Sulfide Phases Research Articles

Chalcophile element partitioning between Cu-rich sulfide phases and silicate melt and implications for the formation of Earth’s continental crust

To constrain the behavior of chalcophile (sulfide-loving) elements during arc magmatic differentiation and to understand the formation conditions of Earth’s continental crust, the partition coefficients (D) of Mn, Co, Cu, Zn, As, Se, Mo, Ag, Cd, Sn, Sb, Te, Re, Au, Pb, and Bi between monosulfide-solid-solution (MSS), Cu-rich sulfide liquid (SL; containing 11–45 wt.% Cu), and hydrous silicate melt (SM) of basaltic to dacitic compositions were determined at 1000–1200 °C, 0.5–1.0 GPa, and fO2 1–1.5 log units above the fayalite–magnetite–quartz (FMQ) buffer. The DSL/SM values are 16–160 for Co, 1100–8400 for Cu, 50–220 for Se, 1200–5900 for Ag, 50–1800 for Cd, 700–3300 for Te, 15–510 for Re, 5700–90,000 for Au, 20–440 for Pb, and 140–3300 for Bi. The DSL/SM values for Mn, Zn, As, Mo, Sn, and Sb are below 1–40. The DMSS/SM values are 55–260 for Co, 530–1700 for Cu, 74–110 for Se, 30–110 for Ag, 4–40 for Cd, 15–70 for Te, 200–5900 for Re, and 140–270 for Au. The DMSS/SM values for Mn, Zn, As, Mo, Sn, Sb, Pb, and Bi are below 1–3. The DSL/SM of Au increase with increasing Cu content of the sulfide liquid, but the DSL/SM of the other elements little affected by the Cu concentration in the sulfide liquid. Because of their distinct dissolution mechanisms in the silicate melt, the DSL/SM and DMSS/SM of Mn, Co, Zn, Cd, Sn, and Pb are mainly controlled by the silicate melt FeOtot content ([FeOtot]); the DSL/SM and DMSS/SM for Re, Mo, As, Sb, and Bi are mainly controlled by [FeOtot] and fO2; the DSL/SM and DMSS/SM for Cu, Ag, and Au are mainly controlled by [FeOtot] and the content of reduced sulfur in the silicate melt; and the DSL/SM and DMSS/SM for Se and Te are mainly controlled by fO2. Using all available DSL/SM and DMSS/SM data, a partitioning model was developed for predicting DSL/SM and DMSS/SM of chalcophile elements as a multi-function of temperature, pressure, fO2, and silicate melt and sulfide compositions. Sulfide phase relations suggest that the sulfides precipitating from arc magmas containing >100 µg/g Cu in the silicate melt occur as Cu-rich sulfide liquid, whereas the sulfides precipitating from arc magmas containing 30–70 µg/g Cu in the silicate melt occur as mixed MSS and Cu-rich sulfide liquid. Modeling the Cu evolution trends of global arc magmas illustrates that the precipitating sulfides are dominantly MSS in continental arcs with a crustal thickness of >30 km, with the proportion of sulfide liquid being less than 20%; whereas, in island arcs with a crustal thickness of <20 km, the proportion of sulfide liquid may reach up to 90%. Applying the model to predict the evolution trends of Ag, As, Sn, Sb, Se, Mo, Re, Mo, Au, Pb, and Bi in global arc magmas under various fO2 conditions, we find that when no more than 10% of the precipitating sulfides are sulfide liquid, the chalcophile element patterns of oxidized magmas (0–1 log unit above FMQ) in continental arcs match that of Earth’s bulk continental crust, which implies that Earth’s continental crust formed mainly in oxidized continental arcs.

