Biomarker Preservation (Kiritimati, Central Pacific)
by Yan Shen, Pablo Suarez-Gonzalez and Joachim Reitner
Minerals 2022, 12(2), 267; https://doi.org/10.3390/min12020267 - 20 Feb 2022
Cited by 2 | Viewed by 2983
Abstract
Microbial mats represented the earliest complex ecosystems on Earth, since fossil mineralized examples (i.e., microbialites) date back to the Archean Eon. Some microbialites contain putative remains of organic matter (OM), however the processes and pathways that lead to the preservation of OM within [...] Read more.
Microbial mats represented the earliest complex ecosystems on Earth, since fossil mineralized examples (i.e., microbialites) date back to the Archean Eon. Some microbialites contain putative remains of organic matter (OM), however the processes and pathways that lead to the preservation of OM within microbialite minerals are still poorly understood. Here, a multidisciplinary study is presented (including petrographic, mineralogical and organic geochemical analyses), focusing on a modern calcifying mat from a hypersaline lake in the Kiritimati atoll (Central Pacific). The results show that this mat has a complex history, with two main growth phases under hypersaline conditions, separated by an interruption caused by desiccation and/or freshening of the lake. The mineral precipitates of the mat are predominantly aragonitic and two contrasting precipitation modes are observed: the main growth phases of the mat were characterized by the slow formation of irregular micritic particles with micropeloidal textures and subspherical particles, linked to the degradation of the exopolymer (EPS) matrix of the mat; whereas the interruption period was characterized by the rapid development of a thin but laterally continuous crust composed of superposed fibrous aragonite botryoids that entombed their contemporaneous benthic microbial community. These two precipitation modes triggered different preservation pathways for the OM of the mat as the thin crust shows a particular lipid biomarker signature, different from that of other layers and the relatively rapid precipitation of the crust protecting the underlying lipids from degradation, causing them to show a preservation equivalent to that of a modern active microbial community, despite them being >1100 years old. Equivalent thin mineral crusts occur in other microbialite examples and, thus, this study highlights them as excellent targets for the search of well-preserved biomarker signatures in fossil microbialites. Nevertheless, the results of this work warn for extreme caution when interpreting complex microbialite biomarker signatures, advising combined petrographic, mineralogical and geochemical investigations for the different microbialite layers and mineral microfabrics. Full article
(This article belongs to the Special Issue Carbonate Biomineralization, Environmental, and Diagenetic Significance)
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Figure 1
<p>(<b>a</b>) General location of Kiritimati atoll in the Pacific Ocean and its satellite image, showing reticulate distribution pattern of the lakes (red dot: sampling site, Lake 2); (<b>b</b>) general view of hypersaline Lake 2 in Kiritimati; (<b>c</b>) the microbial mat sampled for this study, with clear color-zonation; note the whitish mineral crust (Layer 3) separating the upper fresher part of the mat from the older, more mineralized layers. <sup>14</sup>C dates of carbonate particles were measured by Blumenberg et al. [<a href="#B30-minerals-12-00267" class="html-bibr">30</a>]. (BP: before present, i.e., before 1950, before the start of the worldwide nuclear bomb tests; note the significant deviation (bomb anomaly) of 239 yrs at the topmost of the mat, as result of the bomb tests).</p> Full article ">Figure 2
<p>Close-up picture of frozen microbial mat sample studied in this work (compare with <a href="#minerals-12-00267-f001" class="html-fig">Figure 1</a>c). Green arrows point to transparent gypsum crystals, which occur only in the uppermost layer. Note common beige, irregular to subspherical, carbonate particles, more abundant downwards in the mat. Red arrows point to dark inclusions within the thin mineral crust of layer 3.</p> Full article ">Figure 3
<p>Different preservation of the exopolymers (EPS) of the organic matrix of the mat. (<b>a</b>,<b>c</b>) Photomicrographs taken with fluorescence microscope. (<b>b</b>,<b>d</b>) Same areas as a, c, however seen with cross-polarized light. (<b>a</b>,<b>b</b>) Carbonate precipitates from the topmost Layer 1, within a dense reticulate net of intertwined delicate fibers of younger and fresher EPS, which show no birefringence (black color in (<b>b</b>)) with cross-polarized light. (<b>c</b>,<b>d</b>) Carbonate precipitates from the lowermost Layer 6, forming in a less dense and more porous matrix of older EPS with a laminated microstructure of coarser individual EPS fibers, which show birefringence (yellow arrow in (<b>d</b>)) with cross-polarized light.</p> Full article ">Figure 4
<p>Mineral precipitates observed within the studied microbial mat: (<b>a</b>) Cross-polarized light photomicrograph of gypsum crystals (Gyp) and subspherical aragonite particles (S) from Layer 1; (<b>b</b>) Cross-polarized light photomicrograph of irregular micritic aggregates from Layer 6, showing their micropeloidal internal texture. Yellow arrow points to thick and birefringent EPS threads; (<b>c</b>) SEM image of an irregular micritic aggregate from Layer 1, showing a detail of its micropeloids (M), formed by intergrown bundles of aragonite needles, and completely surrounded by a matrix of EPS, within which they precipitate; (<b>d</b>) Close-up picture of the loose mineral particles extracted from Layer 2 after complete removal of the organic matter. Note the presence of both subspherical particles and irregular aggregates; (<b>e</b>) SEM image showing a section of coalesced subspherical particles from Layer 2. Note their fibrous radial structure formed by aragonite needles; (<b>f</b>) Large irregular carbonate aggregate from Layer 4 after complete removal of organic matter. Note that it is formed by the coalescence of both subspherical particles and micritic aggregates. Large complex aggregates are typical from the lower older layers of the mat (compare with the younger precipitates of <a href="#minerals-12-00267-f004" class="html-fig">Figure 4</a>d).</p> Full article ">Figure 5
<p>Photomicrographs of subspherical particles of the upper part of layer 4, merged together by micritic aggregates with meniscus morphology: (<b>a</b>) Transmitted light photomicrograph; (<b>b</b>,<b>c</b>) Cross-polarized light photomicrograph.</p> Full article ">Figure 6
<p>Thin mineral crust of layer 3: (<b>a</b>) Close-up picture of the mineral crust of Layer 3 after complete removal of organic matter. Note the botryoidal upper surface of the crust and its local dark color; (<b>b</b>) Transmitted light photomicrograph of the thin crust of layer 3 with two Raman spectra from the crust. The upper left one shows the dominant aragonitic composition of the crust (as in most precipitates of the Kiritimati mats, cf. [<a href="#B27-minerals-12-00267" class="html-bibr">27</a>,<a href="#B40-minerals-12-00267" class="html-bibr">40</a>]). No traces of organic carbon are detected. In contrast, the lower right spectrum shows the organic composition of a dark inclusion rich in coccoid cyanobacteria (see <a href="#minerals-12-00267-f008" class="html-fig">Figure 8</a>). The spectrum has a very broad D-band (disordered) with an unclear main peak (around wave number 1300). The G-band (graphite band) has wave number 1578; (<b>c</b>) Cross-polarized light photomicrograph of a thin section of the mineral crust of Layer 3, showing its internal structure, composed of several superposed laminae of botryoidal carbonate, indicating different precipitation episodes. Yellow arrows point to cavities within the crust, filled by organic matter.</p> Full article ">Figure 7
<p>Elemental distribution within the thin mineral crust of layer 3: (<b>a</b>) Transmitted-light photomicrograph of the thin mineral crust. Red rectangles mark the position of <a href="#minerals-12-00267-f008" class="html-fig">Figure 8</a>a,d and <a href="#minerals-12-00267-f009" class="html-fig">Figure 9</a>a,d; (<b>b</b>,<b>c</b>) μ-XRF maps of Ca, Mg and Sr within the crust, showing the high abundance of Sr, consistent with its aragonitic composition [<a href="#B42-minerals-12-00267" class="html-bibr">42</a>]. Local abundances of Mg correspond to scarce miliolid foraminifera occurring at the base of the crust (<a href="#minerals-12-00267-f009" class="html-fig">Figure 9</a>d and <a href="#minerals-12-00267-f012" class="html-fig">Figure 12</a>b). See further descriptions in the text.</p> Full article ">Figure 8
<p>Detailed transmitted-light photomicrographs of the thin mineral crust of layer 3: (<b>a</b>) Vertical transect of the crust (see location in <a href="#minerals-12-00267-f007" class="html-fig">Figure 7</a>a). Red arrow points to a colony of coccoid cyanobacteria in the overlying layer 2. Yellow arrow points to a fossil colony of coccoid cyanobacteria rich in organic matter (see <a href="#minerals-12-00267-f006" class="html-fig">Figure 6</a>b) and entombed within the crust. See detail in (<b>c</b>); (<b>b</b>) Detail of the upper part of the crust, showing that its cloudy appearance is caused by extremely abundant molds of curved filaments, many of them showing branching; (<b>c</b>) Detail of the boundary of the colony of coccoid cyanobacteria entombed within the crust; (<b>d</b>) Detail of small aragonite botryoids (see location in <a href="#minerals-12-00267-f007" class="html-fig">Figure 7</a>a), which include tufts of filaments. Note that the shape and orientation of the botryoids mimics that of the tufts.</p> Full article ">Figure 9
<p>(<b>a</b>) Transmitted light photomicrograph showing a detail of a carbonate botryoid from layer 3 (see location in <a href="#minerals-12-00267-f007" class="html-fig">Figure 7</a>a). Note the fibrous-radial internal texture and the presence of very abundant curved dark filaments. The cloudier aspect of the outer part is due to a higher abundance of dark filaments. (<b>b</b>) Detailed transmitted light photomicrograph of a botryoid from layer 3 including abundant curved filament tufts, whose morphology seems to be mimicked by the mineral botryoid. (<b>c</b>) Detail of (<b>a</b>), showing the curved dark filaments preserved within the botryoid. (<b>d</b>) Detailed transmitted light photomicrograph of miliolid foraminifers preserved within the lower part of the crust. See location in <a href="#minerals-12-00267-f007" class="html-fig">Figure 7</a>a.</p> Full article ">Figure 10
<p>Thin filaments preserved within the crust of layer 3: (<b>a</b>) Detailed transmitted light photomicrograph of the dense framework of curved filaments preserved within an aragonite botryoid of the crust. Note that most filaments are ~1 µm thick or less; (<b>b</b>,<b>c</b>) Transmitted light photomicrograph of the filaments clearly showing their curved morphology, some of them with branching; (<b>d</b>) Detail of (<b>b</b>) clearly showing the curved and branching morphology of the filaments, which resemble hyphal branching networks of Actinobacteria or fungi, as well as the local swelling knots, which are comparable with reproductive structures like spores. Compare with figures in Li et al. [<a href="#B43-minerals-12-00267" class="html-bibr">43</a>].</p> Full article ">Figure 11
<p>Different filaments in the upper part of the thin mineral crust of layer 3: (<b>a</b>) Transmitted light photomicrograph and; (<b>b</b>) Fluorescence photomicrograph of the same area. Note the cloudy appearance of the botryoid, due to the high abundance of small filament molds, which are highly fluorescent, and which contrast with the larger brown filament molds that are not fluorescent. Some of these larger filaments seem to penetrate the crust from its upper surface.</p> Full article ">Figure 12
<p>SEM images of the thin mineral crust of layer 3: (<b>a</b>) Fibrous-radial structure of a carbonate botryoid from layer 3, formed by aragonite needles, and covered by a thin film of EPS; (<b>b</b>) A freshly-cut section of layer 3, showing irregular and partially-filled cavities (yellow arrows) and a section of a foraminifer (green arrow). Red rectangles mark the position of (<b>c</b>,<b>e</b>); (<b>c</b>) Detail of (<b>b</b>), showing the EPS matrix that infills the cavities observed within the mineral crust of layer 3; (<b>d</b>) Close-up view of a freshly-cut section of the mineral crust of layer 3, showing molds of diatoms (green and yellow arrows) and much more abundant small filaments (red arrows) included within the mineral crust. Most diatom molds are filled by carbonate (green arrows), however locally others are partially empty, with some remains of EPS (yellow arrows); (<b>e</b>) Detail of (<b>b</b>), showing a cavity filled with EPS (yellow arrow) and ubiquitous filament molds. Red arrows only point to some locations with an important concentration of filaments, however many more can be observed throughout the image; (<b>f</b>) Close-up image of many filament molds. Yellow arrow points to a mold that partially preserves the EPS of the filament sheath.</p> Full article ">Figure 13
<p>Thin mineral crust of subfossil microbialites from Kiritimati Lake 21 (01°57′45.63″ N, 157°19′53.03″ W): (<b>a</b>) Transmitted light photomicrograph with an overview of the sample, clearly showing the thin yet laterally continuous mineral crust interrupting the microbialite accretion, around the middle part of the sample; (<b>b</b>) Detail of (<b>a</b>) showing the botryoidal top of the thin mineral crust; (<b>c</b>,<b>d</b>) Detailed transmitted light photomicrographs of the thin mineral crusts. Note the complex laminated inner structure, composed of superposed botryoids, often with cloudy appearance, due to abundant filaments preserved within them; (<b>e</b>) Detail of the filaments preserved within the crust, with the same curved and branched structures as those preserved within the thin crust (layer 3) of the microbial mat of Lake 2, <a href="#minerals-12-00267-f008" class="html-fig">Figure 8</a>, <a href="#minerals-12-00267-f009" class="html-fig">Figure 9</a> and <a href="#minerals-12-00267-f010" class="html-fig">Figure 10</a>; (<b>f</b>) Example of a filament that shows segmentation (sporulation septa) and branching, which are characteristics for Actinobacteria (e.g., Streptomyces, [<a href="#B43-minerals-12-00267" class="html-bibr">43</a>]).</p> Full article ">Figure 14
<p>Partial GC-MS chromatograms (total ion current) showing the distribution of freely extractable lipids (TMS derivatives including hopanoids, fatty acids, sterols, and <span class="html-italic">n</span>-alkanes) in layer 4a of the microbial mat.</p> Full article ">Figure 15
<p>Depth distribution of the summed sterols (carbon ranging C<sub>27</sub>–C<sub>31</sub>), hopanoids and fatty acids in the microbial mat layers (μg/g dry mat).</p> Full article ">Figure 16
<p>Relative abundance of C<sub>27</sub>-C<sub>31</sub> sterols in the mat profile.</p> Full article ">
15 pages, 3272 KiB  
Article
Basic Evaluation of Phase Relation in a Phosphorus-Containing System Saturated with CaSiO3 at Elevated Temperatures for the Utilization of Steelmaking Slag and Sewage Sludge as Phosphorus Resources
by Yu-ichi Uchida, Chiho Watanabe and Hideki Tsuruoka
Minerals 2022, 12(2), 266; https://doi.org/10.3390/min12020266 - 19 Feb 2022
Cited by 6 | Viewed by 1812
Abstract
In view of obtaining fundamental information on phosphorus recovery from steelmaking slag and sewage sludge, a laboratory experiment using the model specimen of a slag/sludge mixture prepared at 1573 K was carried out to investigate phase relation in a [CaO-SiO2-P2 [...] Read more.
