Mineral Chemistry

Clinopyroxenes Multi-stage metasomatism Happo-O'ne Japan The metaperidotites found in the Happo-O'ne region of central Japan are mostly lherzolites to harzburgites with subordinate dunites. Their protoliths originated as a series of refractory residues by near-fractional melting, 15–25% melting in the spinel field, which is confirmed by a HREE melting model of the apparently primary clinopyroxene. These metaperidotites display U-shaped primitive mantle (PM)-normalized REE patterns (0.02–0.5 times PM) and are highly enriched in LILE (0.2–20 times PM) relative to HFSE (b 0.2 times PM), providing evidence for mantle-wedge metasomatism. In-situ analyses confirmed that clinopyroxenes and tremolite are enriched in fluid-mobile elements (B, Sr, Pb, Li, Cs, Ba and Rb; 0.1–100 times PM) coupled with depletion of HFSE (Ta, Hf, Th, Zr, Ti and Nb; b 0.7 times PM) + U; these chemical features of clinopyroxenes and tremolite are similar to those of their whole rocks, and reflect slab-fluid metasomatism. We recognized three stages of clinopyroxenes that are different in morphology and REE patterns, but show the same major-element chemistry. Nearly euhedral clinopyroxene (Cpx1) displays a spoon-shaped REE pattern (0.2–3 times PM), reflecting the first stage (stage 1) of metasomatism. Acicular clinopyroxene (Cpx2) after tremolite +olivine shows a U-shaped REE pattern (0.06–1 times PM) (stage 2), whereas fine-grained clinopyroxene (Cpx3) derived from orthopyroxene shows very low concentrations of REE (stage 3). These three successive stages of retrogressive clinopyroxene formation possibly denote a retrogressive chemical change of the involved fluids during multi-stage metasomatism. The fluid of stage 1 is highly enriched in LREE (0.2–2 times PM), MREE, Pb, Sr, Li and Rb relative to the stage-3 fluid that is very low in MREE, Pb, LREE and Sr, but has high Na, Mn, Ba, B and Cs. The stage-2 fluid, which is low in LREE (0.06–1 times PM), Li and Pb, and very low in Cs, Rb and Hf relative to the fluid of stage 1, is considered to be a transitional fluid between stages 1 and 3. The retrogressive change of the fluid composition is possibly equivalent to a transversal change of the slab-derived fluid within the mantle wedge due to a change of metamorphic condition, depth of the subducting slab and an episode of metasomatism during the exhumation of the Happo-O'ne peridotites.

Propylitic alteration halos to porphyry deposits are characterized by low- to moderate-intensity replacements
of primary feldspars and mafic minerals by epidote, chlorite, calcite ± actinolite, pyrite, prehnite, and zeolites.
The pyrite halo that surrounds porphyry deposits typically extends part way through the propylitic halo and provides
strong responses to conventional geochemical and geophysical exploration techniques. When exploring
outside of the pyrite halo, porphyry deposits have proven to be difficult to detect based simply on the presence
of weak epidote-chlorite alteration.
Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of epidote from propylitic
alteration zones around porphyry and skarn deposits in the central Baguio district, Philippines, have shown
that low-level hypogene geochemical dispersion halos can be detected at considerably greater distances than
can be achieved by conventional rock chip sampling of altered rocks. Epidote chemistry can provide vectoring
information to the deposit center and potentially provides insights into the potential metal endowment of the
porphyry system, providing explorers with both vectoring and fertility assessment tools.
Epidote chemistry varies with respect to distance from porphyry deposit centers, with the highest concentrations
of proximal pathfinder elements (e.g., Cu, Mo, Au, Sn) detected in epidote from close to the potassic
alteration zone. Distal pathfinder elements (e.g., As, Sb, Pb, Zn, Mn) are most enriched in epidote more than
1.5 km from the deposit center. Rare earth elements and Zr are most enriched in epidote from the edge of the
pyrite halo. The lateral zonation in epidote chemistry implies that at Baguio the geochemical dispersion patterns
were produced by lateral outflow of spent fluids from the porphyry center, rather than from ingress of
peripheral, nonmagmatic waters.

