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The microelement composition was studied of pyrite, the main concentrator of gold in sulfidization zones in ore occurrences of the Manitanyrd Ridge. The ore mineralization is assigned to the gold-sulfide-quartz vein and gold-sulfide types. We determined a wide range of ore-forming elements, associated with gold in pyrite. These elements correspond to geochemical features of the late galena-chalcopyrite-sphalerite mineral assemblage of the ore process, as well as to its final stage expressed in the appearance of elements reflecting the mineralogy of gray ores and bismuth sulfosalts. Pyrites from the vein and mineralized zones, from the ores of the deposit and from the secondary lithochemical anomalies, were found to contain the same set of the gold satellite elements: Ag, Cu, Zn, Pb, As. In pyrite of the gold-sulfide-quartz veins, Au has close correlations with the main elements of the ore association. In pyrite of the mineralized zones, all the correlations between Au and the ore-forming elements are absent. The pairwise correlation between the ore-forming elements in these zones also changes completely. It is demonstrated that the identified differences in correlations between Au and the ore-forming elements in pyrite are a criterion for assessment of the lithochemical anomalies and allow one to propose a strategy of prospecting for new ore objects in the Manitanyrd region.

A comprehensive study of the Kyzyk-Chadr porphyry copper deposit included determination of the composition and spatial distribution of trace elements in ore-forming sulfide minerals over the ore-hosting rock volume. The study was carried out using the mass spectrometric analysis with laser ablation of the analyzed material. Steady qualitative and quantitative elements of a “hidden” mineralogical and geochemical zonality have been identified, that are expressed in variations in the concentration of trace elements and their ratios in pyrites and chalcopyrites over the volume of the ore-bearing porphyry copper stockwork. The identified regularities correlate with the established centrifugal vector and concentric pattern of the mineralogical ore-metasomatic zonality of the ore deposit.

Total reduced inorganic S isotope ratios (δ34SCRS) shift toward more negative values across much of the southern North Atlantic just before the onset of the Cenomanian-Turonian Ocean Anoxic Event (OAE-2). At the same time, there is no parallel isotopic change in the significantly larger pool of kerogen (organic) S, which indicates that the distribution and S-isotope composition of sulfide in the environment likely did not drive the change in δ34SCRS. Here, we investigate possible explanations for the negative shift in δ34SCRS values and their divergence from organic S by isolating iron sulfides for morphological identification and grain-specific isotopic analysis using secondary ion mass spectrometry (SIMS). In pre- and syn-OAE-2 sedimentary rocks from Demerara Rise, we find four distinct morphologies of iron sulfides: pyrite framboids (1–20 μm diameter), irregular pyrite aggregates (1–38 μm diameter), large cemented pyrite aggregates (~60 μm diameter), and irregular and cemented aggregates of the pyrite polymorph marcasite (1–45 μm diameter). These different textural groups have distinct S-isotopic compositions that are largely consistent through the onset of OAE-2. As such, the secular change in bulk δ34SCRS values likely reflects the changing proportions of these phases stratigraphically across OAE-2. All textural groups feature resolvable intra-grain δ34S variability, suggesting that the environments in which they formed were characterized by dynamic sulfide δ34S values and/or by partial closed-system distillation. We use grain-specific δ34S distributions to rule out shoaling of the chemocline within the sediments as a mechanism for the observed decrease in δ34SCRS. Instead, we propose that changes in the reactivity of the iron species delivered to Demerara Rise over the ~200 kyr leading up to the onset of OAE-2 impacted the relative contributions of pyrite with S-isotope signatures reflecting the water column, shallow sediments, and deeper sediments to the bulk sedimentary δ34SCRS value. Specifically, the change in iron reactivity at the onset of OAE-2 favored the production of 34S-depleted large, cemented aggregates and framboids at the expense of more 34S-enriched irregular aggregates. Our results underscore that bulk δ34SCRS measurements integrate multiple reduced phases that form via distinct reaction mechanisms and potentially in different parts of the depositional environment. Grain-specific SIMS analyses dramatically enrich our ability to interpret pyrite isotopic patterns in the geologic record.

