Pyrite Ore Research Articles

Fluid-rock interaction, skarn genesis, and hydrothermal alteration within an upper crustal fault zone (Island of Elba, Italy)

The Terranera magnetite-hematite-pyrite deposit of the Island of Elba (Italy) is an historical skarn deposit hosted by a fault zone of regional importance (Zuccale Fault) and by its hanging wall rocks.We combine field observations with petrographic data, electron probe microanalyses (EPMA), XRPD data, fluid inclusion microthermometry, and element imaging by Laser Ablation-Inductively Coupled Plasma-Time of Flight Mass Spectrometry (LA-ICP-TOFMS) to define the ore-forming process at Terranera. We show that in this location the fault is made of four levels of mineralized fault rocks having distinct mineral compositions. In these levels, a mineral association made of diopside, clinozoisite, and other Mg-rich minerals is replaced by magnetite, hematite, pyrite, Mg-hornblende, clinochlore, and other Mg-rich phyllosilicates. This paragenesis is overprinted by goethite and clay minerals. Chlorite-quartz geothermometry and fluid inclusion microthermometry show that ore precipitation occurred at 350–180 °C from fluids of distinct bulk salinities, but goethite and clay mineral overprinting progressed at lower T.We propose that Terranera is a magnesian Fe skarn formed due to the interaction between distinct hydrothermal fluids and a dolomitic protolith, which was preserved within the fault zone. These fluids mixed and cooled during protolith metasomatism, causing ore precipitation due to oxidation and desulfidation. A very similar process was described in a large deposit of Elba (Rio Marina). Argillic alteration was widespread within the fault but met permanently intermediate sulfidation conditions. Trace element composition of hematite shows that Terranera has features that overlap those of skarn and epithermal deposits. In particular, elements that are typical of epithermal deposits (Sb, Ga, Ge, As) occur at mass fractions (50–200 μg/g) that are either unreported or not typical of hematite from skarn deposits. These features identify Terranera as formed in an ore environment that was transitional between that of a skarn and of an epithermal deposit. These features are shared by other historical deposits located at Elba and in the massive pyritic ore district of south Tuscany (e.g., Gavorrano, Fenice Capanne). This indicates that a similar environment might have occurred during the Neogene beyond Elba, in a much larger ore district of south Tuscany.

An overview of the most actual methods of pyrite ash valorization

The obtaining process of sulfuric acid, that involves roasted of pyrite ores, leads to accumulation of a significant amount of secondary matter known as pyrite ash. This waste, that is found worldwide in quantities of millions of tons, it is highlighted by his chemical composition, based on the presence of high concentrations of hematite and magnetite. By implementing worldwide of the concept of circular economy, the use of pyritic ash as an alternative source of iron is a topic of current interest. This study is proposing to present the latest trends in the methods of valorization of pyritic ash that are presented in the specialty literature, which can be implemented in various branches of industry.

Depth profiling of arsenian pyrite in Carlin-type ores through wet chemistry

Depth profiling of arsenian pyrite in Carlin-type ores through wet chemistry

Preparation of pyrite concentrate powder from the Thackaringa mine for quantitative phase analysis using X-ray diffraction.

The quantitative phase analysis using X-ray diffraction of pyrite ore concentrate samples extracted from the Thackaringa mine is problematic due to poor particle statistics, microabsorption and preferred orientation. The influence of sample preparation on these issues has been evaluated, with ball milling of the powder found most suitable for accurate and precise quantitative phase analysis. The milling duration and other aspects of sample preparation have been explored, resulting in accurate phase reflection intensities when particle sizes are below 5 µm. Quantitative phase analysis on those samples yielded precise phase fractions with standard deviations below 0.3 wt%. Some discrepancy between the elemental composition obtained using X-ray powder diffraction data and that determined using wavelength-dispersive X-ray fluorescence was found, and is thought to arise from unaccounted for crystalline phase substitution and the possible presence of an amorphous phase. This study provides a methodology for the precise and accurate quantitative phase analysis of X-ray powder diffraction data of pyrite ore concentrate from the Thackaringa mine and a discussion of the limitations of the method. The optimization process reveals the importance of confirming reproducibility on new samples, with as much prior knowledge as possible.