In view of obtaining fundamental information on phosphorus recovery from steelmaking slag and sewage sludge, a laboratory experiment using the model specimen of a slag/sludge mixture prepared at 1573 K was carried out to investigate phase relation in a [CaO-SiO2-P2O5]-based system. The triangular compositional region, comprising of apices CaO·SiO2 (CS), 3CaO·P2O5 (C3P), and 2CaO·SiO2-3CaO·P2O5 solid solution (C2S-C3Pss), was considered with particular interest. In this region, using SEM-EDX observation it was found that solid saturated CS and the solid C2S-C3Pss with a relatively high phosphorus content can coexist. With the addition of Al2O3 or Fe2O3 to the same specimens, the liquidus phase appeared as a third phase; however, CS and C2S-C3Pss phases were still observed for up to 5mass% addition. The further addition of Al2O3 or Fe2O3 to 10mass% resulted in dissolution of the solid CS phase, although C2S-C3Pss remained as the phosphorus concentrated phase. These results show that phase equilibria based on the ternary system would be stable and be beneficial for phosphorus recovery. Full article
(This article belongs to the Special Issue Slag Valorization for Advanced Metal Production)
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<p>Isothermal section of the CaO-SiO<sub>2</sub>-P<sub>2</sub>O<sub>5</sub> ternary phase diagram at 1573 K.</p> Full article ">Figure 2
<p>Schematic illustration of the experimental setup.</p> Full article ">Figure 3
<p>SEM image of M1-0 (<b>left</b>) and phase composition projected on isothermal section of CaO-SiO<sub>2</sub>-P<sub>2</sub>O<sub>5</sub> ternary phase diagram at 1573 K (<b>right</b>).</p> Full article ">Figure 4
<p>SEM image of M2-0 (<b>left</b>) and phase composition projected on an isothermal section of the CaO-SiO<sub>2</sub>-P<sub>2</sub>O<sub>5</sub> ternary phase diagram at 1573 K (<b>right</b>).</p> Full article ">Figure 5
<p>SEM image of M3-0 (<b>left</b>) and phase composition projected on an isothermal section of the CaO-SiO<sub>2</sub>-P<sub>2</sub>O<sub>5</sub> ternary phase diagram at 1573 K (<b>right</b>).</p> Full article ">Figure 6
<p>SEM image of M3-A2 (2mass% Al<sub>2</sub>O<sub>3</sub>) (<b>left</b>) and phase composition projected on an isothermal section of the CaO-SiO<sub>2</sub>-P<sub>2</sub>O<sub>5</sub> ternary phase diagram at 1573 K (<b>right</b>).</p> Full article ">Figure 7
<p>SEM image of M3-A5 (5mass% Al<sub>2</sub>O<sub>3</sub>) (<b>left</b>) and the phase composition projected on an isothermal section of the CaO-SiO<sub>2</sub>-P<sub>2</sub>O<sub>5</sub> ternary phase diagram at 1573 K (<b>right</b>).</p> Full article ">Figure 8
<p>SEM image of M3-A10 (10mass% Al<sub>2</sub>O<sub>3</sub>) (<b>left</b>) and the phase composition projected on an isothermal section of the CaO-SiO<sub>2</sub>-P<sub>2</sub>O<sub>5</sub> ternary phase diagram at 1573 K (<b>right</b>).</p> Full article ">Figure 9
<p>SEM image of M3-F2 (2mass% Fe<sub>2</sub>O<sub>3</sub>) (<b>left</b>) and the phase composition projected on the isothermal section of the CaO-SiO<sub>2</sub>-P<sub>2</sub>O<sub>5</sub> ternary phase diagram at 1573 K (<b>right</b>).</p> Full article ">Figure 10
<p>SEM image of M3-F5 (5mass% Fe<sub>2</sub>O<sub>3</sub>) (<b>left</b>) and the phase composition projected on an isothermal section of the CaO-SiO<sub>2</sub>-P<sub>2</sub>O<sub>5</sub> ternary phase diagram at 1573 K (<b>right</b>).</p> Full article ">Figure 11
<p>SEM image of M3-F10 (10mass% Fe<sub>2</sub>O<sub>3</sub>) (<b>left</b>) and the phase composition projected on an isothermal section of the CaO-SiO<sub>2</sub>-P<sub>2</sub>O<sub>5</sub> ternary phase diagram at 1573 K (<b>right</b>).</p> Full article ">Figure 12
<p>C<sub>2</sub>S-C<sub>3</sub>P pseudo-binary phase diagram after Fix (<b>left</b>) [<a href="#B31-minerals-12-00266" class="html-bibr">31</a>] and Nurse (<b>right</b>) [<a href="#B30-minerals-12-00266" class="html-bibr">30</a>]. The compositions of C<sub>2</sub>S-C<sub>3</sub>Pss phases observed in the ternary samples are also plotted.</p> Full article ">Figure 13
<p>Composition of the observed phases in the quaternary samples containing Al<sub>2</sub>O<sub>3</sub> projected on a CaO-SiO<sub>2</sub>-Al<sub>2</sub>O<sub>3</sub> diagram.</p> Full article ">Figure 14
<p>Composition of the observed phases in the quaternary samples containing Fe<sub>2</sub>O<sub>3</sub> projected on a CaO-SiO<sub>2</sub>-Fe<sub>2</sub>O<sub>3</sub> diagram.</p> Full article ">Figure 15
<p>(<b>a</b>) Change in P<sub>2</sub>O<sub>5</sub> content in the liquid phase with Al<sub>2</sub>O<sub>3</sub>/Fe<sub>2</sub>O<sub>3</sub> content in the bulk slag; (<b>b</b>) change in P<sub>2</sub>O<sub>5</sub> content in the liquid phase with an optical basicity of the liquid phase.</p> Full article ">Figure 16
<p>Area fraction of each phase that appeared in the SEM analysis.</p> Full article ">
15 pages, 3032 KiB  
Article
Magnesium Coprecipitation with Calcite at Low Supersaturation: Implications for Mg-Enriched Water in Calcareous Soils
by Mostafa Abdollahpour, Frank Heberling, Dieter Schild and Rasoul Rahnemaie
Minerals 2022, 12(2), 265; https://doi.org/10.3390/min12020265 - 19 Feb 2022
Cited by 1 | Viewed by 2415
Abstract
The concentrations of magnesium (Mg) and calcium (Ca) in natural aqueous environments are controlled by sorption and dissolution–precipitation reactions. Ca binding in calcareous soils depends on the degree of solution saturation with respect to CaCO3. Mg may be bound in precipitating [...] Read more.
The concentrations of magnesium (Mg) and calcium (Ca) in natural aqueous environments are controlled by sorption and dissolution–precipitation reactions. Ca binding in calcareous soils depends on the degree of solution saturation with respect to CaCO3. Mg may be bound in precipitating calcite. Here, we investigated Mg incorporation into calcite via the recrystallization of vaterite, which simulates a very low supersaturation in a wide range of Mg to Ca ratios and pH conditions. Increasing the Mg to Ca ratios (0.2 to 10) decreased the partition coefficient of Mg in calcite from 0.03 to 0.005. An approximate thermodynamic mixing parameter (Guggenheim a0 = 3.3 ± 0.2), that is valid for dilute systems was derived from the experiments at the lowest initial Mg to Ca ratio (i.e., 0.2). At elevated Mg to Ca ratios, aragonite was preferentially formed, indicating kinetic controls on Mg partitioning into Mg-calcite. Scanning electron microscopy (SEM-EDX) analyses indicated that Mg is not incorporated into aragonite. The thermodynamic mixing model suggests that at elevated Mg to Ca ratio (i.e., ≥1) Mg-calcite becomes unstable relative to pure aragonite. Finally, our results suggest that the abiotic incorporation of Mg into calcite is only effective for the removal of Mg from aqueous environments like calcareous soil solution, if the initial Mg to Ca ratio is already low. Full article
(This article belongs to the Special Issue Ion Adsorption at Mineral–Water Interfaces)
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Graphical abstract
Full article ">Figure 1
<p>Changes in the Mg to Ca ratio in (<b>a</b>) precipitated solids and (<b>b</b>) equilibrium solutions as a function of the initial ratio in the solution.</p> Full article ">Figure 2
<p>Selected X-ray powder diffraction (XRD) patterns of the precipitated solids for an average actual pH of 8.8.</p> Full article ">Figure 3
<p>Selected scanning electron microscopy (SEM) images of precipitated solids formed during the transformation of vaterite to Mg-calcite and/or aragonite. The Mg to Ca ratios are (<b>a</b>) 0.2, (<b>b</b>) 1, (<b>c</b>) 2, (<b>d</b>) 5, and (<b>e</b>) 10. Images are taken from experiments with an average actual pH of 8.8.</p> Full article ">Figure 4
<p>The partition coefficients for Mg incorporation into Mg-calcite as a function of the equilibrium Mg to Ca ratio in a solution in comparison with the data of Mucci and Morse [<a href="#B9-minerals-12-00265" class="html-bibr">9</a>] and Busenberg and Plummer [<a href="#B27-minerals-12-00265" class="html-bibr">27</a>]. The lines are model predictions using the empirical parameters given in <a href="#minerals-12-00265-t004" class="html-table">Table 4</a>.</p> Full article ">Figure 5
<p>Rozeboom diagram and partition coefficient. The (<b>left</b>) plot shows a Rozeboom diagram of the (Mg,Ca)CO<sub>3</sub> system. The (<b>right</b>) plot shows the partition coefficient as a function of a Mg mole fraction in the solid. The solid and dashed lines are the predictions for X(Mg)<sub>(s)</sub> and <span class="html-italic">D</span> values using dimensionless Guggenheim parameters of 3.3 and 6, respectively. The value <span class="html-italic">a</span><sub>0</sub> = 3.3 ± 0.2 is considered a good estimate for a thermodynamic value. The calculation with <span class="html-italic">a</span><sub>0</sub> = 6 (dashed line) is just for illustrative purposes.</p> Full article ">
14 pages, 5692 KiB  
Article
Preparation of Antimony Sulfide and Enrichment of Gold by Sulfuration–Volatilization from Electrodeposited Antimony
by Wei Wang, Shuai Wang, Jia Yang, Chengsong Cao, Kanwen Hou, Lixin Xia, Jun Zhang, Baoqiang Xu and Bin Yang
Minerals 2022, 12(2), 264; https://doi.org/10.3390/min12020264 - 19 Feb 2022
Cited by 7 | Viewed by 3831
Abstract
Electrodeposited antimony can be treated with sulfuration–volatilization technology, which causes antimony to volatilize in the form of antimony sulfide. During this process, gold is enriched in the residue, thereby realizing the value-added use of antimony and the recovery of gold. In this study, [...] Read more.
Electrodeposited antimony can be treated with sulfuration–volatilization technology, which causes antimony to volatilize in the form of antimony sulfide. During this process, gold is enriched in the residue, thereby realizing the value-added use of antimony and the recovery of gold. In this study, the thermodynamic conditions of antimony sulfide were analyzed by the Clausius–Clapeyron equation. Moreover, the volatilization behavior of antimony sulfide and the enrichment law of gold were studied by heat volatilization experiments. The effects of the sulfide temperature and volatilization pressure on the separation efficiency of antimony and gold enrichment were investigated. The results demonstrate that the sulfuration rate was the highest, namely 96.06%, when the molar ratio of sulfur to antimony was 3:1, the sulfur source temperature was 400 °C, the antimony source temperature was 550 °C, and the sulfuration time was 30 min. Antimony sulfide prepared under these conditions was volatilized at 800 °C over 2 h at an evaporation pressure of 0.2 atm, and the volatilization rate was the highest, namely 92.81%. Antimony sulfide with a stibnite structure obtained from the sulfuration–volatilization treatment of electrodeposited antimony meets the ideal stoichiometric ratio of sulfur and antimony in Sb2S3 (3:2), and gold is enriched in the residue. Full article
(This article belongs to the Special Issue Chemical Engineering and Technology in Mineral Processing and Extractive Metallurgy)
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<p>Process flow chart of electrodeposited antimony sulfide volatilization and enrichment of gold.</p> Full article ">Figure 2
<p>Structure chart of double temperature zone tube furnace: 1—flange connector at inlet, 2—numerical control display, 3—furnace body, 4—holder, 5—control switch, 6—quartz tube, 7—resistance furnace box, and 8—vaccum gauge.</p> Full article ">Figure 3
<p>Saturated vapor pressure curves of Sb, Sb<sub>2</sub>S<sub>3</sub> and Au.</p> Full article ">Figure 4
<p>Sulfide sample pictures: (<b>a</b>) 400 °C, (<b>b</b>) 450 °C, (<b>c</b>) 500 °C, (<b>d</b>) 550 °C, (<b>e</b>) 600 °C, and (<b>f</b>) 650 °C.</p> Full article ">Figure 5
<p>SEM images of antimony sulfide synthesized by electrodeposited antimony sulfide and electrodeposited antimony at different temperatures: (<b>a</b>) 400 °C, (<b>b</b>) 450 °C, (<b>c</b>) 500 °C, (<b>d</b>) 550 °C, (<b>e</b>) 600 °C, and (<b>f</b>) 650 °C.</p> Full article ">Figure 6
<p>EPMA scanning maps of vulcanized sample at 650 °C.</p> Full article ">Figure 7
<p>EPMA scanning maps of recrystallization zone in metal antimony melting at 650 °C.</p> Full article ">Figure 8
<p>Raman spectra of vulcanized samples at different temperatures.</p> Full article ">Figure 9
<p>XPS spectra of volatiles: (<b>a</b>) S 2p core level, (<b>b</b>) Typical XPS survey spectrum, and (<b>c</b>) Sb 3d core level.</p> Full article ">Figure 10
<p>XPS spectra of residue: (<b>a</b>) S 2p core level, (<b>b</b>) typical XPS survey spectrum, and (<b>c</b>) Sb 3d core level.</p> Full article ">
10 pages, 7954 KiB  
Article
Study of Reagent Scheme, Entrainment and Their Relationship in Chalcopyrite Flotation in the Presence of Bentonite and Kaolinite
by Guohua Gu, Jianghui Zhou, Shiya Du, Su Liao and Yanhong Wang
Minerals 2022, 12(2), 263; https://doi.org/10.3390/min12020263 - 18 Feb 2022
Cited by 2 | Viewed by 2038
Abstract
Entrainment has been considered as an important factor affecting clayey ore flotation. In this study, the effect of reagent dosage on chalcopyrite flotation in the presence of bentonite and kaolinite was investigated through entrainment. It was found that increasing the collector and frother [...] Read more.