Keywords: Paleozoic ophiolites U–Pb zircon dating Zircon εHf(t) Komatiite Supra-subduction zone-type magmatism Middle to Late Paleozoic ophiolites, which are remnants of the Paleo-Tethys Ocean, are aligned in two main zones in northern Iran: Darrehanjir–Fariman–Mashhad, and Rasht in the north and Jandagh–Anarak ophiolites to the south. Our new U–Pb zircon dating results show that the ~200 km long Darrehanjir–Mashhad mafic–ultramafic body is not a single ophiolite but a composite igneous complex composed of Permian pillow lavas and pelagic sediments in fault contact with a small outcrop of Devonian intrusive and ultramafic rocks. Darrehanjir intrusive rocks have U–Pb zircon ages of 380.6 ± 3.7 Ma and 382.9 ± 3.7 Ma respectively, ~100 Ma older than published ages for gabbros and radiolarites intercalated with lavas near Mashhad and Fariman. Mantle peridotites from the Devonian complex contain low Cr# spinel, similar to that in MORB-type peridotites. Devonian Darrehanjir gabbros and Permian Mashhad sequences both have boninitic and calc-alkaline signatures, respectively. The δ 18 O zircon values from the Devonian ferrodiorite (δ 18 O zircon ~ 4.6 ± 0.3‰) are slightly lower than the 5.2 to 5.4‰ expected for MORB-type zircons whereas Devonian plagiogranitic zircons mostly have δ 18 O zircon b5‰, perhaps reflecting involvement of hydrothermally altered crust. Similar, strongly positive values of zircon εHf(t) for plagiogranite (av. +14.9) and ferrodiorite (av. +13.8) indicate melt derivation from depleted astheno-sphere. Darrehanjir–Mashhad ophiolitic rocks can be divided into groups with high εNd (N10.3) and low εNd (b5.4) for both Permian and Devonian suites. Most Darrehanjir–Mashhad rocks are characterized by radiogenic 207 Pb/ 204 Pb and 208 Pb/ 204 Pb, indicating the involvement of subducted terrigenous sediments in the source. The Mashhad–Darrehanjir mafic–ultramafic complex demonstrates that this part of Paleo-Tethys evolved from oceanic crust formation above a subduction zone in Devonian time to accretionary convergence in Permian time. Iranian Paleozoic ophiolites and oceanic igneous complexes along with those of the Caucasus and Turkey in the west and Afghanistan, Turkmenistan and Tibet to the east, define a series of diachronous subduction-related marginal basins that were active from at least Early Devonian to Late Permian time.

The ~2.5 Ga Malanjkhand Cu mineralization is hosted by adakitic granitoids in central India. The mineralization represents a large Cu deposit. However, significant debate still surrounds its identification as an analogue of modern circum-Pacific style porphyry Cu deposits. The controversy is intricately linked to several first-order geological issues, such as: the onset of modern plate tectonics and ensuing supercontinent cycles, temporal evolution of the Earth’s continental crust coupled with buoyancy of the sub-continental lithospheric mantle (SCLM) and oxidation state of the sub-arc mantle wedge. The petrology and geochemistry of the early Cretaceous Lower Yangtze River Belt (LYRB) adakitic granitoids, central-eastern China that hosts several porphyry Cu deposits are similar to the ~2.5 Ga Malanjkhand adakitic granitoids of central India, hosting Cu mineralization. The relict amphibole chemistry of both, the LYRB and Malanjkhand granitoids reveal similar “porphyry mineralizing trends” implying high concentrations of H2O and elevated fO2 conditions of the ore-bearing shallowly emplaced adakitic granitoids. Consequently, the Malanjkhand and LYRB adakitic granitoids were generated in near-identical tectonothermal regimes. The LYRB porphyry Cu deposits belong to the circum–Pacific metallogenic belt of the Eurasian active continental margin. Collectively, the mineralogical, petrological and geochemical similarities of the Malanjkhand and the LYRB adakitic granitoids imply porphyry style mineralization of the Malanjkhand Cu deposit. The identification of Malanjkhand mineralization as a truly Neoarchean porphyry Cu deposit along with coeval adakites, calc-alkaline rhyolites, high-Mg andesites (HMA), followed by rift-related tholeiites and A2-type granites helps to constrain the tectonic evolution of central India. The rarity of porphyry Cu deposits in the Earth’s early history is primarily attributed to their lack of preservation. This study opens up exploration possibilities for hitherto unexplored and concealed porphyry Cu deposits in other geologically favorable Precambrian terranes comprising shallowly emplaced adakitic granitoids.