Pyrite ore cargo spills as a source of soil pollution and ecological risk along the abandoned railway corridors of the Tharsis and Rio Tinto mines (Spain).

Abandoned mining railways are a prominent legacy environmental issue facing many metalliferous regions with a long mining history. However, there is a general lack of information on potentially hazardous trace elements occurring in soils alongside railroad lines as a result of hazmat cargo spills. This paper explores for the first time the effects of pyrite ore transportation on soil pollution along the old railways of Tharsis and Rio Tinto, two historical mining districts of world-class importance in the Iberian Pyrite Belt. The railroad-side topsoil was found to be extremely acidic in reaction and contains abundant pyrite, spilled on the tracks during transit, and its oxidation products (jarosite, iron oxyhydroxides, and efflorescent sulfate minerals). Compared to local background concentrations, highly elevated levels of Pb, Zn, Cu, As, Hg, Sb, Bi, Cd, Ag, and Tl were detected in both railroad lines, indicating serious anthropogenic contamination. Exposure to soil contaminants, notably Pb, As, and Tl, could pose hazards to human health and the environment. Accordingly, a specific-site risk assessment is needed before the mining railway lines are converted into recreational trails.

Hidden risks from potentially toxic metal(loid)s in paddy soils-rice and source apportionment using lead isotopes: A case study from China

Pyrite is a typical sulfide mineral which contains various potentially toxic metal(loid)s (PTMs). The pyrite smelting and subsequent industrial utilization activities usually release numerous amounts of PTMs into nearby ecosystem, which may be enriched in the nearby farmland soils and crops, leading to hidden but irreversible harm to human health via the food chain. Herein, the distribution pattern, source apportionment, and potential health risks of Pb, Zn, Cu, Cd and multiple seldom monitored PTMs (Ag, Bi, Sb, Sr, Th, U, W, and V) in the paddy soils and different organs of the rice plants from ten various sites in a typical industrial zone were investigated, where pyrite ores were used for the production of sulfuric acid and subsequent cement over several decades. The results showed that the contents of Cd, Pb and Zn in studied paddy soils generally exceeded the maximum permissible level (MPL) in China, and the contents of Sb and V were approaching the MPL. Moreover, the rice is easier to bioaccumulate Cd, Cu, and Zn than the other studied elements. The hazard quotient (HQ) calculations indicate that the rice containing such multiple elements may cause a high potential non-carcinogenic and carcinogenic health risk for residents, particularly for the senior group. The Pb isotope tracing method combined with PCA (principal component analysis) further uncovered that the pyrite industrial utilization contributed 18.58–55.41 % to the highly enriched PTMs in paddy soils. All these findings indicate that the paddy soil system has been contaminated by the pyrite industrial activities and certain distances or areas should be rigidly forbidden from rice cultivation in the proximity of the pyrite smelting and related industrial sites.

Secondary Minerals from Minothem Environments in Fragnè Mine (Turin, Italy): Preliminary Results

The Fragnè mine, located in the Lanzo valley in the municipality of Chialamberto (Turin, Piedmont Region), represented the most important regional site for Fe–Cu sulfide exploitation over a period of more than eighty years (1884–1965). The entire mining area is part of a structural complex in the Lower Piedmont Unit of the Western Alps, characterized by the presence of amphibolite, metabasite (“prasinite”), and metagabbroic rocks. In particular, the pyrite ore deposit occurs as massive mineralizations within interlayered metabasites and amphibolites. In this work, we describe secondary minerals and morphologies of minothems from the Fragnè mine that are found only in abandoned underground works, such as soda straws, normal and jelly stalactites and stalagmites, jellystones, columns, crusts, blisters, war-clubs, and hair, characterized by different mineralogical associations. All minothems were characterized by minerals formed during acid mine drainage (AMD) processes. Blisters are composed only of schwertmannite, war-clubs by schwertmannite, and goethite with low crystallinity and hair by epsomite and hexahydrite minerals. Jelly stalactites and stalagmites are characterized by schwertmannite often in association with bacteria, while solid stalactites and stalagmites are characterized by jarosite and goethite. The results indicate that the mineralogical transformation from schwertmannite to goethite observed in some minothems is probably due to aging processes of schwertmannite or local pH variations due to bacterial activity. On the basis of these results, we hypothesize that all the jelly samples, in association with strong bacterial activity, are slowly transformed into more solid goethite, and are thus precursors of goethite stalactites.