Temporally limited late accretion after core formation in the Moon

AbstractHighly siderophile element (HSE: Au, Re, Pd, Pt, Rh, Ru, Ir, Os) abundances in planetary silicate mantles provide constraints on accretion and differentiation, as well as late accretion additions after core formation. The first in situ analyses of the HSE in mare basalt sulfide and metal phases enable the determination of the distribution of these elements during fractional crystallization processes. Metals have low Ni/Co (&lt;8) and strong HSE inter‐element fractionation (Pd/Ir = 18–100) and, with troilite (Ni/Co &lt; 4.2, Pd/Ir = 14–74), host 75–100% of the HSE in mare basalts. The compositions of these metal and sulfide grains are inconsistent with assimilation of impact‐contaminated HSE‐rich regolith materials. Furthermore, regolith contamination cannot explain the threshold of abundances of iridium (~50 ppt) in mare basalt bulk rock compositions. Instead, bulk rock mare basalts have HSE patterns consistent with inheritance from partial melting of mantle sources with no residual metal or sulfide. Mare basalt HSE and siderophile element abundances can be accounted for by their mantle sources recording prior separation of a small lunar core, fractionating Ni/Co and Hf/W and removing ~99% of the HSE after lunar formation. Following this event, late accretion of ~0.02% of lunar mass led to limited enrichment of the HSE in chondritic‐relative abundances. Signatures of core formation preclude elevated HSE abundances in the lunar silicate interior and indicate that disproportional late accretion in the Earth–Moon system may, in part, be due to later core formation in the Moon relative to Earth.

Hydrocracking of 1-methylnaphtalene (1MN) over modified clays-supported NiMoS and NiWS catalyst

A series of catalysts was synthesized using two delaminated mesoporous Colombian clays as supports (vermiculite and bentonite), and incorporating NiMo and NiW as active species, taking advantage of their acidic and mesoporous properties to be used in hydroconversion of hydrocarbons. The synthesized solids were characterized by N2 physisorption, temperature programmed reduction (TPR-H2), diffuse reflectance infrared spectroscopy using NH3 as the probe molecule (DRIFT), temperature programmed desorption (TPD-NH3) and X-ray photoelectron spectroscopy (XPS). These catalysts were evaluated in the hydrocracking of 1-methyl naphthalene (HCK 1MN), finding that the catalyst with NiMo as its active phase supported on delaminated vermiculite, presents the best catalytic performance, associated, among others, with the important formation of the NiMoS sulfided phase, detected by XPS.

Arsenic fractionation and mobility in sulfidic wetland soils during experimental drying

In this study, two Czech wetland soils enriched in authigenic sulfide minerals (especially realgar) were collected from the saturated zone (60–100 cm), flooded with local groundwater and allowed to dry for up to 98 days. The objective was to examine the mobility of As, Fe, S and trace metals using selective chemical extractions, S isotopes and X-ray diffraction through the drying process. During the initial stage of incubation (∼20 days), the re-flooding of the soils triggered a microbially-mediated SO42− reduction, which immobilized the Co, Cu and Ni. The reductive dissolution of As-bearing Fe (oxyhydr)oxides and the release of As were documented only in the Fe-rich/organic-low soil. Over the next stage of incubation (∼75 days), the exposure and drying of the soils led to the oxidation of the Fe and As sulfides. The arsenic and trace metals released via oxidation of the sulfide phases (particularly Fe sulfides) were almost entirely sequestered by the Fe(III) (oxyhydr)oxides, but acidification during the oxidation stage of the incubation resulted in the pH-dependent release of the As and trace metals (Co, Cu, Ni) (especially in the Fe-rich/organic-low soil). These findings suggest that sulfidic soils in wetlands can be considered as long-term sources of As during major drought events.

SULFIDE RECRYSTALLIZATION AND GOLD REMOBILIZATION DURING THE 2.0 GA STAGE OF THE MINAS OROGENY: IMPLICATIONS FOR GOLD MINERALIZATION IN THE QUADRILÁTERO FERRÍFERO AREA, BRAZIL