Post-collisional volcanism in northwestern Iran is represented by the Saray high-K rocks including leucite-bearing under-saturated and leucite-free silica saturated rocks. We report Ar–Ar age data which constrain the age as ca. 11 Ma (late Miocene). Most of clinopyroxene phenocrysts from the volcanic rocks have complex oscillatory zoning, with high Ti and Al cores, low Ti and high Al mantled clinopyroxenes, grading into low Ti and Al outer rims. All the rocks are highly enriched in incompatible trace elements and have identical Sr–Nd–Pb isotopes. Enrichment in incompatible elements and other geochemical features for the Saray lavas suggest a metasomatized sub-continental lithospheric mantle (SCLM) as the magma source. The negative Nb–Ta–Ti anomalies for the Saray lavas compare with the features of subduction-related magmatism with negligible contamination with ancient crustal components. The highly radiogenic 87 Sr/ 86 Sr and 207 Pb/ 204 Pb isotopic values of the Saray lavas imply the involvement of slab terrigenous sediments and/or a continental lithosphere. Isotopically, the volcanic rocks define a binary trend, representing 5–8% mixing between the primary mantle and sediment melts. Our melting models suggest residual garnet in the source and are incompatible with partial melting of amphibole and/or phlogopite bearing lherzolites, although the complex geochemical features might indicate the result of mixing between melts produced by different sources or a homogenous melt passing through a compositionally-zoned mantle during multiple stages of partial melting and melt migration. The geochronological, geochemical and isotopic data for the Saray rocks suggest that these Late Miocene magmas were derived from a small degree of partial melting of subduction-metasomatized (subcontinental) lithospheric mantle source in a post-collisional setting.

The Neyriz ophiolite along the northeast flank of the Zagros fold-thrust belt in southern Iran is an excellent example of a Late Cretaceous supra-subduction zone (SSZ)-related ophiolite on the north side of the Neotethys. The ophiolite comprises a mantle sequence including lherzolite, harzburgite, diabasic dikes, and cumulate to mylonitic gabbro lenses, and a crustal sequence comprising a sheeted dike complex and pillow lavas associated with pelagic limestone and radiolarite. Mantle harzburgites contain less CaO and Al 2 O 3 , are depleted in rare earth elements, and contain spinels that are more Cr-rich than lherzolites. Mineral compositions of peridotites are similar to those of both abyssal and SSZ-peridotites. Neyriz gabbroic rocks show boninitic (SSZ-related) affinities, while crustal rocks are similar to early arc tholeiites. Mineral compositions of gabbroic rocks resemble those of SSZ-related cumulates such as high forsterite olivine, anorthite-rich plagioclase, and high-Mg# clinopyroxene. Initial εNd(t) values range from +7.9 to +9.3 for the Neyriz magmatic rocks. Samples with radiogenic Nd overlap with least radiogenic mid-ocean ridge basalts and with Semail and other Late Cretaceous Tethyan ophiolitic rocks. Initial 87 Sr/ 86 Sr ranges from 0.7033 to 0.7044, suggesting modification due to seafloor alteration. Most Neyriz magmatic rocks are characterized by less radiogenic 207 Pb/ 204 Pb (near the northern hemisphere reference line), suggesting less involvement of sediments in their mantle source. Our results for Neyriz ophiolite and the similarity to other Iranian Zagros ophiolites support a subduction initiation setting for its generation.

