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Mineral Chemistry of Granitoids: Constraints on Crystallization Conditions and Petrological...
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Mineral Chemistry of Granitoids: Constraints on Crystallization Conditions and Petrological Evolution

A special issue of Minerals (ISSN 2075-163X). This special issue belongs to the section "Mineral Geochemistry and Geochronology".

Deadline for manuscript submissions: closed (31 October 2024) | Viewed by 11605

Special Issue Editors

Prof. Dr. Ignez de Pinho Guimarães

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Guest Editor
Programa de Pós-Graduação Em Geociências, Departamento de Geologia, Universidade Federal de Pernambuco, Recife 50740-550, PE, Brazil
Interests: petrological aspects of igneous rocks, including whole rock geochemistry, mineral chemistry, geochronology and isotope geochemistry
Prof. Dr. Jefferson Valdemiro De Lima

E-Mail Website
Guest Editor
Department of Geology, Federal University of Pernambuco, Recife 50740-550, PE, Brazil
Interests: geochemistry and petrology of igneous rocks

Special Issue Information

Dear Colleagues,

Mineral chemistry is an important tool for estimating crystallization parameters (temperature, pressure and oxygen fugacity) during the petrological evolution of granitic magmas, since the chemistry and redox conditions of parental magma play an important role in the composition of granitoid minerals. In addition to information about the physicochemical conditions of the magma, the chemical signature of the primary ferromagnesian phases can provide information about the magma’s nature and its affinity with the different magmatic series. Recent work has used trace element signatures in accessory minerals to estimate the source and petrological evolution of granitic magmas. This approach provides a powerful tool for the chemical study of granitoids, since it works with the chemical signatures of less mobile elements to corroborate information provided by conventional mineral chemistry.

This Special Issue aims to address the importance of the mineral chemistry of granitoids in understanding the geological history of the regions in which they are located. The study of granitoids is fundamental to understanding the crustal evolution of a region, since granitic magmatism is the main factor involved in the geochemical differentiation of the continental crust.

Prof. Dr. Ignez de Pinho Guimarães
Prof. Dr. Jefferson Valdemiro De Lima
Guest Editors

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Keywords

  • mineral chemistry
  • crystallization parameters
  • geobarometry
  • geothermometry
  • accessory mineral trace elements

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23 pages, 5679 KiB  
Article
Mineralogical and Geochemical Response to Fluid Infiltration into Cambrian Orthopyroxene-Bearing Granitoids and Gneisses, Dronning Maud Land, Antarctica
by Ane K. Engvik, Fernando Corfu, Ilka C. Kleinhanns, Heinrich Taubald and Synnøve Elvevold
Minerals 2024, 14(8), 772; https://doi.org/10.3390/min14080772 - 29 Jul 2024
Viewed by 703
Abstract
Fluid infiltration into Proterozoic and Early Palaeozoic dry, orthopyroxene-bearing granitoids and gneisses in Dronning Maud Land, Antarctica, has caused changes to rock appearance, mineralogy, and rock chemistry. The main mineralogical changes are the replacement of orthopyroxene by hornblende and biotite, ilmenite by titanite, [...] Read more.
Fluid infiltration into Proterozoic and Early Palaeozoic dry, orthopyroxene-bearing granitoids and gneisses in Dronning Maud Land, Antarctica, has caused changes to rock appearance, mineralogy, and rock chemistry. The main mineralogical changes are the replacement of orthopyroxene by hornblende and biotite, ilmenite by titanite, and various changes in feldspar structure and composition. Geochemically, these processes resulted in general gains of Si, mostly of Al, and marginally of K and Na but losses of Fe, Mg, Ti, Ca, and P. The isotopic oxygen composition (δ18OSMOW = 6.0‰–9.9‰) is in accordance with that of the magmatic precursor, both for the host rock and infiltrating fluid. U-Pb isotopes in zircon of the altered and unaltered syenite to quartz-monzonite indicate a primary crystallization age of 520.2 ± 1.0 Ma, while titanite defines alteration at 485.5 ± 1.4 Ma. Two sets of gneiss samples yield a Rb-Sr age of 517 ± 6 Ma and a Sm-Nd age of 536 ± 23 Ma. The initial Sr and Nd isotopic ratios suggest derivation of the gneisses from a relatively juvenile source but with a very strong metasomatic effect that introduced radiogenic Sr into the system. The granitoid data indicate instead a derivation from Mid-Proterozoic crust, probably with additions of mantle components. Full article
(This article belongs to the Special Issue Mineral Chemistry of Granitoids: Constraints on Crystallization Conditions and Petrological Evolution)
►▼ Show Figures

Figure 1

Figure 1
<p>(<b>a</b>) Geographical situation map of central Dronning Maud Land. (<b>b</b>) Geological map of the studied part of Mühlig–Hofmannfjella and Orvinfjella. The numbers indicate the sampled localities (Table 1) (modified from [<a href="#B16-minerals-14-00772" class="html-bibr">16</a>]).</p> Full article ">Figure 2
<p>Field photos. (<b>a</b>) Nunatak of orthopyroxene-bearing granitoid with the characteristic dark brownish outcrop color (Håhelleregga). (<b>b</b>) Alteration halo around discordant aplitic vein crosscutting migmatitc gneiss (locality 7, Kubusfjellet). The vein (arrow) is about 5 cm thick with an alteration halo extending 0.5 m into the host rock. The field of view is 1.5 m. (<b>c</b>) Alteration halo around the pegmatitic vein cutting dark brownish-colored orthopyroxene-bearing syenite (locality 5, Trollslottet). The field of view is about 1 m. (<b>d</b>) A high density of crisscrossing veins causes heavy alteration of the dark orthopyroxene-bearing syenite of the Trollslottet nunatak (Locality 5, the cliff face is about 70 m high).</p> Full article ">Figure 3
<p>Micrographs of pristine orthopyroxene-bearing gneiss and granitoid intrusions (mineral abbreviations following Whitney and Evans [<a href="#B38-minerals-14-00772" class="html-bibr">38</a>]. (<b>a</b>) Garnet-orthopyroxene gneiss with major quartz, perthitic K-feldspar, and plagioclase occur equigranular with embayed and triple-point grain boundaries (sample AHA193A, plane light). (<b>b</b>) Euhedral orthopyroxene in the quartz and feldspar matrix (sample AHA217, orthopyroxene granite, plane light). (<b>c</b>) Coarse subhedral amphibole with medium-grained biotite and orthopyroxene (sample AHA144, orthopyroxene-bearing quartz-monzonite, plane light). (<b>d</b>) Amphibole and biotite in the matrix of quartz and perthitic K-feldspar; note the coarse crystals of biotite (sample AHA197, orthopyroxene-bearing granite, plane light). (<b>e</b>) Amphibole and biotite in the matrix of perthite, plagioclase, and quartz; note the well-developed coarse crystals of amphibole and biotite (sample AHA197, orthopyroxene-bearing granite, plane light). (<b>f</b>) Fine-grained quartz and feldspars of aplite but with a strong heterogeneity including some coarse grains. Remark dusty appearance of quartz and feldspar (sample AHA200II, crossed polarizers).</p> Full article ">Figure 4
<p>Replacement of mafic minerals in alteration zones (micrographs, plane light). (<b>a</b>) Biotite + quartz fine-grained symplectites (sample AHA107, altered quartz-monzonite). (<b>b</b>) Amphibole + quartz fine-grained symplectites (sample AHA107, altered quartz-monzonite). (<b>c</b>) Replacement of amphibole along cleavage planes and microfractures to biotite (white arrows) and Fe-oxide (black arrow; sample AHA145 altered quartz-monzonite). (<b>d</b>) Replacement of amphibole to biotite along cleavage planes, micro-cracks, and sub-grain boundaries (sample AHA145, altered quartz-monzonite). (<b>e</b>) Replacement of coarse biotite to finer biotite grains and of ilmenite to titanite (sample AHA199, altered quartz monzonite).</p> Full article ">Figure 5
<p>Feldspars in alteration zones. (<b>a</b>,<b>b</b>) Replacement of original feldspar to subgrains and production of a high density of micropores, fluid inclusions, and tiny grains of sericite and biotite. Plane light (<b>a</b>) and crossed polarizers (<b>b</b>) (sample AHA145, altered quartz-monzonite). (<b>c</b>) Replacement of perthitic K-feldspar to microcline (crossed polarizers, sample AHA 193C, altered gneiss). (<b>d</b>) Alteration of perthitic K-feldspar along microfractures (arrows) and replacement to microcline (crossed polarizers, sample AHA199, altered syenite). (<b>e</b>,<b>f</b>) Sericitization (arrows) and growth of biotite (brown phase) and titanite along microfractures in plagioclase. Plane light (<b>e</b>) and crossed polarizers (<b>f</b>) (sample AHA145, altered quartz-monzonite).</p> Full article ">Figure 6
<p>TAS-plot. Arrows link the unaltered and altered samples with their direction pointing to the alteration. Symbols are the same as in Figure 8 and Figure 9.</p> Full article ">Figure 7
<p>U-Pb analyses of zircon and titanite in orthopyroxene-bearing granite (sample AHA197) and alteration zone (sample AHA199). Ellipses (full lines for zircon and dashed lines for titanite) indicate 2 sigma uncertainty.</p> Full article ">Figure 8
<p>Radiogenic isotopic plot. Arrows link the unaltered to the altered sample and their direction points to the alteration. (<b>a</b>,<b>b</b>) <sup>87</sup>Rb/<sup>86</sup>Sr vs. <sup>87</sup>Sr/<sup>86</sup>Sr. (<b>c</b>) <sup>147</sup>Sm/<sup>144</sup>Nd vs. <sup>143</sup>Nd/<sup>144</sup>Nd. See <a href="#sec5-minerals-14-00772" class="html-sec">Section 5</a>.</p> Full article ">Figure 9
<p>Geochemical variation crossing alteration zones from unaltered rock (<b>left</b>) to altered rock (<b>right</b>). Symbols are the same as in <a href="#minerals-14-00772-f006" class="html-fig">Figure 6</a>.</p> Full article ">
14 pages, 3745 KiB  
Article
Discrimination of Muscovitisation Processes Using a Modified Quartz–Feldspar Diagram: Application to Beauvoir Greisens
by Michel Cathelineau and Zia Steven Kahou
Minerals 2024, 14(8), 746; https://doi.org/10.3390/min14080746 - 25 Jul 2024
Viewed by 766
Abstract
Alteration in greisen-type granites develops through the progressive replacement of feldspars by potassic micas. Under the name ‘greisen’, quartz–muscovite assemblages display differences and include a variety of facies with variable relative proportions of quartz and muscovite. In principle, feldspar conversion to muscovite is [...] Read more.
Alteration in greisen-type granites develops through the progressive replacement of feldspars by potassic micas. Under the name ‘greisen’, quartz–muscovite assemblages display differences and include a variety of facies with variable relative proportions of quartz and muscovite. In principle, feldspar conversion to muscovite is written usually considering constant aluminium, and should result in a modal proportion of six quartz plus one muscovite. In Beauvoir greisens, which result from albite-rich granite, the relative proportion of quartz–muscovite is in favour of muscovite. Such a balance results from a reaction that implies imputs of potassium and aluminium, thus different from the classic one. The Q’-F’ diagram provides a graphical solution for discriminating between reaction paths. A representative series of greisen data from the literature is compared in this diagram: Beauvoir B1 unit, Cligga Head, Cinovec, Panasqueira, Zhengchong, and Hoggar. Full article
(This article belongs to the Special Issue Mineral Chemistry of Granitoids: Constraints on Crystallization Conditions and Petrological Evolution)
►▼ Show Figures