Abstract The historic Quadrilátero Ferrífero mining district in Brazil is a polydeformed Archean terrane recording several tectonic events. This history has hampered the accurate dating of its important gold deposits, given that most of the geochronological clocks have been affected by multiple thermal events. To determine an accurate time constraint for the mineralizing events in this region, we provide the first Re-Os dating for a gold deposit in the Quadrilátero Ferrífero, obtained from 13 mineral separates of disseminated sulfide phases (pyrrhotite, coarse-grained arsenopyrite, fine-grained arsenopyrite, and pyrite) at the recently discovered São Sebastião deposit (northwest Quadrilátero Ferrífero). Three distinct successive sulfidation stages are interpreted at the deposit. The final stage, texturally associated with gold, is marked by fine-grained arsenopyrite and pyrite (assemblage III) and is associated with high-temperature (~600°C) features. A Re-Os errorchron is obtained when considering the data of all samples collectively; however, a comprehensive Re-Os isochron age of 1987 ± 72 Ma (2σ; n = 4; IsoplotR model 3; initial 187Os/188Os = 2.1 ± 0.7) is obtained from assemblage III. A 187Re-187Osr isochron at 1988 ± 56 Ma (mean square of weighted deviates = 0.1, initial 187Osr = –0.1 ± 2.6 ppt; n = 4) is obtained if an initial 187Os/188Os composition of ca. 2.1, is used, this being consistent with the fact that the 187Os in the sulfides in assemblage III is largely radiogenic (187Osr). Earlier assemblages (I and II) individually show variable initial 187Os/188Os, indicative of disturbance to the Re-Os systematics at ~2.0 Ga. This age is considered the best estimate for the timing of gold mineralization at São Sebastião, being coincident with the waning stages of the Minas orogeny, the thermal effects of which are restricted to the southern Quadrilátero Ferrífero. Hence, we consider that the hot fluids from which assemblage III crystallized were responsible for resetting the Re-Os systematics in assemblages I and II and were central to Paleoproterozoic gold deposition in the region. This ~2.0 Ga age challenges previous notions of a late Archean, ~2.7 Ga mineralizing event in the Quadrilátero Ferrífero and makes it possible that gold remobilization occurred elsewhere in the region, particularly in areas representing deeper crustal levels.

Effect of the Annealing Atmosphere on Crystal Phase and Thermoelectric Properties of Copper Sulfide.

Cu2-xS has become one of the most promising thermoelectric materials for application in the middle-high temperature range. Its advantages include the abundance, low cost, and safety of its elements and a high performance at relatively elevated temperatures. However, stability issues limit its operation current and temperature, thus calling for the optimization of the material performance in the middle temperature range. Here, we present a synthetic protocol for large scale production of covellite CuS nanoparticles at ambient temperature and atmosphere, and using water as a solvent. The crystal phase and stoichiometry of the particles are afterward tuned through an annealing process at a moderate temperature under inert or reducing atmosphere. While annealing under argon results in Cu1.8S nanopowder with a rhombohedral crystal phase, annealing in an atmosphere containing hydrogen leads to tetragonal Cu1.96S. High temperature X-ray diffraction analysis shows the material annealed in argon to transform to the cubic phase at ca. 400 K, while the material annealed in the presence of hydrogen undergoes two phase transitions, first to hexagonal and then to the cubic structure. The annealing atmosphere, temperature, and time allow adjustment of the density of copper vacancies and thus tuning of the charge carrier concentration and material transport properties. In this direction, the material annealed under Ar is characterized by higher electrical conductivities but lower Seebeck coefficients than the material annealed in the presence of hydrogen. By optimizing the charge carrier concentration through the annealing time, Cu2-xS with record figures of merit in the middle temperature range, up to 1.41 at 710 K, is obtained. We finally demonstrate that this strategy, based on a low-cost and scalable solution synthesis process, is also suitable for the production of high performance Cu2-xS layers using high throughput and cost-effective printing technologies.

Synthesis and Performance of Presulfided NiMoP/Al2O3-SiO2 Catalyst

Presulfided NiMoP/Al2O3-SiO2 catalysts were synthesised. The BET surface area and BJH pore volume gradually decrease with P loading due to the ingress of active phases into the pores of the support. No bulk Ni sulfide phase is observed either in the XRD pattern or in the HRTEM micrographs of all catalysts. The mainly high active center is multilayered Ni-Mo-S type II phase benefited from the weak bond between Al2O3-SiO2 support and active components. The incorporation of phosphorous enhances the dispersion of MoS2 particles and formed more multilayered Ni-Mo-S type II phase. The route of hydrogenation activity increases with the content of P up to 1.2 wt.%, and the route of direct desulfurization activity in the hydrodesulfurization of dibenzothiophene decreases simultaneously. This is attributed to the higher MoS2 stacking number and shorter MoS2 slab length.