Iron and arsenic sulfides are considered as the most important gold hosts in the sediment-hosted disseminated invisible gold deposits. The Zarshuran gold deposit (155 tons Au with average grade of 2.63 g/t) is formed in the Lower Cambrian black shale and siltstone (Zarshuran unit) and Fe-rich carbonates (Chaldagh unit) host rocks. As-sulfide (e.g., realgar and orpiment) and arsenian pyrites are the most important host minerals of gold in this deposit. Based on EPMA data, pyrite with As content below the detection limit to 3.99 wt% occurs in six different types, respectively, Py0 (gold content of 0.01 ppm), Py1 (gold content of 0.02 ppm), Py2 (gold content of 0.03 ppm), Py3 (gold content of 0.02 ppm), Py4 (gold content of 0.04 ppm), and Py5 (gold content of 0.01 ppm). According to the evidences, gold can be present as participating in chemical bounded (Au+ and Au+3) or nanoparticle inclusions (Au0). The weak geochemical correlation (R2 = −0.6) between As and S elements in pyrites indicates that there is pyrite with a complex composition [Fe(S,As)2Au2S0], which As− has replaced S2−. Mineralogy and the abundance of Fe and S in the rock units suggest that gold mineralization in the Zarshuran deposit is well occurs in response to sulfidation process. Sulfidation occurs when H2S-rich ore-forming fluids react with Fe-bearing carbonate host rock to form pyrite, marcasite, and pyrrhotite minerals. Introduction Sediment-hosted disseminated gold deposits with high gold grade (> 1000 g/t) are known to contain gold as participating in chemical bounded (Au+ and Au+3) or nanoparticle inclusions (Au0)in the pyrite composition (Deditius et al., 2014). The Zarshuran gold deposit (155 t @ 2.63 g/t Au; Madan-Zamin Company, 2020) is situated 35 km north of Takab in the Takab-Angouran metallogenic district, NW Iran. According to Mehrabi et al. (1999) and Asadi et al. (2000), gold mineralization in the Zarshuran deposit is in many respects like the Carlin-style and Carlin-like gold deposits, respectively. Gold substitution has been reported to be below detection limit to a maximum of 0.64 wt.% and 3 wt.% in arsenian pyrite and arsenopyrite lattice, respectively (Voute et al., 2019). Here, we examine the relationship between geochemistry and textures of pyrite, with a view to constraining the mechanism of gold precipitation. We use electron probe microanalysis (EPMA) to study the composition of different pyrite types. The results show that distribution of ferrous iron (Fe2+) is controlled by the initial diagenesis of Fe-C-S systems. Materials and methods During field studies, mineralization outcrops and their associated host rocks were identified. After preparing thin and thin-polished sections, mineralogical studies were carried out by transmitted and reflected polarizing ZIESS Axioplan2 microscope. To identify and classify different pyrite types and investigate the possibility of presence of gold and trace minerals, eight thin-polished sections were prepared, and carbon coated. This study was carried out by scanning electron microscope (SEM) with EVO MA15 model in the Central Laboratory of Kharazmi University (Tehran, Iran). Then, to achieve the chemical composition of different types of pyrite, 104 points were examined by EPMA (model JEOL JXA-8530F) in the Laboratory of Geo Forschungs Zentrum (GFZ). Spot analysis was performed with a voltage of 20 kV, electron beam current of 10 nA, X-ray diameter of 2 μ and radiation time of 5 to 20 seconds. The standard examples used to calibrate the various elements in this experiment were as follows: FeS2 (for Fe and S), CoAsS (for As and Co), and free gold (for Au). The detection limits of the elements are Fe (300 ppm), As (200 ppm), S (300 ppm) and Au (200 ppm). To identify rare minerals such as mackinawite (Fe9S8), HR microscopic confocal Raman technique was used in the Central Laboratory of Shiraz University (Shiraz, Iran). The experiment was performed with an X50 laser, a wavelength of 785 nm with a power of 100 mw and a radiation time of 20s. Results and discussion Based on SEM and optical-microscopic studies, six types of pyrite have been identified in the Zarshuran deposit. They are (1) framboidal pyrite (Py0) (avg. = 30 μm in diameter), (2) fine-grained disseminated pyrite (Py1) (< 20 μm in diameter), (3) coarse-grained euhedral pyrite (Py2) (avg. = 100 μm in diameter), (4) porous/sponge pyrite (Py3) (avg. = 300 μm in diameter), (5) colloform pyrite (Py4) (avg. = 550 μm in diameter), (6) vein pyrites (Py5) (avg. = 55 μm in thickness). Decalcification and sulfidation of host rocks are two important mechanisms in genesis of sediment-hosted gold deposits, and the importance of sulfidation depends on the reactivity of Fe2+ and H2S rocks (Voute et al., 2019). The interaction of H2S-rich hydrothermal fluids with reactive iron originating from the host rocks (Cail and Cline, 2001) or through hydrothermal fluids added to the environment (Reich et al., 2005) which results in formation of Au(-As)-rich pyrite. Arsenic in pyrite can occur in various oxidation states that correspond to different crystallographic sites in the lattice and different substitution mechanisms. As− substitution for S2− is found in reducing conditions and often in sediment-hosted gold deposits; while As cations (As2+, As3+, As5+) replace Fe2+ under oxidation conditions (Reich et al., 2005; Deditius et al., 2014). The diagram of arsenic versus sulfur in the Zarshuran deposit shows that the concentration of As in the formed pyrites is strongly related to the decrease in concentration of S. Based on this, it can be concluded that As replaces S in the pyrite structure and in the form of As−..; Moreover, As species are common in pyrites of gold deposits with sedimentary host rocks. In the Zarshuran deposit the occurrence of gold in As-Hg-Sb sulfides in late drusy quartz veins (Daliran et al., 2018) is more important than the presence of gold in various pyrites. Finally, all evidence suggest that gold mineralization in the Zarshuran deposit occurs well in response to sulfidation process of Fe-bearing carbonate rocks. The correlation between gold content and degree of sulfidation in the Zarshuran deposit indicates that sulfidation process is a much more important mechanism to gold precipitation relative to addition of pyrite (pyritization).

The depletion of mining resources forces the mining industry to process more heterogeneous and complex orebodies. The inherent heterogeneity of these orebodies and their relation to processing recoveries have received considerable interest in recent years. The properties of ores, such as mineral composition and association, are known to affect flotation performance. Even ores with similar compositions can vary significantly regarding their texture, where the same minerals can occur in different forms. Therefore, very careful geometallurgical planning is needed to overcome the recovery losses. Glencore's Mount Isa Copper Operation has reported historical difficulties decreasing the copper losses associated with natural floatable pyrites. Understanding the rock properties of naturally floatable pyrites and how they relate to chalcopyrite losses is crucial for concentrator operations. The Mount Isa geometallurgy team is looking for proxies for predicting copper losses and natural floatable pyrites to improve mine planning. This paper presents an approach for predicting the collector-less flotation of pyrite, as well as chalcopyrite losses from rock properties. The statistical analysis between the rock quality and ore type gives an indication of the chalcopyrite losses and natural floatable pyrites, which has potential use in geometallurgy plans. [ABSTRACT FROM AUTHOR]

The Mutnovskoe deposit is one of the largest and most prospective ore deposits in South Kamchatka. The northern and southern flanks within the main veining zone Opredelyayushchaya, composed of low-sulfide (gold-silver) and sulfide-polymetallic (gold-silver-polymetallic) types of ores, respectively, are distinguished. The paper presents the results of the complex mineralogical and geochemical studies of the gold-silver-polymetallic ores of the southern flank of the deposit. Features of textures and structures, mineral, chemical compositions and genesis of the ores, as well forms of precious and base metals occurrences are shown. Typomorphic features of pyrite, sphalerite, galena, chalcopyrite, tennantite-tetrahedrite, Au, Ag, Pb and Bi tellurides, native gold, Bi, Se and Ag sulfosalts are characterized. The pyrite-sphalerite-quartz, sphalerite-galena-quartz, and chalcopyrite-ten- nantite-tetrahedrite mineral associations are distinguished. The temperatures and composition of ore-forming solutions are shown.