Figure 1

Figure 1
<p>Location of the Beauvoir granite in the French Massif Central (inset) and location of the three studied drill holes (orange circles) from the Imerys 2022 campaign (PER N, C and S), and of the GPF deep drill hole.</p> Full article ">Figure 2
<p>Principle of using the Q’-F’ diagram with the location of the main rock-forming minerals and the main alteration trend. Qtz: quartz; Kln: kaolinite; Toz: topaz; Lpd: lepidolite; Ab: albite; Ksp: K-feldspar; E (square): eutectic of the granite system by [<a href="#B33-minerals-14-00746" class="html-bibr">33</a>]. Diff. granites: differentiated granite field.</p> Full article ">Figure 3
<p>Petrography of the Beauvoir granite and related greisen from two samples collected from a drill hole realised in the central part of the Beauvoir quarry by Imerys (see <a href="#minerals-14-00746-t001" class="html-table">Table 1</a> for whole-rock analyses). (<b>a</b>,<b>c</b>) fresh granite at 52 m depth, macroscopic view and corresponding thin section under crossed Nichols: coloured laths are lepidolites (Lpd), albite (Ab) is visible as elongated thin laths, and quartz (Qtz); (<b>b</b>,<b>d</b>) greisen at 117 m depth and corresponding thin section under crossed Nichols: albite is entirely replaced by fine-grained muscovite (Mu) and a part of the lepidolite is still visible as well as magmatic quartz. Fine-grained quartz is associated with fine-grained muscovite.</p> Full article ">Figure 4
<p>The Q’-F’ diagram applied to the Beauvoir granite to greisen series: in red, the reference samples are characterised by petrography and quantitative mineralogy; labels of red data points refer to the samples from <a href="#minerals-14-00746-t001" class="html-table">Table 1</a> (drill holes PER C and S (centre and south), numbers: depth in meter); and in green, the data for drill cores from the northern area of the quarry (PER North). The GPF data, in blue circles, are from [<a href="#B16-minerals-14-00746" class="html-bibr">16</a>]. Lpd: lepidolite population from Beauvoir after [<a href="#B35-minerals-14-00746" class="html-bibr">35</a>]). Ab: albite’ Tpz: topaz; Qtz: quartz; Lpd: lepidolite; and Mu: muscovite. Lepidolite and muscovite analyses from [<a href="#B34-minerals-14-00746" class="html-bibr">34</a>]. The blue arrows indicate enrichments in micas.</p> Full article ">Figure 5
<p>The Q’-F’ diagram applied to the Panasqueira granite to greisen series: in red, the reference samples characterised in petrography and quantitative mineralogy from Beauvoir; in orange and yellow (data noted a and b), respectively, from [<a href="#B6-minerals-14-00746" class="html-bibr">6</a>,<a href="#B36-minerals-14-00746" class="html-bibr">36</a>] compiled in Marignac et al. [<a href="#B6-minerals-14-00746" class="html-bibr">6</a>], and in blue (data noted c from [<a href="#B20-minerals-14-00746" class="html-bibr">20</a>]). Trend I corresponds to quartz–mica development, and trend II corresponds to quartz loss and further mica enrichment. Micas are indicated by triangles using the same colours as whole rock from the same two references (micas from greisenised G4 granite (noted a) [<a href="#B6-minerals-14-00746" class="html-bibr">6</a>]; micas from cupola greisen [<a href="#B20-minerals-14-00746" class="html-bibr">20</a>] (noted c)).</p> Full article ">Figure 6
<p>The Q’-F’ diagram applied to the Cligga Head (CH, data from [<a href="#B9-minerals-14-00746" class="html-bibr">9</a>]) and Cinovec (C, data from [<a href="#B6-minerals-14-00746" class="html-bibr">6</a>,<a href="#B7-minerals-14-00746" class="html-bibr">7</a>,<a href="#B25-minerals-14-00746" class="html-bibr">25</a>]) granite to greisen series. The trend for Beauvoir whole-rock analyses is red (in pink, Beauvoir (noted B) lepidolite (Lpd)). Muscovite data are sourced from the same literature references as for the whole-rock analyses (Znw: zinnwaldite from Cinovec [<a href="#B8-minerals-14-00746" class="html-bibr">8</a>]; Mu: muscovites from Cligga Head [<a href="#B9-minerals-14-00746" class="html-bibr">9</a>]).</p> Full article ">Figure 7
<p>The Q’-F’ diagram applied to the Zengchong (China, data from [<a href="#B21-minerals-14-00746" class="html-bibr">21</a>] in yellow) and Hoggar (in grey, data from [<a href="#B22-minerals-14-00746" class="html-bibr">22</a>]) granite to greisen series. Yellow stars correspond to mica analyses from [<a href="#B21-minerals-14-00746" class="html-bibr">21</a>] for Zenchong greisens. In red are the Beauvoir data points and their reference line for comparison.</p> Full article ">Figure 8
<p>The Q’-F’ diagram with the main alteration trends depending on the mobility of aluminium with three vectors: A: at constant Si (Cst Si); B: with the addition of one Al<sup>3+</sup>, consisting of a combination of A (constant Si) and C (at constant Al); and additional processes such as quartz precipitation (D) or quartz dissolution and replacement by micas (E). *: Pseudo-greisens as defined by [<a href="#B6-minerals-14-00746" class="html-bibr">6</a>,<a href="#B22-minerals-14-00746" class="html-bibr">22</a>] as silicified granite, then dequartzified partially with quartz replacement by muscovite. n.f. Mu: newly formed muscovite; Qtz: quartz; and Lpd: lepidolite.</p> Full article ">Figure 9
<p>Summary of the main mineral reactions and transformations related to the examined greisen types. The main element supplies needed for the transformations are put forward. Zwd: zinnwaldite; Mu: muscovite; Mu(Zwd) muscovite–zinnwaldite series; Tpz: topaz; Qtz: quartz; and Fl: fluorite. Data have been simplified and summarised from the literature, except Beauvoir (Cinovec [<a href="#B6-minerals-14-00746" class="html-bibr">6</a>,<a href="#B7-minerals-14-00746" class="html-bibr">7</a>], Cligga Head [<a href="#B9-minerals-14-00746" class="html-bibr">9</a>], Panasqueira [<a href="#B5-minerals-14-00746" class="html-bibr">5</a>,<a href="#B20-minerals-14-00746" class="html-bibr">20</a>], and Hoggar [<a href="#B22-minerals-14-00746" class="html-bibr">22</a>]).</p> Full article ">
19 pages, 5698 KiB  
Article
Mesoproterozoic (ca. 1.3 Ga) A-Type Granites on the Northern Margin of the North China Craton: Response to Break-Up of the Columbia Supercontinent
by Bo Liu, Shengkai Jin, Guanghao Tian, Liyang Li, Yueqiang Qin, Zhiyuan Xie, Ming Ma and Jiale Yin
Minerals 2024, 14(6), 622; https://doi.org/10.3390/min14060622 - 18 Jun 2024
Viewed by 963
Abstract
Mesoproterozoic (ca. 1.3 Ga) magmatism in the North China Craton (NCC) was dominated by mafic intrusions (dolerite sills) with lesser amounts of granitic magmatism, but our lack of knowledge of this magmatism hinders our understanding of the evolution of the NCC during this [...] Read more.
Mesoproterozoic (ca. 1.3 Ga) magmatism in the North China Craton (NCC) was dominated by mafic intrusions (dolerite sills) with lesser amounts of granitic magmatism, but our lack of knowledge of this magmatism hinders our understanding of the evolution of the NCC during this period. This study investigated porphyritic granites from the Huade–Kangbao area on the northern margin of the NCC. Zircon dating indicates the porphyritic granites were intruded during the Mesoproterozoic between 1285.4 ± 2.6 and 1278.6 ± 6.1 Ma. The granites have high silica contents (SiO2 = 63.10–73.73 wt.%), exhibit alkali enrichment (total alkalis = 7.71–8.79 wt.%), are peraluminous, and can be classified as weakly peraluminous A2-type granites. The granites have negative Eu anomalies (δEu = 0.14–0.44), enrichments in large-ion lithophile elements (LILEs; e.g., K, Rb, Th, and U), and depletions in high-field-strength elements (HFSEs; e.g., Nb, Ta, and Ti). εHf(t) values range from –6.43 to +2.41, with tDM2 ages of 1905–2462 Ma, suggesting the magmas were derived by partial melting of ancient crustal material. The geochronological and geochemical data, and regional geological features, indicate the Mesoproterozoic porphyritic granites from the northern margin of the NCC formed in an intraplate tectonic setting during continental extension and rifting, which represents the response of the NCC to the break-up of the Columbia supercontinent. Full article
(This article belongs to the Special Issue Mineral Chemistry of Granitoids: Constraints on Crystallization Conditions and Petrological Evolution)
►▼ Show Figures

Figure 1

Figure 1
<p>Schematic tectonic map of the NCC (modified after Zhao et al., 2001 [<a href="#B24-minerals-14-00622" class="html-bibr">24</a>]). Dengfeng (DF), Fuping (FP), Hengshan (HS), Huaian (HA), Lüliang (LL), Northern Hebei (NH), Taihua (TH), Wutai (WT), Zanghuang (ZH), and Zhongtiao (ZT).</p> Full article ">Figure 2
<p>Simplified geologic map of the Huade area, Inner Mongolia.</p> Full article ">Figure 3
<p>Representative field and photomicrographs of the Mesoproterozoic intrusions. (<b>a</b>) field characteristics of Xiaoyingtu intrusion; (<b>b</b>) pluton intruded into the strata of the Paleoproterozoic era Huade Group; (<b>c</b>) characteristics of medium-fine grained porphyritic biotite monzogranite granite hand specimen characteristics; (<b>d</b>) gray-black diorite inclusion; (<b>e</b>) medium-fine grained porphyritic biotite monzogranite; (<b>f</b>) porphyritic biotite syenogranite; (<b>g</b>) biotite syenogranite (orthogonal polarization); (<b>h</b>) medium-fine grained porphyritic biotite syenogranite (orthogonal polarization); (<b>i</b>) fine-grained porphyritic biotite monzogranite (orthogonal polarization).</p> Full article ">Figure 4
<p>Cathode luminescence images of representative zircons from the Mesoproterozoic granites in the study area.</p> Full article ">Figure 5
<p>LA-ICP-MS zircon U-Pb concordia diagrams of the Mesoproterozoic granite samples in the study area.</p> Full article ">Figure 6
<p>TAS (total-alkali-SiO<sub>2</sub>) diagram (<b>a</b>), after Middlemost,1994 [<a href="#B29-minerals-14-00622" class="html-bibr">29</a>]), A/CNK-A/NK diagram (<b>b</b>), after Maniar and Piccoli, 1989 [<a href="#B30-minerals-14-00622" class="html-bibr">30</a>]), SiO<sub>2</sub>-FeO/(FeO + MgO) diagram (<b>c</b>), after Frost et al., 2001 [<a href="#B31-minerals-14-00622" class="html-bibr">31</a>]), SiO<sub>2</sub>-K<sub>2</sub>O covariant diagram (<b>d</b>), after Peccerillo and Taylor, 1976 [<a href="#B32-minerals-14-00622" class="html-bibr">32</a>]). Literature data from Zhang Shuanhong, 2014 [<a href="#B33-minerals-14-00622" class="html-bibr">33</a>]; Meng Baohang, 2016 [<a href="#B34-minerals-14-00622" class="html-bibr">34</a>]; Phase Vibration Group, 2020 [<a href="#B14-minerals-14-00622" class="html-bibr">14</a>].</p> Full article ">Figure 7
<p>Chondrite-normalized REE patterns and (<b>a</b>) a primitive mantle-normalized multi-element diagram (<b>b</b>) of the Mesoproterozoic granites in the study area; standard reference values of chondrites and primitive mantle are from Sun and McDonough, 1989 [<a href="#B35-minerals-14-00622" class="html-bibr">35</a>]. Literature data from Zhang Shuanhong, 2014 [<a href="#B33-minerals-14-00622" class="html-bibr">33</a>]; Meng Baohang, 2016 [<a href="#B34-minerals-14-00622" class="html-bibr">34</a>]; Phase Vibration Group, 2020 [<a href="#B14-minerals-14-00622" class="html-bibr">14</a>].</p> Full article ">Figure 8
<p>Correlation between Hf isotopic compositions and crystallization ages of porphyritic biotite monzogranite.</p> Full article ">Figure 9
<p>Classification diagrams for the genetic types of Mesoproterozoic granites in the study area: (<b>a</b>) 10,000 Ga/Al versus Ce; (<b>b</b>) 10,000 Ga/Al versus Zr; (<b>c</b>) 10,000 Ga/Al versus K<sub>2</sub>O/MgO; (<b>d</b>) (Zr + Nb + Ce + Y) versus TFeO/MgO; (<b>e</b>) Nb-Y-Ce; (<b>f</b>) Nb-Y-3Ga; (<b>a</b>–<b>d</b>) are after Whalen et al. (1987) [<a href="#B37-minerals-14-00622" class="html-bibr">37</a>], and (<b>e</b>) and (<b>f</b>) are after Eby. (1992) [<a href="#B38-minerals-14-00622" class="html-bibr">38</a>]; A-, I- and S-, A-, I- and S-type granite; FG. Differentiated I-type granite area; OGT. Undifferentiated I- and S-type granite area; A1. Non-orogenic granite; A2. Post-orogenic granite.</p> Full article ">Figure 10
<p>C/MF-A/MF diagram of Mesoproterozoic granite in the study area (Alther et al., 2000 [<a href="#B52-minerals-14-00622" class="html-bibr">52</a>]).</p> Full article ">Figure 11
<p>Diagrams of the tectonic environment of trace elements of Mesoproterozoic granite in the study area (after Pearce et al., 1984 [<a href="#B55-minerals-14-00622" class="html-bibr">55</a>]). WPG-within plate granite; ORG- ocean ridge granite; VAG- volcanic arc granite; syn-COLG-syn-collision granite; Post-CEG-post collision granite.</p> Full article ">Figure 12
<p>Reconstruction of the initial Mesoproterozoic fragmentation of the Columbia supercontinent (Modified by Evans, 2011 [<a href="#B59-minerals-14-00622" class="html-bibr">59</a>]).</p> Full article ">
24 pages, 12991 KiB  
Article
Petrogenesis and Geodynamic Evolution of A-Type Granite Bearing Rare Metals Mineralization in Egypt: Insights from Geochemistry and Mineral Chemistry
by Mohamed M. Ghoneim, Ahmed E. Abdel Gawad, Hanaa A. El-Dokouny, Maher Dawoud, Elena G. Panova, Mai A. El-Lithy and Abdelhalim S. Mahmoud
Minerals 2024, 14(6), 583; https://doi.org/10.3390/min14060583 - 31 May 2024
Viewed by 1237
Abstract
During the Late Precambrian, the North Eastern Desert of Egypt underwent significant crustal evolution in a tectonic environment characterized by strong extension. The Neoproterozoic alkali feldspar granite found in the Homret El Gergab area is a part of the Arabian Nubian Shield and [...] Read more.
During the Late Precambrian, the North Eastern Desert of Egypt underwent significant crustal evolution in a tectonic environment characterized by strong extension. The Neoproterozoic alkali feldspar granite found in the Homret El Gergab area is a part of the Arabian Nubian Shield and hosts significant rare metal mineralization, including thorite, uranothorite, columbite, zircon, monazite, and xenotime, as well as pyrite, rutile, and ilmenite. The geochemical characteristics of the investigated granite reveal highly fractionated peraluminous, calc–alkaline affinity, A-type granite, and post-collision geochemical signatures, which are emplaced under an extensional regime of within-plate environments. It has elevated concentrations of Rb, Zr, Ba, Y, Nb, Th, and U. The zircon saturation temperature ranges from 753 °C to 766 °C. The formation of alkali feldspar rare metal granite was affected by extreme fractionation and fluid interactions at shallow crustal levels. The continental crust underwent extension, causing the mantle and crust to rise, stretch, and become thinner. This process allows basaltic magma from the mantle to be injected into the continental crust. Heat and volatiles were transferred from these basaltic bodies to the lower continental crust. This process enriched and partially melted the materials in the lower crust. The intrusion of basaltic magma from the mantle into the lower crust led to the formation of A-type granite. Full article
(This article belongs to the Special Issue Mineral Chemistry of Granitoids: Constraints on Crystallization Conditions and Petrological Evolution)
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Figure 1