Mechanochemical synthesis of tetrahedrite materials using mixtures of synthetic and ore samples collected in the Portuguese zone of the Iberian Pyrite Belt

Considering that the synthesis of tetrahedrite-based materials usually uses high purity elements, the evaluation of the direct application of ore samples as raw materials for their synthesis is a pertinent issue. In the present study, multiphase synthetic tetrahedrite samples were mixed with tetrahedrite-tennantite ore samples (in weight ratios of 0.8/0.2, 0.5/0.5 and 0.2/0.8) to produce tetrahedrite-based materials by solid-state mechanochemical synthesis. The ore samples were obtained from the abandoned Barrigão mine dumps and from the Neves Corvo mine, both located in the Portuguese zone of the Iberian Pyrite Belt, whose main constituents were found to be As-rich tetrahedrite and tennantite-(Fe), respectively. Depending on the ore sample and on the mixture ratios, the displacement reactions occurring during the synthesis process gave rise to different phase transformation paths. For the ratios of 0.5/0.5 and 0.2/0.8, the mixtures with the Barrigão ore were found to consist of a single sulfide phase, tetrahedrite-tennantite-(Fe), plus quartz, while famatinite was also observed in the 0.8/0.2 mixture. Tetrahedrite-tennantite-(Fe) phase was the main constituent of all mixtures with the Neves Corvo ore, but in all of them other sulfide phases, famatinite-luzonite and pyrite, were also present in addition to quartz. Despite being dissimilar, these results are very promising and encouraging, by confirming the possible direct usage of ore samples and of dump material for the synthesis of tetrahedrite-based materials with all the potential environmental-economic gains that can be obtained.

Free-standing ultra-thin Janus indium oxysulfide for ultrasensitive visible-light-driven optoelectronic chemical sensing

Atomically-thin Janus heterojunctions exhibit extraordinary electronic and optoelectronic properties, mainly due to their intrinsic built-in electric field. However, current investigations are limited within layered metal chalcogenides. Here, a free-standing ultra-thin Janus metal oxychalcogenide is realized from non-layered In 2 S 3 . In the presence of strong mechanical agitation in the liquid medium, the original tetragonal crystal is cleaved. Ambient oxygen atoms are subsequently diffused and incorporated into limited part of the crystal structure, forming the oxysulfide phase with the gradual transition into a hexagonal structure. While the integrity of the covalent bonding system is maintained, a tensile strain is generated as a result of the crystal coordination mismatching between the pure sulfide and oxysulfide phases, leading to a more than two orders enhancement on visible-light-driven exciton lifetime compared to that of pure In 2 S 3 . Such an impressive excitonic interaction provides the fundamentals to establish an ultra-sensitive and power-saving optoelectronic chemical sensing platform. As an example, dipoles generated by the surface adsorbed NO 2 molecules cause significant re-distribution of photoinduced charges in the anisotropic non-layered Janus structure under visible light low-power excitation, resulting in a superior sub-ppb detection limit of NO 2 gas at room temperature. • Free-standing Janus indium oxysulfide is formed from In 2 S 3 with oxygen incorporation. • Surface crystal transfer is due to the replacement of sulfur by diffused oxygen. • Deteriorated exciton binding energy and recombination rate; prolonged PL lifetime. • Visible-light-driven gas sensor is ultrasensitive to NO 2 gas at room temperature. • The limit of detection (LOD) is in parts-per-trillion (ppt) range.