Chemical Looping Combustion of a Biomass Char in Fe2O3-, CuO-, and SrFeO3−δ-Based Oxygen Carriers

This research focuses on the combustion of biomass char in fluidized beds of various particulate solids, which, under the conditions of the reaction, were either inert or capable of supplying oxygen to reactions. The latter were termed oxygen carriers. The solids used were SiO2, as an inert material, and three oxygen carriers: (1) Fe2O3 prepared from a natural pyrite ore, (2) CuO supported on mayenite, and (3) SrFeO3−δ strontium ferrite perovskite. Combustion experiments were undertaken by introducing a sample of partially devolatilized biomass (commercial “biochar”) to a hot bubbling bed (inner diameter of 30 mm), fluidized by a mixture of oxygen and nitrogen, then analyzing the composition of the off-gas and the burnout time of the char sample. In the temperature range investigated in this work (1023–1168 K), CuO and SrFeO3−δ but not Fe2O3 thermally decomposed, releasing gaseous O2 [so-called “chemical looping oxygen uncoupling” (CLOU)]. Hence, to make the combustion conditions comparable to various oxygen carriers, all experiments were performed using a fluidizing gas with a fixed partial pressure of O2 (pO2) of ∼0.015 bar. Despite the same nominal pO2, the occurrence of the oxygen uncoupling reaction increased the total net amount of O2(g) available in the process, affecting external mass transfer of O2 to the char particle and accelerating its rate of combustion. The time needed to totally combust 0.1 g of biochar particles in different beds at 1168 K followed the trend CuO < SrFeO3−δ < Fe2O3 ≈ silica sand. The difference in the performance of CuO and SrFeO3−δ was ascribed to the lower oxygen availability via CLOU in perovskite compared to copper oxide. Interestingly, combustion in the bed of Fe2O3 particles took a similar amount of time as combustion in the inert bed of SiO2, despite iron oxide playing an active role in the process. The finding is explained by Fe2O3 reacting with CO produced from incomplete char combustion, which results in the reduced oxide competing with char for O2(g) and effectively decreasing the local pO2.

Пирит зон сульфидизации терригенных комплексов Яно-Колымского орогенного пояса (Северо-Восток России): генерации, типохимизм, минеральные ассоциации

Finely disseminated sulfide mineralization in terrigenous carbon-bearing strata is known to have a certain metal-bearing potential and to be an additional source of ores for deposits. In the zones of finely disseminated sulfide mineralization in the Debinsky, Chay-Yuryinsky and Orotukan-Srednekansky faults of the Yana-Kolyma orogenic belt, three generations of pyrite have been identified and studied: sedimentogenic, hydrothermal-metamorphogenic, and tentatively ore-hydrothermal with different sets of mineral associations. The studies were carried out in the Late Triassic and Early Jurassic sediments adjacent to the faults in the basins of the Spokoyny-Matrosova Creek, the Chay-Yurya River, the Ozyorny Creek, the Khara-Yuryakh Creek, the Nera River, and the Pravy Srednekan River. It was found that the sulfide mineralization had been formed in several stages. Morphological and genetic varieties of pyrite permit to distinguish sedimentary and metamorphogenic pyrite from ore pyrite. According to the quantitative analysis performed on a Camebax microanalyzer with an EDS detector X-Max Oxford, the main trace impurities in pyrite are As, Co, and Ni.

Nanoscale isotopic evidence resolves origins of giant Carlin-type ore deposits

Abstract The western North American Great Basin's Carlin-type deposits represent the largest accumulation of gold in the Northern Hemisphere. The controversy over their origins echoes the debate between Neptunists and Plutonists at the birth of modern geology: were the causative processes meteoric or magmatic? Sulfur isotopes have long been considered key to decoding metal cycling in the Earth's crust, but previous studies of Carlin-type pyrite lacked the spatial resolution to quantify differences among the numerous generations of sulfide mineralization. We developed a new dual-method, nanoscale approach to examine the fine-grained ore pyrite. The δ34S of the ore pyrite varies systematically with Au concentration at the nanoscale, indicating that both magmatic and meteoric fluids contributed during mineralization, but the magmas brought the gold. Repeated oscillations in fluid ratios upgraded the metal content, resulting in high gold endowment. Our results demonstrate that high-spatial-resolution studies are key to elucidate the spatiotemporal evolution of complex hydrothermal systems.