Figure 1
<p>(<b>a</b>) Geologic map showing the Arabian Nubian Sheild (ANS). (<b>b</b>) Geological map showing the distribution of the Neoproterozoic basement rocks in the Eastern Desert, Egypt [<a href="#B2-minerals-14-00583" class="html-bibr">2</a>].</p> Full article ">Figure 2
<p>Geologic map of Homret El Gergab, North Eastern Desert, Egypt, modified after Abd El-Hadi [<a href="#B22-minerals-14-00583" class="html-bibr">22</a>].</p> Full article ">Figure 3
<p>(<b>a</b>) Quartz vein (Qz) cutting the Dokhan Volcanics (DV). (<b>b</b>) Sharp intrusive contact between the alkali feldspar granite (Gr) and Dokhan Volcanics (DV). (<b>c</b>) Exfoliation in alkali feldspar granite, (<b>d</b>,<b>e</b>). Open cut in granite for prospecting feldspars. (<b>f</b>) Distribution of alkali feldspar granite at Wadi Abu Masananah.</p> Full article ">Figure 4
<p>Photomicrographs of the studied alkali feldspar granite at Homret El Gergab, North Eastern Desert of Egypt, clarifying that (<b>a</b>) flame and patchy perthites are associated with antiperthite; (<b>b</b>) perthite encloses plagioclase; (<b>c</b>) biotite is highly altered to ferrichlorite and is associated with quartz; (<b>d</b>) fine muscovite flacks are associated with quartz; (<b>e</b>) quartz encloses euhedral zircon crystal; and (<b>f</b>) zircon is enclosed in iron oxides. Abbreviations: Per, perthite; Ant, antiperthite; Plg, plagioclase; Bt, Biotite; Qz, quartz; Mus, muscovite; Kfs, K-feldspar; Zrn, zircon; Irx, iron oxide.</p> Full article ">Figure 5
<p>Harker variation diagrams illustrate the distributions of major oxides and trace elements in relation to silica in the studied granite.</p> Full article ">Figure 6
<p>Geochemical discrimination diagrams present the nomenclature of the studied granite. (<b>a</b>) Ternary An–Ab–Or normative diagram by Barker [<a href="#B23-minerals-14-00583" class="html-bibr">23</a>]. (<b>b</b>) Binary diagram shows the total alkalis versus silica, according to Middlemost [<a href="#B24-minerals-14-00583" class="html-bibr">24</a>].</p> Full article ">Figure 7
<p>Normalized multi-element pattern according to Sun and McDonough [<a href="#B25-minerals-14-00583" class="html-bibr">25</a>] of the studied granite.</p> Full article ">Figure 8
<p>Histograms showing the concentrations of U and Th in the studied granitic samples from Homret El Gergab, North Eastern Desert, Egypt.</p> Full article ">Figure 9
<p>Back-scattered images (BSE) of radioactive minerals associated with other accessory minerals from alkali feldspar granite, Homret El Gergab, North Eastern Desert, Egypt. (<b>a</b>) Fine-grained uranothorite is associated with monazite and is enclosed in feldspar. (<b>b</b>) Fine-grained xenotime and thorite are associated with rutile. (<b>c</b>) Fine-grained xenotime and thorite occur along the rims of zircon. (<b>d</b>) Thin films of thorite occur along the periphery of zircon. (<b>e</b>) Thorite and zircon are enclosed in biotite. (<b>f</b>) Columbite crystals are enclosed in quartz. (<b>g</b>) Highly deformed columbite crystals are enclosed in K-feldspar. (<b>h</b>) Large zircon crystals enclose microinclusions of columbite. Abbreviations: uthr, uranothorite; thr, thorite; Zrn, zircon; Mnz, monazite; Xtm, xenotime; Col, columbite; Rt, rutile; Qz, quartz; Ab, Albite; Kfs, K-feldspar; Bt, Biotite.</p> Full article ">Figure 10
<p>Back-scattered images (BSE) of Zr and REE minerals associated with other accessories from alkali feldspar granite, Homret El Gergab, North Eastern Desert, Egypt. (<b>a</b>) Zoned zircon crystals are enclosed in feldspar. (<b>b</b>) Fine-grained monazite and zircon are enclosed in feldspar. (<b>c</b>) Xenotime is overgrown along the rims of zircon. (<b>d</b>) Fine-grained xenotime is adjacent to zircon. (<b>e</b>) Hematite is along the periphery of monazite. (<b>f</b>) Quartz encloses monazite. (<b>g</b>) Pyrite encloses rutile. (<b>h</b>) Quartz encloses rutile. Abbreviations: Zrn, zircon; Mnz, monazite; Xtm, xenotime; Rt, rutile; Hem, hematite; Qz, quartz; Ab, Albite; Kfs, K-feldspar.</p> Full article ">Figure 11
<p>Magma-type discrimination diagrams of the studied granite. (<b>a</b>) Binary molar Al<sub>2</sub>O<sub>3</sub>/(Na<sub>2</sub>O + K<sub>2</sub>O) versus Al<sub>2</sub>O<sub>3</sub>/(CaO + Na<sub>2</sub>O + K<sub>2</sub>O) diagram of Maniar and Piccoli [<a href="#B30-minerals-14-00583" class="html-bibr">30</a>]. (<b>b</b>) Binary K<sub>2</sub>O versus SiO<sub>2</sub> diagram of Rickwood [<a href="#B31-minerals-14-00583" class="html-bibr">31</a>].</p> Full article ">Figure 12
<p>Tectonic setting discrimination diagrams of the studied granite. (<b>a</b>) Binary Rb versus (Y + Nb) diagram of Pearce et al. [<a href="#B32-minerals-14-00583" class="html-bibr">32</a>]. (<b>b</b>) Binary Nb versus Y diagram of Pearce et al. [<a href="#B32-minerals-14-00583" class="html-bibr">32</a>]. (<b>c</b>) Binary discrimination K<sub>2</sub>O/MgO versus 10,000*Ga/Al diagram of Whalen et al. [<a href="#B33-minerals-14-00583" class="html-bibr">33</a>]. (<b>d</b>) Binary discrimination Nb versus 10,000*Ga/Al diagram of Whalen et al. [<a href="#B33-minerals-14-00583" class="html-bibr">33</a>].</p> Full article ">Figure 13
<p>Petrogenesis discrimination diagrams show the distribution of the analyzed alkali feldspar granite samples. (<b>a</b>) Binary K<sub>2</sub>O versus Rb diagram, where MT refers to the magmatic trend and PH refers to the pegmatitic hydrothermal trend, according to Shaw [<a href="#B40-minerals-14-00583" class="html-bibr">40</a>]. The shaded area illustrates the field of the Ras ed Dome ring complex, Sudan, according to O’Halloran [<a href="#B37-minerals-14-00583" class="html-bibr">37</a>]. (<b>b</b>) Binary Rb versus Sr diagram. (<b>c</b>) Binary Ba versus Rb diagram of Mason [<a href="#B42-minerals-14-00583" class="html-bibr">42</a>].</p> Full article ">Figure 14
<p>Simplified geodynamic model for the origin of the Homret El Gergab alkali feldspar granite modified after Tavakoli et al. [<a href="#B59-minerals-14-00583" class="html-bibr">59</a>].</p> Full article ">
20 pages, 9159 KiB  
Article
Petrogenesis of the Newly Discovered Neoproterozoic Adakitic Rock in Bure Area, Western Ethiopia Shield: Implication for the Pan-African Tectonic Evolution
by Junsheng Jiang, Wenshuai Xiang, Peng Hu, Yulin Li, Fafu Wu, Guoping Zeng, Xinran Guo, Zicheng Zhang and Yang Bai
Minerals 2024, 14(4), 408; https://doi.org/10.3390/min14040408 - 16 Apr 2024
Cited by 1 | Viewed by 1056
Abstract
The Neoproterozoic Bure adakitic rock in the western Ethiopia shield is a newly discovered magmatic rock type. However, the physicochemical conditions during its formation, and its source characteristics are still not clear, restricting a full understanding of its petrogenesis and geodynamic evolution. In [...] Read more.
The Neoproterozoic Bure adakitic rock in the western Ethiopia shield is a newly discovered magmatic rock type. However, the physicochemical conditions during its formation, and its source characteristics are still not clear, restricting a full understanding of its petrogenesis and geodynamic evolution. In this study, in order to shed light on the physicochemical conditions during rock formation and provide further constraints on the petrogenesis of the Bure adakitic rock, we conduct electron microprobe analysis on K-feldspar, plagioclase, and biotite. Additionally, we investigate the trace elements and Hf isotopes of zircon, and the Sr-Nd isotopes of the whole rock. The results show that the K-feldspar is orthoclase (Or = 89.08~96.37), the plagioclase is oligoclase (Ab = 74.63~85.99), and the biotite is magnesio-biotite. Based on the biotite analysis results, we calculate that the pressure during rock formation was 1.75~2.81 kbar (average value of 2.09 kbar), representing a depth of approximately 6.39~10.2 km (average value of 7.60 km). The zircon thermometer yields a crystallization temperature of 659~814 °C. Most of the (Ce/Ce*)D values in the zircons plotted above the Ni-NiO oxygen buffer pair, and the calculated magmatic oxygen fugacity (logfO2) values vary from −18.5 to −4.9, revealing a relatively high magma oxygen fugacity. The uniform contents of FeO, MgO, and K2O in the biotite suggest a crustal magma source for the Bure adakitic rock. The relatively low (87Sr/86Sr)i values of 0.70088 to 0.70275, positive εNd(t) values of 3.26 to 7.28, together with the positive εHf(t) values of 7.64~12.99, suggest that the magma was sourced from a Neoproterozoic juvenile crust, with no discernable involvement of a pre-Neoproterozoic continental crust, which is coeval with early magmatic stages in the Arabian Nubian Shield elsewhere. Additionally, the mean Nd model ages demonstrate an increasing trend from the northern parts (Egypt, Sudan, Afif terrane of Arabia, and Eritrea and northern Ethiopia; 0.87 Ga) to the central parts (Western Ethiopia shield; 1.03 Ga) and southern parts (Southern Ethiopia Shield, 1.13 Ga; Kenya, 1.2 Ga) of the East African Orogen, which indicate an increasing contribution of pre-Pan-African crust towards the southern part of the East African Orogen. Based on the negative correlation between MgO and Al2O3 in the biotite, together with the Lu/Hf-Y and Yb-Y results of the zircon, we infer that the Bure adakitic rock was formed in an arc–arc collision orogenic environment. Combining this inference with the whole rock geochemistry and U-Pb age of the Bure adakitic rock, we further propose that the rock is the product of thickened juvenile crust melting triggered by the Neoproterozoic Pan-African Orogeny. Full article
(This article belongs to the Special Issue Mineral Chemistry of Granitoids: Constraints on Crystallization Conditions and Petrological Evolution)
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<p>Geological map of the Arabian-Nubian Shield, northeast Africa (after [<a href="#B14-minerals-14-00408" class="html-bibr">14</a>]).</p> Full article ">Figure 2
<p>Sketch of the regional geology of the western Ethiopian terrain (after [<a href="#B15-minerals-14-00408" class="html-bibr">15</a>]).</p> Full article ">Figure 3
<p>Hand specimen photograph (<b>a</b>) and microphotograph (<b>b</b>) for the Bure adakitic rock. Qtz—quartz; Bt—biotite; Kfs—K-feldspar.</p> Full article ">Figure 4
<p>Ternary classification diagram for feldspar (<b>a</b>), [<a href="#B36-minerals-14-00408" class="html-bibr">36</a>]); Mg–(Al<sup>Ⅵ</sup> + Fe<sup>3+</sup> + Ti)–(Fe<sup>2+</sup> + Mn) classification diagram for biotite (<b>b</b>), [<a href="#B37-minerals-14-00408" class="html-bibr">37</a>]).</p> Full article ">Figure 5
<p>Electron microprobe line profile analysis of K-feldspar (<b>a</b>,<b>b</b>), plagioclase (<b>c</b>,<b>d</b>) and biotite (<b>e</b>,<b>f</b>) for the Bure adakitic rock.</p> Full article ">Figure 6
<p>Diagram of the chemical variation of Al<sub>2</sub>O<sub>3</sub> vs. MgO in the biotite.</p> Full article ">Figure 7
<p>Chondrite-normalized REE patterns (<b>a</b>) and Ce/Ce* vs. Sm<sub>N</sub>/La<sub>N</sub> (<b>b</b>); [<a href="#B41-minerals-14-00408" class="html-bibr">41</a>]). The Chondrite data for the normalization and plotting are from [<a href="#B46-minerals-14-00408" class="html-bibr">46</a>].</p> Full article ">Figure 8
<p>Diagrams of Hf (<b>a</b>) and Sr-Nd isotopes (<b>b</b>) for the Bure adakitic rock. Zircon Hf isotope-age data obtained from the Arabian Nubian Shield [<a href="#B51-minerals-14-00408" class="html-bibr">51</a>]; Mozambique Belt [<a href="#B52-minerals-14-00408" class="html-bibr">52</a>]; ranges for depleted mantle (DM), chondritic uniform reservoir (CHUR), and juvenile crust from Griffin et al. [<a href="#B53-minerals-14-00408" class="html-bibr">53</a>]. Sr-Nd isotopic data of the Depleted Mantle [<a href="#B54-minerals-14-00408" class="html-bibr">54</a>] and the Arabian Nubian Shield [<a href="#B10-minerals-14-00408" class="html-bibr">10</a>,<a href="#B28-minerals-14-00408" class="html-bibr">28</a>,<a href="#B55-minerals-14-00408" class="html-bibr">55</a>].</p> Full article ">Figure 9
<p>Correlative diagram between biotite composition and oxygen buffer-reagents [<a href="#B57-minerals-14-00408" class="html-bibr">57</a>].</p> Full article ">Figure 10
<p>(Ce/Ce*)<sub>D</sub> of the zircons vs. 10,000/T (<b>a</b>); [<a href="#B58-minerals-14-00408" class="html-bibr">58</a>]) and log<span class="html-italic">f</span>O<sub>2</sub> vs. T (<b>b</b>); [<a href="#B59-minerals-14-00408" class="html-bibr">59</a>]) diagrams for the Bure adakitic rock.</p> Full article ">Figure 11
<p>MgO–FeO–Al<sub>2</sub>O<sub>3</sub> discrimination diagram of the tectonic setting (<b>a</b>); [<a href="#B66-minerals-14-00408" class="html-bibr">66</a>]) and TFeO/(TFeO + MgO) vs. MgO diagram (<b>b</b>); [<a href="#B67-minerals-14-00408" class="html-bibr">67</a>]) of biotite. A: anorogenic alkaline suites; C: calc-alkaline orogenic suites; P: peraluminous suites; C: crustal source; M: mixing source between crust and mantle; M: mantle source.</p> Full article ">Figure 12
<p>The mean Nd-model ages of the EAO in Africa [<a href="#B22-minerals-14-00408" class="html-bibr">22</a>]. Eg—Egypt; Su—Sudan; As—Arabian Shield; En—Eritrea and northern Ethiopia; SES—Southern Ethiopia Shield; K—Kenya.</p> Full article ">Figure 13
<p>Lu/Hf vs. Y (<b>a</b>) and Yb vs. Y (<b>b</b>) diagrams of zircons [<a href="#B69-minerals-14-00408" class="html-bibr">69</a>] for the Bure adakitic rock. N-MORB: normal mid-ocean ridge basalt; VAB: volcanic arc basalt; WPB: within-plate basalt.</p> Full article ">
27 pages, 11292 KiB  
Article
Lithium-, Phosphorus-, and Fluorine-Rich Intrusions and the Phosphate Sequence at Segura (Portugal): A Comparison with Other Hyper-Differentiated Magmas
by Michel Cathelineau, Marie-Christine Boiron, Andreï Lecomte, Ivo Martins, Ícaro Dias da Silva and Antonio Mateus
Minerals 2024, 14(3), 287; https://doi.org/10.3390/min14030287 - 8 Mar 2024
Cited by 1 | Viewed by 1423
Abstract
Near the Segura pluton, hyper-differentiated magmas enriched in F, P, and Li migrated through shallowly dipping fractures, which were sub-perpendicular to the schistosity of the host Neoproterozoic to Lower Cambrian metasedimentary series, to form two swarms of low-plunging aplite–pegmatite dykes. The high enrichment [...] Read more.