The Arak basin in the northern part of the Malayer-Esfahan metallogenic belt (MEMB) of Iran hosts 9 Zn-Pb sulfide deposits within a Jurassic sedimentary succession of black, fine-grained sandstone, siltstone and shale. This succession was deposited in an extensional back-arc environment between the Sanandaj- Sirjan Zone (SSZ) and the Central Iranian microcontinent. Two of the 9 deposits (Western Haft-Savaran and Hossein-Abad) are the focus of study. Here, three ore facies can be distinguished, based on the morphology of the orebodies and the sulfide mineralogy and textures: (a) stockwork, (b) massive, and (c) bedded mineralization. The stockwork and massive mineralization are interpreted to have formed in the subsurface, whereas bedded mineralization was sedimented on the seafloor. The Fe contents of sphalerites from massive and stockwork mineralization from the two deposits, together with the presence of pyrrhotite inclusions, indicate that sphalerite precipitated from relatively low fS 2 (< 10 −11 ) fluid. Homogenization temperatures of fluid inclusions in sphalerite, quartz and siderite in massive mineralization range from 105 to 309 °C, and average 208 °C, with salinities between 4.03 and 11.1 wt% NaCl eq., and averaging 5.77 wt% NaCl eq. These widely ranging salinities and homogenization temperatures reflect mixing of shallow connate water with venting metalliferous fluid that is of deep basinal origin, and deposition of mineralization predominantly below the seafloor. Collectively, the host rock types, ore facies and textures, deposition in an reduced ambient environment, fluid inclusion temperatures and salinities, and mineralizing fluid behaviour at the seafloor are all compatible with a vent-proximal sedimentary exhalative (SEDEX) origin for the Western Haft-Savaran and Hossein-Abad deposits.

The ophiolitic peridotites in the Wadi Arais area, south Eastern Desert of Egypt, represent a part of Neoproterozoic ophiolites of the Arabian-Nubian Shield (ANS). We found relics of fresh dunites enveloped by serpentinites that show abundances of bastite after orthopyr-oxene, reflecting harzburgite protoliths. The bulk-rock chemistry confirmed the harzburgites as the main protoliths. The primary mantle minerals such as orthopyroxene, olivine and chromian spinel in Arais serpentinites are still preserved. The orthopyroxene has high Mg# [0Mg/ (Mg + Fe 2+)], ~0.923 on average. It shows intra-grain chemical homogeneity and contains, on average, 2.28 wt.% A1 2 O 3 , 0.88 wt.% Cr 2 O 3 and 0.53 wt.% CaO, similar to primary orthopyroxenes in modern forearc peridotites. The olivine in harzburgites has lower Fo (93−94.5) than that in dunites (Fo 94.3 −Fo 95.9). The Arais olivine is similar in NiO (0.47 wt.% on average) and MnO (0.08 wt.% on average) contents to the mantle olivine in primary peridotites. This olivine is high in Fo content, similar to Mg-rich olivines in ANS ophiolitic harzburgites, because of its residual origin. The chromian spinel, found in harzburgites, shows wide ranges of Cr#s [0Cr/(Cr + Al)], 0.46−0.81 and Mg#s, 0.34−0.67. The chromian spinel in dunites shows an intra-grain chemical homogeneity with high Cr#s (0.82−0.86). The chromian spinels in Arais peridotites are low in TiO 2 , 0.05 wt.% and Y Fe [0 Fe 3+ /(Cr + Al + Fe 3+)], ~0.06 on average. They are similar in chemistry to spinels in forearc peridotites. Their compositions associated with olivine's Fo suggest that the harzbur-gites are refractory residues after high-degree partial melting (mainly ~25−30 % partial melting) and dunites are more depleted, similar to highly refractory perido-tites recovered from forearcs. This is in accordance with the partial melting (>20 % melt) obtained by the whole-rock Al 2 O 3 composition. The Arais peridotites have been possibly formed in a sub-arc setting (mantle wedge), where high degrees of partial melting were available during subduction and closing of the Mozambique Ocean, and emplaced in a forearc basin. Their equilibrium temperature based on olivine−spinel thermometry ranges from 650 to 780 °C, and their oxygen fugacity is high (Δlog ƒO 2 02.3 to 2.8), which is characteristic of mantle-wedge peridotites. The Arais peridotites are affected by secondary processes forming microinclusions inside the dunitic olivine, abundances of car-bonates and talc flakes in serpentinites. These microinclusions have been formed by reaction between trapped fluids and host olivine in a closed system. Lizardite and chrysotile, based on Raman analyses, are the main serpentine minerals with lesser antigorite, indicating that serpentines were possibly formed under retrograde metamorphism during exhumation and near the surface at low T (<400 °C).