In this study, we examined the morphological, chemical, and structural details of tetrahedral pyrite crystals from the Jean Baptiste mine in Lavrion, Greece. Pyrite occurs in three generations. Tetrahedral crystals of the first generation are left- or right-handed with the lowest cubic 23 symmetry. In this generation, there are twins with higher cubic m3 and hexagonal 6 symmetry. All crystals of the second generation are primarily interpenetrated into twins with a cubic 4m3 symmetry. Some, however, continue to twin up to crystals with the highest cubic m3m and hexagonal 6mm symmetry. Third-generation crystals overgrow second-generation crystals in a non-oriented manner. Chemical analysis confirms chemically pure pyrite, and single-crystal X-ray analysis of the first- and the second-generation crystals confirms the pyrite-specific m3 symmetry. The morphology of the single crystals and twins indicates that first generation of single pyrite crystals should have the lowest cubic 23 symmetry, which is not confirmed by the structural analysis. This discrepancy may be due to changed pT conditions and the consequent transformation of the original pyrite structure with symmetry 23 into a secondary structure with m3 symmetry, or to suboptimal conditions in determining the structure by X-ray diffraction.

The existence of pyrite provides a basis for the restoration of sedimentary and diagenetic environment, also, it can be regarded as a reference for the prediction of organic-rich shale. Shales of the Lower Cambrian Niutitang Formation drilled at three different sedimentary locations (wells Yichang EYY1, Weiyuan W001-4 and Hanzhong SNY1) in the Yangtze region have been taken as samples in this study. The pyrites founded within these samples have been analyzed with XRD, microscope, scanning electron microscope and carbon and sulfur contents. By the comparison of analytical results, it was indicated that there were four types of pyrite in these samples including framboidal, cubic automorphic, strip-shaped and irregular non-self-formed. The framboidal pyrite was mostly developed, and its particle size was relatively smaller and varied in a narrow range, reflecting the synsedimentary origin, generally has a good and positive correlation with the content of organic matter, while other types of pyrite may be diagenetically originated. The morphological differences of pyrite in shale samples from three wells indicated that the sedimentary water of well SNY1 is quiet and has the strongest reductivity. The lower part of the sedimentary water of wells W001-4 and EYY1 experienced a transformation from oxygen-poor to anaerobic, and the high-abundance pyrite in the shales of well W001-4 might be affected by hydrothermal activities in the Mianyang-Changning tension trough. Compared with calcareous shale, siliceous shale and silicic-calcareous transitional shale are more favorable for the formation of pyrite. Pyrite has a positive effect on the development and preservation of organic pores, which is beneficial to the enrichment and storage of natural gas in shale reservoirs.

Daerah Wombo Kecamatan Tanantovea Kabupaten Donggala Provinsi Sulawesi Tengah merupakan salah satu daerah yang diduga mempunyai potensi mineralisasi bijih. Hal ini diindikasikan dengan adanya kenampakan permukaan berupa batuan diorit yang telah mengalami alterasi. Penelitian ini bertujuan untuk mengidentifikasi karakteristik alterasi hidrotermal dan mineralisasi bijih dengan metode penelitian lapangan dan analisis laboratorium berupa petrografi, XRD dan mineragrafi. Berdasarkan analisis petrografi dan XRD, alterasi hidrotermal dicirikan oleh alterasi propilitik (klorit-zeolit-kalsit) dan alterasi argilik (illit-kuarsa-kalsit). Berdasarkan analisis mineragrafi, mineralisasi bijih di daerah penelitian dicirikan oleh kehadiran pirit (FeS2), kalkopirit (CuFeS2) dan kovelit (CuS). Hasil interpretasi menunjukkan bahwa urutan pembentukan mineral bijih berdasarkan pengamatan tekstur yaitu diawali dengan pirit yang hadir mengisi rekahan-rekahan pada batuan, kalkopirit intergrowth dengan pirit yang menandakan kalkopirit hadir bersamaan dengan pirit, replacement kovelit terhadap kalkopirit dan pirit menunjukkan kehadiran kovelit setelah pirit dan kalkopirit.

Speciation of inorganic sulfur species, mainly pyrite and metastable iron sulfides by operationally defined methods, is widely used for risk assessment of acid sulfate soils by quantifying the acidity producing elements, as well as for general characterisation of marine sediments and subaqueous soils. “Traditional” sulfur speciation methods commonly use highly specialised glassware which can be cumbersome for the operator, or, require long reaction times which limit the usability of the method. We present a simplified method which has a sufficiently low limit of detection (0.002%) and quantitation (0.006%) required for the analysis of sulfidic sulfur in acid sulfate soil materials. Commercially available sulfide reagents were used for determining reproducibility and the method was assessed on natural sulfidic soil materials, including fine to coarse grained soil materials as well as sulfide bearing peat, with a large variation of metastable sulfide and pyrite content.

BACKGROUND Alum shale (Middle Cambrian to Lower Ordovician) is a set of significant marine source rock in Northern Europe, and the maturity is from immature to over mature. Because of high maturities of the Lower-Paleozoic marine source rocks in China, the immature-early mature Alum shales are important samples for the comparative studies of hydrocarbon generation potential. Thus, the analyses of organic matter, mineral composition and sedimentary characteristics of the Alum shale with low maturity, are the fundamental for the comparative studies on the Lower Paleozoic marine source rocks at home and abroad. OBJECTIVES To uncover the mineral and organic matter compositions, and the sedimentary characteristics of Alum shales. METHODS Based on the organic carbon content (TOC) and organic petrological observations, the integrated mineral analysis (TIMA) technology was used to scan the sample. Scan parameters were refined to obtain the mineral composition, content and particle size distribution of shale. RESULTS The TOC and TRS contents of studied Alum shale (%Rb=0.3) were 11.16%-12.24% and 4.30%-5.31%, respectively. The maceral compositions included the lamalginite from planktonic algae degradation and vitrinite-like macerals from benthic algae. Solid bitumen filled in the fractures and pores. The organic matter (OM) and pyrite (Py) contents acquired from TIMA scanning analyses were 9.79%-10.64% and 4.17%-4.49%, respectively. The OM/Py ratios ranged from 2.18 to 2.55, similar to the C/S ratios from Rock-eval pyrolysis. Grain sizes of OM were 0.9-27.0μm, and 80% grains had sizes of 1.2-5.5μm. Grain size of Py distributed from 0.9 to 17.0μm, and the proportion of grains with the size of lower than 0.5μm was higher than 78%, indicating an oxygen-lacking or sulfurized environment. CONCLUSIONS A combination of C/S ratio, and characteristics of organic petrology and Py grain size distribution indicates the Alum shale was deposited in a closed or sulfurized water system. A new technical support for the research of source rocks (including shale) in the field of petroleum geology is provided through the methods used and discussed in this study.