Near the Segura pluton, hyper-differentiated magmas enriched in F, P, and Li migrated through shallowly dipping fractures, which were sub-perpendicular to the schistosity of the host Neoproterozoic to Lower Cambrian metasedimentary series, to form two swarms of low-plunging aplite–pegmatite dykes. The high enrichment factors for the fluxing elements (F, P, and Li) compared with peraluminous granites are of the order of 1.5 to 5 and are a consequence of the extraction of low-viscosity magma from the crystallising melt. With magmatic differentiation, increased P and Li activity yielded the crystallisation of the primary amblygonite–montebrasite series and Fe-Mn phosphates. The high activity of sodium during the formation of the albite–topaz assemblage in pegmatites led to the replacement of the primary phosphates by lacroixite. The influx of external, post-magmatic, and Ca-Sr-rich hydrothermal fluids replaced the initial Li-Na phosphates with phosphates of the goyazite–crandallite series and was followed by apatite formation. Dyke emplacement in metasediments took place nearby the main injection site of the muscovite granite, which plausibly occurred during a late major compression event. Full article
(This article belongs to the Special Issue Mineral Chemistry of Granitoids: Constraints on Crystallization Conditions and Petrological Evolution)
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<p>(<b>a</b>) Map of main geological units in Portugal and Spain; CIZ—Central Iberian Zone; OMZ—Ossa–Morena Zone; SPZ—South Portuguese Zone; PLT—Pulo do Lobo Terrane (contiguous to the SW Iberian suture); PTZ—Porto–Tomar Shear Zone; TBCSZ—Tomar–Badajoz–Córdoba Shear Zone. (<b>b</b>) Simplified map of the Góis–Panasqueira–Argemela–Segura Sn-W strip, which is south of the Central Iberian Zone (CIZ, Portugal) according to the 1:500.000 geological map and the SIORMINP mineral occurrence map of the Portuguese Geological Survey (LNEG) [<a href="#B28-minerals-14-00287" class="html-bibr">28</a>]. Different shades of green represent the Beiras Group formations, and the blues the Ordovician–Silurian units defining the upright D3 synclines in this sector of the CIZ NE-SW faults represent late-D3 shear zones that were systematically reactivated in the Alpine orogenic cycle, thus controlling the shapes and disposition of the Cenozoic basins (in orange). The remaining colours represent Cadomian (fuchsia), Ordovician (cherry and dark pink), and Late Variscan (320–300 Ma) granitoids (dark and light orange and light pink). Coloured small circles indicate mineralisation occurrences as in the official SIORMINP catalogue (LNEG). (<b>c</b>) Geological setting of the studied Segura area in the northwestern border of the Segura–Cabeza de Araya Batholith and an indication of the sample location for dykes. The geological map was adapted from the geological maps of Portugal at 1:500,000 [<a href="#B29-minerals-14-00287" class="html-bibr">29</a>]; the coordinate system is WGS 84 29T, UTM (zone 29).</p> Full article ">Figure 2
<p>Outcrops of the aplite–pegmatite dykes and granites in the Segura region. (<b>a</b>) Inner facies of the Cabeza de Araya batholith, with large euhedral cordierite crystals (noted Crd) and predominant biotite; (<b>b</b>) inner rim of the Cabeza de Araya batholith, showing a two-mica coarse-grained facies with local tourmaline and showing large retrogressed cordierite crystals; (<b>c</b>) medium- to-coarse-grained muscovite leucogranite with tourmaline from the outer rim of the Cabeza de Ayara pluton in Segura region, intruding spotted schists of the Beiras Group (BG); (<b>d</b>) low-dipping dyke hosted in BG metasediments in the Cerro Queimado area (see <a href="#minerals-14-00287-f001" class="html-fig">Figure 1</a>b); (<b>e</b>) sub-horizontal dyke intrusive in BG metasediments in the Cerro Queimado area; (<b>f</b>) aplite dyke from the southern area to the southwest of Segura; (<b>g</b>) pegmatite exposure at the level of the river (southwest of the Segura batholith); (<b>h</b>,<b>i</b>) two other views of the dykes intruding on the metasediments, thereby showing geometric arrays due to the forced intrusion on the schists, which open in several directions and fall as enclaves within the magma.</p> Full article ">Figure 3
<p>Textures of the Segura dykes. (<b>a</b>,<b>b</b>) Contact between the aplite and pegmatite in the samples from the northern zone of the Segura batholith (Cerro Queimado). Facies are leucocratic with black dots corresponding to the Nb-Ta oxides (Nb-Ta). The development of pegmatite occurs through the growth of albite (Ab) and quartz (Qtz) as subparallel crystals and minor K-feldspar (Kspar). (<b>c</b>) Macroscopic feature of the tourmaline (To) bearing aplite from the southern zone of the Segura dyke swarm. (<b>d</b>) Pegmatite with comb quartz and albite development.</p> Full article ">Figure 4
<p>Composite micro-XRF chemical maps of aplite and pegmatite dykes. (<b>a</b>) Boundary between aplite and pegmatite showing the growth of albite (in red), quartz (grey), and amblygonite (light yellow) perpendicularly to the boundary, as well as K-feldspar (in orange: Al, K); (<b>b</b>) pegmatite texture with phosphates included in quartz; (<b>c</b>) amblygonite (in green-yellow), albite, K-feldspar, and quartz; (<b>d</b>) same chemical map with the Fe phosphate in violet-blue; (<b>e</b>) amblygonite on both sides of the cavities filled with quartz (black arrow indicates how the cavity has been filled) and apatite (in orange) replaces the K-feldspars; (<b>f</b>) amblygonite as euhedral crystals formed on albite and cemented by quartz and, in orange, apatite filling microfractures. Toz: topaz; Amb: amblygonite; Fe-Mn Ph: eosphorite–childrenite Fe-Mn phosphate series; Kspar: K-feldspar; Ab: albite; Ap: apatite; Qtz: quartz.</p> Full article ">Figure 5
<p>(<b>a</b>) Boundary between aplite and pegmatite (macroscopic photograph), with an indication of the zone mapped in figures (<b>b</b>,<b>c</b>); (<b>b</b>) transmitted light microphotograph of the thick section; (<b>c</b>) chemical micro-XRF map showing amblygonite (yellow) on both sides of the cavity filled with quartz and the Fe-Mn phosphate (in green); (<b>d</b>) magnified detail of zone (<b>c</b>) showing the distribution of the amblygonite formed onto K-feldspars and topaz as inclusions in quartz (in red); (<b>e</b>) microtextures of Li-phosphates (Li-ph) (amblygonite and mixed lacroixite/amblygonite); (<b>f</b>) magnification of the amblygonite/lacroixite at the micron scale; (<b>g</b>,<b>h</b>) crystals of Fe-Mn phosphates (BSE SEM image), showing the euhedral growth bands. Toz: topaz; Li-ph: Li phosphates; Amb: amblygonite; Na-ph: Na-phosphate (lacroixite-dominated); Fe-Mn-Ph: eosphorite–childrenite Fe-Mn phosphate series; Kspar: K-feldspar; Ab: albite; Ap: apatite; Qtz: quartz.</p> Full article ">Figure 6
<p>(<b>a</b>) Amblygonite crystals developed on the edge of a cavity filled with quartz; (<b>b</b>) crandallite and Fe-Mn-rich apatite formed in microfractures; (<b>c</b>) detail of the amblygonite crystal of figure (<b>a</b>); (<b>d</b>) micro-XRF composite chemical map showing the replacement of amblygonite by complex assemblages of phosphates at the boundary between the crystal and feldspars; (<b>e</b>) detail of the complex zone of replacement formed by crandallite and goyazite and later Mn-rich apatite; (<b>f</b>) detail of the growth bands of the goyazite crystals with the earliest bands of crandallite; (<b>g</b>) complex association of phosphates replacing amblygonite. Amblygonite may contain calcium with no clear evidence of the addition of crandallite patches, and apatite is enriched in Fe and Mn; (<b>h</b>) association of the four types of phosphates with mutual replacements, with the same abbreviations as those in <a href="#minerals-14-00287-f004" class="html-fig">Figure 4</a>; Goy: goyazite; Cdl: crandallite; Chd: chidrenite; Lac: lacroixite; Mn-Ap: Mn-rich apatite; Qtz: quartz; and Mu: muscovite.</p> Full article ">Figure 7
<p>Representative Raman spectra of two phosphate series. (<b>a</b>) The eosphorite–childrenite series and (<b>b</b>) the Li phosphate series represented by amblygonite and intermediate phases with a spectrum closer to montebrasite.</p> Full article ">Figure 8
<p>(<b>a</b>) Fe and Mn (apfu) in Fe-Mn phosphates (base P = 1) for three distinct crystals represented by three distinct colors. The figure shows that the amplitude of the Fe-Mn exchange covers the same range in each crystal. (<b>b</b>) Na versus Li (apfu) diagram for the Na-Li (lacroixite) phosphates (montebrasite–amblygonite) series. The intermediate composition corresponds to the partial replacement of the Na-Li-end-members by the Na-end-member. (<b>c</b>) Ca versus the Sr (apfu) plot for the crandallite–goyazite series.</p> Full article ">Figure 9
<p>Na<sub>2</sub>O versus K<sub>2</sub>O diagram for the Segura aplites, pegmatites, and granites. Data are compared with those from the literature as follows: 1: Segura [<a href="#B5-minerals-14-00287" class="html-bibr">5</a>], 2: Argemela [<a href="#B10-minerals-14-00287" class="html-bibr">10</a>], 3: Tres Arroyos [<a href="#B3-minerals-14-00287" class="html-bibr">3</a>], 4: Beauvoir [<a href="#B11-minerals-14-00287" class="html-bibr">11</a>], and 5: Panasqueira [<a href="#B37-minerals-14-00287" class="html-bibr">37</a>]. Enveloppe colors correspond to data point colors.</p> Full article ">Figure 10
<p>Diagram A (=Al – (K+ Na + Ca)) versus B (=Fe+ Mg+ Mn) from [<a href="#B38-minerals-14-00287" class="html-bibr">38</a>] applied to the Segura facies and with a comparison with the reference peraluminous differentiated granites. 1: Segura [<a href="#B5-minerals-14-00287" class="html-bibr">5</a>], 2: Argemela [<a href="#B10-minerals-14-00287" class="html-bibr">10</a>], 3: Tres Arroyos [<a href="#B3-minerals-14-00287" class="html-bibr">3</a>], and 4: Beauvoir [<a href="#B11-minerals-14-00287" class="html-bibr">11</a>]. For Panasqueira, only the envelope is shown.</p> Full article ">Figure 11
<p>CaO versus P<sub>2</sub>O<sub>5</sub> diagram applied to the same series of granites as in <a href="#minerals-14-00287-f009" class="html-fig">Figure 9</a>. It shows the increased phosphorus content of the Segura aplites and pegmatites and the shift from the apatite line, which is high in the Segura and Argemela magmas compared with the other P-rich magmas: 1: Segura [<a href="#B5-minerals-14-00287" class="html-bibr">5</a>], 2: Argemela [<a href="#B10-minerals-14-00287" class="html-bibr">10</a>], 3: Tres Arroyos [<a href="#B3-minerals-14-00287" class="html-bibr">3</a>], 4: Beauvoir [<a href="#B11-minerals-14-00287" class="html-bibr">11</a>], and 5: Panasqueira [<a href="#B37-minerals-14-00287" class="html-bibr">37</a>].</p> Full article ">Figure 12
<p>F versus P<sub>2</sub>O<sub>5</sub> diagram showing the increased phosphorus content of the Segura aplites and pegmatites (red symbols) as a function of fluorine content. Reference lines in the direction of the phosphate end-members are reported. 1: Segura: [<a href="#B5-minerals-14-00287" class="html-bibr">5</a>], 2: Argemela [<a href="#B10-minerals-14-00287" class="html-bibr">10</a>], and 3: Tres Arroyos [<a href="#B3-minerals-14-00287" class="html-bibr">3</a>].</p> Full article ">Figure 13
<p>P<sub>2</sub>O<sub>5</sub> versus the aluminium saturation index (ASI = [Al/(Ca − 1.67P + Na + K)]) diagram. 1: Segura [<a href="#B5-minerals-14-00287" class="html-bibr">5</a>], 2: Argemela [<a href="#B10-minerals-14-00287" class="html-bibr">10</a>], 3: Tres Arroyos [<a href="#B3-minerals-14-00287" class="html-bibr">3</a>], and 4: Beauvoir [<a href="#B11-minerals-14-00287" class="html-bibr">11</a>].</p> Full article ">Figure 14
<p>Schematic representation of the mineralogical evolution of the Segura aplites and pegmatites with the time from the magmatic to hydrothermal stages, especially for the phosphates. Amb: amblygonite, Lac: lacroixite, Cdl: crandallite, and Ap: Apatite.</p> Full article ">Figure 15
<p>(<b>a</b>) Conceptual model of the intrusive dykes (vertical cross-section) in the westernmost sector of the Cabeza de Araya batholith, the intrusion of the muscovite-rich outer facies and dykes in the metasediments. The magma migration pathways are as follows: arrow 1 corresponds to an additional layer of the Cabeza de Araya batholith like the other facies that compose it, with a feeder zone whose centre is located far to the southeast, and arrow 2 to an autonomous magma intrusion that is independent of the initial pathways. (<b>b</b>) Inset in figure (<b>a</b>), with the extraction of a low-viscosity magma migrating through open tension gashes and fractures in the metasediments.</p> Full article ">
17 pages, 5319 KiB  
Article
Zircon U-Pb and Whole-Rock Geochemistry of the Aolunhua Mo-Associated Granitoid Intrusion, Inner Mongolia, NE China
by Hao Li, Xuguang Li, Jiang Xin and Yongqiang Yang
Minerals 2024, 14(3), 226; https://doi.org/10.3390/min14030226 - 23 Feb 2024
Viewed by 1053
Abstract
The Aolunhua Mo deposit is a typical porphyry deposit, which is located in the middle southern section of the Da Hinggan Range metallogenic belt. Here, we report LA-ICP-MS zircon U-Pb age data from the Mo-associated granitoid, together with the element geochemistry of the [...] Read more.
The Aolunhua Mo deposit is a typical porphyry deposit, which is located in the middle southern section of the Da Hinggan Range metallogenic belt. Here, we report LA-ICP-MS zircon U-Pb age data from the Mo-associated granitoid, together with the element geochemistry of the zircons, discussing the source material of the ore-forming rock of the deposit. The zircon data constrain the crystallization age of the granite porphyry as 135.0 ± 1.0 Ma, correlating it with the widespread Yanshanian intermediate–felsic magmatic activity. The Th/U ratio of the zircon is greater than 0.1, with a significant positive Ce anomaly (Ce* = 1.72–188.71) and a negative Eu anomaly (Eu* = 0.05–0.57). The zircons show depleted LREE and enriched HREE patterns, as well as low La and Pr contents, suggesting crystallization from crust-derived magmas. Based on the geology of the ore deposit and the age data, in combination with the regional geodynamic evolution, we infer that the Aolunhua Mo deposit was formed near the peak stage of Sn poly-metallic metallogenesis in the Da Hinggan Range region at around 140 Ma, associated with a tectonic setting, characterized by the transition from compression to extension. Based on a comparison with the newly found Mo deposits along the banks of the Xilamulun River, we propose that the Tianshan–Linxi is an important Mo-metallogenic belt. It also suggests an increased likelihood for the occurrence of Mo along the north bank of the Xilamulun River. Full article
(This article belongs to the Special Issue Mineral Chemistry of Granitoids: Constraints on Crystallization Conditions and Petrological Evolution)
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Graphical abstract