Zun-Kholba Orogenic Gold Deposit, Eastern Sayan, Russia: Geology and Genesis

In this paper, we present a new point of view on the deposit geology and genesis of the largest gold deposit in Eastern Sayan, Zun-Kholba. Quartz–sulfide replacement ores and shallow quartz veins are of great economic importance. At the deposit, quartz–pyrite ore bodies are dominant, whereas paragenetically late base metal-bearing quartz veins occur only at shallow levels. The study of the fluid inclusions, stable isotopes (C–O–S), and mineral geothermometry allowed us to determine the P–T conditions of ore deposition. It is established that the temperature of ore formation changed from 380 to 433 °C at the deepest levels of the deposit to 316 °C at the shallowest levels. The pressure estimates for gold deposition at 570–950 bar were calculated for the 1490-m level in the center of the deposit. The determined P–T conditions can help estimate the average depth of deposit formation at about 3.6 km. Ore mineral assemblages were formed from homogeneous fluids of low to moderate salinity (2.4–7.9 wt.% eq. NaCl). The sulfur isotope composition of sulfide minerals (δ34S = 0–4.6‰), as well as pyrite geochemistry, corresponds to that of older volcanogenic massive sulfide (VMS) occurrences, which are widespread within the Eastern Sayan ophiolitic belts. Lens-like fragments of metamorphosed VMS-type sulfide ores are also present in the Zun-Kholba deposit. The oxygen isotope data indicate a metamorphic origin for the ore-forming fluids. Migrating metamorphic fluids may have become enriched in gold, sulfur, and other metals during the flow through the complex ore-hosting lithologies, including ophiolitic bodies with sulfide-rich VMS fragments that are characterized by a relatively high content of gold and related ore elements. The obtained data allow us to suggest a metamorphic devolatilization model for the genesis of the Zun-Kholba gold deposit.

MİNERALOGİCAL COMPOSİTİON, TEXTURE-STRUCTURAL PROPERTİES AND MİNERAL FORMATİON SEQUENCE OF THE ORE OF GOSHA GOLD- PYRİTE FİELD

As a result of microscopic researches it has been determined that mineralogical composition of the ore field consists of hypogenic,vein and hypergen minerals. A number of factors in formation of ore texture types and structure, including morphological properties of ore minerals, characters of ore solutions, affect of tectonic processes after ore formation are not excluded. Due to the influence of the above mentioned factors stratum, massive, nested textures replace each other in sequence in Gosha ore field. Stratum texture consists of fine, medium and big grain pyrite, quartz, carbonate sequence. Mass texture consists mainly of hardenied pyrite which gradually passes into the granular ore. Nested texture is formed in initval stage of ore formation as a result of pyrite cry stallation and is commonly found in non-ore area. Breccia - like texture is usually found on the edges of ore. Such a texture type mainly consists of pyrite and it is formed by the incorporation of ore solutions into derivative quartz. In the article, along with the texture properties of ore, its structure has already been studied. The structures found in the ore of the field are as follows: rhythmic zoning, porphyry-shaped, residual, cataclysmic. Ore formation process in Gosha field begins from quartz-pyrite. Then it proceeded with quatrz-gold-telluride, quartz-semisulfide, quatrz-carbonate and quartz-goldhelite-hydrochetite stages. This, mineralogical composition, texture-structure properties, mineral formation sequence of Gosha¬pyrite field ore give reason to say that it did not undergo post-metamorphism after the ore formation, and that the field was formed at a low depth, where metacolloid processes were widespread. Keywords: mineralformation, texture, structure, metacolloid, pyrite.