Entrainment has been considered as an important factor affecting clayey ore flotation. In this study, the effect of reagent dosage on chalcopyrite flotation in the presence of bentonite and kaolinite was investigated through entrainment. It was found that increasing the collector and frother dosage had little influence on copper recovery in the presence of bentonite, but decreased the copper grade substantially, owing to the increase in entrainment. With regard to kaolinite, increasing the reagent dosage increased the copper grade prominently, due to the decrease in entrainment. The substantial variation was related to the different interactions between the reagent and different clay minerals. The smaller surface area and hydration property of bentonite made most of the reagent remain in the solution, facilitating high entrainment, while kaolinite, with its larger surface area, adsorbed most of the reagent, which decreased the entrainment. The results of this study suggest a guideline of controlling reagent scheme in clayey ore flotation, based on the specific structure and properties of different clay minerals. Full article
(This article belongs to the Special Issue Progress of Reagents in Minerals Flotation)
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<p>Effect of reagent dosage on chalcopyrite flotation in the presence of bentonite with different concentrations: (<b>a</b>) copper recovery; (<b>b</b>) copper grade.</p> Full article ">Figure 2
<p>Effect of reagent dosage on chalcopyrite flotation in the presence of kaolinite with different concentrations: (<b>a</b>) copper recovery; (<b>b</b>) copper grade.</p> Full article ">Figure 3
<p>Effect of reagent dosage on mass and water recovery in the presence of bentonite: (<b>a</b>) mass recovery; (<b>b</b>) water recovery.</p> Full article ">Figure 4
<p>Effect of reagent dosage on mass and water recovery in the presence of kaolinite: (<b>a</b>) mass recovery; (<b>b</b>) water recovery.</p> Full article ">Figure 5
<p>Effect of reagent dosage on the degree of entrainment (ENT) in the presence of bentonite.</p> Full article ">Figure 6
<p>Effect of reagent dosage on the degree of entrainment (ENT) in the presence of kaolinite.</p> Full article ">Figure 7
<p>Residual collector concentration in the conditioning stage of chalcopyrite flotation in the presence of 20 wt.% bentonite or kaolinite.</p> Full article ">Figure 8
<p>Residual frother concentration in the conditioning stage of chalcopyrite flotation in the presence of 20 wt.% bentonite or kaolinite.</p> Full article ">Figure 9
<p>A schematic view of the mechanism of reagent adsorption for different clay minerals.</p> Full article ">
29 pages, 18360 KiB  
Article
Interplay of Multiple Sediment Routing Systems Revealed by Combined Sandstone Petrography and Heavy Mineral Analysis (HMA) in the South Pyrenean Foreland Basin
by Xavier Coll, Marta Roigé, David Gómez-Gras, Antonio Teixell, Salvador Boya and Narcís Mestres
Minerals 2022, 12(2), 262; https://doi.org/10.3390/min12020262 - 18 Feb 2022
Cited by 6 | Viewed by 3588
Abstract
Combined sandstone petrography and heavy mineral analysis allow to decipher different sediment routing systems that could not be resolved by one method alone in the South Pyrenean foreland basin. We apply this approach to deltaic and alluvial deposits of the southern part of [...] Read more.
Combined sandstone petrography and heavy mineral analysis allow to decipher different sediment routing systems that could not be resolved by one method alone in the South Pyrenean foreland basin. We apply this approach to deltaic and alluvial deposits of the southern part of the Jaca basin, and in the time equivalent systems of the nearby Ainsa and Ebro basins, in order to unravel the evolution of source areas and the fluvial drainage from the Eocene to the Miocene. Our study allows the identification of four petrofacies and five heavy-mineral suites, which evidence the interplay of distinct routing systems, controlled by the emergence of tectonic structures. Two distinct axially-fed systems from the east coexisted in the fluvial Campodarbe Formation of the southern Jaca basin that were progressively replaced from east to west by transverse-fed systems sourced from northern source areas. In the late stages of evolution, the Ebro autochthonous basin and the Jaca piggy-back basin received detritus from source areas directly north of the basin from the Axial Zone and from the Basque Pyrenees. Coupling sandstone petrography with heavy mineral provenance analysis allows challenging the existing model of the South Pyrenean sediment dispersal, highlighting the relevance of this approach in source-to-sink studies. Full article
(This article belongs to the Special Issue Provenance Analysis of Clastics Applied to Sedimentary Geology and Petrology)
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<p>(<b>a</b>) Simplified geological map of the Pyrenees (redrawn from Teixell et al. [<a href="#B35-minerals-12-00262" class="html-bibr">35</a>]), showing the location of the study area (white frame). White line indicates cross-section in <a href="#minerals-12-00262-f001" class="html-fig">Figure 1</a>b. White box corresponds to study area. Ga: Gavarnie thrust, SPTF: South Pyrenean Frontal Thrust. (<b>b</b>) Crustal cross-section of the west-central Pyrenees (simplified from Teixell et al. [<a href="#B36-minerals-12-00262" class="html-bibr">36</a>]), showing both the South Pyrenean Zone and the North Pyrenean Zone.</p> Full article ">Figure 2
<p>Geological map of the central Pyrenees (modified from a synthesis by Rodríguez-Fernández et al. [<a href="#B107-minerals-12-00262" class="html-bibr">107</a>]) showing the potential source rock terrains for the late Eocene–Oligocene systems of the Jaca basin. Dark frame represents the location of the study area. AB: Aquitanian basin; NPZ: North Pyrenean Zone; AZ: Axial Zone.</p> Full article ">Figure 3
<p>Geological map of the of the Jaca basin (modified from Puigdefàbregas [<a href="#B23-minerals-12-00262" class="html-bibr">23</a>]). Yellow-purple lines show the location of the analyzed sections. Numbers refer to each section: (1) San Felices section, (2) Rodellar-Bibán section, (3) Monrepós section, (4) Gállego section, (5) Salinas section, (6) Martés section, (7) Luesia section, and (8) Ainsa section. Numbers and symbols refer to each of the analyzed samples for sandstone petrography analyses.</p> Full article ">Figure 4
<p>Compositional plots for all the analyzed samples. Feldspar (F), metamorphic r.f. (MRF), plutonic r.f. (PRF), volcanic r.f. (VRF), hybrid sandstone r.f. (Hy.Sst), siliciclastic sandstone (Sst), micas (Mic), silicified r.f. (Sil), radiolarite r.f. (Rad), Fe-Oxide replacement r.f. (RL), and carbonate extrabasinal grains (CE). (<b>a</b>) Compositional plot discriminates the four main groups of petrofacies described for all the analyzed samples showing the confidence region (90%) of the entire population of each petrofacies, while the small ternary diagram on the right side shows the mean confidence regions (90%) for each petrofacies. (<b>b</b>) Biplot showing the statistical significance of the four petrofacies model (100% of the variance is explained). (<b>c</b>) Biplot displaying the results of a correspondence analysis where F and L have been considered as two different variables in order to illustrate the compositional variations of feldspar (F) and lithics (L). (<b>d</b>) Biplot showing the compositions of samples and petrofacies considering a wide range of grains.</p> Full article ">Figure 5
<p>Optical photomicrographs of the described petrofacies. (<b>A</b>) General view of “carbonate extrabasinal enriched” petrofacies, with abundant micritic and bioclastic limestone (Lms) fragments and quartz (Qz), K-feldpar (Fk), plutonic rock fragments (Prf), and dolomite grains (Dol) (XPL). Sample ROD1, Belsué-Atarés Formation. (<b>B</b>) “Siliciclastic dominant” petrofacies characterized by the highest contents of quartz (Q), metamorphic rock fragments (Mrf), and limestone grains (Lms) and by the absence of hybrid sandstone rock fragments (XPL). Sample GAL4, Campodarbe Formation. (<b>C</b>) General view of “hybrid clast-dominated” petrofacies showing the large amount of hybrid sandstone rock fragments (HSnd) and limestone rock fragments (Lms) (PPL). (<b>D</b>) Appearance of “mixed lithic and carbonatic” petrofacies, showing the coexistence of hybrid sandstone rock fragments (HSnd) with abundant carbonatic (Lms) and siliciclastic grains radiolarite (Ch), quartz (Qz), and metamorphic grains (Mrf) (XPL).</p> Full article ">Figure 6
<p>(<b>a</b>) General stratigraphic cross-section sketch with symbols representing the relative position of the analyzed samples presented in <a href="#minerals-12-00262-f003" class="html-fig">Figure 3</a>, used here to understand the petrofacies scheme below. (<b>b</b>) Colored stratigraphic cross-section sketch in order to illustrate the distribution of the petrofacies laterally and through time. Yellow color corresponds to “hybrid clast-dominated” petrofacies, green color to “carbonate extrabasinal enriched” petrofacies, blue color to “mixed lithic and carbonatic” petrofacies, and pink color to “siliciclastic dominant” petrofacies. Colored arrows are used to facilitate reading of the provenance information. Dashed lines represent the boundaries between petrofacies.</p> Full article ">Figure 7
<p>Heavy-mineral compositional plots. (<b>a</b>) Biplot displaying the results of correspondence analysis applied to all analyzed samples and considering all encountered minerals. OtHM include scarce minerals (Mz, Xtm, Cpx, Sp, Sph, Cld, And, and Ky). Colored symbols indicate sample’s section. (<b>b</b>) Biplot displaying the results of correspondence analysis applied to all analyzed samples. Colored symbols indicate the petrofacies. (<b>c</b>) Biplot displaying the results of correspondence analysis applied to samples belonging to the Grs+OtHM enriched heavy-mineral suite only considering Grs, Ttn, Ep, St, and OtHM. (<b>d</b>) Biplot displaying the results of correspondence analysis applied to samples belonging to the Grs+OtHM enriched heavy-mineral suite only considering Grs, Ttn, and Ep.</p> Full article ">Figure 8
<p>(<b>a</b>) Colored stratigraphic cross-section in order to illustrate the distribution of the heavy-mineral suites laterally and through time. (<b>b</b>) Colored stratigraphic cross-section in order to illustrate the distribution of the petrofacies and heavy-mineral suites laterally and through time.</p> Full article ">Figure 9
<p>Paleogeographic scheme of the Jaca basin during Bartonian–Priabonian times. (<b>a</b>) Early Bartonian. (<b>b</b>) Priabonian. Circles and squares highlight distinct components. PRF: plutonic rock fragments, F: feldspar grains, CE: carbonate extrabasinal grains, HyS: hybrid sandstone rock fragments, VRF: volcanic rock fragments, Ap: apatite, ZTR: ZTR, Ep: epidote, Grs: grossular, Ttn: titanite. Circle colors correspond to petrofacies described in <a href="#minerals-12-00262-f004" class="html-fig">Figure 4</a>. Square colors correspond to heavy-mineral suites described in <a href="#minerals-12-00262-f007" class="html-fig">Figure 7</a>. Arrows indicate petrofacies (fill) and heavy-mineral suite (stroke). Reconstruction of the maps based on Puigdefàbregas, Bentham et al., Hogan, Montes, Caja et al., Huyghe et al., Roigé et al., Boya, Coll et al. [<a href="#B23-minerals-12-00262" class="html-bibr">23</a>,<a href="#B24-minerals-12-00262" class="html-bibr">24</a>,<a href="#B27-minerals-12-00262" class="html-bibr">27</a>,<a href="#B29-minerals-12-00262" class="html-bibr">29</a>,<a href="#B30-minerals-12-00262" class="html-bibr">30</a>,<a href="#B39-minerals-12-00262" class="html-bibr">39</a>,<a href="#B63-minerals-12-00262" class="html-bibr">63</a>,<a href="#B67-minerals-12-00262" class="html-bibr">67</a>,<a href="#B72-minerals-12-00262" class="html-bibr">72</a>,<a href="#B76-minerals-12-00262" class="html-bibr">76</a>,<a href="#B97-minerals-12-00262" class="html-bibr">97</a>].</p> Full article ">Figure 10
<p>Paleogeographic scheme of the Jaca and Ebro basins during Rupelian–Aquitanian times. (<b>a</b>) Rupelian. (<b>b</b>) Chattian–Aquitanian. Circles and squares highlight distinct components. MRF: metamorphic rock fragments, SRF: sedimentary rock fragments, CE: carbonate extrabasinal grains, HyS: hybrid sandstone rock fragments, Ap: apatite, ZTR: ZTR, Ep: epidote, Grs: grossular, Ttn: titanite, St: staurolite. Circle colors correspond to petrofacies described in <a href="#minerals-12-00262-f004" class="html-fig">Figure 4</a>. Square colors correspond to heavy-mineral suites described in <a href="#minerals-12-00262-f007" class="html-fig">Figure 7</a>. Arrows indicate petrofacies (fill) and heavy-mineral suite (stroke). Reconstruction of the maps based on Hirst and Nichols, Puigdefàbregas, Friend et al., Arenas, Nichols and Hirst, Jones, Roigé et al., Boya, Coll et al. [<a href="#B23-minerals-12-00262" class="html-bibr">23</a>,<a href="#B29-minerals-12-00262" class="html-bibr">29</a>,<a href="#B30-minerals-12-00262" class="html-bibr">30</a>,<a href="#B39-minerals-12-00262" class="html-bibr">39</a>,<a href="#B53-minerals-12-00262" class="html-bibr">53</a>,<a href="#B76-minerals-12-00262" class="html-bibr">76</a>,<a href="#B97-minerals-12-00262" class="html-bibr">97</a>,<a href="#B99-minerals-12-00262" class="html-bibr">99</a>,<a href="#B161-minerals-12-00262" class="html-bibr">161</a>,<a href="#B162-minerals-12-00262" class="html-bibr">162</a>,<a href="#B163-minerals-12-00262" class="html-bibr">163</a>].</p> Full article ">Figure 11
<p>Summary of source areas and sediment routings in the South Pyrenean Basin from late Eocene to early Miocene displayed in a present-day map, not restored. Coarse arrows indicate composition of source areas (stroke color: heavy-mineral suite, fill: petrofacies). Thin arrows indicate sediment routing approximately. (<b>a</b>) Late Eocene routing systems. Two different axially-fed east sourced systems (one more meridional) coexist with a transverse-fed north sourced system supplying the Jaca basin. (<b>b</b>) Oligocene routing systems. Two different axially-fed east sourced systems (one more meridional) coexist with two transverse-fed north sourced systems supplying the Jaca basin. (<b>c</b>) Early Miocene routing systems. Two different transverse-fed north sourced systems supply sediment to the Ebro basin in the western area, whereas in the eastern part, two transverse-fed north sourced systems supply the Huesca fan.</p> Full article ">
13 pages, 3559 KiB  
Article
Kinetic Analysis of Recovering Zinc from Electric Arc Furnace Dust by Vacuum Carbothermic Reduction at 20 Pa
by Shaobo Ma, Zhaohui Zhang, Xiangdong Xing, Shuxiang Xu and Xintao Li
Minerals 2022, 12(2), 261; https://doi.org/10.3390/min12020261 - 18 Feb 2022
Cited by 5 | Viewed by 2141
Abstract
Electric arc furnace dust (EAFD) presents a contamination hazard due to its heavy metal leachability. The traditional disposal methods of landfill or stacking not only pose a threat to the environment but also waste metal resources. This paper adopted vacuum carbothermic reduction to [...] Read more.