Impact of proximity between NiMoS and zeolitic HY sites on cyclohexene hydroconversion: An infrared operando study of sulfide catalysts

This work evaluates the effects of sulfide phase location on zeolite-containing catalysts in cyclohexene hydroconversion using the infrared operando technique. Parallels between activity, product yield, and surface species changes with time on stream and under pyridine poisoning were assessed on pure HY zeolite, sulfided NiMo/HY, NiMo/Al2O3, and NiMo/Al2O3 + HY. Isomerization activity could be related to zeolitic acidic OH groups and hydrogenation activity to sulfide phase sites. From the changes due to pyridine pulse injection, intrinsic activities could be calculated for isomerization (1-methyl-1-cyclopentene) and hydrogenation (cyclohexane) routes. The turnover frequency value for isomerization is greater than that for hydrogenation by one order of magnitude. Hence, the poisoning effect of one N-molecule on isomerization will be 10 times higher than that on the hydrogenation route. Whatever the location of the sulfide phase, the coke is mostly formed on the zeolite. As a consequence, on NiMo/HY, the close proximity between acidic and sulfide sites results in lower formation of hydrogenated products, due to blockage of some sulfide sites by coke. In contrast, the hydrogenation activity of NiMo/Al2O3 + HY is less affected by coke, NiMoS being mostly located on alumina. However, the results show that the close proximity between acid and sulfide sites allows a higher degree of hydrogenation of the isomerization product (1-methyl-1-cyclopentene). Thus, the higher proximity has a beneficial effect on methylcyclopentane formation.

Experimental Investigation of Apollo 16 “Rusty Rock” Alteration by a Lunar Fumarolic Gas

AbstractThe Apollo 16 sample 66095, named “Rusty Rock”, is enriched in volatile and moderately volatile elements. The impact melt breccia is characterized by abundant Fe‐rich sulfide and chloride alteration phases, including FeS, ZnS, and FeCl2. These phases have previously been interpreted to be the result of fumarolic alteration of the breccia. Here we present the results of two different experimental approaches, which aim to constrain the temperature conditions and the process under which the “Rusty Rock” alteration formed. The first experimental set‐up assumes that the metals Zn, Cu, and Fe were introduced into the rock by a C‐O‐S‐Cl gas phase, and that the Fe‐rich sulfides and chlorides were deposited from this gas phase. This “gas deposition” experiment suggests that the alteration assemblage formed over the temperature range of 538–638 ± 5°C. The second experimental set‐up simulates a scenario, where Fe metal particles in the lunar rock react with a Zn‐C‐O‐S‐Cl gas phase at six different temperatures between 396 ± 5°C and 1,005 ± 5°C. This latter “metal reaction” experiment resulted in the formation of sulfide and chloride coatings on the Fe metal chips. The “Rusty Rock” alteration phases FeCl2 and (Zn,Fe)S were abundantly present in the coating of the Fe metal chip reacted at 580 ± 10°C. Both experiments lead to results which are in agreement, providing a temperature of 580 ± 50°C for the fumarolic alteration on the Moon, as observed in the Apollo 16 “Rusty Rock”.

Insights into the Mechanism of the Mechanochemical Formation of Metastable Phases.

The mechanochemical reaction kinetics of sulfur with copper to form a metastable copper sulfide phase at room temperature is investigated in ultrahigh vacuum by modifying the properties of the copper during cleaning in vacuum. The measured kinetics is in agreement with a theory first proposed by Karthikeyan and Rigney that predicts that the rate depends linearly both on the contact time and on the strain-rate sensitivity of the substrate. The mechanism for this process was investigated using thin samples of copper fabricated using a focused-ion-beam and by measuring the crystal structure and elemental composition of the copper subsurface region by electron microscopy after reaction. The measured sulfur depth distributions produced by shear-induced surface-to-bulk transport were in good agreement with values calculated using rate constants that also model the reaction kinetics. Sulfur was found both in crystalline regions and also concentrated along grain boundaries, implying that formation of metastable phases is facilitated by both the presence of dislocations and by grain boundaries.

Influence of H2S on the pitting corrosion of 316L stainless steel in oilfield brine

Coupon immersion tests were performed on 316L stainless steel in a simulated oilfield environment to evaluate the effect of H2S partial pressure on pit depth and density. Pitting was most significant at intermediate partial pressures of H2S, for which free H2S in the pit solution is maximised. Inhibition of pitting at higher partial pressures is attributed to blocking of the pit surface by metal sulphide phases. The key role of pH in the pit solution is to determine the solubility of metal sulphides and the availability of free H2S to adsorb on the reacting pit surface and sustain activity.