Two hydrothermal events associated with Au mineralization in the Youjiang Basin, southwestern China

The Youjiang Basin in southwestern China hosts remarkably large amounts of Carlin-type Au deposits. In such deposits, Au is mainly ionically bound to arsenian pyrite characterized by core and rim textures. Understanding the formation mechanism of zoned pyrite may improve our understanding of the genesis of massive Carlin-type Au deposits. This study examined the elemental content, mineral composition, and pyrite texture and chemistry of wall rock and ore from the Lannigou Au deposit, one of the largest Carlin-type Au deposits in the Youjiang Basin, to identify the genetic mechanisms of zoned pyrite.Five distinct types of pyrites, i.e., pyrite 1 (Py1), 2 (Py2), 3 (Py3), 4 (Py4), and ore pyrite (OPy), were identified in the Lannigou Au deposit. Py1, Py2, and Py3 were mainly observed in the wall rock, whereas Py4 and OPy, constituting the core and rim of zoned pyrite, respectively, were only discovered in the ore. Mineral mapping of the wall rock and ore indicated that pyrite is scarce in the wall rock (0.021 vol%). However, the amount of zoned pyrite significantly increased in the ore (1.275 vol%). Py1, Py2, and Py3, showing framboidal, nodular, and fine euhedral microcrystal textures, had high Pb, Co, Ni, Mn, Zn, and Mo contents (medians ranging from 10 to 1,000 ppm) and variable δ34S compositions ranging from −5.1 to 35.4‰, implying a sedimentary (syngenetic or diagenetic) origin. Py4 was homogeneous and contained numerous illite and quartz inclusions and fractures. In contrast, OPy showed multiple As-rich sub-bands and a lack of illite or quartz inclusions and fractures. Py4 had significantly lower Au, As, Tl, and Cu contents than OPy; however, Py4 had Pb, Co, Ni, Mn, Zn, and Mo contents similar to OPy. The range of δ34S values for Py4 and OPy were both narrow, but Py4 (7.6 to 13.3‰, with an average of 9.1‰) had lower δ34S values than OPy (9.4–14.1‰, with an average of 12.4‰). These texture and chemical features indicate that Py4 likely sedimented from a pre-ore hydrothermal fluid, but not at the early stage of the ore-forming fluid.Hydrothermal pyrite cores were also widespread and exhibited textural and chemical differences compared to Au-rich pyrite rims from other Au deposits in the Youjiang Basin. Based on the two geochronological clusters of Au deposits in the Youjiang Basin, we inferred the occurrence of at least two episodes of large-scale hydrothermal events. The two hydrothermal fluid episodes, which contributed to the zoned pyrite formation, likely originated from the mixing of initial magmatic fluid with δ34S values of ∼0 ± 5‰ and basin brine with elevated δ34S values (δ34S > 18‰). Pre-ore hydrothermal pyrite likely resulted in the rapid non-equilibrium crystallization of ore pyrite; thus, more Carlin-suite elements were captured by ore pyrite. Additionally, low-grade Au orebodies may have locally formed during the pre-ore hydrothermal event. These multiple hydrothermal events may have been crucial for the formation of massive Carlin-type Au deposits in the Youjiang Basin.

Biomining metals from pyritic ores: physiological, biochemical, and biophysical considerations

Microorganisms and their enzymes drive global biogeochemical cycles and impact ecosystem processes that directly influence plant, animal, and environmental health. Key reactions are catalyzed by metalloenzymes with active sites that contain iron (Fe), nickel (Ni), cobalt (Co), and molybdenum (Mo) sulfide cofactors. However, under anoxic conditions, such metals are bio-unavailable, raising questions of how anaerobes biosynthesize such metalloenzymes. Recent work indicates that methanogens can convert pyrite (FeS2), the most abundant iron sulfide mineral in Earth's crust, into metalloenzymes that interconvert CO2 to CH4, N2 to NH3, and H2 to H+.

Mineralogical and geochemical peculiarities and PT conditions of ores from the Kyzyl-Tashtyg VMS polymetallic deposit, Eastern Tuva: Fluid inclusion and S, O, C isotopic data