Graphical abstract
Full article ">Figure 1
<p>Simplified tectonic map of the southern Da Hinggan Range and its adjacent areas. Legend: 1—major fault; 2—boundary between countries; 3—fault numbers; 4—porphyry type ore deposits. ① Deep fracture of the north margin of the North China plate. ② Fault of the Xilamulun River. ③ Erenhot – Hegenshan deep fault. ④ Onor–Elunchun fault. ⑤ Derburgan fault. ⑥ Da Hinggan Range Major Fault. ⑦ Nenjiang fault. (<b>A</b>) Location of reginal tectonic of study area; (<b>B</b>) Location in Central Asian Orogenic Belt; (<b>C</b>) Geological map of the Da Hinggan Range; (<b>D</b>) Aolunhua area geological map.</p> Full article ">Figure 2
<p>Occurrence and mineral composition of granite porphyry in the Aolunhua deposit Mineral abbreviations: Qtz—quartz, Kfs—K feldspar, Pl—plagioclase, Bi—biotite. (<b>a</b>) Granite porphyry occurrence sample; (<b>b</b>) Photo under orthogonal polarization of granite showing Pl, Qtz; (<b>c</b>) Photo under orthogonal polarization of granite showing Kfs, Qtz; (<b>d</b>) Photo under orthogonal polarization of granite showing Bt, Pl, Qtz.</p> Full article ">Figure 3
<p>Cathodo-luminescence (CL) image of the representative zircons of the granite porphyries from the Aolunhua Mo deposit. (<b>a</b>) no band; (<b>b</b>) crystalline band; (<b>c</b>) no band; (<b>d</b>) oscillatory band; (<b>e</b>) no band; (<b>f</b>) oscillatory band.</p> Full article ">Figure 4
<p>LA-ICP-MS U-Pb age concordia (<b>a</b>) and the weighted mean age histogram (<b>b</b>) of zircons from fine-grain porphyritic granodiorite (sample AL 03).</p> Full article ">Figure 5
<p>Primitive mantle normalized trace element spider diagrams (<b>a</b>) and the chondrite normalized REE patterns (<b>b</b>) for zircon grains from the Aolunhua granodiorite.</p> Full article ">Figure 6
<p>The A/CNK-A/NK (<b>a</b>) and R1-R2 (<b>b</b>) diagrams for rock samples from the Aolunhua deposit. In (<b>b</b>): 1—mantle differentiation; 2—pre-collisional; 3—post collisional uplift; 4—late orogenic; 5—non-orogenic; 6—syn-collisional; 7—post orogenic.</p> Full article ">Figure 7
<p>The (Yb+Nb)-Rb (<b>a</b>), Y-Nb (<b>b</b>) and Y-Sr/Y (<b>c</b>) diagrams for rock samples from the Aolunhua deposit.</p> Full article ">
20 pages, 9627 KiB  
Article
U-Pb Geochronology, Geochemistry and Geological Significance of the Yongfeng Composite Granitic Pluton in Southern Jiangxi Province
by Yunbiao Zhao, Fan Huang, Denghong Wang, Na Wei, Chenhui Zhao and Ze Liu
Minerals 2023, 13(11), 1457; https://doi.org/10.3390/min13111457 - 20 Nov 2023
Viewed by 1255
Abstract
The Yongfeng composite granitic pluton, located in the southern section of the Nanling area, is composed of the Yongfeng and Longshi biotite monzonitic granites. In order to reveal the genesis of this composite granitic pluton and its relationship with mineralization, this study conducted [...] Read more.
The Yongfeng composite granitic pluton, located in the southern section of the Nanling area, is composed of the Yongfeng and Longshi biotite monzonitic granites. In order to reveal the genesis of this composite granitic pluton and its relationship with mineralization, this study conducted zircon U-Pb dating, whole-rock major and trace element analysis, and biotite electron probe analysis. The results show that the Yongfeng composite granitic pluton is rich in silicon and alkali, weakly peraluminous, and poor in calcium and iron. It shows the enrichment of light rare earth elements and a significant fractionation of light and heavy rare earth elements. It also shows the enrichment of large ion lithophile elements and depletion of Ba, K, P, Eu, and Ti relative to the primitive mantle. The contents of TFe2O3, MgO, CaO, TiO2, and P2O5 are low and decrease with increasing SiO2 content. The Yongfeng composite granitic pluton does not contain alkaline dark minerals. Its average zircon saturation temperature is 776 °C, average TFe2O3/MgO is 4.81, and average Zr + Nb + Ce + Y is 280.6 ppm, which correspond to a highly fractionated I-type granite. The Yongfeng and Longshi granites were respectively formed at 152.0 ± 1.0 Ma–151.3 ± 1.1 Ma and 148.9 ± 1.2 Ma. They were formed in the extensional tectonic setting during the post-orogenic stage, under the control of the breakup or retreat of the backplate after the subduction of the Pacific Plate into the Nanling hinterland. The magmatic system of the Yongfeng composite granitic pluton is characterized by high fractionation, high content of F, high temperature, and low oxygen fugacity, which is conducive to mineralization of Sn, Mo, and fluorite. Full article
(This article belongs to the Special Issue Mineral Chemistry of Granitoids: Constraints on Crystallization Conditions and Petrological Evolution)
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Figure 1
<p>(<b>a</b>) Regional geological sketch of the Yongfeng composite granite pluton (modified according to [<a href="#B14-minerals-13-01457" class="html-bibr">14</a>]); (<b>b</b>) Distribution map of granite in South China (modified according to [<a href="#B15-minerals-13-01457" class="html-bibr">15</a>]).</p> Full article ">Figure 2
<p>Field photos of the Yongfeng composite granitic pluton. (<b>a</b>) reddish medium–coarse grained porphyritic biotite monzonitic granite; (<b>b</b>) grayish white medium–coarse grained porphyritic biotite monzonitic granite.</p> Full article ">Figure 3
<p>Typical petrographic photos of the Yongfeng composite granitic pluton (<b>a</b>,<b>b</b>,<b>d</b>) are orthogonal-polarization micrographs and (<b>c</b>) is a single-polarization micrograph. (Bit-biotite, Cal-calcite, Mic-microcline, Pth-striped feldspar, Ms-muscovite, Qtz-quartz, Pl-plagioclase, Srt-sericite).</p> Full article ">Figure 4
<p>Chondrite-normalized REE patterns for the zircons from the Yongfeng composite granitic pluton (REE data for magmatic and hydrothermal zircons from [<a href="#B19-minerals-13-01457" class="html-bibr">19</a>]; the chondrite normalization values are from [<a href="#B20-minerals-13-01457" class="html-bibr">20</a>]).</p> Full article ">Figure 5
<p>The cathodoluminescence (CL) images of zircons from the Yongfeng composite granitic pluton (the white circle is the analysis location).</p> Full article ">Figure 6
<p>The zircon U-Pb age concordance diagram and weighted average age diagram of the Yongfeng composite granitic pluton (<b>a</b>) YF-1, (<b>b</b>) YF-2, (<b>c</b>) XGml-1; The zircon U-Pb age concordance diagram of (<b>d</b>) XGls-12 and (<b>e</b>) XGyf-1; (<b>f</b>) The weighted average age diagram of XGyf-1.</p> Full article ">Figure 7
<p>ANOR−Q′ diagram (<b>a</b>), SiO<sub>2</sub> − (Na<sub>2</sub>O + K<sub>2</sub>O − CaO) diagram (<b>b</b>), SiO<sub>2</sub> − K<sub>2</sub>O diagram (<b>c</b>), and A/CNK-A/NK diagram (<b>d</b>) of the Yongfeng composite granitic pluton. The data of the Longshi granite, Liangcun granite, Fogang granite, and Nanzhen-Daliangshan-Sansha-Dajing granite are respectively cited from [<a href="#B9-minerals-13-01457" class="html-bibr">9</a>,<a href="#B23-minerals-13-01457" class="html-bibr">23</a>,<a href="#B24-minerals-13-01457" class="html-bibr">24</a>,<a href="#B25-minerals-13-01457" class="html-bibr">25</a>].</p> Full article ">Figure 8
<p>SiO<sub>2</sub> vs. Al<sub>2</sub>O<sub>3</sub> (<b>a</b>), MgO (<b>b</b>), Na<sub>2</sub>O (<b>c</b>), K<sub>2</sub>O (<b>d</b>), TiO<sub>2</sub> (<b>e</b>), CaO (<b>f</b>), P<sub>2</sub>O<sub>5</sub> (<b>g</b>), TFe<sub>2</sub>O<sub>3</sub> (<b>h</b>), and Zr (<b>i</b>) variation diagrams of the Yongfeng composite granitic pluton. The data of the Longshi granite is cited from [<a href="#B9-minerals-13-01457" class="html-bibr">9</a>].</p> Full article ">Figure 9
<p>Chondrite-normalized REE patterns (<b>a</b>) and primitive-mantle-normalized trace element spider diagram (<b>b</b>) of the Yongfeng composite granitic pluton (chondrite and primitive mantle normalizing values from [<a href="#B20-minerals-13-01457" class="html-bibr">20</a>]. The data of the Longshi granite, Liangcun granite, Fogang granite, and Nan-zhen-Daliangshan-Sansha-Dajing granite are respectively cited from [<a href="#B9-minerals-13-01457" class="html-bibr">9</a>,<a href="#B23-minerals-13-01457" class="html-bibr">23</a>,<a href="#B24-minerals-13-01457" class="html-bibr">24</a>,<a href="#B25-minerals-13-01457" class="html-bibr">25</a>].</p> Full article ">Figure 10
<p>(<b>a</b>) (10 × TiO<sub>2</sub>) − FeO − MgO diagram, base map according to [<a href="#B26-minerals-13-01457" class="html-bibr">26</a>]; (<b>b</b>) Mg − (Al<sup>VI</sup> + Fe<sup>3+</sup> + Ti) − (Fe<sup>2+</sup> + Mn) diagram, base map according to [<a href="#B27-minerals-13-01457" class="html-bibr">27</a>] of the biotite from the Yongfeng composite granitic pluton. The data of the Longshi granite is cited from [<a href="#B8-minerals-13-01457" class="html-bibr">8</a>].</p> Full article ">Figure 11
<p>(<b>a</b>) (Zr + Nb + Ce + Y) − (TFe<sub>2</sub>O<sub>3</sub>/MgO) diagram, base map according to [<a href="#B52-minerals-13-01457" class="html-bibr">52</a>]; (<b>b</b>) (Zr + Nb + Ce + Y) − (K<sub>2</sub>O + Na<sub>2</sub>O)/CaO diagram, base map according to [<a href="#B52-minerals-13-01457" class="html-bibr">52</a>]; (<b>c</b>) Rb-Th diagram; (<b>d</b>) Rb-Y diagram of the Yongfeng composite granitic pluton. The data of Longshi granite is cited from [<a href="#B9-minerals-13-01457" class="html-bibr">9</a>].</p> Full article ">Figure 12
<p>(Rb/Sr) − (Rb/Ba) diagram. (<b>a</b>) base map according to [<a href="#B68-minerals-13-01457" class="html-bibr">68</a>]) and (Al<sub>2</sub>O<sub>3</sub> + TFeO + MgO + TiO<sub>2</sub>)-Al<sub>2</sub>O<sub>3</sub>/(TFeO + MgO + TiO<sub>2</sub>); (<b>b</b>) base map according to [<a href="#B69-minerals-13-01457" class="html-bibr">69</a>]) of the Yongfeng composite granitic pluton. The data of the Longshi granite and Liangcun granite are respectively cited from [<a href="#B9-minerals-13-01457" class="html-bibr">9</a>,<a href="#B23-minerals-13-01457" class="html-bibr">23</a>].</p> Full article ">Figure 13
<p>Tectonic setting discrimination diagrams of the Yongfeng composite granitic pluton and Liangcun granite (<b>a</b>–<b>d</b>), with base map according to [<a href="#B75-minerals-13-01457" class="html-bibr">75</a>,<a href="#B76-minerals-13-01457" class="html-bibr">76</a>,<a href="#B77-minerals-13-01457" class="html-bibr">77</a>,<a href="#B78-minerals-13-01457" class="html-bibr">78</a>], respectively. The data of the Longshi granite and Liangcun granite are respectively cited from [<a href="#B9-minerals-13-01457" class="html-bibr">9</a>,<a href="#B23-minerals-13-01457" class="html-bibr">23</a>]).</p> Full article ">
29 pages, 13985 KiB  
Article
Integration of Whole-Rock Geochemistry and Mineral Chemistry Data for the Petrogenesis of A-Type Ring Complex from Gebel El Bakriyah Area, Egypt