Abstract Submarine caldera volcanoes may host several hydrothermal systems along the caldera wall and related to volcanic cones. Fluid boiling and magmatic volatile influx are common processes in shallow (

The Dongguashan deposit is the largest and deepest Cu (Au) deposit in the Tongling region, eastern China. The presence of skarn and stratiform ore bodies in the same system of the Dongguashan deposit has caused much debate as to whether the mineralization was associated with magmatic-hydrothermal or sedimentary origin. In this study, in situ (LA-ICP-MS and EPMA) elemental compositions of medium-to coarse-grained euhedral pyrite from the stratiform and skarn ore bodies, and pyritization marble are investigated in the Dongguashan deposit. The results of the studied pyrite samples have relatively consistent trace element composition characteristics and several genetically significant elemental combinations. Gold and Ag are mainly of lattice bound appearance in pyrite. The Pb, Cu, Sb and Tl elements are mainly incorporated into the pyrite structure as substitutions. The distinctly trace element distribution correlations (e.g., Mn, Se and Tl) of the studied pyrites indicate that they were formed in a high temperature and oxidizing environment. Low Au (1) and Se/Tl (>10) ratios of the studied pyrites imply that the Dongguashan deposit is most likely to be a magmatic-hydrothermal origin.

ABSTRACT: The Dongyang gold deposit is a newly discovered epithermal deposit in Fujian Province, Southeast China, along the Circum-Pacific metallogenic belt. Herewith, the authors present mineralogical, scanning electron microscope, and laser ablation inductively coupled clasma mass spectrometry analysis to reveal the relations between Au and Te, As, S, Fe, etc., and discuss the gold precipitation process. The pyrites in this deposit are Fe-deficient, and are enriched in Te and As. The authors infer that As was mainly in form of As-complexes, and Te-Au-Ag inclusions/solid solution also exsits in the Py I. Along with the depletion of Te and As, they were less active chemically in the Py II, and Au may be incorporated into As-rich and Fe-deficient surface sites by chemisorption onto As-rich growth surfaces. Because of the incorporation of new fluid, Te and As became the most active chemically in the Py III, which was the main elements precipitation stage, and As dominantly substituted for S in the lattice of pyrite, due to the more reducing condition. The authors propose Au was in form of invisible gold, and the incorporation of gold can be considered as post-pyrite event, while the Au-bearing minerals were result of post incorporation of gold in arsenian pyrite.

The article is devoted to molybdenum mineralization of the Eastern flank of Au-Mo Serhiivka deposit, located in the Middle Dnipro megablock of the Ukrainian Shield (USh). The generalized description of mineralization is performed on such important questions: discovery and exploration history, structure and composition of the host rocks, metamorphic and metasomatic alteration of rocks, structural position and localization conditions of molybdenum mineralization, ore composition, description of major ore minerals, morphology of mineralization and the most widespread views about its genesis. Molybdenum ores were discovered and named East-Serhiivka occurrence for the first time in 1974, before the discovery of gold mineralization, which occurred in 1985. Serhiivka deposit consists of two Mesoarchaean volcanic-plutonic associations (VPA) of different composition: the early mafic and the late felsic. The Eastern flank of the deposit, where the molybdenum mineralization is concentrated, is a structural knot similar to the lying letter “T”. It is formed by complex joint of the sub-latitudinal Serhiivka and sub-meridional Solone subvolcanic bodies and the East-Serhiivka massif of plagiogranitoids of the late VPA, which intrude basic rocks of early VPA. Molybdenum mineralization is localized in linearly elongated zones with a chaotic network of thin quartz, carbonate-quartz veinlets and poor (2–5 %) sulfide impregnation, including molybdenite. About 20 vein-impregnated ore zones have been recovered with up to 100–150 m thickness and 0,01 to 0,3 %, sometimes more than 1 % average molybdenum grade. The ores are subdivided into two major mineral types: 1) quartz-molybdenite; 2) quartz-sulfide-gold-molybdenite. The main components of ores molybdenite and native gold are associated with pyrite, chalcopyrite, magnetite, occasionally – pyrrhotite, arsenopyrite, scheelite, bismuth telluride, silver and others. Typical non-metallic minerals are quartz, carbonate, feldspar, chlorite, amphibole, biotite, sericite. It is supposed hydrothermal-metamorphogenic genesis of molybdenum (and gold) ores. Molybdenite and gold are rarely detected in the same intersections, which indicates separate genesis of these minerals. According to the accepted classification molybdenum mineralization is systemized as linear stockwork. Molybdenum ores of Serhiivka deposit are mostly considered as independent, separate from gold mineralization, potentially workable mine. It is the most prospective one in the Middle Dnipro region, USh and Ukraine in general. We suggest a comprehensive approach to studying, resource and reserves evaluation of Serhiivka deposit, taking into account the potential of both molybdenum and gold mineralization, as well as concentrations of rhenium and osmium in molybdenite. Geological exploration on the base of this approach will increase investment prospects of Serhiivka gold-molybdenum deposit.

Pyrite is one of the most common minerals in shale, but its type, genesis and effect on shale gas accumulation are still in the initial study stage. The shale in the Upper Ordovician Wufeng Formation and the Lower Silurian Longmaxi Formation in the Sichuan Basin and its periphery was studied. Strawberry-like, stratified, tuberculosis, euhedral and anhedral pyrites were identified through thin section observation, scanning electronic microscopy analyses. The pyrites in the Wufeng-Longmaxi formations are mainly developed during the syngenetic and early diagenetic stages. The strawberry-like pyrites are formed in the syngenetic stage, indicating a reducing environment, which is conducive for organic matter enrichment and preservation. The pyrite content has a positive correlation with the organic carbon content. The layers with a high content of pyrites are usually rich in organic matter. Strawberry-like pyrites, together with biogenic quartz and terrestrial detrital quartz, formed a rigid particle grid supporting the original intergranular pores, which was beneficial to hydrocarbon charging, preservation and organic matter-hosted pore development. The bottom of the Wufeng -Longmaxi shale with well developed strawberry-like pyrite in the Sichuan Basin and its periphery, indicate it not only has a good condition for organic matter enrichment, but also is conducive to the formation of high-quality shale gas reservoirs. The strawberry-like pyrite content can be used as a clue for identifying shale gas "sweet spots".