The paper is devoted to the mineralogical and geochemical peculiarities and ore-forming conditions of the formation of the Kyzyl-Tashtyg pyrite-polymetallic deposit in Eastern Tuva. The ore mineral assemblages of the deposit were formed due to aqueous fluids containing Na, Mg, and K chlorides at the pressure of 900 bar and the variations of fO2, fS2, fSe2, and fTe2. The earliest pyrite ores in the central parts of the ore bodies were formed at relatively high temperatures of 400–260 °C due to a fluid of the composition NaCl-H2O and MgCl2-NaCl-H2O with the salinity of 4–11.3 wt% NaCl eq. The copper-zinc ores were deposited at 377–145 °C from the NaCl-H2O fluid with the salinity of 2.6–10 NaCl eq. and the copper ores – at 200–165 °C from the NaCl-KCl-H2O fluid with the salinity of 3.5–6.5 NaCl eq. The latest polymetallic and barite-polymetallic ores were formed at 330–130 and 270–140 °C, from the NaCl-KCl-H2O ± MgCl2-H2O fluid with the salinity of 3.5–8.8 and 2–8.5 wt% NaCl eq., respectively. The calculated δ34SH2S values of the fluid range from + 0.2 to + 6.6 ‰, which indicates the participation of sulfur of magmatic origin and borrowed from the host rocks. The δ34O isotopic composition of the fluid suggests that the fluid of magmatic genesis (+8.7… + 7.1 ‰) participated in the early stages of ore mineralization, and at the final stages, it was mixed with meteoric waters (-4.0…-0.7 ‰). The temperature decrease of mineral formation and fluid salinity from early to latest stages confirms the participation of heated meteoric waters. The results of the study of the geological structure, mineral assemblages, fluid inclusions, and stable isotope ratios provided to conclude that the formation of the Kyzyl-Tashtyg deposit was initiated by hydrothermal-magmatic activity, associated with the introduction of subvolcanic bodies of rhyolite and rhyolite-dacite and involvement of fluids separated during crystallization of felsic magma, as well as heated meteoric waters enriched with oxygen, which contributed to the growth of fO2 and variations fS2, fSe2, fTe2 and determined the diversity of mineral types of ores.

Primary source of placer gold in the Luk Ulo Metamorphic Complex, Central Java, Indonesia

AbstractThe Luk Ulo Metamorphic Complex, Central Java is a product of the Cretaceous subduction and accretion, and includes diverse types of protoliths. Two‐types of primary mineralization have been recognized in this area, namely, (1) seafloor basalt‐hosted massive sulfide mineralization and (2) low‐grade metamorphic rocks‐hosted vein type mineralization. Later erosion of these types of primary mineralization formed placer gold deposits along rivers. However, the source has never been identified. Thus, this study aims at understanding the source of placer gold, the characteristics of the primary mineralization, and the tectonic evolution of the study area on the basis of mineralogy, mineral chemistry, whole‐rock geochemistry, and sulfur isotope analyses. Volcanogenic massive sulfide (VMS)‐type mineralization was identified in the seafloor basalt and few deep‐sea sedimentary rocks, and both the ores and host rocks preserved pre‐metamorphic textures and minerals. The characteristics of this VMS‐type mineralization include (1) crustiform quartz veins with pyrite cutting the host rocks, (2) zonation of local silicification to interlayered chlorite/smectite‐chlorite‐laumontite‐calcite‐epidote alteration from central to outer zone, (3) pyrite‐dominated ores with minor amounts of arsenian pyrite, chalcopyrite, and marcasite, (4) unmetamorphosed host rocks and ores, and (5) sulfur isotope signature with a median δ34S of +3.1‰ suggesting sulfur derived from magmatic source and/or sulfur extracted from basaltic rocks with a small contribution of biogenic sulfur. On the other hand, low‐grade metamorphic rocks‐hosted vein type mineralization was identified as orogenic‐type gold mineralization, and the mineralized veins formed after the peak of metamorphism. It is characterized by (1) pyrite‐arsenian pyrite ores with minor amounts of arsenopyrite, galena, tetrahedrite, chalcopyrite, and sphalerite, (2) quartz‐illite‐graphite alteration assemblage, (3) mineralized veins cross‐cutting the foliation of metamorphic host rocks, (4) high antimony contents of pyrite (up to 1.7 wt%) and rutile (up to 160 ppm), (5) relatively high ore‐forming temperature (423 ± 9°C, calculated from arsenopyrite and graphite geothermometers), and (6) remobilized‐sedimentary sulfur signature of the ores with a median δ34S of −9.8‰. Several lines of evidence suggest that placer gold was likely derived from the erosion of orogenic‐type gold ores in the surrounding areas. This evidence includes the presence of gold‐bearing ores hosted by low‐grade metapelites and metagranitoid with characteristics of orogenic‐type gold mineralization, whereas the VMS‐type ores are barren in gold. The occurrence of the mid‐oceanic ridge‐ and accretion zone‐related mineralization in this area reflects the subduction and amalgamation of oceanic and continental crustal blocks during the Cretaceous period. Discovery of gold mineralization hosted in the Cretaceous basement rocks of the Sunda arc indicates the importance to broaden the gold exploration targets to include not only young volcanic rocks, but also relatively old metamorphic basement rocks.