Electric arc furnace dust (EAFD) presents a contamination hazard due to its heavy metal leachability. The traditional disposal methods of landfill or stacking not only pose a threat to the environment but also waste metal resources. This paper adopted vacuum carbothermic reduction to dispose of EAFD and the zinc metal could be obtained as a product. The reduction ratios of the EAFD were carried out under various reaction temperatures and times at 20 Pa. Furthermore, the kinetics of the reduction process was also studied. The reduction ratio of the reaction process can be facilitated through increasing the temperature or lengthening the time and can reach up to 99.6% under the condition of 1373 K with 60 min. The zinc ferrite and zinc oxide were reduced first and then iron oxide reduction occurred. The reduction process could be divided into three stages: Stage 1 involved the direct reduction of zinc ferrite and zinc oxide, and the control step was the phase boundary reaction with the apparent activation energy of 48.54 kJ/mol; Stage 2 involved the reduction of zinc oxide and iron oxide, and the control step was also the phase boundary reaction with the apparent activation energy of 56.27 kJ/mol; Stage 3 involved the escape of gas phase products and the control step was diffusion with the apparent activation energy of 105.3 kJ/mol. Full article
(This article belongs to the Topic Recycling and Value-Added Utilization of Secondary Raw Materials)
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<p>XRD pattern of the EAFD.</p> Full article ">Figure 2
<p>Relationship between the standard Gibbs free energy and temperature for Equations (1)–(5).</p> Full article ">Figure 3
<p>The Gibbs free energy at different vacuum degrees.</p> Full article ">Figure 4
<p>The experimental process.</p> Full article ">Figure 5
<p>XRD patterns of the reduction products at different reduction times. (<b>a</b>) 0 min (<b>b</b>) 15 min (<b>c</b>) 30 min (<b>d</b>) 40 min (<b>e</b>) 50 min (<b>f</b>) 60 min.</p> Full article ">Figure 6
<p>Changes in morphology of reduction products with time: (<b>a</b>) 15 min, (<b>b</b>) 30 min, (<b>c</b>) 40 min, (<b>d</b>) 50 min, (<b>e</b>) 60 min; (1) hollow region, (2) light white region, (3) dark gray region, (4) bright white region.</p> Full article ">Figure 7
<p>Condensate collected and XRD analysis: (<b>a</b>) condensate collected (<b>b</b>) XRD analysis.</p> Full article ">Figure 8
<p>Effect of the reaction temperature (<b>a</b>) and reaction time (<b>b</b>) on zinc reduction ratio at 20 Pa.</p> Full article ">Figure 9
<p>Relationship between <span class="html-italic">F</span>(<span class="html-italic">α</span>) and time at different temperatures: (<b>a</b>) 0 &lt; <span class="html-italic">t</span> &lt; 15 min; (<b>b</b>) 15 &lt; <span class="html-italic">t</span> &lt; 30 min; (<b>c</b>) 30 &lt; <span class="html-italic">t</span> &lt; 60 min.</p> Full article ">Figure 10
<p>Linear fitting curves of the relationship between ln<span class="html-italic">k</span> and 1/<span class="html-italic">T</span>.</p> Full article ">Figure 11
<p>Schematic diagram of the mechanism of vacuum carbothermic reduction of EAFD.</p> Full article ">
13 pages, 3527 KiB  
Article
Clean Utilization of Limonite Ore by Suspension Magnetization Roasting Technology
by Jianping Jin, Xinran Zhu, Pengchao Li, Yanjun Li and Yuexin Han
Minerals 2022, 12(2), 260; https://doi.org/10.3390/min12020260 - 17 Feb 2022
Cited by 10 | Viewed by 3315
Abstract
As a typical refractory iron ore, the utilization of limonite ore with conventional mineral processing methods has great limitations. In this study, suspension magnetization roasting technology was developed and utilized to recover limonite ore. The influences of roasting temperature, roasting time, and reducing [...] Read more.
As a typical refractory iron ore, the utilization of limonite ore with conventional mineral processing methods has great limitations. In this study, suspension magnetization roasting technology was developed and utilized to recover limonite ore. The influences of roasting temperature, roasting time, and reducing gas concentration on the magnetization roasting process were investigated. The optimal roasting conditions were determined to be a roasting temperature of 480 °C, a roasting time of 12.5 min, and a reducing gas concentration of 20%. Under optimal conditions, an iron concentrate grade of 60.12% and iron recovery of 91.96% was obtained. The phase transformation, magnetism variation, and microstructure evolution behavior were systematically analyzed by X-ray diffraction, vibrating sample magnetometer, and scanning electron microscope. The results indicated that hematite and goethite were eventually transformed into magnetite during the magnetization roasting process. Moreover, the magnetism of roasted products significantly improved due to the formation of ferrimagnetic magnetite in magnetization roasting. This study has implications for the utilization of limonite ore using suspension magnetization roasting technology. Full article
(This article belongs to the Topic Advances in Separation and Purification Techniques)
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<p>XRD pattern of the limonite ore.</p> Full article ">Figure 2
<p>Distribution characteristics of the main minerals in the ore: (<b>a</b>–<b>c</b>) denote the limonite inlay structure; (<b>d</b>–<b>f</b>) denote the inlay structure of hematite.</p> Full article ">Figure 3
<p>Flow chart of the experiment process.</p> Full article ">Figure 4
<p>Effect of roasting conditions on the recovery and Fe grade of the magnetic concentrate: (<b>a</b>) roasting temperature, (<b>b</b>) roasting time, (<b>c</b>) reducing gas concentration, (<b>d</b>) magnetic field intensity.</p> Full article ">Figure 5
<p>XRD pattern analysis of raw ore, roasted sample, and iron ore concentrate.</p> Full article ">Figure 6
<p>XRD analysis of roasted samples at different roasting times.</p> Full article ">Figure 7
<p>Magnetization curves of roasted products.</p> Full article ">Figure 8
<p>Magnetic susceptibility curves of roasted products.</p> Full article ">Figure 9
<p>Hysteresis loops of roasted products.</p> Full article ">Figure 10
<p>SEM–EDS analysis of raw ore and roasted products: (<b>a</b>–<b>c</b>) raw ore; (<b>d</b>–<b>f</b>) roasted product of 3 min; (<b>g</b>–<b>i</b>) roasted product of 12.5 min.</p> Full article ">
24 pages, 8518 KiB  
Article
Evolution of Ore-Forming Fluids and Gold Deposition of the Sanakham Lode Gold Deposit, SW Laos: Constrains from Fluid Inclusions Study
by Shusheng Liu, Linnan Guo, Jun Ding, Lin Hou, Siwei Xu, Meifeng Shi, Huimin Liang, Fei Nie and Xiaoyu Cui
Minerals 2022, 12(2), 259; https://doi.org/10.3390/min12020259 - 17 Feb 2022
Cited by 4 | Viewed by 2528
Abstract
The Sanakham gold deposit is a newly discovered gold deposit in the Luang Prabang (Laos)–Loei (Thailand) metallogenic belt. It consists of a series of auriferous quartz-sulfide veins, which is distinguished from the regional known porphyry-related skarn and epithermal gold deposits. There are four [...] Read more.
The Sanakham gold deposit is a newly discovered gold deposit in the Luang Prabang (Laos)–Loei (Thailand) metallogenic belt. It consists of a series of auriferous quartz-sulfide veins, which is distinguished from the regional known porphyry-related skarn and epithermal gold deposits. There are four mineralization stages identified in Sanakham, with native gold grains mainly occurring in stages II and III. Evolution of ore-forming fluids and gold deposition mechanisms in Sanakham are discussed based on fluid inclusion petrography, microthermometry, and Laser Raman spectroscopy. The original ore-forming fluids belong to a medium-high temperature (>345 °C) CH4-rich CH4–CO2–NaCl–H2O system. In stages II and III, the ore fluids evolve into a NaCl–H2O–CO2 ± CH4 system characterized by medium temperature (~300 °C), medium salinity (~10 wt% NaCl eq.), and CO2-rich (~10% mol). They might finally evolve into a NaCl–H2O system with temperature decreasing and salinity increasing in stage IV. Two fluid immiscibility processes occurred in stages II and III, which created high-CH4 & low-CO2 and low-CH4 & high-CO2 end-members, and CO2-poor and CO2-rich endmembers, respectively. Gold-deposition events are suggested to be associated with the fluid immiscibility processes, with P–T conditions and depth of 236–65 MPa, 337–272 °C, and 8.7–6.5 km, respectively. Full article
(This article belongs to the Special Issue Understanding Hydrothermal Ore Deposits: Insights from In-situ Analyses)
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<p>Regional geological map. (<b>a</b>) Simplified tectonic map showing structural units of Laos andadjacent regions; (<b>b</b>) simplified geological map of the Luang Prabang–Loei metallogenic belt (geochronological data from [<a href="#B4-minerals-12-00259" class="html-bibr">4</a>,<a href="#B5-minerals-12-00259" class="html-bibr">5</a>,<a href="#B6-minerals-12-00259" class="html-bibr">6</a>,<a href="#B7-minerals-12-00259" class="html-bibr">7</a>,<a href="#B8-minerals-12-00259" class="html-bibr">8</a>,<a href="#B9-minerals-12-00259" class="html-bibr">9</a>,<a href="#B10-minerals-12-00259" class="html-bibr">10</a>,<a href="#B11-minerals-12-00259" class="html-bibr">11</a>,<a href="#B12-minerals-12-00259" class="html-bibr">12</a>,<a href="#B13-minerals-12-00259" class="html-bibr">13</a>,<a href="#B14-minerals-12-00259" class="html-bibr">14</a>,<a href="#B15-minerals-12-00259" class="html-bibr">15</a>,<a href="#B16-minerals-12-00259" class="html-bibr">16</a>], modified from [<a href="#B5-minerals-12-00259" class="html-bibr">5</a>,<a href="#B10-minerals-12-00259" class="html-bibr">10</a>]). A = andesite; B = basalt; Br = breccia; D = dacite; Db = diabase; Dr = diorite; G = gabbro; Gd = Granodiorite; M = monzonite; R = rhyolite; T = tuff.</p> Full article ">Figure 2
<p>Simplified geological map of the Sanakham gold deposit and geological cross-sections along line AA’.</p> Full article ">Figure 3
<p>Typical alteration and mineralization in the Sanakham gold deposit (<b>d</b>–<b>i</b> are reflected light images). (<b>a</b>), Milky quartz–pyrite vein in quartz monzodiorite; (<b>b</b>), quartz–sulfide vein in quartz monzodiorite; (<b>c</b>), banded sulfide assemblages; (<b>d</b>), quartz—calcite vein crosscut quartz—sulfide vein; (<b>e</b>), coexistence of sulfides and quartz in hand sample; (<b>f</b>), sulfides occurred as massive aggregates; (<b>g</b>,<b>h</b>), stage I euhedral to subhedral coarse-grained pyrite and stage II subhedral to anhedral fine-grained pyrite and pyrrhotite; (<b>i</b>), stage II pyrite and pyrrhotite occurred around stage I arsenopyrite; (<b>j</b>,<b>k</b>), native gold coexisting with pyrrhotite or chalcopyrite that fills in fractures of pyrite; (<b>l</b>), sulfide aggregations in stage III. Apy, arsenopyrite; Au, native gold; Ccp, chalcopyrite; Gn, galena; Po, pyrrhotite; Py, pyrite.</p> Full article ">Figure 4
<p>Paragenetic sequence of hydrothermal minerals in the Sanakham gold deposit, with line thickness indicating the relative abundance of minerals.</p> Full article ">Figure 5
<p>Photomicrographs of typical fluid inclusions and FIA groups in the Sanakham gold deposit. (<b>a</b>) Typical type <span class="html-italic">M</span> CH<sub>4</sub>-rich fluid inclusion consisting of H<sub>2</sub>O liquid and carbonic vapor (CH<sub>4</sub> + CO<sub>2</sub> ± C<sub>2</sub>H<sub>6</sub> ± H<sub>2</sub>S) phases at room temperature; (<b>b</b>) type <span class="html-italic">M</span> FI consisting of three (H<sub>2</sub>O liquid + carbonic liquid + carbonic vapor) phases at about −20°C; (<b>c</b>) type <span class="html-italic">M</span> CH<sub>4</sub>-rich fluid inclusion with daughter mineral (chalcopyrite); (<b>d</b>) type <span class="html-italic">C1</span> liquid-rich CO<sub>2</sub> inclusion; (<b>e</b>) type <span class="html-italic">C2</span> vapor-rich CO<sub>2</sub> inclusion; (<b>f</b>) type <span class="html-italic">W</span> two-phase H<sub>2</sub>O-NaCl inclusion; (<b>g</b>) primary cluster of Group 1 FIA in stage I quartz; (<b>h</b>) primary cluster of Group 2 FIA in stage II quartz; (<b>i</b>) group 3 FIA in stage II quartz consisting of type <span class="html-italic">M</span> and <span class="html-italic">C1</span> inclusions with various volumes of the carbonic phases; (<b>j</b>) Group 4 FIA occurred as cluster, pseudo-secondary trail, and isolated type <span class="html-italic">C1</span> inclusions in stage III quartz; (<b>k</b>) primary cluster of Group 5 FIA consisting of type <span class="html-italic">C1</span> and <span class="html-italic">C2</span> inclusions showing opposite modes of homogenization at approximately the same temperature; (<b>l</b>) pseudo-secondary Group 5 FIA trail in stage III quartz; (<b>m</b>) pPseudo-secondary Group 6 FIA trails containing type <span class="html-italic">W</span> fluid inclusions in stage IV quartz.</p> Full article ">Figure 6
<p>Ranges of <span class="html-italic">T</span><sub>h TOT</sub> (<b>a</b>), <span class="html-italic">T</span><sub>m carbon</sub> (<b>b</b>), salinity (<b>c</b>), bulk density (<b>d</b>), bulk X<sub>CO2</sub> + X<sub>CH4</sub> (<b>e</b>), and carbonic X<sub>CH4</sub> (<b>f</b>) versus Groups 1–6 FIA in the four stages, respectively. The points in the middle of the bars are the mean value.</p> Full article ">Figure 7
<p>Laser Raman spectra of vapor bubbles (red color), aqueous (green color), or daughter minerals (in the <b>d</b> figure) of fluid inclusions in the Sanakham gold deposit. (<b>a</b>), Type <span class="html-italic">C1</span> inclusion; (<b>b</b>–<b>d</b>), type <span class="html-italic">M</span> inclusion.4.4. Composition and Density of Fluid Inclusions.</p> Full article ">Figure 8
<p>Homogenization temperature (<span class="html-italic">T</span><sub>h TOT</sub>) versus salinity (wt% NaCl eq.) diagram showing the evolution of the ore-forming fluids for different groups of FIA from stages II and III quartz in the Sanakham gold deposit. The horizontal and vertical bars are the ranges of <span class="html-italic">T</span><sub>h TOT</sub> and salinity of every single FIA.</p> Full article ">Figure 9
<p>Homogenization temperature (<span class="html-italic">T</span><sub>h TOT</sub>) versus calculated equivalent mole fraction CO<sub>2</sub> of type <span class="html-italic">C1</span> and <span class="html-italic">C2</span> inclusions in stages II and III. The dashed curves delimit the two-phase regions of the H<sub>2</sub>O–CO<sub>2</sub>–NaCl system at 100 and 200 MPa, respectively. Data after Bowers and Helgeson (1983) [<a href="#B30-minerals-12-00259" class="html-bibr">30</a>]. g, gas; l, liquid.</p> Full article ">Figure 10
<p>Estimated P-T conditions for the formation of the quartz veins in stages II and III in the Sanakham deposit. Representative isochores for mean bulk densities, respectively, for type <span class="html-italic">C1</span> inclusions, and the solvus for H<sub>2</sub>O–CO<sub>2</sub> fluids containing 10 wt% NaCl eq. and 10 mol% CO<sub>2</sub> (calculated after reference [<a href="#B30-minerals-12-00259" class="html-bibr">30</a>]). The blue and red dashed lines define the range of <span class="html-italic">T</span><sub>h TOT</sub> and bulk density of type <span class="html-italic">C1</span> inclusions in Groups 3 and 5 FIA, respectively. The dotted lines represent the range of trapping pressures.</p> Full article ">Figure 11
<p>Evolution of ore-forming fluids and related gold-deposition processes in the Sanakham gold deposit.</p> Full article ">
23 pages, 1392 KiB  
Article
An Evaluation on the Impact of Ore Fragmented by Blasting on Mining Performance
by Ayyub Nikkhah, Ali Behrad Vakylabad, Ahmad Hassanzadeh, Tomasz Niedoba and Agnieszka Surowiak
Minerals 2022, 12(2), 258; https://doi.org/10.3390/min12020258 - 17 Feb 2022
Cited by 16 | Viewed by 5138
Abstract
In open-pit mines, the blast operation should be effectively optimized, leading to minimization of production costs through the application of specific technical specifications. However, there is inadequate information in the literature to link blasting to comminution stages. To this end, the effective parameters [...] Read more.