The distribution of trace elements in pyrite has been documented for the first time in quartz veins hosted in the Mesoproterozoic metasedimentary sequence of the Tombador Formation, São Francisco Craton, northeast Brazil. In this study, Electron Microprobe Analyses (EPMA) were used to determine the trace-element compositions of pyrite in these hydrothermal quartz veins. Three pyrite types have been distinguished and interpreted from petrographical relationships and trace-element patterns. Pre-existing pyrite (Py1), derived from the host-rock quartzite, is Ni-poor with concentrations varying from 600 – 6,100 ppm. Elongated syn-tectonic pyrite (Py2) has similar trace-element composition to the Py1, with Ni amounts ranging between 830 and 7,870 ppm. In contrast, possibly post-tectonic, euhedral to subhedral hydrothermal pyrite (Py3), contains higher contents of Ni (7,970 – 26,120 ppm). Mafic and/or metasedimentary rocks from the Espinhaço Supergroup were probably the source of Ni for this fluid-flow event. Fluid generation is related to the devolatilization of the base of the thickened crust, with migration of fluids by preexisting structures. Several shear zones and large-scale NNW-trending folds were developed during the inversion of the Espinhaço basin, as a result of the ca. 0.6 Ga Brasiliano orogenic event. Regional fluid movement through the crust at this time is supported by several mineralized veins and hydrothermal deposits in the São Francisco Craton and adjacent Neoproterozoic belts.

In-situ recovery (ISR) of uranium (U) from sandstone-type roll-front deposits is a technology that involves the injection of solutions that consist of ground water fortified with oxygen and carbonate to promote the oxidative dissolution of U, which is pumped to recovery facilities located at the surface that capture the dissolved U and recycle the treated water. The ISR process alters the geochemical conditions in the subsurface creating conditions that are more favorable to the migration of uranium and other metals associated with the uranium deposit. There is a lack of clear understanding of the impact of ISR mining on the aquifer and host rocks of the post-mined site and the fate of residual U and other metals within the mined ore zone. We performed detailed petrographic, mineralogical, and geochemical analyses of several samples taken from about 7m of core of the formerly the ISR-mined Smith Ranch-Highland uranium deposit in Wyoming. We show that previously mined cores contain significant residual uranium (U) present as coatings on pyrite and carbonaceous fragments. Coffinite was identified in three samples. Core samples with higher organic (>1wt.%) and clay (>6-17wt.%) contents yielded higher 234U/238U activity ratios (1.0-1.48) than those with lower organic and clay fractions. The ISR mining was inefficient in mobilizing U from the carbonaceous materials, which retained considerable U concentrations (374-11,534ppm). This is in contrast with the deeper part of the ore zone, which was highly depleted in U and had very low 234U/238U activity ratios. This probably is due to greater contact with the lixiviant (leaching solution) during ISR mining. EXAFS analyses performed on grains with the highest U and Fe concentrations reveal that Fe is present in a reduced form as pyrite and U occurs mostly as U(IV) complexed by organic matter or as U(IV) phases of carbonate complexes. Moreover, U-O distances of ~. 2.05. Å were noted, indicating the potential formation of other poorly defined U(IV/VI) species. We also noted a small contribution from U. O at 1.79. Å, which indicates that U is partially oxidized. There is no apparent U-S or U-Fe interaction in any of the U spectra analyzed. However, SEM analysis of thin sections prepared from the same core material reveals surficial U associated with pyrite which is probably a minor fraction of the total U present as thin coatings on the surface of pyrite.Our data show the presence of different structurally variable uranium forms associated with the mined cores. U associated with carbonaceous materials is probably from the original U mobilization that accumulated in the organic matter-rich areas under reducing conditions during shallow burial diagenesis. U associated with pyrite represents a small fraction of the total U and was likely deposited as a result of chemical reduction by pyrite. Our data suggest that areas rich in carbonaceous materials had limited exposure to the lixiviant solution, continue to be reducing, and still hold significant U resources. Because of their limited access to fluid flow, these areas might not contribute significantly to post-mining U release or attenuation. Areas with pyrite that are accessible to fluids seem to be more reactive and could act as reductants and facilitate U reduction and accumulation, limiting its migration.

Pyrite is one of the widespread sulfide minerals of the mud volcanoes of Azerbaijan. A characteristic feature of these pyrites is the scarcity of their crystalline forms. Only in some volcanic products its fairly cubic, cubic­octahedral crystals be found). But, in emissions of mud volcanoes its aggregate species are very common, differing in shape and development. It should be noted that the shape and variability of pyrite aggregates can provide valuable information about the crystallization process, and about the direction of moving crystal­forming solutions. In this aspect, the identification of the relationship between the shape of pyrite aggregates and their genesis, the pattern of distribution of isomorphic and mechanical impurities in pyrites from mud volcanoes is of great scientific interest.

Among fossil fuels, coal is the most widely used all over the world for generating power and electricity and it is a stable source of energy. Despite all these benefits, coal mining has serious hazards, such as coal spontaneous combustion. There are many factors that influence the tendency for coal to spontaneously combust in coal mines. Pyrite can promote the risk of this phenomenon. This promotion is accelerated by the combination of pyrite and moisture content at the same time. This combination is very rarely discussed in literature. So, in this research, the accelerating effect of reactive pyrite and moisture content on coal spontaneous combustion was measured experimentally using crossing point temperature (CPT) and R70 test methods. For this purpose, a new experimental apparatus was assembled and made in Iran. Reaction rate data obtained from the experimental results showed that pyrite has a twofold action. It first catalyzes the oxidation reaction. Then, in a moist environment, pyrite is itself oxidized, which provides a secondary heat source, and so accelerates the process of coal spontaneous combustion. Since the pyrite oxidation reaction consumes moisture, there is a mutual effect of accelerated heating as less heat is used up in moisture evaporation. The results show that pyrite content can linearly accelerate the coal spontaneous combustion process, while moisture content under 20% increases it, and if the moisture exceeds 20%, the rate of this process is reduced. The results of this research are helpful in the assessment and management of coal spontaneous combustion issues in coal mines.