Comparative analysis of the sources of mercury concentration formation in the water of the Paatsjoki River basin

Abstract. We overview the content of mercury compounds in ore formations, the deposit development of which is the source of mercury compounds entering the environment. The vast majority of mercury in pyritic ores passes into concentrates and is taken in this composition for processing; only a small amount of it (up to 2 7% of the total amount in ores) goes into processing waste that is stored in tailings dams. We analyze the mercury concentrations in the water objects in the Paatsjoki River basin, the watershed of which is associated both with the Monchegorsk copper-nickel deposit where the mercury concentration can reach 9 g/t and with the production sites of PJSC MMC Norilsk Nickel. From 2017 to 2020, the concentration of mercury compounds in the water of the cascade of reservoirs on the Paatsjoki River, in the transborder sections of the Russian Federation border with Finland and Norway, increased evenly from the earlier to the later time of reservoir creation. The concentrations of mercury compounds in the waters of reservoirs generally exceeded the concentrations in the water of the Kolosjoki River at the observation site of the Nickel settlement in the area of the JSC Kola MMC activity. We conclude that the activation of microbial processes occurring in the bottom sediments during the formation of reservoirs with the increase in the amount of organic matter received and under certain geochemical conditions in the region affect the levels of mercury concentrations in the water.

Минеральный состав руд, использовавшихся на укрепленном поселении бронзового века Устье-I (Южное Зауралье)

At the fortified settlement of the Bronze Age, Ustye-I (South Trans-Urals), metal products of copper, arsenic and tin bronzes, numerous fragments of metallurgical slags, as well as fragments of copper ores have been discovered. According to the results of early studies, pure copper predominates among metal items (53.4% of finds), but also a significant part contains an admixture of arsenic (25.4% of finds), tin (13.6% of finds) and both components simultaneously (7.6% of finds). Several alloying components of the samples are simultaneously found in slags: Pb (50% of cases), As (49% of cases), Zn (40% of cases), Bi (38% of cases), Sn (7% of cases), Ni (4% of cases), Sb (1% of cases). To identify the relationship between the incoming raw materials and the received metal, 15 ore samples were examined. The ores studied are ‘gravelly’ clasts with a size of 5 mm to several centimeters, and ‘sandy’ ores with a size of 2–3 mm. According to their mineral composition, ores are subdivided into malachite, azurite, and limonite. The main copper minerals are malachite and azurite; chrysocolla is found occasionally, chalcopyrite, cuprite are rarely found. Copper is bound to Fe- and Mn-hydroxides. We have identified copper slag fragments in ‘sandy’ ores. In all types of ores, natural alloying components are very rare and are represented by Pb and Zn. These elements can form their own minerals (mottramit, a mineral of the plumbogummite family) or act as an impurity to malachite (up to 0.62 wt% ZnO), azurite (up to 1.12 ZnO and up to 2.37 PbO), iron hydroxides (up to 2.66 ZnO and up to 2.02 PbO) or manganese hydroxides (up to 0.41 ZnO and up to 9.48 PbO). No As and Sn impurities were found. The presence of numerous fragments of brown iron ore at the settlement, the close location of copper mines indicates that the settlers were engaged in the extraction and processing of copper ore. The widespread occurrence of ores, consisting mainly of malachite and azurite, indicates that the ores were mined from the upper parts of the oxidation zone, and the metal smelted from these ores must correspond to pure copper. The distribution of Pb and Zn impurities indicates that some of the copper ores originate from the oxidation zones of pyrite ores or deposits of other formational types with a similar ore composition. The difference in the compositions of the ores found at the settlement and the compositions of slag and metal is associated with several sources of ores. The sources of copper ores could be mines located near the settlement. Arsenic-bearing ores could have come from mines in adjacent areas. Tin ores were brought in as a result of trans-regional exchange with the Central Asian region.