File ini merupakan laporan prakerin bidang kimia analisis, di laporan ini membahas segala sesuatu mengenai batu bara, khususnya mengenai verifikasi metode general analisis batu bara, semoga laporan ini bisa menjadi referensi untuk teman teman, semoga bermanfaat.

The Vazante–Paracatu region represents the most important Zn district known in Brazil and includes the Vazante hypogene non-sulfide Zn deposit composed mainly of willemite (Zn2SiO4) and sphalerite-rich carbonate-hosted Zn–(Pb) deposits. Fagundes is a ...

In the past decade, significant research efforts have been devoted to mineral chemistry studies to assist porphyry exploration. These activities can be divided into two major fields of research: (1) porphyry indicator minerals (PIMs), which are used to identify the presence of, or potential for, porphyry-style mineralization based on the chemistry of magmatic minerals such as zircon, plagioclase and apatite, or resistate hydrothermal minerals such as magnetite; and (2) porphyry vectoring and fertility tools (PVFTs), which use the chemical compositions of hydrothermal minerals such as epidote, chlorite and alunite to predict the likely direction and distance to mineralized centres, and the potential metal endowment of a mineral district. This new generation of exploration tools has been enabled by advances in and increased access to laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), shortwave length infrared (SWIR), visible near-infrared (VNIR) and hyperspectral technologies. PIMs and PVFTs show considerable promise for exploration and are starting to be applied to the diversity of environments that host porphyry and epithermal deposits globally. Industry has consistently supported development of these tools, and in the case of PVFTs encouraged by several successful blind tests where deposit centres have successfully been predicted from distal propylitic settings. Industry adoption is steadily increasing but is restrained by a lack of the necessary analytical equipment and expertise in commercial laboratories, and also by the ongoing reliance on well-established geochemical exploration techniques (e.g. sediment, soil and rock chip sampling) that have aided the discovery of near-surface resources over many decades, but are now proving less effective in the search for deeply buried mineral resources and for those concealed under cover.

Sandwiched between the Adriatic Carbonate Platform and the Dinaride Ophiolite Zone, the Bosnian Flysch forms a c 3000 m thick, intensely folded stack of Upper Jurassic to Cretaceous mixed carbonate and siliciclastic sediments in the Dinarides. New petrographic, heavy mineral, zircon U/Pb and fission-track data as well as biostratigraphic evidence allow us to reconstruct the palaeogeology of the source areas

The Happo-O'ne peridotite complex is situated in the northeastern part of the Hida Marginal Tectonic Zone, central Japan, characterized by the high-P/T Renge meta-morphism, and is considered as a serpentinite mélange of Paleozoic age. Peridotitic rocks, being massive or foliated, have been subjected to hydration and metamorphism. Their protoliths are mostly lherzolites to harzburgites with subordinate dunites. We found a characteristic mineral assemblage, olivine