Abstract The stability, structure, and elastic properties of pyrite‐type (FeS2 structured) FeO2H were determined using density functional theory‐based computations with an internally consistent Coulombic self‐interaction term (Ueff). The properties of pyrite‐type FeO2H are compared to that of pyrite‐type AlO2H, with which it likely forms a solid solution at high temperature, as well as the respective lower pressure CaCl2‐type polymorphs of both endmembers: ϵ‐FeOOH and δ‐AlOOH. Due to substantial differences in the CaCl2‐type → pyrite‐type structural transition pressures of these endmembers, the stabilities of the (Al,Fe)O2H solid solution polymorphs are anticipated to be compositionally driven at lower mantle pressures. As the geophysical properties of (Al,Fe)OOH are structurally dependant, interpretations regarding the contribution of pyrite‐type FeO2H to seismically observed features must take into account the importance of this broad phase loop. With this in mind, Fe‐rich pyrite‐type (Al,Fe)OOH may coexist with Al‐dominant CaCl2‐type δ‐(Al,Fe)OOH in the deep Earth. Furthermore, pyrite‐type (Al0.5–0.6,Fe0.4–0.5)O2H can reproduce the reduced compressional and shear velocities characteristic of seismically observed ultra low velocity zones in the Earth's lowermost mantle while Al‐dominant but Fe‐bearing CaCl2‐type δ‐(Al,Fe)OOH may contribute to large low shear velocity provinces.

The Uyanga ore knot district of the Khangay metallogenic zone are hosted by the lower-middle Devonian volcanogenic-sedimentary Erdenetsogt formation. About 40 samples were collected from the host rocks, veins and quartz veins in the Uyanga ore knot district in 2016. The new Burgetei, Ult and Senjit gold occurrences were studied. The quartz-sulfide, gold-arsenic and gold-antimony-mercury mineralization are determined in the berecitization, silicification, limonitization and glauconization altered metasomatic zones within the Uyanga ore knot districts. The rocks of the Erdenetsogt formation have an irregular gold content: 0.96 g/t Au is determined in quartz vein taken from trench of the Burgetei occurrence (BG-7/16), Au content is highest up to 3.5 g/t in the quartzite-jasper (Ult-7/16 and Ult-9/16) cut by quartz veins in the Ult occurrence. The Senjit occurrence represents Au-Hg-Sb epizonal level of orogenic gold deposits structure with highest Hg content up to 851 ppm. This year no sulfide minerals were found in the siltstone of this occurrence. The Au content of arsenical pyrite of the Burgetei and Ult is below the detection limit by electron microprobe analysis. The Au content of arsenopyrite of the Ult occurrence is highest (up to 238 ppm). Therefore, the ore-mineral assemblages in the gold occurrences reflect the differences between the three explored sites, formed in the course of fluid evolution during the fluid-rock interaction. Variable concentrations of indicative elements (As, Te, Sb, Hg) and their ratios confirm this fact. The geodynamic position, the type of the hydrothermal alteration of both igneous and sedimentary rocks, textures and mineral assemblages, the mineralization sequences are consistent with orogenic classification for the Burgetei, Ult and Senjit gold occurrences.

The late Paleozoic magmatic rocks are widely distributed in the Mandakh area which is located in the Gurvansaikhan and Manlai terrains, where porphyry Cu deposits occur. In this paper we discuss petrochemical features and mineral assemblages of magmatic rocks in the Mandakh area. Furthermore, we compared petrochemical characteristics of magmatic rocks in the Mandakh area with host magmatic rocks of the Tampakan deposit (Philippines), Cerro Colorado deposit (Chili) and negative criteria of Cu deposits (Japan) due to try to characterize potential of the porphyry copper deposit related to magmatic rocks in Mandakh area. Geochemical features of magmatic rocks in Mandakh area are calc-alkaline, magnetite-series, I-type and similar to adakite type. The Devonian intrusive rocks comprised of syenite and syenogranite, while the Carboniferous intrusive rocks consist of granodiorite, monzodiorite, quartz-monzonite and hornblende granite. Devonian magmatic rocks are more alkaline in composition. Although, Devonian and Carboniferous magmatic rocks are slightly different from each other. Comparing with bonanza copper deposits in the world, they are possible to host porphyry mineralization.

The Gaosongshan epithermal gold deposit in Heilongjiang, Northeast China, is hosted by the Lower Cretaceous intermediate-basic volcanic rocks. Three auriferous quartz veins including eleven gold orebodies were all discovered in tectonoclastic zones. Genetic mineralogy study including the thermoelectricity, rare earth elements and trace elements of pyrite and rare earth elements of quartz were carried out. Thermoelectric conductive type of pyrite is mainly N-P type. Calculating the thermoelectric parameters XNP and denudation percentage γ of pyrites from orebodies 1-I, 2-II and 2-IV, suggests that gold orebodies are all eroded to their middle-lower parts. The variable range of Co concentrations (51.3-264.0ppm) and Ni concentrations (68.9-258.0ppm) and Co: Ni ratio (0.31-1.90), together with relatively small Sr/Ba ratio in ore-bearing pyrites (0.11-0.50), supports a hydrothermal origin of mineralization at Gaosongshan gold deposit. Compared with volcanic rocks, the chondrite-normalized REE patterns of ore-bearing pyrites and quartz are all LREE enriched with similar ΣLREE/ΣHREE ratio ranging from 7.37-13.68 in ore-bearing pyrites, 4.74-15.37 in ore-bearing quartz and no Ce anomalies. δEu values in ore-bearing pyrites and quartz are 0.65-1.66 (average=0.93) and 0.66-1.62 (average=1.03), respectively. δEu values of volcanic rocks are 0.86­1.07 (average 0.94), suggesting no obvious negative Eu anomalies. Similar REE characteristics of ore-bearing pyrites and quartz and volcanic rocks, together with previous oxygen and hydrogen isotope studies of quartz, suggest that the ore-forming fluids of the Gaosongshan gold deposit were mainly magmatic origin which was associated with andesitic magma and was partly mixed with atmospheric water. Comparing trace elements characteristics of ore-bearing pyrites with volcanic rocks, together with previous S isotopic studies, it is concluded that the ore-forming materials were derived from the surrounding rocks. Slight changes of Y/Ho (23.80­27.28), Zr/Hf (35.41­47.83), Nb/Ta (10.96­18.52) in ore-bearing pyrites indicate that the ore-forming fluid system is relatively stable during the ore-forming process.