Acid mine drainage at the Bahia Gold Belt (Brazil): microbial isolation and characterization.

Acid mine drainage occurs due to the chemical and microbiological oxidation of sulfide minerals and can be a source of potentially toxic elements contamination of groundwater and surface water. The objective of this study was to identify microorganisms involved in sulfide oxidation in the tailings of a Bahia Gold Belt mine (Brazil). Samples of solids and water were collected at the mine tailings dam and characterized. The microorganisms were isolated after enrichment and subsequent purification. The major constituents of the tailings are Si, Fe, Al, S, and K. The sulfur content of the tailings is 0.98%. The major phases are quartz, muscovite, and clinochlore. Gravity concentrates of the tailings show several particles of pyrite, that is, the major sulfide phase. Molecular analysis identified the microorganisms isolated in the acid mine drainage process in this region. Five bacterium species were found: Acidithiobacillus spp., Acidithiobacillus ferrooxidans, Acidiphilium spp., Leptospirillum type II, and Sulfobacillus spp. No organisms of the archaea or eukaryote domains were found. The isolate was used in the bioleaching of copper sulfide ore, and the copper extraction was about 60% in 60days for ground ore.

Geochemistry and Microthermometry of Fluid Inclusions of Cu and Fe Mineralization in North Khour Volcanic Rocks, Northwestern Birjand

The volcanic complex of North Khour is located in southern khorasan province, in 90 km of northwest of Birjand.The study volcanic igneous rocks are including Basaltic andesite, Andesite and trachyandesite, Latite, Dacite to Rhyodacite and pyroclastic rocks are including Tuff and breccia. The majority texture of these rocks is porphyry. Magmatic series of most samples are calc alkaline but some samples have inclination to tholleiitic serie. Furthermore in diagram of magmatic arc definition, the study rocks are situating in field of continental arc and seems which magmatism of area has been result of subduction of a oceanic crust under the continental crust. Because of the area is an upper part of a cu porphyry system, this paper is a very important research to know more about this system. Iron mineralization in area is as magnetite, hematite and as lower amount of goethite and with attention to the field observations, it seems this mineralization has magmatic origin. Burnite as alone Cu ore has been formed as primary and very little. The presence of bornite and pyrite as sulfide phases as very little and absence of other Cu primary sulfide ores in area together with secondary Cu mineralization phases in very high amounts, is showing a hydrothermal solution with high oxidation degree which has passed the latest magmatic differentiation and has caused to form surface Cu ores as calcosite in supergene zone. The thermobarrometry studies of fluid inclusions has specified degree of 10 weight percent of NaCl, 50 megapascal pressure and temperature range of 200-220 centigrade degrees for this mineralization.Therefore it seems that mineralization is related to upper parts of a Cu–porphyry system which is showing a lower temperature.

Cu(-Ag) mineralizace z Tismic u Českého Brodu (perm blanické brázdy, Česká republika)

A mineralogical study of samples newly collected from dump material at the formerly mined locality Tismice near Český Brod (central Bohemia) revealed the presence of covellite/yarrowite, acanthite, malachite and azurite. In addition, psammitic to aleuritic detrital material originated from host Permian sandstones/arkoses is a common compound of the studied ore samples. The Cu carbonates clearly prevail among ore minerals, whereas sulphide phases are accessories. The silver-enriched covellite/yarrowite, strongly replaced by malachite and azurite, has a coarse-grained texture implying that its primary hydrothermal or late hydrothermal origin cannot be excluded. The other recorded ore minerals are clearly supergene in origin. Although the nature of the mineralization from Tismice is in general similar to other occurrences of epigenetic vein Cu mineralization hosted by the Permian sediments in the vicinity of the town of Český Brod, the enrichment in silver is reported for the first time here.

Versatile precursor-dependent copper sulfide nanoparticles as a multifunctional catalyst for the photocatalytic removal of water pollutants and the synthesis of aromatic aldehydes and NH-triazoles.