In open-pit mines, the blast operation should be effectively optimized, leading to minimization of production costs through the application of specific technical specifications. However, there is inadequate information in the literature to link blasting to comminution stages. To this end, the effective parameters for the performance of mining unit operations were scrutinized in this work. In this regard, the rock fragmentation distribution (RFD) caused by blasting was considered the main determinative criterion for providing the optimum conditions for the blasting operation at Sarcheshmeh copper mine. By carrying out a statistical analysis of the experimental data, operational parameters affecting the blasting were optimized. The relationship between parameters was obtained using the technique of regression and in accordance with the evaluation criterion under which correlation coefficient (R2) was used to determine the best fitting model. A high correlation coefficient of the loading cycle of the machine’s bucket (Cl) with the independent variables showed that the C1 was more affected by the RFD, as well as the dimensions of the blast block. Because of the wide variations in the nature and structure of rock mass in different mines, in each case, sufficient data should be collected, and these relationships should be analyzed statistically for each individual mine showing wide ranges of fractures and cracks. Therefore, due to these wide variations of ore characteristics, with the current data it seems very difficult to quickly find a significant operational relationship between downstream processes such as crushing efficiency and blasting operations. Therefore, the focus of this research was limited to the effective parameters for blast efficiency. According to the analysis of the data obtained from 20 blasts under different operating conditions, the diameter of the hole was 241.3 mm (such as blast number 20), the ratio of length to width of the explosive block was about 6 (average blasts with high fragmentation efficiency), and the best index of mining operations was 0.22 (such as blast number 20). Full article
(This article belongs to the Section Mineral Exploration Methods and Applications)
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<p>The algorithm used to evaluate the impacts of the RFD on mining performance.</p> Full article ">Figure 2
<p>Process of image analysis in Split-Desktop software.</p> Full article ">Figure 3
<p>Radar chart of <math display="inline"><semantics> <mrow> <msub> <mi mathvariant="normal">d</mi> <mrow> <mn>50</mn> </mrow> </msub> </mrow> </semantics></math> and <math display="inline"><semantics> <mrow> <msub> <mi mathvariant="normal">d</mi> <mrow> <mn>80</mn> </mrow> </msub> </mrow> </semantics></math> in 20 blast blocks of Sarcheshmeh Copper Mine.</p> Full article ">Figure 4
<p>Comparison relation between <math display="inline"><semantics> <mrow> <msub> <mi mathvariant="normal">C</mi> <mi mathvariant="normal">l</mi> </msub> </mrow> </semantics></math> measured and predicted for models (3, 4, 5, 6, and 7).</p> Full article ">
13 pages, 620 KiB  
Article
Technical Assessment of Secondary Sedimentation Process in Copper Sulphide Tailings with the Presence of Clays, in Continental and Sea Water
by Catalina López-Espejo and Christian F. Ihle
Minerals 2022, 12(2), 257; https://doi.org/10.3390/min12020257 - 17 Feb 2022
Cited by 1 | Viewed by 1701
Abstract
Recovery of process water for recirculation is crucial, as the cost of adding additional fresh water is an economic constraint that is often prohibitive. Solid–liquid separation is a key process in the recovery of water resources. Therefore, research is needed to understand how [...] Read more.
Recovery of process water for recirculation is crucial, as the cost of adding additional fresh water is an economic constraint that is often prohibitive. Solid–liquid separation is a key process in the recovery of water resources. Therefore, research is needed to understand how fine particles, particularly quartz, kaolinite and sodium bentonite, impact the optimal separation process. In the present work, the effect of the presence of these clays in the solid–liquid separation of synthetic copper sulfide tailings is evaluated, quantifying the impact on the separation efficiency, considering the average settling rate and the turbidity of the supernatant. The physicochemical variables that control the suspension were monitored and the observed trends were explained by variations in properties such as zeta potential and pH. The characterization and quantification of the impact of the clays in the operation will allow us to lay the foundation for the development of a novel approach for the secondary treatment of the cloudy supernatant water of the thickeners. After the study, disparate effects on sedimentation efficiency could be distinguished depending on the type of clay and the water in which it is immersed. While in the case of tailings with the presence of kaolinite clays it is seen that the higher sedimentation efficiency occurs in the case of flocculation in distilled water, the salinity or presence of cationic coagulants is detrimental to it. In the case of tailings with the presence of bentonite clays, the sedimentation efficiency increases as there is a higher concentration of cationic salts (coagulation-synthetic sea water). In contrast, in the case of distilled water, the flocculation efficiency is very low, so it is recommended to add a cationic additive, which is supported by an associated low economic cost. In the case of tailings with the presence of ultrafine quartz content, a clear effect in the increase or decrease of sedimentation efficiency cannot be distinguished with the addition of flocculants, coagulants, or when working in sea water. Overall, the results suggest the convenience of splitting thickening and clarification as two distinct unit processes that may be treated using flocculant and salts, according to the fine mineral contents. Full article
(This article belongs to the Special Issue Fluid Engineering in Mineral Processing)
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<p>Zeta potential at different pH of endless synthetic tailings solution, with Cp = 10% and a flocculant dose of 25 g/dry ton.</p> Full article ">Figure 2
<p>Variation in the settling rate of the MQ and KQ cases for different doses of flocculant.</p> Full article ">
14 pages, 4956 KiB  
Article
An Investigation into the Adsorption of Ammonium by Zeolite-Magnetite Composites
by Xiaoming Huang, Ning Wang, Zhang Kang, Xiao Yang and Min Pan
Minerals 2022, 12(2), 256; https://doi.org/10.3390/min12020256 - 17 Feb 2022
Cited by 9 | Viewed by 3072
Abstract
The discharging of ammonium from industrial, domestic, and livestock sewage has caused eutrophication of the water environment. The objectives of this study are to synthesize magnetic zeolite (M-Zeo) by an eco-friendly, economical, and easy procedure and to investigate its suitability as an adsorbent [...] Read more.
The discharging of ammonium from industrial, domestic, and livestock sewage has caused eutrophication of the water environment. The objectives of this study are to synthesize magnetic zeolite (M-Zeo) by an eco-friendly, economical, and easy procedure and to investigate its suitability as an adsorbent to remove ammonium from an aqueous solution. Based on characterization from XRD, BET, and SEM-EDS, Fe3O4 was proved to successfully load on natural zeolite. The effect of pH, temperatures, reacting times, initial ammonium concentrations, and regeneration cycles on ammonium adsorption was examined by batch experiments. The ammonium adsorption process can be best described by the Freundlich isotherm and the maximum adsorptive capacity of 172.41 mg/g was obtained. Kinetic analysis demonstrated that the pseudo-second-order kinetic model gave the best description on the adsorption. The value of pH is a key factor and the maximum adsorption capacity was obtained at pH 8. By using a rapid sodium chloride regeneration method, the regeneration ratio was up to 97.03% after five regeneration cycles, suggesting that M-Zeo can be recycled and magnetically recovered. Thus, the economic-efficient, great ammonium affinity, and excellent regeneration characteristics of M-Zeo had an extensively promising utilization on ammonium treatment from liquid. Full article
(This article belongs to the Section Clays and Engineered Mineral Materials)
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<p>XRD patterns of the N-Zeo and M-Zeo.</p> Full article ">Figure 2
<p>SEM images of N-Zeo (<b>a</b>), M-Zeo (<b>b</b>), and EDS of M-Zeo (<b>c</b>).</p> Full article ">Figure 2 Cont.
<p>SEM images of N-Zeo (<b>a</b>), M-Zeo (<b>b</b>), and EDS of M-Zeo (<b>c</b>).</p> Full article ">Figure 3
<p>N<sub>2</sub> adsorption–desorption isotherms and pore size distributions.</p> Full article ">Figure 4
<p>(<b>a</b>) Impact of pH on NH<sub>4</sub><sup>+</sup>-N removal efficiency from liquid by using M-Zeo as adsorbent; (<b>b</b>) distribution of ammonium species in liquid.</p> Full article ">Figure 5
<p>(<b>a</b>) Adsorption isotherms of ammonium on M-Zeo under different temperatures; (<b>b</b>) plots of lnK<sub>d</sub> vs. 1/T.</p> Full article ">Figure 6
<p>(<b>a</b>) Adsorption kinetics of ammonium on M-Zeo and the pseudo-second-order model; (<b>b</b>) the intraparticle diffusion model.</p> Full article ">Figure 6 Cont.
<p>(<b>a</b>) Adsorption kinetics of ammonium on M-Zeo and the pseudo-second-order model; (<b>b</b>) the intraparticle diffusion model.</p> Full article ">Figure 7
<p>The adsorption capacities with regeneration times.</p> Full article ">
27 pages, 5607 KiB  
Article
Origin and Composition of Ferromanganese Deposits of New Caledonia Exclusive Economic Zone
by Paul Staszak, Julien Collot, Pierre Josso, Ewan Pelleter, Samuel Etienne, Martin Patriat, Sandrine Cheron, Audrey Boissier and Yaël Guyomard
Minerals 2022, 12(2), 255; https://doi.org/10.3390/min12020255 - 16 Feb 2022
Cited by 5 | Viewed by 3173
Abstract
Located in the South-West Pacific, at the northern extremity of the mostly submerged Zealandia continent, the New Caledonian Exclusive Economic Zone (EEZ) covers 1,470,000 km² and includes basins, ridges and seamounts where abundant ferromanganese crusts have been observed. Several investigations have been conducted [...] Read more.