by Ahmed A. Abd El-Fatah, Adel A. Surour, Mokhles K. Azer and Ahmed A. Madani
Minerals 2023, 13(10), 1273; https://doi.org/10.3390/min13101273 - 29 Sep 2023
Cited by 2 | Viewed by 1664
Abstract
El Bakriyah Ring Complex (BRC) is a prominent Neoproterozoic post-collisional granite suite in the southern part of the Central Eastern Desert of Egypt. The BRC bears critical materials (F, B, Nb, and Ta) in appreciable amounts either in the form of rare-metals dissemination [...] Read more.
El Bakriyah Ring Complex (BRC) is a prominent Neoproterozoic post-collisional granite suite in the southern part of the Central Eastern Desert of Egypt. The BRC bears critical materials (F, B, Nb, and Ta) in appreciable amounts either in the form of rare-metals dissemination or in the form of fluorite and barite vein mineralization. The complex consists of inner syenogranite and outer alkali feldspar granite that have been emplaced in a Pan-African assemblage made up of granitic country rocks (granodiorite and monzogranite), in addition to post-collisional fresh gabbro as a part of the Arabian-Nubian Shield (ANS) in northeast Africa. Granites of the BRC are characterized by enrichment in silica, alkalis, Rb, Y, Ga, Nb, Ta, Th, and U and depletion in Sr, Ba, and Ti. Geochemical characterization of the BRC indicates that the magma is a crustal melt, which originated from the partial melting of metasedimentary sources. Concentrations of rare-earth elements (REEs) differ in magnitude from the ring complex and its granitic country rocks but they have similar patterns, which are sub-parallel and show LREEs enrichment compared to HREEs. The presence of a negative Eu anomaly in these rocks is related to plagioclase fractionation. The abundance of fluorine (F) in the different granite varieties plays an important role in the existence of a tetrad influence on the behavior of REEs (TE1, 3 = up to 1.15). Geochemical parameters suggest the crystallization of the BRC granite varieties by fractional crystallization and limited assimilation. Mn-columbite and Mn-tantalite are the most abundant rare-metals dissemination in the BRC granite varieties. We present combined field, mineralogical and geochemical data that are in favor of magma originating from a metasedimentary source for the BRC with typical characteristics of A-type granites. Our geodynamic model suggests that the Gebel El Bakriyah area witnessed the Neoproterozoic post-collisional stage of the ANS during its late phase of formation. This stage was characterized by the emplacement of fresh gabbros followed by the syenogranite and alkali-feldspar granite of the BRC into an arc-related assemblage (granodiorite and monzogranite). It is believed that the mantle-derived magma was interplated and then moved upward in the extensional environment to a shallower level in the crust owing to events of lithospheric delamination. This presumably accelerated the processes of partial melting and differentiation of the metasedimentary dominated source (Tonian-Cryogenian) to produce the A-type granites building up the BRC (Ediacaran). Full article
(This article belongs to the Special Issue Mineral Chemistry of Granitoids: Constraints on Crystallization Conditions and Petrological Evolution)
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Figure 1
<p>(<b>a</b>) Location map of the study area. (<b>b</b>) Geological map of the Gebel El Bakriyah area was recently constructed by the present authors [<a href="#B25-minerals-13-01273" class="html-bibr">25</a>].</p> Full article ">Figure 2
<p>Geologic setup and field relationships. (<b>a</b>) General view of the granite varieties forming the El Bakriyah ring complex (BRC); namely syenogranite core (SG) and alkali feldspar granite rim (AFG) non-conformably capped by the Nubian sandstone (NS). (<b>b</b>) The rugged peak of alkali feldspar granite (AFG) capped by Nubian sandstone (NS) and juxtaposing syenogranite (SG). (<b>c</b>) Mineralized fluorite vein (V), with some barite, cross-cutting the alkali feldspar granite (AFG). (<b>d</b>) Excavated pit for the extraction of fluorite and barite. (<b>e</b>) Monzogranite (MG) intruding weathered granodiorite (GR).</p> Full article ">Figure 3
<p>Photomicrographs of Gebel El Bakriyah granitic rocks. (<b>a</b>) Large plagioclase crystal (Pl), microcline (Mic), quartz (Qz), and chlorite (Chl) as primary and secondary constituents of granodiorite, Crossed-Nicols (CN). (<b>b</b>) Alteration of feldspars to sericite (Ser) and occurrence of euhedral terminated zircon in syenogranite, CN. (<b>c</b>) Intergrowths of quartz and K-feldspars to form graphic and granophyric textures in monzogranite, CN. (<b>d</b>) Muscovitization (Mus) of primary biotite in syenogranite, C.N. (<b>e</b>) Coarse hornblende (Hbl) in contact with perthite (Per) in monzogranite, CN. (<b>f</b>) Hornblende crystal (Hbl) surrounded by quartz (Qz) and plagioclase (Pl). Notice that hornblende partially encloses muscovite (Mus) and pethite (Per) in syenogranite, CN. (<b>g</b>) Homogeneous ilmenite (Ilm) extensively altered to titanite (Tnt) reaction rim in granodiorite, CN. (<b>h</b>) Fluorite (Fl) with typical cubic habit enclosing Nb-Ta minerals.</p> Full article ">Figure 4
<p>(<b>a</b>) Nomenclature of the granitic rocks from the Gebel El Bakriyah area using the total alkali-silica (TAS) classification diagram [<a href="#B28-minerals-13-01273" class="html-bibr">28</a>]. (<b>b</b>) Plots of the studied granitic rocks, based on their modal compositions, on the QAP diagram [<a href="#B29-minerals-13-01273" class="html-bibr">29</a>]. (<b>c</b>) Peraluminous nature of the Gebel El Bakriyah younger granites on the A/CNK vs. A/NK diagram [<a href="#B30-minerals-13-01273" class="html-bibr">30</a>].</p> Full article ">Figure 5
<p>Spider diagrams based on trace elements and rare-earth elements (REEs). (<b>a</b>,<b>b</b>) Patterns of chondrite-normalized REEs of the Gebel El Bakriyah area [<a href="#B31-minerals-13-01273" class="html-bibr">31</a>]. (<b>c</b>,<b>d</b>) Patterns of primitive mantle-normalized multi-element variation [<a href="#B32-minerals-13-01273" class="html-bibr">32</a>].</p> Full article ">Figure 6
<p>(<b>a</b>) Composition of the feldspars in Gebel El Bakriyah granitic rocks using the Ab-Or-An ternary diagram of [<a href="#B34-minerals-13-01273" class="html-bibr">34</a>]. (<b>b</b>) The primary origin of biotite is based on the (FeO<sup>t</sup> + MnO)–10*TiO<sub>2</sub>–MgO discrimination diagram of [<a href="#B35-minerals-13-01273" class="html-bibr">35</a>]. (<b>c</b>) Nomenclature of biotite (Fe- and Mg-bearing) using the classification of [<a href="#B36-minerals-13-01273" class="html-bibr">36</a>]. (<b>d</b>) Na-Ca amphibole plots after [<a href="#B37-minerals-13-01273" class="html-bibr">37</a>]. (<b>e</b>) Mn-rich end-members of the Nb-Ta oxides. (<b>f</b>) Chlorite composition in the Gebel El Bakriyah granitic rocks [<a href="#B38-minerals-13-01273" class="html-bibr">38</a>].</p> Full article ">Figure 7
<p>(<b>a</b>) The Ab–Or–Qz normative diagram of the studied granitic rocks [<a href="#B48-minerals-13-01273" class="html-bibr">48</a>] (over a pressure range from 0.5 kbar to 10 kbar of water-saturated melt) [<a href="#B49-minerals-13-01273" class="html-bibr">49</a>]. (<b>b</b>) Plots of amphibole composition indicating crystallization in low oxygen fugacity (low f<sub>O2</sub>) magmatic condition [<a href="#B50-minerals-13-01273" class="html-bibr">50</a>]. (<b>c</b>) Calc-alkaline and alkaline magma composition for the different granite varieties using the contents of FeO<sup>t</sup> and Al<sub>2</sub>O<sub>3</sub> in biotite [<a href="#B51-minerals-13-01273" class="html-bibr">51</a>]. (<b>d</b>) Plots of SiO<sub>2</sub> vs. (FeO<sup>t</sup>/(FeO<sup>t</sup> + MgO) for the Gebel El Bakriyah younger granites show a ferroan nature that confines the A-type granite field [<a href="#B52-minerals-13-01273" class="html-bibr">52</a>]. (<b>e</b>) Rb vs. Y + Nb tectonic discrimination diagram for the Gebel El Bakriyah granites [<a href="#B45-minerals-13-01273" class="html-bibr">45</a>].</p> Full article ">Figure 8
<p>(<b>a</b>) Fractional crystallization (FC) and lesser assimilation assignment for the Gebel El-Bakriyah A-type granites based on the Zr vs. Th/Nb diagram [<a href="#B65-minerals-13-01273" class="html-bibr">65</a>]. (<b>b</b>) Positive correlation of Nb vs. Ta contents as an indicator of fractional crystallization in felsic magma. (<b>c</b>) Plots of La vs. La/Sm ratio indicating two processes: namely the partial melting and fractional crystallization for the studied granites (after [<a href="#B66-minerals-13-01273" class="html-bibr">66</a>]). (<b>d</b>) Ni vs. Rb compositional variation diagram showing fractional crystallization and partial melting trends of the studied granites [<a href="#B67-minerals-13-01273" class="html-bibr">67</a>]. (Abbreviations of crystallization trends: FC = Fractional crystallization, AFC = Assimilation-Fractional Crystallization, and BA = Bulk Assimilation (BA).</p> Full article ">Figure 9
<p>(<b>a</b>) Rb/Ba vs. Rb/Sr for the studied granites [<a href="#B62-minerals-13-01273" class="html-bibr">62</a>]. (<b>b</b>) The compositions of the studied granitic rocks, compared to compositional ranges of various experimental metasediment- and amphibolite-derived melts [<a href="#B89-minerals-13-01273" class="html-bibr">89</a>]. (<b>c</b>) Crust and mixed crust-mantle source of the Gebel El Bakriyah A-type granite based on amphibole chemistry [<a href="#B90-minerals-13-01273" class="html-bibr">90</a>]. (<b>d</b>) Crystallization of Mg-biotite and Fe-biotite from mixed crust-mantle and crust source for the monzogranite + syenogranite and alkali feldspar granite, respectively [<a href="#B91-minerals-13-01273" class="html-bibr">91</a>]. (<b>e</b>) The crystallization temperature of biotite in the Gebel El Bakriyah A-type granite [<a href="#B68-minerals-13-01273" class="html-bibr">68</a>]. (<b>f</b>) Magmatic origin of apatite from the investigated granites [<a href="#B72-minerals-13-01273" class="html-bibr">72</a>]. (<b>g</b>) Lanthanide tetrad effect in some granite varieties [<a href="#B64-minerals-13-01273" class="html-bibr">64</a>].</p> Full article ">Figure 10
<p>A suggested geodynamic model for the generation of A-type magma by dehydration melting of lithospheric delamination in an extensional tectonic regime during the Late Neoproterozoic in the Arabian-Nubian Shield (ANS). The Gebel El Bakriyah complex witnessed two successive post-collisional magmatic episodes, the first is mafic that formed the younger gabbros [<a href="#B24-minerals-13-01273" class="html-bibr">24</a>] and the A-type granites (present study).</p> Full article ">