A series of copper sulfide (CS) nanoparticles (NPs) were synthesized just by varying the amount of the sulfur precursor and have been explored for the first time as a three-way heterogeneous catalyst in the photocatalytic oxidation of a number of aromatic alcohols, photocatalytic degradation and the reduction of water pollutants, and the facile synthesis of pharmaceutically important moiety 4-aryl-NH-1,2,3-triazoles. The green and novel protocol was successfully developed for the synthesis of covellite (CuS, Cu2+) and the covellite-villamaninite (CuS–CuS2) (copper in Cu2+, Cu1+) phases of copper sulfide, employing EDTA both as the chelating and capping agent via a simple precipitation method at room temperature using water as the solvent. A blue shift in the absorption spectra and band gap in the range of 2.02–2.07 eV prompted the investigation of the as-synthesized CS nanoparticles as the photocatalyst under visible light irradiation. In the absence of any oxidizing or reducing agent, covellite CuS nanoparticles showed the highest photocatalytic efficiency for the degradation of methylene blue (MB) and the reduction of carcinogenic and mutagenic Cr(vi) to non-toxic Cr(iii). Interestingly, the mixed phase of CS (CuS–CuS2), where Cu is present in both +1 and +2 oxidation states, was found to be the most efficient catalyst compared to CuS toward the visible light-mediated selective oxidation of various benzyl alcohols to their corresponding aldehydes. However, in the synthesis of substituted NH-1,2,3-triazoles, single-phase CS nanoparticles (i.e., CuS) provided the best catalytic result. This significant outcome certainly opens up the scope for realizing the present demand of low-cost multifunctional semiconductor nano-materials, which will have a huge impact on the economy and environment when they show more than two potential applications.

Spectral and Chemical Characterization of Copiapite and Rozenite from Padinjarathara in Wayanad, Southern India: Implications for Mars Exploration

Copiapite (Fe2+Fe3+4(SO4)6(OH)2 ∙ 20 H2O) and rozenite (Fe2+(SO4) ∙ 4H2O) are secondary hydrous sulfate minerals, mostly formed because of oxygenation and weathering events of primary sulfides on Earth. Acidophiles, mainly archaea and bacteria, and specifically anaerobic methanogens (methane-producing microorganisms) have been detected in regions where alteration of primary sulfide phases to secondary sulfates are predominant. These secondary sulfate minerals are significant in defining past geological environments on Earth and other rocky planets such as Mars. We discuss here the results of chemical and spectral analyses of copiapite and rozenite found in massive sulfide zones associated with banded iron formations (BIFs) in the Wayanad region in Kerala, southern India. The results from different spectroscopic techniques — VNIR reflectance, TIR (emitted radiation), FTIR, Laser Raman, and X-ray diffraction — were recorded and matched with existing literatures and databases. Different matching algorithms like Spectral Feature Fitting (SFF), Spectral Similarity Value (SSV), Modified Spectral Angle Similarity (MSAS), and Pearsonian Correlation Coefficient (PCC) were utilized in order to quantitatively match the reflectance spectra with the reference spectra (USGS and RELAB). The genesis of copiapite and rozenite in the area is through seasonal and temporary development of an acidic environment, with the high elevations of the Wayanad plateau providing the necessary low-humidity condition during the dry season. Copiapite and rozenite were detected as alteration products in different regions on Mars, which can provide insights into environmental conditions that prevailed during the biogeochemical evolution of Mars. The study of copiapite and rozenite formation in a terrestrial environment will therefore enhance our understanding of similar mineral precipitation, genesis, and fluvial processes on Mars. Future missions to Mars could also use the data obtained from the present study to calibrate similar instruments to detect these secondary sulfate minerals.