Located in the South-West Pacific, at the northern extremity of the mostly submerged Zealandia continent, the New Caledonian Exclusive Economic Zone (EEZ) covers 1,470,000 km² and includes basins, ridges and seamounts where abundant ferromanganese crusts have been observed. Several investigations have been conducted since the 1970s on the nature and composition of ferromanganese crusts from New Caledonia’s seamounts and ridges, but none have covered the entire EEZ. We present data from 104 ferromanganese crusts collected in New Caledonia’s EEZ during twelve oceanographic cruises between 1974 and 2019. Samples were analysed for mineralogy, geochemical compositions, growth rates, and through a statistical approach using correlation coefficients and factor analysis. Crust thicknesses range from 1 mm to 115 mm, with growth rates between 0.45 mm/Ma and 102 mm/Ma. Based on textures, structures, discrimination plots, and growth rates, we distinguish a group of hydrogenetic crusts containing the highest mean contents of Co (0.42 wt%), Ni (0.31 wt%), and high contents of Mo, V, W, Pb, Zn, Nb, from a group of hydrothermal and/or diagenetic deposits showing high mean contents of Mn (38.17 wt%), Ba (0.56 wt%) and low contents of other trace metals. Several samples from this later group have exceptionally high content of Ni (0.7 wt%). The data shows that crusts from the southern part of the EEZ, notably seamounts of the Loyalty Ridge and the Lord Howe Rise, present high mineral potential for prospectivity owing to high contents of valuable metals, and constitute a great target for further investigation. Full article
(This article belongs to the Special Issue Oceanic Ferromanganese Deposits)
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<p>(<b>A</b>) Nature of basement of the South-West Pacific (modified after [<a href="#B33-minerals-12-00255" class="html-bibr">33</a>]); (<b>B</b>) Age of basement formation of the South-West Pacific (modified after [<a href="#B33-minerals-12-00255" class="html-bibr">33</a>]).</p> Full article ">Figure 2
<p>(<b>A</b>) Bathymetric map of the South-West Pacific; (<b>B</b>) Bathymetric map of southern New Caledonia.</p> Full article ">Figure 3
<p>Fe-Mn deposits photographs with centimetre scale bars. (<b>A</b>) Cross-section of DR08C showing a columnar/porous texture with interstitial sediments filling pores, deposited on a vacuolar basalt; (<b>B</b>) Cross section of the thickest crust sample of the data set GO327D, four layers are identified and sub-sampled; (<b>C</b>) Current-polished centimetre-scale botryoidal surface of sample 110D; (<b>D</b>) V-DR08B showing massive/laminated textures without any sub-layers deposited on a hyaloclastite breccia; (<b>E</b>) Hydrothermal deposit from sample DW778D; (<b>F</b>) Imbrication of Mn-rich and Ca-rich zones in sample DW2482; (<b>G</b>) Sample DW4998E composed primarily of 10 Å manganates and calcite on a strongly altered hyaloclastite breccia impregnated with Fe-oxyhydroxides; (<b>H</b>) Sample DW4998D showing a metallic grey Mn-rich zone and fluorapatite/Mg-calcite/calcite area.</p> Full article ">Figure 4
<p>BSE images of selected Fe-Mn deposits samples. (<b>A</b>–<b>D</b>): Fe-Mn crusts; (<b>E</b>–<b>H</b>): Hydrothermal Mn + Ca ± Fe deposits; (<b>A</b>) Large columnar structure with quartz infill; (<b>B</b>) Laminar structure (bottom) evolving upwards to columnar structure; (<b>C</b>) Massive columnar texture formed by dense pillar structure with little amount of carbonate infill; (<b>D</b>) Well-crystallised needle-like Mn-oxyhydroxides with overgrowth or crosscut by Ca-phosphate (fluorapatite); (<b>E</b>) Well-crystallised needle-like Mn-oxyhydroxides infilling cavity and surrounded by pyrolusite; (<b>F</b>) Pyrolusite and ± calcite replacing areas composed of alternating layers of amorphous crystalline and microcrystalline Mn-oxyhydroxides; (<b>G</b>) Radially-oriented and spherulitic structure showing alternating layers of amorphous crystalline, microcrystalline and crystalline Mn-oxyhydroxides cemented by a massive microcrystalline Mn-oxyhydroxides; (<b>H</b>) Microcrystalline and crystalline Mn-oxyhydroxides observed between hydrothermally altered hyaloclastite clasts replaced by clays and Fe-oxyhydroxides; a subsequent carbonate and Ca-phosphate (fluorapatite) infilling event is observed.</p> Full article ">Figure 5
<p>Ternary classification schemes of Fe-Mn samples from New Caledonia’s EEZ (<span class="html-italic">n</span> = 104) after (<b>A</b>) [<a href="#B70-minerals-12-00255" class="html-bibr">70</a>] and (<b>B</b>) [<a href="#B72-minerals-12-00255" class="html-bibr">72</a>].</p> Full article ">Figure 6
<p>Genetic discrimination plot of the selected hydrogenetic crusts after [<a href="#B73-minerals-12-00255" class="html-bibr">73</a>].</p> Full article ">Figure 7
<p>PAAS-normalised REE plots for selected hydrogenetic crusts.</p> Full article ">Figure 8
<p>(<b>A</b>) Histogram of growth rates of New Caledonia’s EEZ crusts samples using [<a href="#B66-minerals-12-00255" class="html-bibr">66</a>] equation; (<b>B</b>) Graph of the growth rate variation versus crust thickness of the samples with one or more sub-samples (<span class="html-italic">n</span> = 9).</p> Full article ">Figure 9
<p>Histograms of factor scores for the four factors (computed for the hydrogenetic bulk and macro-layers samples, <span class="html-italic">n</span> = 89).</p> Full article ">Figure 10
<p>Element enrichment of New Caledonian crusts compared to (<b>A</b>) the California margin (CA), Atlantic and Indian oceans’ Fe-Mn crusts, (<b>B</b>) the Pacific Ocean Fe-Mn crusts, and (<b>C</b>) polymetallic nodules from the Clarion–Clipperton Zone (CCZ), the Peru Basin and the Indian Ocean (after [<a href="#B1-minerals-12-00255" class="html-bibr">1</a>,<a href="#B76-minerals-12-00255" class="html-bibr">76</a>,<a href="#B77-minerals-12-00255" class="html-bibr">77</a>]). Values greater than 1 are enriched compared to other oceans crusts, whereas values lower than 1 are depleted. Fe/Mn* and Si/Al* ratios are calculated using mean ocean values.</p> Full article ">Figure 11
<p>Repartition of selected elements with water depth. Black dots are the bulk crusts (<span class="html-italic">n</span> = 74), red dots are the macro-layers crusts (<span class="html-italic">n</span> = 24), and blue dots are the non-hydrogenetic deposits. Graph of crust thickness only considers bulk crusts with a measurable/known thicknes.</p> Full article ">Figure 12
<p>Map of hydrogenetic sample’s Co + Cu + Ni (%) concentration, focused on the Southern part of New Caledonia EEZ, with indications of slope values and surface area (contour lines = 500 m).</p> Full article ">
12 pages, 2163 KiB  
Article
Recrystallization of Triple Superphosphate Produced from Oyster Shell Waste for Agronomic Performance and Environmental Issues
by Somkiat Seesanong, Chaowared Seangarun, Banjong Boonchom, Chuchai Sronsri, Nongnuch Laohavisuti, Kittichai Chaiseeda and Wimonmat Boonmee
Minerals 2022, 12(2), 254; https://doi.org/10.3390/min12020254 - 16 Feb 2022
Cited by 7 | Viewed by 3688
Abstract
Calcium dihydrogen phosphate monohydrate (Ca(H2PO4)2·H2O) (a fertilizer) was successfully synthesized through a recrystallization process using prepared triple superphosphate (TSP) derived from oyster shell waste as the starting material. This bio-green, eco-friendly process to produce an [...] Read more.
Calcium dihydrogen phosphate monohydrate (Ca(H2PO4)2·H2O) (a fertilizer) was successfully synthesized through a recrystallization process using prepared triple superphosphate (TSP) derived from oyster shell waste as the starting material. This bio-green, eco-friendly process to produce an important fertilizer can promote a sustainable society. The shell-waste-derived TSP was dissolved in distilled water and kept at 30, 50, and 80 °C. Non-soluble powder and TSP solution were obtained. The TSP solution fractions were then dried, and the recrystallized products (RCP30, RCP50, and RCP80) were obtained and confirmed as Ca(H2PO4)2·H2O. Conversely, the non-soluble products (NSP30, NSP50, and NSP80) were observed as calcium hydrogen phosphate dihydrate (CaHPO4·2H2O). The recrystallized yields of RCP30, RCP50, and RCP80 were found to be 51.0%, 49.6%, and 46.3%, whereas the soluble percentages were 98.72%, 99.16%, and 96.63%, respectively. RCP30 shows different morphological plate sizes, while RCP50 and RCP80 present the coagulate crystal plates. X-ray diffractograms confirmed the formation of both the NSP and RCP. The infrared adsorption spectra confirmed the vibrational characteristics of HPO42−, H2PO4−, and H2O existed in CaHPO4·2H2O and Ca(H2PO4)2·H2O. Three thermal dehydration steps of Ca(H2PO4)2·H2O (physisorbed water, polycondensation, and re-polycondensation) were observed. Ca(H2PO4)2 and CaH2P2O7 are the thermodecomposed products from the first and second steps, whereas the final product is CaP2O6. Full article
(This article belongs to the Special Issue Value Recovery from Phosphate Mining and Processing Tailings & Byproducts)
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<p>Schematic diagram designed for Ca(H<sub>2</sub>PO<sub>4</sub>)<sub>2</sub>·H<sub>2</sub>O (MCPM) preparation using oyster-shell-derived TSP (triple superphosphate) as the precursor.</p> Full article ">Figure 2
<p>Morphological characteristics (scanning electron microscopic (SEM) images by using the gold-coating technique for sample preparation) of Ca(H<sub>2</sub>PO<sub>4</sub>)<sub>2</sub>·H<sub>2</sub>O products recrystallized after dissolving TSP at 30 °C (RCP30 (<b>a</b>)), 50 °C (RCP50 (<b>b</b>)), and 80 °C (RCP80 (<b>c</b>)).</p> Full article ">Figure 3
<p>X-ray diffraction (XRD) patterns of (<b>a</b>) non-soluble powders CaHPO<sub>4</sub>·2H<sub>2</sub>O (NSP30, NSP50, and NSP80) and (<b>b</b>) recrystallized CaHPO<sub>4</sub>·2H<sub>2</sub>O (RCP30, RCP 50, and RCP80) compounds obtained in the 2<span class="html-italic">θ</span> range of 5°–60°.</p> Full article ">Figure 4
<p>Infrared adsorption (FTIR) spectra of (<b>a</b>) non-soluble powders CaHPO<sub>4</sub>·2H<sub>2</sub>O (NSP30, NSP50, and NSP80) and (<b>b</b>) recrystallized CaHPO<sub>4</sub>·2H<sub>2</sub>O (RCP30, RCP 50, and RCP80) compounds obtained in the wavenumber from 4000–370 cm<sup>−1</sup>.</p> Full article ">Figure 5
<p>Thermal decomposition behaviors (TG/DTA thermograms) of RCP30 (<b>a</b>), RCP50 (<b>b</b>), and RCP80 (<b>c</b>) obtained from room temperature to 800 °C.</p> Full article ">
14 pages, 10201 KiB  
Article
Quantification of Lithium and Mineralogical Mapping in Crushed Ore Samples Using Laser Induced Breakdown Spectroscopy
by Kheireddine Rifai, Marc Constantin, Adnan Yilmaz, Lütfü Ç. Özcan, François R. Doucet and Nawfel Azami
Minerals 2022, 12(2), 253; https://doi.org/10.3390/min12020253 - 16 Feb 2022
Cited by 15 | Viewed by 4966
Abstract
This article reports on the quantification of lithium and mineralogical mapping in crushed lithium ore by laser-induced breakdown spectroscopy (LIBS) using two different calibration methods. Thirty crushed ore samples from a pegmatite lithium deposit were used in this study. Representative samples containing the [...] Read more.
This article reports on the quantification of lithium and mineralogical mapping in crushed lithium ore by laser-induced breakdown spectroscopy (LIBS) using two different calibration methods. Thirty crushed ore samples from a pegmatite lithium deposit were used in this study. Representative samples containing the abundant minerals were taken from these crushed ores and mixed with resin to make polished disks. These disks were first analyzed by TIMA (TESCAN Integrated Mineral Analyzer) and then by a LIBS ECORE analyzer to determine the minerals. Afterwards, each of the thirty crushed ore samples (<10 mm) were poured into rectangular containers and analyzed by the ECORE analyzer, then mineral mapping was produced on the scanned surfaces using the mineral library established on the polished sections. For the first method the lithium concentrations were inferred from the empirical mineral chemistry formula, whereas the second one consisted of building a conventional calibration curve with the crushed material to predict the lithium concentration in unknown crushed materials. Full article
(This article belongs to the Section Crystallography and Physical Chemistry of Minerals & Nanominerals)
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<p>ECORE LIBS drill core scanner.</p> Full article ">Figure 2
<p>LIBS spectra for the ten identified minerals in the polished sections obtained using ECORE.</p> Full article ">Figure 3
<p>Mineral maps obtained by ECORE and TIMA.</p> Full article ">Figure 4
<p>Optical photos (<b>top</b>) of eight representative crushed ore sample split in the above-described containers and ECORE mineral maps (<b>bottom</b>).</p> Full article ">Figure 4 Cont.
<p>Optical photos (<b>top</b>) of eight representative crushed ore sample split in the above-described containers and ECORE mineral maps (<b>bottom</b>).</p> Full article ">Figure 4 Cont.
<p>Optical photos (<b>top</b>) of eight representative crushed ore sample split in the above-described containers and ECORE mineral maps (<b>bottom</b>).</p> Full article ">Figure 5
<p>Li ECORE concentration vs ICP-AES concentration.</p> Full article ">Figure 6
<p>Li averaged net intensity of line 610.36 nm of the calibration set as a function of Li concentration obtained by ICP-AES.</p> Full article ">Figure 7
<p>Li ECORE predicted concentrations of line 610.36 nm of the validation set <span class="html-italic">vs</span> Li ICP–AES concentrations.</p> Full article ">Figure 8
<p>Relative standard deviation of the ECORE Li concentration between the first set and the second one as a function of Li concentrations obtained by ICP–AES (red line correspond to average RSD).</p> Full article ">
24 pages, 14980 KiB  
Article
Modeling Interfacial Tension of N2/CO2 Mixture + n-Alkanes with Machine Learning Methods: Application to EOR in Conventional and Unconventional Reservoirs by Flue Gas Injection
by Erfan Salehi, Mohammad-Reza Mohammadi, Abdolhossein Hemmati-Sarapardeh, Vahid Reza Mahdavi, Thomas Gentzis, Bo Liu and Mehdi Ostadhassan
Minerals 2022, 12(2), 252; https://doi.org/10.3390/min12020252 - 16 Feb 2022
Cited by 16 | Viewed by 3878
Abstract
The combustion of fossil fuels from the input of oil refineries, power plants, and the venting or flaring of produced gases in oil fields leads to greenhouse gas emissions. Economic usage of greenhouse and flue gases in conventional and unconventional reservoirs would not [...] Read more.