Совершенствование термопарного метода для испытаний энергоемких эмульсий на совместимость с сульфидными рудами

The results are presented concerning improving the thermostatic method for studying the chemical compatibility of modern industrial emulsion explosives based on the ammonium nitrate with surrounding materials, the increased reactivity of which can lead to spontaneous ignition and even explosion. An assessment of the compatibility of emulsion explosives with sulphide ores was conducted using an original thermocouple methodology developed at the D. Mendeleyev University of Chemical Technology of Russia, fixation of the thermal effects of the interaction of shell-free explosives based on the ammonium nitrate with sulfide minerals. Improved thermocouple method allows to determine chemical compatibility of the industrial explosives with the reactive rocks. It is distinguished by the possibility of continuous recording of the thermocouple measurements during tests using an oscilloscope and combines the reliability of the results with small laboratory weights of the test samples (no more than 20 g, which ensures safety testing). Temperature measurement accuracy is ± 2 °С. It is concluded that the method used is able to identify the cases of the most dangerous interaction from the practice point of view using the emulsion explosives when the pyrite content in the ore exceeds 85 %. The results of experiments on the applicability of thermocouple measurements to testing low-activity rocks, highly reactive pyrite ores, mixed sulfide ores of medium activity, as well as on the identification of the main regularities of heat release during the interaction of emulsion explosives with the sulfide ores are considered.

In situ multiple sulfur isotopes and chemistry of pyrite support a sedimentary source-rock model for the Linwang Carlin-type gold deposit in the Youjiang basin, southwest China

The Linwang gold deposit is a representative example of Carlin-type gold deposits in Youjiang basin, southwest China. High-grade ores are hosted in silicified and brecciated siltstone, sandstone, and mudstone of the Middle Triassic and are controlled by high-angle reverse faults. Optical microscopy pyrite texture, in situ laser ablation-inductively coupled mass spectrometry (LA-ICP-MS) trace elements, and secondary ion mass spectrometry (SIMS) multiple sulfur isotopes analyses are used to examine the different types of pyrites to constrain the sources of reduced sulfur and metals for the Linwang deposit.Petrography and pyrite chemistry studies distinguished three generations of pyrite: Pre-ore pyrite (Py 1) and ore pyrites (Py 2 and Py3). Pre-ore pyrite is framboidal, anhedral to euhedral pyrite with highest concentrations of Co, Ni, and Pb and is interpreted to have a sedimentary (diagenetic) origin. Ore pyrites were formed by hydrothermal fluids via sulfidation of Fe-bearing minerals in the host rocks. They commonly rimed and partially replaced the pre-ore pyrite and have an As-rich inner rim (Py 2) and an Au-rich outer rim (Py 3) with lowest contents of Co, Ni, and Pb. All pyrites contain Au, As, Sb, Cu, Tl, and Se, with increasing concentrations from Py 1 to Py 3.In situ SIMS multiple S isotope analyses show that all pyrites in the Linwang deposit have narrow ranges of δ34S values, with average of +5.13‰ for Py 1, +4.84‰ for Py 2, and +4.53‰ for Py 3, and near zero of Δ33S values (−0.02‰ to +0.03‰), suggesting that the S within the Linwang deposit was most likely sourced from the Triassic sedimentary rocks that host the deposit. A near zero Δ33S signature in all pyrites indicates no record of the assimilation of Archean sulfur, implying the deep basement of Archean rocks beneath the basin were not involved the formation of the Linwang deposit.Oxygen and hydrogen isotope compositions of ore fluids (δ18OH2O = +11.7‰ to +16.5‰, δD = −71‰ to −57‰) indicate a metamorphic origin. Based on these data, we propose a sedimentary source-rock model for the Linwang deposit in which the ore fluids were generated by release of previous Au-bearing sedimentary pyrites during metamorphism of sedimentary rocks. The stress relaxation of Yanshanian orogeny resulted in the ore fluids flowed upward along the fault zones into structural highs where they reacted with Fe-bearing minerals in the host rocks to deposit Au-rich pyrite. The preconcentration of Au, As, and Sb in sedimentary pyrite and gold deposition process are key to the formation of the Linwang deposit and may apply to the genesis of other Carlin-type gold deposits in the Youjiang basin.