Arsenian Pyrite and Cinnabar from Active Submarine Nearshore Vents, Paleochori Bay, Milos Island, Greece

Active, shallow-water (2–10 m below sea level) and low temperature (up to 115 °C) hydrothermal venting at Paleochori Bay, nearshore Milos Island, Greece, discharges CO2 and H2S rich vapors (e.g., low-Cl fluid) and high-salinity liquids, which leads to a diverse assemblage of sulfide and alteration phases in an area of approximately 1 km2. Volcaniclastic detritus recovered from the seafloor is cemented by hydrothermal pyrite and marcasite, while semi-massive to massive pyrite-marcasite constitute mounds and chimney-like edifices. Paragenetic relationships indicate deposition of two distinct mineralogical assemblages related to the venting of high-Cl and low-Cl fluids, respectively: (1) colloform As- and Hg-bearing pyrite (Py I), associated with marcasite, calcite, and apatite, as well as (2) porous and/or massive As-rich pyrite (Py II), associated with barite, alunite/jarosite, and late-stage hydrous ferric oxides. Mercury, in the form of cinnabar, occurs within the As-rich pyrite (Py I) layers, usually forming distinct cinnabar-enriched micro-layers. Arsenic in colloform pyrite I shows a negative correlation with S indicating that As1− dominates in the pyrite structure suggesting formation from a relatively reducing As-rich fluid at conditions similar to low-sulfidation epithermal systems. On the contrary, As3+ dominates in the structure of porous to massive pyrite II suggesting deposition from a sulfate-dominated fluid with lower pH and higher fO2. Bulk sulfide data of pyrite-bearing hydrothermal precipitates also show elevated As (up to 2587 ppm) together with various epithermal-type elements, such as Sb (up to 274 ppm), Tl (up to 513 ppm), and Hg (up to 34 ppm) suggesting an epithermal nature for the hydrothermal activity at Paleochori Bay. Textural relationships indicate a contemporaneous deposition of As and Hg, which is suggested to be the result of venting from both high-salinity, liquid-dominated, as well as CO2- and H2S-rich vapor-dominated fluids that formed during fluid boiling. The CO2- and H2S-rich vapor that physically separated during fluid boiling from the high-salinity liquid led to calcite formation upon condensation in seawater together with the precipitation of As- and Hg-bearing pyrite I. This also led to the formation of sulfuric acid, thereby causing leaching and dissolution of primary iron-rich minerals in the volcaniclastic sediments, finally resulting in pyrite II precipitation in association with alunite/jarosite. The Paleochori vents contain the first documented occurrence of cinnabar on the seafloor in the Mediterranean area and provide an important link between offshore hydrothermal activity and the onshore mercury and arsenic mineralizing system on Milos Island. The results of this study therefore demonstrate that metal and metalloid precipitation in shallow-water continental arc environments is controlled by epithermal processes known from their subaerial analogues.

Mineralogy and spectroscopy (visible near infrared and Fourier Transform Infrared) of Mukundpura CM2: Implications for asteroidal aqueous alteration

We report the textures, mineralogy and mineral chemistry of the Mukundpura matrix component, a clast-bearing, brecciated, new CM2 carbonaceous chondrite. Like other CMs, Mukundpura is matrix-enriched and has experienced different degrees of aqueous alteration with evidences of fracturing and compaction of clasts due to the impact. A few relict chondrule clasts and CAIs (diopside and spinel) survived despite of the alteration amidst accessory phases of olivine, magnetite, sulphides and calcite. X-Ray Diffraction (XRD), Visible Near Infrared (VNIR) and Fourier Transform Infrared (FTIR) spectroscopic studies reveal higher phyllosilicate content (∼90 %) comprising of both Mg and Fe-serpentine and abundant serpentine-sulphide intergrowths. Even then, the presence of accessory olivine as relict clasts can be interpreted from the presence of certain typical olivine absorptions in the FTIR spectra. The non-stoichiometric, Tochilinite-Cronstedtite occurrences probably relate to broadening of XRD and FTIR spectra and can be explained by coupled Al–Si and Mg–Al substitutions in talc and serpentine. The FTIR spectra suggest widespread transformation of olivine to serpentine, unlike the largely unaltered chondrules. The correlations of mineralogical alteration index with FeO/SiO2 and S/SiO2 in different domains of matrix suggest different extent of alterations. Thus, the aqueous alteration is extensive but not pervasive. The majority of alteration seems to have occurred within the asteroidal parent body. The Mukundpura CM2 thus preserves a unique combination of relict chondrules and highly aqueous altered variegated matrix clasts, although the surface mineralogy resembles the C-type asteroids recently probed by OSIRIS-REx and Hayabusa-2 missions.