Review

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Review
A Review of the Mineral Chemistry and Crystallization Conditions of Ediacaran–Cambrian A-Type Granites in the Central Subprovince of the Borborema Province, Northeastern Brazil
by Jefferson Valdemiro de Lima, Ignez de Pinho Guimarães, José Victor Antunes de Amorim, Caio Cezar Garnier Brainer, Lucilene dos Santos and Adejardo Francisco da Silva Filho
Minerals 2024, 14(10), 1022; https://doi.org/10.3390/min14101022 - 11 Oct 2024
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Abstract
Ediacaran–Cambrian magmatism in the Central Subprovince (Borborema Province, NE Brazil) generated abundant A-type granites. This study reviews published whole-rock and mineral chemistry data from thirteen Ediacaran–Cambrian A-type intrusions and a related dike swarm. It also presents new mineral chemistry and whole-rock data for [...] Read more.
Ediacaran–Cambrian magmatism in the Central Subprovince (Borborema Province, NE Brazil) generated abundant A-type granites. This study reviews published whole-rock and mineral chemistry data from thirteen Ediacaran–Cambrian A-type intrusions and a related dike swarm. It also presents new mineral chemistry and whole-rock data for one of these intrusions, along with zircon trace element data for five of the intrusions. Geochronological data from the literature indicate the formation of these A-type intrusions during a 55 Myr interval (580–525 Ma), succeeding the post-collisional high-K magmatism in the region at c. 590–580 Ma. The studied plutons intruded Paleoproterozoic basement gneisses or Neoproterozoic supracrustal rocks. They are ferroan, metaluminous to peraluminous and mostly alkalic–calcic. The crystallization parameters show pressure estimates mainly from 4 to 7 kbar, corresponding to crustal depths of 12 to 21 km, and temperatures ranging from 1160 to 650 °C in granitoids containing mafic enclaves, and from 990 to 680 °C in those lacking or containing only rare mafic enclaves. The presence of Fe-rich mineral assemblages including ilmenite indicates that the A-type granites crystallized under low ƒO2 conditions. Zircon trace element analyses suggest post-magmatic hydrothermal processes, interpreted to be associated with shear zone reactivation. Whole-rock geochemical characteristics, the chemistry of the Fe-rich mafic mineral assemblages, and zircon trace elements in the studied granitoids share important similarities with A2-type granites worldwide. Full article
(This article belongs to the Special Issue Mineral Chemistry of Granitoids: Constraints on Crystallization Conditions and Petrological Evolution)
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Figure 1