BACKGROUND Microscopy and Electron Microprobe are the main methods for the study of gold-bearing minerals. Using these methods, the content and morphology of gold-bearing minerals and their spatial relationship with other minerals were studied in the Zhaojiazhuang gold deposit. The gold-bearing minerals were qualitatively and quantitatively analyzed. OBJECTIVES To summarize the gold-bearing minerals with the significance of prospecting and the features of indicator minerals. METHODS Microscopy and Electron Microprobe. RESULTS The main gold-bearing mineral is pyrite, then chalcopyrite and sphalerite. The contents of Au in the main gold-bearing minerals follow the sequence of fine-grained pyrite > coarse-grained pyrite > strawberry pyrite > chalcopyrite. The distribution of Au in different stages of pyrite (coarse pyrite, fine pyrite, strawberry pyrite) is uniform. Fine-grained and strawberry pyrite have higher gold content (average 0.14%-0.18%), indicating that these types of pyrite formed by tectonic hydrothermal fluids where Au concentrates more easily. There are two occurrences of gold in the Zhaojiazhuang Au deposit. Visible gold is wrapped in gangue minerals, or embedded in mineral crystal gaps and cracks in the form of fissure gold. Invisible gold exists in the gold-bearing minerals in the form of nano-scale gold particles. Invisible gold is the main existence form of Au. CONCLUSIONS This study provides evidence for the study of the genesis, metallogenic process and mechanism of the same deposits and it is easy to select suitable methods for ore selection and smelting based on the characteristics of gold-bearing minerals.

We report on the application of the U-Th-He method for the direct dating of pyrite from the alteration halo of the Novogodnee-Monto Au-Fe-skarn deposit, Polar Urals. The deposit is genetically related to the formation of volcanogenic complexes of the Ural Paleozoic belt. A modification of the original methodology for measuring U, Th and He isotopes in a single grain allowed us to determine a U-Th-He age of 382 ± 8 Ma (2σ) based on six pyrite samples from the altered rocks of the deposit (U mass fraction ~0.2 mg/kg; Th/U ~3.5; 4He specific volume ~10−5 cm3·STP·g−1). This age is consistent with estimates of the age of ore formation and coeval with the end of the period of island arc magmatic activity. Our results indicate that U-Th-He dating for pyrite samples of ~1 mg in weight from the hydrothermal-metasomatic halo of ore bodies is possible, providing a crucial next step in the development of U-Th-He pyrite geochronology.

Studying elemental geochemistry of hypogene sulphides can discriminate the hydrothermal fluids responsible for ore formation. To determine whether Golpu porphyry Cu-Au deposits are related to the Nambonga North porphyry system which is located 2.5 km apart in the Wafi-Golpu Mineral District, Papua New Guinea, we compare the trace element compositions of drill core chalcopyrites and pyrites analysed using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICPMS). The results for the Golpu chalcopyrites revealed high concentrations of Au, As, Se, Mo, Sb, Te and Bi and lower concentrations of Ag and Zn compared to those from Nambonga. Pd and Pt were below the detection limit in chalcopyrites for both deposits. The results for the Golpu pyrites indicated high concentrations of Pt, Au, Se, Mo, Sb, and Te and lower concentrations of Cu, Zn, As, Ag, Pb, Pd and Bi compared to those from Nambonga North. Au concentrations in the pyrites from both the porphyry deposits were higher compared to chalcopyrites, which mean that pyrite is the Au-bearing sulphide responsible for the higher Au content. In contrast, Cu values in pyrites from Nambonga North are higher than those from Golpu. Overall, it is envisaged that the ore fluids were exsolved at different times during the evolution of both porphyry deposits, although these porphyry centres may be related in space and time.

This study is focused on the mineralogical, chemical, and isotopic characterization of pyrites from the rocks of the Bazhenov Formation (Upper Jurassic–Lower Cretaceous organic-rich shales, Western Siberia, Russia). Scanning electron microscopy (SEM) revealed pyrites of different morphologies: small and large framboids, small crystals, and large euhedral crystals; all morphotypes were usually combined into aggregates. Isotope ratio mass spectrometry (IRMS) and secondary ion mass spectrometry (SIMS) showed that small framboids and microcrystalline pyrite are isotopically light, with δ34SCDT varying from −55 to −20‰. Large framboids and euhedral crystals of pyrite are isotopically heavy with δ34SCDT up to +26‰. Both morphology and δ34S were suggested to be controlled by the redox conditions and sedimentation regime. The abundance of small framboids suggests that pyrite sedimentation occurred under anoxic conditions; the presence of the large framboids and euhedral crystals of pyrite suggest the accumulation of sediments occurred at suboxic conditions, possibly in the presence of oxygen.

The Central gold belt of peninsular Malaysia comprises a number of gold deposits located in the east of the N-S striking Bentong-Raub Suture Zone. The Tersang gold deposit is a mesothermal, orogenic gold deposit, which is hosted in sandstone, shale, rhyolite and breccia. The deposit has an inferred and indicated resource of 120,000 ounces of gold in the JORC category. Detrital zircon grains from the host sandstones returned a maximum depositional age ranging from Early Carboniferous to Early Permian (333.5 ± 2.5 Ma-261.5 ± 4.9 Ma) and those of the rhyolite indicated a crystallization age of 218.8 ± 1.7 Ma. Pyrite trace element mapping has revealed four pyrite phases. Laser Ablation ICPMS analyses on pyrite has shown that pyrite phase 1 has the lowest Au concentration (mean 0.4 ppm) and is interpreted to have preceded the main Au mineralisation stage. Pyrite phases 2 and 3 are the main Au mineralisation stage with Au mean range from 1.5 to 4.5 ppm and contributed most of the invisible gold to the ore-forming system. Pyrite phase 4 has low gold concentrations (mean 0.5 ppm) and post-dated the main Au mineralisation stage recorded in pyrite phases 2 and 3. The trace element chemistry of pyrite indicates that Au mineralisation recorded in pyrite is likely a product of four stages ore forming system centred on the rhyolite corridor. In terms of gold exploration, gold has a positive correlation with As, Ag, Cu, Se, Sb, Pb and Tl in pyrite. These metals can be used as pathfinders to detect proximity to ore for orogenic gold deposit type in the central gold belt of Peninsular Malaysia.