The combustion of fossil fuels from the input of oil refineries, power plants, and the venting or flaring of produced gases in oil fields leads to greenhouse gas emissions. Economic usage of greenhouse and flue gases in conventional and unconventional reservoirs would not only enhance the oil and gas recovery but also offers CO2 sequestration. In this regard, the accurate estimation of the interfacial tension (IFT) between the injected gases and the crude oils is crucial for the successful execution of injection scenarios in enhanced oil recovery (EOR) operations. In this paper, the IFT between a CO2/N2 mixture and n-alkanes at different pressures and temperatures is investigated by utilizing machine learning (ML) methods. To this end, a data set containing 268 IFT data was gathered from the literature. Pressure, temperature, the carbon number of n-alkanes, and the mole fraction of N2 were selected as the input parameters. Then, six well-known ML methods (radial basis function (RBF), the adaptive neuro-fuzzy inference system (ANFIS), the least square support vector machine (LSSVM), random forest (RF), multilayer perceptron (MLP), and extremely randomized tree (extra-tree)) were used along with four optimization methods (colliding bodies optimization (CBO), particle swarm optimization (PSO), the Levenberg–Marquardt (LM) algorithm, and coupled simulated annealing (CSA)) to model the IFT of the CO2/N2 mixture and n-alkanes. The RBF model predicted all the IFT values with exceptional precision with an average absolute relative error of 0.77%, and also outperformed all other models in this paper and available in the literature. Furthermore, it was found that the pressure and the carbon number of n-alkanes would show the highest influence on the IFT of the CO2/N2 and n-alkanes, based on sensitivity analysis. Finally, the utilized IFT database and the area of the RBF model applicability were investigated via the leverage method. Full article
(This article belongs to the Special Issue Shale and Tight Reservoir Characterization and Resource Assessment)
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<p>A schematic flowchart of the applied algorithms for the development of IFT models.</p> Full article ">Figure 2
<p>Schematic of a RBF network.</p> Full article ">Figure 3
<p>Flowchart of the random forest and decision tree algorithms.</p> Full article ">Figure 4
<p>Flowchart of the ECBO algorithm.</p> Full article ">Figure 5
<p>The run time and computational accuracy for various methods.</p> Full article ">Figure 6
<p>Cross plots of all proposed models.</p> Full article ">Figure 6 Cont.
<p>Cross plots of all proposed models.</p> Full article ">Figure 7
<p>Error distribution graphs of the implemented models (percent relative error vs. experimental IFT data).</p> Full article ">Figure 7 Cont.
<p>Error distribution graphs of the implemented models (percent relative error vs. experimental IFT data).</p> Full article ">Figure 8
<p>Cumulative frequency against ARE for all of the models.</p> Full article ">Figure 9
<p>Comparing AAPRE for all available models and correlations for estimating the IFT of N<sub>2</sub>/CO<sub>2</sub> mixture + n-alkanes.</p> Full article ">Figure 10
<p>The experimental values and RBF predictions for the IFT of N<sub>2</sub>/CO<sub>2</sub> mixture + n-hexane.</p> Full article ">Figure 11
<p>Importance assessment of input parameters on IFT of N<sub>2</sub>/CO<sub>2</sub> mixture + n-alkanes.</p> Full article ">Figure 12
<p>Identification of RBF model usability scope and doubtful data using William’s plot.</p> Full article ">
38 pages, 1844 KiB  
Review
Ecological and Biotechnological Relevance of Mediterranean Hydrothermal Vent Systems
by Carmen Rizzo, Erika Arcadi, Rosario Calogero, Valentina Sciutteri, Pierpaolo Consoli, Valentina Esposito, Simonepietro Canese, Franco Andaloro and Teresa Romeo
Minerals 2022, 12(2), 251; https://doi.org/10.3390/min12020251 - 16 Feb 2022
Cited by 17 | Viewed by 9946
Abstract
Marine hydrothermal systems are a special kind of extreme environments associated with submarine volcanic activity and characterized by harsh chemo-physical conditions, in terms of hot temperature, high concentrations of CO2 and H2S, and low pH. Such conditions strongly impact the [...] Read more.
Marine hydrothermal systems are a special kind of extreme environments associated with submarine volcanic activity and characterized by harsh chemo-physical conditions, in terms of hot temperature, high concentrations of CO2 and H2S, and low pH. Such conditions strongly impact the living organisms, which have to develop adaptation strategies to survive. Hydrothermal systems have attracted the interest of researchers due to their enormous ecological and biotechnological relevance. From ecological perspective, these acidified habitats are useful natural laboratories to predict the effects of global environmental changes, such as ocean acidification at ecosystem level, through the observation of the marine organism responses to environmental extremes. In addition, hydrothermal vents are known as optimal sources for isolation of thermophilic and hyperthermophilic microbes, with biotechnological potential. This double aspect is the focus of this review, which aims at providing a picture of the ecological features of the main Mediterranean hydrothermal vents. The physiological responses, abundance, and distribution of biotic components are elucidated, by focusing on the necto-benthic fauna and prokaryotic communities recognized to possess pivotal role in the marine ecosystem dynamics and as indicator species. The scientific interest in hydrothermal vents will be also reviewed by pointing out their relevance as source of bioactive molecules. Full article
(This article belongs to the Special Issue Hydrothermal Systems Across Time and Space: Advances and Perspectives)
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<p>Graphic showing a vent forming a hydrothermal plume with interactions between seawater, magmatic fluid and crustal rocks. Release of some chemicals (i.e., Manganese, iron, iron oxyhydroxide, carbon dioxide, hydrogen sulfide, methane) is generated by the mixing of the hot hydrothermal fluids and cold seawater. Simplified view of microbial metabolisms in HVSs. The characteristics are generalized and do not refer to a particular vent location.</p> Full article ">Figure 2
<p>Main hydrothermal vent systems in the Mediterranean area: central Tyrrhenian Back-Arc, Aeolian Arc, Aegean Arc and strait of Sicily. Triangles are deep site, while rings are shallow site.</p> Full article ">
32 pages, 3509 KiB  
Review
Chemical Composition Data of the Main Stages of Copper Production from Sulfide Minerals in Chile: A Review to Assist Circular Economy Studies
by Kayo Santana Barros, Vicente Schaeffer Vielmo, Belén Garrido Moreno, Gabriel Riveros, Gerardo Cifuentes and Andréa Moura Bernardes
Minerals 2022, 12(2), 250; https://doi.org/10.3390/min12020250 - 16 Feb 2022
Cited by 24 | Viewed by 10826
Abstract
The mining industry has faced significant challenges to maintaining copper production technically, economically, and environmentally viable. Some of the major limitations that must be overcome in the coming years are the copper ore grade decline due to its intense exploitation, the increasing requirements [...] Read more.
The mining industry has faced significant challenges to maintaining copper production technically, economically, and environmentally viable. Some of the major limitations that must be overcome in the coming years are the copper ore grade decline due to its intense exploitation, the increasing requirements for environmental protection, and the need to expand and construct new tailings dams. Furthermore, the risk of a supply crisis of critical metals, such as antimony and bismuth, has prompted efforts to increase their extraction from secondary resources in copper production. Therefore, improving conventional processes and developing new technologies is crucial to satisfying the world’s metal demands, while respecting the policies of environmental organizations. Hence, it is essential that the chemical composition of each copper production stage is known for conducting these studies, which may be challenging due to the huge variability of concentration data concerning the ore extraction region, the process type, and the operational conditions. This paper presents a review of chemical composition data of the main stages of copper production from sulfide minerals, such as (1) copper minerals, (2) flotation tailings, (3) flotation concentrates, (4) slags and (5) flue dust from the smelting/converting stage, (6) copper anodes, (7) anode slimes, (8) contaminated electrolytes from the electrorefining stage, (9) electrolytes cleaned by ion-exchange resins, and (10) elution solutions from the resins. In addition, the main contributions of recent works on copper production are summarized herein. This study is focused on production sites from Chile since it is responsible for almost one-third of the world’s copper production. Full article
(This article belongs to the Special Issue Recent Advances in Copper Ore Processing and Extraction)
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<p>Flowchart of the copper production from sulfide minerals showing the inputs and outputs of the main process stages.</p> Full article ">Figure 2
<p>Reported (symbols) and forecasted (lines) ore grade by country (Adapted from [<a href="#B43-minerals-12-00250" class="html-bibr">43</a>] with permission).</p> Full article ">Figure 3
<p>Projection of copper production in Chile in the coming years from oxide and sulfide (concentrate) ores (Adapted from [<a href="#B5-minerals-12-00250" class="html-bibr">5</a>] with permission).</p> Full article ">Figure 4
<p>Historic copper production data (symbols) and modelled (line) scenarios for selected countries [<a href="#B45-minerals-12-00250" class="html-bibr">45</a>].</p> Full article ">Figure 5
<p>Mineralogical composition of copper concentrates from the world’s leading copper producers. Ccp, Cc, Cv, Py, and Po are chalcopyrite, chalcocite, covellite, pyrite, and pyrrhotite, respectively [<a href="#B77-minerals-12-00250" class="html-bibr">77</a>].</p> Full article ">Figure 6
<p>Number of accidents involving tailings dam failures in several countries from 1910 to 2018 [<a href="#B81-minerals-12-00250" class="html-bibr">81</a>].</p> Full article ">Figure 7
<p>The evolution of the presence of As, Sb, and Bi as impurities in copper anodes over the last 30 years worldwide [<a href="#B101-minerals-12-00250" class="html-bibr">101</a>].</p> Full article ">Figure 8
<p>Distribution (mass fraction) of Cu, Fe, As, Sb and Bi present in the anode, slag, and flue dust from Chuquicamata mine.</p> Full article ">Figure 9
<p>Flowchart of the copper production from sulfide minerals showing the concentration ranges of copper and antimony in the main Chilean process stages.</p> Full article ">
16 pages, 5922 KiB  
Article
First Demonstration of Recognition of Manganese Crust by Deep-Learning Networks with a Parametric Acoustic Probe
by Feng Hong, Minyan Huang, Haihong Feng, Chengwei Liu, Yong Yang, Bo Hu, Dewei Li and Wentao Fu
Minerals 2022, 12(2), 249; https://doi.org/10.3390/min12020249 - 16 Feb 2022
Cited by 5 | Viewed by 2709
Abstract
The quantitative evaluations of mineral resources and delineation of promising areas in survey regions for future mining have attracted many researchers’ interest. Cobalt-Rich manganese crusts (Mn-crusts), as one of the three significant strategic submarine mineral resources, lack effective and low-cost detection devices for [...] Read more.
The quantitative evaluations of mineral resources and delineation of promising areas in survey regions for future mining have attracted many researchers’ interest. Cobalt-Rich manganese crusts (Mn-crusts), as one of the three significant strategic submarine mineral resources, lack effective and low-cost detection devices for surveying since the challenging distribution requires a high vertical and horizontal resolution. To solve this problem, we have built an engineering prototype parametric acoustic probe named PPPAAP19. With the echo data acquired by the probe, the interpretation of the accurate thickness information and the seabed classification using the deep learning network-based method are realized. We introduce the acoustic dataset of the minerals collected from two sea trials. Firstly, the preprocessing method and data augment strategy used to form the dataset are described. Afterward, the performances of several baseline approaches are assessed on the dataset, and the experimental results show that they all achieve high accuracy for binary classification. We find that the end-to-end approach for binary classification based on a 1D Convolution Neural Network has a comprehensive advantage. Such a demonstration validates the possibility of binary classification for recognizing the ferromanganese crust only in an acoustic manner, which may significantly contribute to the efficiency of the survey. Full article
(This article belongs to the Special Issue Deep-Sea Ferromanganese Nodules and Related Mineral Resources: Genesis, Exploration, and Mining)
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<p>The photo of Programmable Phased Parametric Array Acoustic Probe 2019 (PPPAAP19): (<b>a</b>) Front view of PPPAAP19; (<b>b</b>) the designed array located at the bottom of PPPAAP19 with the receiving transducer marked with red and the other 18 transmitting transducers around it.</p> Full article ">Figure 2
<p>System description of PPPAAP19 with the host computer.</p> Full article ">Figure 3
<p>Binary classification with different approaches.</p> Full article ">Figure 4
<p>Binary classification with the approach of STFT+2D-CNN.</p> Full article ">Figure 5
<p>Binary classification with the approach of FFT+DNN.</p> Full article ">Figure 6
<p>Binary classification with the approach of time-domain signal+1D-CNN.</p> Full article ">Figure 7
<p>Experimental configurations to acquire the echo data: (<b>a</b>) PPPAAPP19 mounted on the mobile drilling rig in 2019; (<b>b</b>) PPPAAPP19 mounted on JIAOLONG HOV in 2020. The development of the device has a label that indicates it is supported by National key R&amp;D Program.</p> Full article ">Figure 7 Cont.
<p>Experimental configurations to acquire the echo data: (<b>a</b>) PPPAAPP19 mounted on the mobile drilling rig in 2019; (<b>b</b>) PPPAAPP19 mounted on JIAOLONG HOV in 2020. The development of the device has a label that indicates it is supported by National key R&amp;D Program.</p> Full article ">Figure 8
<p>Estimated height away from the seabed in 2020 standardized sea trial.</p> Full article ">Figure 9
<p>Pictures of (<b>a</b>,<b>b</b>) two different kinds of scenarios of the 2019 sea trial that contain FC and NonFC and (<b>c</b>,<b>d</b>) scenarios of the 2020 sea trial that contains NonFC from different perspectives.</p> Full article ">Figure 10
<p>Samples of the survey area. (<b>a</b>) Several samples of FC and NonFC. (<b>b</b>) Other samples of FC and NonFC and the card indicates that they were obtained by Guangzhou Marine Geological Survey.</p> Full article ">Figure 11
<p>Some of the waveforms of FC, colored green, and those of NonFC, colored red.</p> Full article ">Figure 12
<p>Confusion matrices of different methods. (<b>a</b>) STFT+2D-CNN; (<b>b</b>) FFT+DNN; (<b>c</b>) Time-domain signal+1D-CNN.</p> Full article ">
20 pages, 25170 KiB  
Article
Ion-Exchange-Induced Transformation and Mechanism of Cooperative Crystal Chemical Adaptation in Sitinakite: Theoretical and Experimental Study
by Taras L. Panikorovskii, Galina O. Kalashnikova, Anatoly I. Nikolaev, Igor A. Perovskiy, Ayya V. Bazai, Victor N. Yakovenchuk, Vladimir N. Bocharov, Natalya A. Kabanova and Sergey V. Krivovichev
Minerals 2022, 12(2), 248; https://doi.org/10.3390/min12020248 - 15 Feb 2022
Cited by 5 | Viewed by 2867
Abstract
The microporous titanosilicate sitinakite, KNa2Ti4(SiO4)2O5(OH)·4H2O, was first discovered in the Khibiny alkaline massif. This material is also known as IONSIV IE-911 and is considered as one of the most effective sorbents [...] Read more.