The giant, high-grade Resolution porphyry Cu-Mo deposit in the Superior district of Arizona is hosted in Pro-terozoic and Paleozoic basement and in an overlying Cretaceous volcaniclastic breccia and sandstone package. Resolution has a central domain of potassic alteration that extends more than 1 km outboard of the ore zone, overlapping with a propylitic halo characterized by epidote, chlorite, and pyrite that is particularly well developed in the Laramide volcaniclastic rocks and Proterozoic dolerite sills. The potassic and propylitic assemblages were overprinted in the upper parts of the deposit by intense phyllic and advanced argillic alteration. The district was disrupted by Tertiary Basin and Range extension, and the fault block containing Resolution and its Cretaceous host succession was buried under thick mid-Miocene dacitic volcanic cover, obscuring the geologic, geophysical, and geochemical footprint of the deposit. To test the potential of propylitic mineral chemistry analyses to aid in the detection of concealed porphyry deposits, a blind test was conducted using a suite of epidote-chlorite ± pyrite-altered Laramide volcaniclastic rocks and Proterozoic dolerites collected from the propylitic halo, with samples taken from two domains located to the north and south and above the Resolution ore zone. Laser ablation-inductively coupled plasma-mass spectrometry (LA-ICP-MS) data of epidote provided indications of deposit fertility and proximity. Competition for chalcophile elements (As, Sb, Pb) between coexisting pyrite and epidote grains led to a subdued As-Sb fertility response in epidote, consistent with epidote collected between 0.7 and 1.5 km from the center of a large porphyry deposit. Temperature-sensitive trace elements in chlorite provided coherent spatial zonation patterns, implying a heat source centered at depth between the two sample clusters, and application of chlorite proximi-tor calculations based on LA-ICP-MS analyses provided a precisely defined drill target in this location in three dimensions. Drilling of this target would have resulted in the discovery of Resolution, confirming that epidote and chlorite mineral chemistry can potentially add value to porphyry exploration under cover.

Manganocummingtonite occurs with spessartine, quartz and pyrolusite in the Chikmara area, Sausar fold belt, central India. Its composition is [Ca 0.3–0.35 (Mg 3.3–3.5 Mn 1.6–1.8 Fe 2+ 1.4–1.5)(Si 7.931-7.997 Al iv 0.003-0.069)O 22 (OH 1.5-2.0 F 0.0-0.5)] being fairly rich in Ca, which is indicative of metamorphic temperature in the amphibolite facies. The garnet contains 77.5% spessartine, 13% almandine and minor andradite, grossular and pyrope components. Unusually, there is no carbonate, pyroxene, pyroxmangite, rhodonite, magnetite or hematite. The available Al in the rock stabilized garnet and this mineral incorporated minor Fe 3+ present in the rock as andradite component. The manganocummingtonite–garnet pairs developed at ~600°C during amphibolite facies metamorphism in low X CO 2 system, stabilized with X Mn/(Mn+Fe 2+ +Mg) = 0.25 to 0.28 in the amphibole and 0.85 in the garnet and formed under unusually low fO 2 conditions for the Sausar region, near channelized fluids which deposited quartz may have controlled the fO 2 .

The Higo terrane in west-central Kyushu Island, southwest Japan consists from north to south of the Manotani, Higo and Ryuhozan metamorphic complexes, which are intruded by the Higo plutonic complex (Miyanohara tonalite and Shiraishino granodiorite). The Higo ...

Talc mineralisation occurs as hematite–talc schist between soft hematite ore and dolomitic itabirite at Gongo Soco, Quadrilátero Ferrífero of Minas Gerais, Brazil. The hematite–talc schist and soft hematite have a prominent tectonic foliation of tabular hematite. Tabular hematite without preferential orientation is superimposed on the tectonic foliation. The talcose schist is enriched in F and has a constant Fe/S ratio. Electron-microprobe analyses indicate trace amounts of S in different generations of hematite. The whole-rock Fe/S ratio possibly represents sulfate S from hematite-hosted fluid inclusions. Fluid inclusions in foliation-overprinting hematite and chlorite geothermometry from talcose rocks suggest, respectively, temperatures from <200°C to ~300°C. Tourmaline, a rarely observed mineral in the hematite–talc schist, belongs to the alkali group and falls in the dravite compositional field. Boron-isotope determinations of tourmaline crystals, using secondary ion mass spectrometry, vary from −20‰ to −12‰ δ11B. This compositional isotopic range and the tourmaline chemical composition suggest a meta-evaporitic origin. A non-marine evaporitic setting is the most likely source of acidic, highly oxidising fluids, which resulted in the abundant F-bearing talc and the presence of otherwise immobile Ti in hematite. Oxidising brines were channelled along shear zones and converted dolomitic itabirite into the Gongo Soco soft hematite and the talc mineralisation. The latter is envisaged as the hydrothermal wall-rock alteration of dolomitic itabirite, which gave rise to the soft hematite ore.