Figure 1
<p>Geological maps illustrating the regional context and the location of the studied plutons [<a href="#B73-minerals-14-01022" class="html-bibr">73</a>]. (<b>A</b>) Major domains and shear zones of the Borborema Province [<a href="#B73-minerals-14-01022" class="html-bibr">73</a>]. Abbreviations—PaSZ: Patos Shear Zone; WPSZ and EPSZ: West and East Pernambuco Shear Zones; SSZ: Sobral Shear Zone; SPSZ: Senador Pompeu Shear Zone; JSZ: Jaguaribe Shear Zone; JCSZ: João Câmara Shear Zone; PASZ: Portoalegre Shear Zone; RSZ: Riachão Shear Zone; TSZ: Tauá Shear Zone; (<b>B</b>) Central Subprovince of the Borborema Province with studied plutons highlighted in orange (adapted from Lima et al. [<a href="#B73-minerals-14-01022" class="html-bibr">73</a>]). Abbreviations—CoSZ: Coxixola Shear Zone; CSZ: Congo Shear Zone; AISZ: Afogados da Ingazeira Shear Zone; SCSZ: Serra do Caboclo Shear Zone. Studied plutons: 1—Aroeiras Pluton; 2—Bravo Pluton; 3—Pilõezinhos Pluton; 4—Serra Branca Pluton; 5—Serra Branca dike swarms; 6—Queimadas Pluton; 7—Marinho Pluton; 8—Prata Complex; 9—Serra da Engabelada Pluton; 10—Serrote Santo Antonio Pluton; 11—Pereiro Pluton; 12—Serra do Velho Zuza Pluton; 13—Açude do Caroá Pluton; 14—Boqueirão Pluton.</p> Full article ">Figure 2
<p>Field aspects of the studied granitoids. (<b>A</b>) Porphyritic syenogranite from the principal facies of the Aroeiras Complex; (<b>B</b>,<b>C</b>) the mingling of diorite with the syenogranite in the Aroeiras Complex; (<b>D</b>) the porphyritic syenogranite of the Pilõezinhos Pluton enclosing the dioritic enclave; (<b>E</b>) a general view of the other facies of the Pilõezinhos Pluton, characterized by fine-grained granitic rocks enclosing an intermediate-composition enclave; (<b>F</b>) typical leucocratic granitic rock from the Serra Branca Pluton; (<b>G</b>) a leucocratic dike from the Serra Branca Suite; (<b>H</b>) the mega-dike field aspects of the Queimadas Pluton. (Red line—contact zone with the basement orthogneiss/migmatite; green line—shear zone; (<b>I</b>) Diorite as enclaves enclosed by felsic granite of the Marinho Pluton. The felsic granite also encloses pockets of mesocratic granite, interpreted as a hybrid rock, which in turn encloses elongated oriented enclaves of mafic diorite (red circles); (<b>J</b>) the dike of rapakivi granite (Marinho Pluton), cut by narrow dikes (up to 20 cm wide) of leucogranite (LD). Red arrows—K-feldspar surrounded by plagioclase of oligoclase composition; (<b>K</b>) the typical features of magmatic interaction between mafic and felsic magma of the Prata Complex; (<b>L</b>) porphyritic granite of the Pereiro Pluton, cut by veins of leucogranites. K-feldspar (red arrows) occurs as euhedral crystals oriented by magmatic flux processes.</p> Full article ">Figure 3
<p>Geochemical characteristics of studied granitoids. (<b>A</b>) Alumina saturation index diagram; (<b>B</b>) FeO<sub>T</sub>/(FeO<sub>T</sub> + MgO) versus SiO<sub>2</sub> diagram; (<b>C</b>) SiO<sub>2</sub> versus Mali (modified alkali lime index) diagram.</p> Full article ">Figure 4
<p>Tectonic setting discrimination diagrams for studied granitoids. (<b>A</b>) Pearce et al. [<a href="#B86-minerals-14-01022" class="html-bibr">86</a>]: WPG: within-plate granites; syn-COLG: syn-collisional granites; post-COLG: post-collisional; ORG: ocean ridge granites; VAG: volcanic arc granite; (<b>B</b>) diagram from Whalen et al. [<a href="#B87-minerals-14-01022" class="html-bibr">87</a>]: FG: fractionated granite field; OTG: unfractionated granite field; A: A-type granites.</p> Full article ">Figure 5
<p>Trace elements of the studied granitoids in the tectonic discriminant diagrams of Eby [<a href="#B34-minerals-14-01022" class="html-bibr">34</a>]. A1: Non-orogenic granite; A2: Post-collisional/post-orogenic granite.</p> Full article ">Figure 6
<p>(<b>A</b>) Composition of amphibole crystals plotted in the Si<sup>IV</sup> × (Na + K + Ca) diagram [<a href="#B92-minerals-14-01022" class="html-bibr">92</a>] indicating a magmatic origin for the studied amphiboles; (<b>B</b>) studied amphiboles in the A* sum: <sup>A</sup>(Li + Na + K + 2Ca + 2Pb) versus C* sum: <sup>C</sup>(Al + Fe<sup>3+</sup> + Mn<sup>3+</sup> + Cr + V + Sc + 2Ti + 2Zr)-<sup>W</sup>O-<sup>C</sup>Li calcium amphiboles classification diagram [<a href="#B91-minerals-14-01022" class="html-bibr">91</a>], revealing compositions mainly within the pargasite–hastingsite range.</p> Full article ">Figure 7
<p>Chemical characteristics of the studied biotite crystals; ternary diagrams produced from Gündüz and Asan [<a href="#B94-minerals-14-01022" class="html-bibr">94</a>]. (<b>A</b>) MgO × 10TiO<sub>2</sub> × FeO<sub>t</sub> + MnO ternary diagram [<a href="#B95-minerals-14-01022" class="html-bibr">95</a>], showing the studied biotites straddling between the primary and re-quilibrated fields; (<b>B</b>) Classification of biotite crystals in the Al<sup>IV</sup> + Fe<sup>3 +</sup> +Ti × Fe<sup>2+</sup> + Mn × Mg ternary diagram [<a href="#B93-minerals-14-01022" class="html-bibr">93</a>], showing predominantly Fe-rich compositions.</p> Full article ">Figure 8
<p>Chemical classification of the studied biotites. (<b>A</b>) Fe/(Fe + Mg) versus S.I. [100MgO/(MgO + FeO + Fe<sub>2</sub>O<sub>3</sub> + Na<sub>2</sub>O + K<sub>2</sub>O)] diagram; (<b>B</b>) Fe# × Al<sup>IV</sup> diagram; (<b>C</b>) Mg × Al<sub>T</sub> diagram after Nachit et al. [<a href="#B96-minerals-14-01022" class="html-bibr">96</a>]; (<b>D</b>–<b>F</b>) discriminant diagrams after Abdel-Rahman [<a href="#B97-minerals-14-01022" class="html-bibr">97</a>]. Legend: A: alkaline anorogenic; C: calc-alkaline; P: peraluminous.</p> Full article ">Figure 9
<p>An-Ab-Or ternary diagram for the classification of the studied plagioclase and K-feldspar [<a href="#B98-minerals-14-01022" class="html-bibr">98</a>].</p> Full article ">Figure 10
<p>Variation diagrams for studied zircon crystals. (<b>A</b>) Hf (ppm) × Nb/Ta; (<b>B</b>) Hf (ppm) × Zr/Hf.</p> Full article ">Figure 11
<p>Chondrite-normalized REE patterns [<a href="#B117-minerals-14-01022" class="html-bibr">117</a>] of the zircon crystals from the studied plutons. (<b>A</b>) Serrote Santo Antônio Pluton; (<b>B</b>) Marinho Pluton; (<b>C</b>) Queimadas Pluton; (<b>D</b>) Velho Zuza Pluton; (<b>E</b>) Pereiro Pluton.</p> Full article ">Figure 12
<p>Th × Σ LREE and Y × Σ LREE plot for studied zircon crystals. (<b>A</b>,<b>B</b>) Serrote Santo Antônio Pluton; (<b>C</b>,<b>D</b>) Marinho Pluton; (<b>E</b>,<b>F</b>) Queimadas Pluton; (<b>G</b>,<b>H</b>) Velho Zuza Pluton; (<b>I</b>,<b>J</b>) Pereiro Pluton. A zircon grain from the Marinho Pluton (FMJ-55-Zr-12) has anomalous Th and LREE concentrations (<a href="#app1-minerals-14-01022" class="html-app">Supplementary Table SIII</a>) and, therefore, was not included in (<b>C</b>,<b>D</b>).</p> Full article ">Figure 13
<p>Discriminant diagrams based on the trace element chemistry of the analyzed zircons. (<b>A</b>) An Nb/Hf vs. Th/U plot for the studied zircon crystals. The A-type and I-type fields are from Hawkesworth and Kemp [<a href="#B8-minerals-14-01022" class="html-bibr">8</a>] using zircon data of peralkaline A-type granites akin to those of Nigeria and I-type granites from the Lachlan Fold Belt (SE Australia), respectively; (<b>B</b>) the 10<sup>4</sup>(Eu/Eu*)<sub>N</sub>/Yb<sub>N</sub> vs. Ce/√(U × Ti) plot [<a href="#B112-minerals-14-01022" class="html-bibr">112</a>] for the studied zircon crystals.</p> Full article ">Figure 14
<p>Bar graph illustrating the temperature range at which the studied magmas crystallized. Colors as in the other figures. Abbreviations: PP—Pilõezinhos Pluton; SBS—Serra Branca Suite; BP—Bravo Pluton; ACP—Açude do Caroá Pluton; QP—Queimadas Pluton; MP—Marinho Pluton; BP—Boqueirão Pluton; VZP—Velho Zuza Pluton; SSAP—Serrote Santo Antônio Pluton; SEP—Serra da Engabelaba Pluton; AC—Aroeiras Complex; PC—Prata Complex and PEP—Pereiro Pluton.</p> Full article ">Figure 15
<p>Bar graph illustrating the crystallization pressures of the studied granitoids. PP—Pilõezinhos Pluton; SBS—Serra Branca Suite; BP—Bravo Pluton; ACP—Açude do Caroá Pluton; QP—Queimadas Pluton; MP—Marinho Pluton; BQ—Boqueirão Pluton and AC—Aroeiras Complex.</p> Full article ">Figure 16
<p>Chemical diagrams for inferring fO<sub>2</sub> conditions. (<b>A</b>) Al<sup>IV</sup> × Fe/(Fe + Mg) diagram for the studied amphiboles, with fields according to Anderson and Smith [<a href="#B132-minerals-14-01022" class="html-bibr">132</a>]; (<b>B</b>) Al<sub>T</sub> (total aluminum) × Fe/(Fe + Mg) diagram for the studied biotites.</p> Full article ">Figure 17
<p>Bivariate discriminant plot (Sm/La)<sub>N</sub> × (Ce/Ce*)<sub>N</sub> of the analyzed zircon crystals.</p> Full article ">
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