The microporous titanosilicate sitinakite, KNa2Ti4(SiO4)2O5(OH)·4H2O, was first discovered in the Khibiny alkaline massif. This material is also known as IONSIV IE-911 and is considered as one of the most effective sorbents for Cs+ and Sr2+ from water solutions. We investigate a mechanism of cooperative crystal chemical adaptation caused by the incorporation of La3+ ions into sitinakite structure by the combination of theoretical (geometrical–topological analysis, Voronoi migration map calculation, structural complexity calculation) and empirical methods (PXRD, SCXRD, Raman spectroscopy, scanning electron microscopy). The natural crystals of sitinakite (a = 7.8159(2), c = 12.0167(3) Å) were kept in a 1M solution of La(NO3)3 for 24 h. The ordering of La3+ cations in the channels of the ion-exchanged form La3+Ti4(SiO4)2O5(OH)·4H2O (a = 11.0339(10), b = 11.0598(8), c = 11.8430(7) Å), results in the symmetry breaking according to the group–subgroup relation P42/mcm → Cmmm. Full article
(This article belongs to the Special Issue Minerals as Advanced Materials)
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<p>(<b>a</b>) Geology of the Khibiny massif and Mt. Koashva within purple star after [<a href="#B46-minerals-12-00248" class="html-bibr">46</a>] with modifications; (<b>b</b>) the Koashva quarry, Khibiny alkaline massif, Kola Peninsula, Russia. The purple star indicates the location for the sitinakite bearing vein no. 8; (<b>c</b>) short-prismatic sitinakite (1) crystals with aegirine needles (2) and amorphous bitumens (3).</p> Full article ">Figure 2
<p>Backscattered images of (<b>a</b>) La-exchanged natural sitinakite (1) at 200 °C for 24 h with aegirine (2) inclusion; (<b>b</b>) synthetic La-exchanged sitinakite at 200 °C for 24 h; (<b>c</b>) formation of anatase (3) crusts on the surface of synthetic La-exchanged sitinakite at 200 °C for 24 h.</p> Full article ">Figure 3
<p>Raman spectra of initial sitinakite and La-exchanged natural sitinakite. The most significant differences in the positions or intensity in both spectra are indicated by gray lines.</p> Full article ">Figure 4
<p>Calculated powder XRD pattern of initial sitinakite and La-exchanged form.</p> Full article ">Figure 5
<p>Diffraction patterns of synthetic sitinakite and its La-exchanged forms after 1, 4, 12 and 24 h sorption at 200 °C. The most significant differences in the positions or intensity in both patterns are indicated by the gray rectangles.</p> Full article ">Figure 6
<p>Reconstructed sections of reciprocal space obtained for the (<span class="html-italic">hk</span>0) and (<span class="html-italic">h</span>0<span class="html-italic">l</span>) sections for sitinakite (<b>a</b>,<b>c</b>) and its La-exchanged form (<b>b</b>,<b>d</b>) and enlarged fragments of these sections (<b>e</b>–<b>g</b>). White arrows and numbers indicate reflections and their indices. The examples of additional reflections, which cannot be indexed in the tetragonal cell are indicated by question marks. On the corresponding schemas, large dark red circles and small unfilled circles belong to the tetragonal (<span class="html-italic">a</span> = 7.8159, <span class="html-italic">c</span> = 12.0167 Å) and orthorhombic (<span class="html-italic">a</span> = 11.0339, <span class="html-italic">b</span> = 11.0598, <span class="html-italic">c</span> = 11.8430 Å) cells, respectively; black and red arrows indicate tetragonal and orthorhombic cell vectors, respectively.</p> Full article ">Figure 7
<p>The crystal structure of sitinakite projected along the <span class="html-italic">c</span> axis (<b>a</b>); the [Ti<sub>4</sub>O<sub>4</sub>]<sup>8+</sup><sub>∞</sub> column with adjacent SiO<sub>4</sub> tetrahedra in sitinakite (<b>b</b>); the connection of [Ti<sub>4</sub>O<sub>4</sub>]<sup>8+</sup> clusters in ivanyukite-K [<a href="#B17-minerals-12-00248" class="html-bibr">17</a>] (<b>c</b>); the channel I defined by an 8-membered ring (<b>d</b>), the 6-membered rings of the channels II (<b>e</b>) and III (<b>f</b>) with Na and K atoms in the sitinakite structure.</p> Full article ">Figure 8
<p>The crystal structure of La-exchanged sitinakite projected along <span class="html-italic">c</span> axis with channel I (<b>a</b>); along [110] direction with channel III (<b>b</b>); along <span class="html-italic">a</span> axis with channel II (<b>c</b>); coordination of La1, La2, La3, Si1, Ti1 and Ti2 atoms (<b>d</b>). The occupancy La-sites are indicated by different sectors filled by the green color.</p> Full article ">Figure 9
<p>Tiling representation of the titanosilicate framework in the crystal structure of sitinakite. The unit cell is outlined.</p> Full article ">Figure 10
<p>The small t-kzd, t-lov, t-cub tiles (<b>a</b>) and the large new tile [4<sup>8</sup>.6<sup>6</sup>.8<sup>2</sup>] in the crystal structure of sitinakite. Na, K and La cations are located within the large tile (<b>b</b>).</p> Full article ">Figure 11
<p>Migration paths for Na and K (<b>a</b>) for sitinakite and La (<b>b</b>) for La-exchanged form.</p> Full article ">Figure 12
<p>Largest cavity corresponding to the tile [4<sup>8</sup>.6<sup>6</sup>.8<sup>2</sup>]: in sitinakite with the Na2 site (<b>a</b>); in La-exchanged sitinakite with the La1 site (<b>b</b>); in La-exchanged sitinakite with La3 site (<b>c</b>); the hinge-like deformation in the Ti1O<sub>6</sub> octahedra associated with the La1 site (<b>d</b>); and associated with the La3 site (<b>e</b>). Green and grey arrows represent distortions caused by the La incorporation.</p> Full article ">Figure 13
<p>The modulated character of low-occupied H<sub>2</sub>O sites along [010] direction associated with La1 sites.</p> Full article ">
14 pages, 3874 KiB  
Article
Mineral Composition Impact on the Thermal Conductivity of Granites Based on Geothermal Field Experiments in the Songliao and Gonghe Basins, China
by Xiaoqi Ye, Ziwang Yu, Yanjun Zhang, Jianguo Kang, Shaohua Wu, Tianrui Yang and Ping Gao
Minerals 2022, 12(2), 247; https://doi.org/10.3390/min12020247 - 15 Feb 2022
Cited by 10 | Viewed by 3386
Abstract
Accurate estimation of thermal conductivity of rocks is of paramount importance for projects such as the development of hot dry rock and the geological storage of nuclear waste. In this paper, 30 granite samples from the Songliao and Gonghe Basins in China were [...] Read more.
Accurate estimation of thermal conductivity of rocks is of paramount importance for projects such as the development of hot dry rock and the geological storage of nuclear waste. In this paper, 30 granite samples from the Songliao and Gonghe Basins in China were tested by X-ray diffraction, polarizing microscope, and Thermal Conductivity Scanning (TCS) measurements. Different mineral contents determine the thermal conductivity of the rock as a whole. The geometric average model and the harmonic average model have great limitations. Combined with the above two models, a new model is proposed for estimating the thermal conductivity, and results are less different from the measured values and have universal applicability. The relative estimation error on the thermal conductivity calculated by mineral composition is significantly reduced. The accuracy of thermal conductivity calculation can be improved by mineral composition. Full article
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<p>The relationship between the three major rock types and different mineral components [<a href="#B19-minerals-12-00247" class="html-bibr">19</a>]; (<b>a</b>) Relationship between metamorphic rocks, intrusive rocks, and different mineral compositions; (<b>b</b>) Relationship between volcanic rocks, sedimentary rocks, and different mineral compositions.</p> Full article ">Figure 2
<p>Geographical map of Songliao Basin. The sampling site Xujiaweizi is circled in red in the figure, and sampling depth is 3000–4000 m.</p> Full article ">Figure 3
<p>The geographical location of the Gonghe Basin. The red box is the sampling point of the Gonghe Basin on the north bank of the Longyangxia Dam.</p> Full article ">Figure 4
<p>Outcrop of granite on the north bank of Longyangxia Dam.</p> Full article ">Figure 5
<p>Thermal conductivity scanning (TCS).</p> Full article ">Figure 6
<p>The relationship between the thermal conductivity of main constituent minerals and the range of the thermal conductivity of rock samples. The thermal conductivity of different minerals: Quartz: 7.70W/(m∙K); Alkaline Feldspars: 2.30 W/(m∙K); Plagioclase: 1.80 W/(m∙K); Clay minerals: 2.6 W/(m∙K); Mica: 0.43 W/(m∙K); Calcite: 3.57 W/(m∙K); Hornblende: 5.30 W/(m∙K); Biotite: 2.13 W/(m∙K). [<a href="#B12-minerals-12-00247" class="html-bibr">12</a>,<a href="#B31-minerals-12-00247" class="html-bibr">31</a>]).</p> Full article ">Figure 7
<p>Polarized microscope photo of granite [<a href="#B29-minerals-12-00247" class="html-bibr">29</a>] (where: Q is Quartz; Pl is Plagioclase; (<b>a</b>) Granodiorite in the Songliao Basin; (<b>b</b>) Syenogranite in the Songliao Basin; (<b>c</b>) Granodiorite in the Gonghe Basin; (<b>d</b>) Adamellite in the Gonghe Basin; Bi is Biotite; Ab is Alkali Feldspar).</p> Full article ">Figure 8
<p>Variation of thermal conductivity with porosity at the same quartz content: (<b>a</b>) Relationship between thermal conductivity and porosity of rock samples with 27% quartz content; (<b>b</b>) Relationship between thermal conductivity and porosity of rock samples with 45% quartz content.</p> Full article ">Figure 9
<p>Comparison of calculated and measured values of Geometric Model, Harmonic Model, and Mixed Model (in dry or saturated state).</p> Full article ">Figure 10
<p>Error comparison of Geometric Model, Harmonic Model, and Mixed Model (in dry or saturated state).</p> Full article ">
19 pages, 4025 KiB  
Article
Orthogonal Test Design for the Optimization of Preparation of Steel Slag-Based Carbonated Building Materials with Ultramafic Tailings as Fine Aggregates
by Jiajie Li, Chengzhou Wang, Wen Ni, Sitao Zhu, Shilong Mao, Fuxing Jiang, Hui Zeng, Xikui Sun, Bingxiang Huang and Michel Hitch
Minerals 2022, 12(2), 246; https://doi.org/10.3390/min12020246 - 15 Feb 2022
Cited by 21 | Viewed by 2861
Abstract
The high carbonation potential makes ultramafic tailings ideal aggregates for carbonated building materials. This paper investigates the preparation condition of ultramafic tailings and steel slag through orthogonal experiments. The results show that compressive strength has a positive exponential correlation with the CO2 [...] Read more.
The high carbonation potential makes ultramafic tailings ideal aggregates for carbonated building materials. This paper investigates the preparation condition of ultramafic tailings and steel slag through orthogonal experiments. The results show that compressive strength has a positive exponential correlation with the CO2 uptake of the carbonated compacts. The optimized conditions include a slag-tailings ratio of 5:5, a carbonation time of 12 h, a grinding time of 0 min, and a water-solid ratio of 2.5:10, when the compressive strength of the carbonated compacts reaches 29 MPa and the CO2 uptake reaches 66.5 mg CO2/g. The effects on the compressive strength ordered from high to low impact are the slag/tailings ratio, carbonation time, grinding time of steel slag, and water–solid ratio. The effects on the CO2 uptake ordered from high to low impact are the slag–tailings ratio, water–solid ratio, carbonation time, and grinding time of steel slag. A high water–solid ratio hinders the early carbonation reactions, but promotes the long-term carbonation reaction. Steel slag is the main material being carbonated and contributes to the hardening of the compacts through carbonation curing at room temperature. Ultramafic tailings assist steel slag in hardening through minor carbonation and provide fibrous contents. The obtained results lay a solid foundation for the development of tailings-steel slag carbonated materials. Full article
(This article belongs to the Topic Recycling and Value-Added Utilization of Secondary Raw Materials)
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<p>The experiment flowchart.</p> Full article ">Figure 2
<p>The relationship between compressive strength and CO<sub>2</sub> uptake of carbonated tailings-steel slag compacts.</p> Full article ">Figure 3
<p>The effect curve of four factors on (<b>a</b>) compressive strength; (<b>b</b>) CO<sub>2</sub> uptake capacity. A is the grinding time for steel slag, B is the water/solid ratio, C is the slag/tailings ratio, D is the carbonation time.</p> Full article ">Figure 4
<p>(<b>a</b>) The compressive strength of compacts grouped by the slag/tailings ratio; (<b>b</b>) The CO<sub>2</sub> uptake capacity of compacts grouped by the slag–tailings ratio. The slag/tailings ratios of C1, C2, C3, C4 are 0, 1:9, 3:7 and 5:5, respectively.</p> Full article ">Figure 5
<p>CO<sub>2</sub> uptake and compressive strength of samples grouped by the grinding time of steel slag. The black bars show the values of compressive strength. The blue lines display the values of CO<sub>2</sub> uptake. The grinding time for steel slag of A1, A2, A3, A4 are 0, 30, 60 and 120 min, respectively.</p> Full article ">Figure 6
<p>X-ray diffraction pattern of ultramafic tailings, steel slag, and S4.</p> Full article ">Figure 7
<p>TG-DTA curve of ultramafic tailings, steel slag, and S4.</p> Full article ">Figure 8
<p>The micrograph and EDS spectra of samples. (<b>a</b>) The micrograph of ultramafic tailings; (<b>b</b>) The micrograph of steel slag; (<b>c</b>,<b>d</b>)The micrograph of S4; (<b>a1</b>) The EDS spectra of chrysotile on (<b>a</b>); (<b>b1</b>) The EDS spectra of C<sub>2</sub>S on (<b>b</b>); (<b>c1</b>) The EDS spectra of CaCO<sub>3</sub> on (<b>c</b>); (<b>d1</b>) The EDS spectra on Chrysotile on (<b>d</b>). The scale bar in (<b>a</b>,<b>b</b>,<b>d</b>) are 10 µm and in (<b>c</b>) is 3 µm.</p> Full article ">Figure 8 Cont.
<p>The micrograph and EDS spectra of samples. (<b>a</b>) The micrograph of ultramafic tailings; (<b>b</b>) The micrograph of steel slag; (<b>c</b>,<b>d</b>)The micrograph of S4; (<b>a1</b>) The EDS spectra of chrysotile on (<b>a</b>); (<b>b1</b>) The EDS spectra of C<sub>2</sub>S on (<b>b</b>); (<b>c1</b>) The EDS spectra of CaCO<sub>3</sub> on (<b>c</b>); (<b>d1</b>) The EDS spectra on Chrysotile on (<b>d</b>). The scale bar in (<b>a</b>,<b>b</b>,<b>d</b>) are 10 µm and in (<b>c</b>) is 3 µm.</p> Full article ">
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