Most sulfate and sulfide ores are composed of low electrical magnetic materials. In the process of combustion, the sulfur in sulfate and sulfide ores cannot be released completely, because it is difficult to produce a large enough electromagnetic induction eddy current. Thus, the results are lower than real values when the sulfur in sulfate and sulfide ores is determined by High Frequency Infrared Carbon-Sulfur Spectrometer. In this study, the barite and pyrite samples are diluted with silicon dioxide to acquire different contents of sulfur. By optimizing the sample weight and flux types, determination of sulfur by High Frequency Infrared Carbon-Sulfur Spectrometer was developed. Results show that the sample weight is 0.07 g when the content of sulfur is higher than 2% whereas sample weight is 0.1 g when the sulfur content is below 2%. Furthermore, the sulfur in barite and pyrite can be released completely into the infrared absorption area when adding 0.4 g of tin grain, 0.4 g of iron grain, and 0.5 g of tungsten grain to the sample. The recovery of sulfur can reach 95.8%-104.2%(barite) and 95.3%-105.1%(pyrite), which is far higher than the recovery of 83.3%-91.1% and 91.5-97.5% for the conventional analysis of sulfur by Infrared Carbon-Sulfur Spectrometer. This method precision is less than 5% and can determine the accurate content of sulfur.

This paper presents results of a petrographic, mineralogical and geochemical study of ore, gangue and rock-forming minerals that occur within the Upper Cambrian (Furongian)-age siliciclastic rocks of the Wiśniówka massif (western part of the Main Range, Holy Cross Mountains, south-central Poland). This area is characterized by the presence of ubiquitous pyrite that makes up two stratiform mineralization zones assigned to the early and middle Late Cambrian, giving rise to acid mine drainage. The oldest zone comprises additionally sedimentary breccias with intraclast-supported pyrite cement. The predominant microscopic (colloform) and partly framboidal pyrite typically shows high concentrations of As (up to 8.23 wt%) and a distinct enrichment in the light sulfur isotope (δ34S from −41.4 to −23.6‰). The occurrences of large amounts of As-rich pyrite showing strongly negative δ34S values are rather uncommon in Paleozoic sedimentary formations worldwide that exhibit distinctly smaller amounts of As and mostly enrichments in heavier sulfur isotope (δ34S up to 63‰). Another specific feature of the Wiśniówka rock series is the presence of REE-bearing aluminophosphate and phosphate minerals that occur primarily in clayey-silty shales and bentonites. Based on the results obtained, a sequence of hydrothermal index minerals was discriminated, including pyrite (whose grains are usually made of alternating arsenic-rich and arsenic-poor bands), as well as paragenetic assemblages of dickite, nacrite, xenotime and the crandallite series of aluminum-phosphate-sulfate minerals. Both mineral composition and specific microtextures are indicative of multistage hydrothermal activity that took place in the Wiśniówka depositional basin during the Late Cambrian time. This is in distinct contrast to the remaining part of the Main Range, which is devoid of the hydrothermal pyrite imprint. Moreover, the results of this study give insight into the complex sedimentary and early diagenetic history of the southwestern passive margin of the Baltica craton. This currently makes up a part of the Łysogóry Block (Terrane) that borders on the Trans-European Suture Zone separating the Precambrian East-European Craton from the Paleozoic Platform of Central Europe. This study is important because we still lack the full knowledge about the hydrothermal processes that took place in Early Paleozoic depositional basins. Unlabelled Image • Siliciclastic rocks of the Wiśniówka area (south-central Poland) were examined. • Large amounts of As-rich pyrite showing strongly negative δ34S values were found. • Pyrite makes up two stratiform zones that formed in the Late Cambrian. • REE-bearing minerals predominate in clayey-silty shales. • Hydrothermal activity took place in the Late Cambrian depositional basin. [ABSTRACT FROM AUTHOR]

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Determination of trace elements in analyzed mineral phase by Laser Ablation-Inductively Coupled Plasma-Mass Spectrometry (LA-ICP-MS) is a new in situ technique for mineral phase analyses. As an important mineral in porphyry copper deposits, the major and trace elements of pyrite can provide important information for the ore-forming process. A method for determination of the trace elements in pyrite by LA-ICP-MS and major elements by Electron Microprobe was developed and has been applied to the Baishantang porphyry copper ore district. For the LA-ICP-MS experiment, the laser beam is 60 μm, the carrier gas is helium, the repetition frequency is 5 Hz, the laser energy is 6 J/cm2, and the analysis time of single point is 60 s. Iron was used as an internal standard and MASS-1 was used to calibrate the data. Analysis precision of most elements is better than 10%. For the similar optical properties of pyrite and arsenopyrite, the differences of physical properties can be used to distinguish them. Pyrite in the Baishantang porphyry copper deposit is depleted in sulfur but rich in iron, indicating a hydrothermal origin. The trace element composition of pyrite indicates that pyrite was formed at a medium depth and belongs to the medium-low temperature hydrothermal type related to volcanism. This conclusion has provided important evidence for the ore genesis and the source of ore-forming fluids of the Baishantang porphyry copper deposit, which can also guide the next-step exploration.

The Moodies Group, the uppermost unit in the Barberton Greenstone Belt (BGB) in South Africa, is a ~3.7-km-thick coarse clastic succession accumulated on terrestrial-to-shallow marine settings at around 3.22 Ga. The multiple sulfur isotopic composition of pyrite of Moodies intervals was newly obtained to examine the influence of these depositional settings on the sulfur isotope record. Conglomerate and sandstone rocks were collected from three synclines north of the Inyoka Fault of the central BGB, namely, the Eureka, Dycedale, and Saddleback synclines. The sulfur isotopic composition of pyrite was analyzed by Secondary Ion Mass Spectrometry (SIMS) for 6 samples from the three synclines and by Isotope Ratio Mass Spectrometry (IR-MS) for 17 samples from a stratigraphic section in the Saddleback Syncline. The present results show a signal of mass-independent fractionation of sulfur isotopes (S-MIF), although t-tests statistically demonstrated that the Moodies S-MIF signals (mostly 0‰ < ∆33S < +0.5‰) are significantly small compared to the signal of the older Paleoarchean (3.6–3.2 Ga) records. These peculiar signatures might be related to initial deposition of detrital pyrite of juvenile origin from the surrounding intrusive (tonalite–trondhjemite–granodiorite; TTG) and felsic volcanic rocks, and/or to secondary addition of hydrothermal sulfur during late metasomatism. Moreover, fast accumulation (~0.1–1 mm/year) of the Moodies sediments might have led to a reduced accumulation of sulfur derived from an atmospheric source during their deposition. As a result, the sulfur isotopic composition of the sediments may have become susceptible to the secondary addition of metasomatic sulfur on a mass balance point of view. The sulfur isotopic composition of Moodies pyrite is similar to the composition of sulfides from nearby gold mines. It suggests that, after the Moodies deposition, metasomatic pyrite formation commonly occurred north of the Inyoka Fault in the central BGB at 3.1–3.0 Ga.