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Abstract—: The paper presents newly acquired data on concentrations of chalcophile elements and chalcogens (Se and Te) in sulfide-bearing rocks and Cu-Ni ores from the bottom portion of the Yoko-Dovyren Massif, northern Baikal area, Russia. Positive covariations between Pd, Pt, Au, S, and Te in the samples highlight sulfide control on the behavior of these elements, which was related to the redistribution of essentially Fe-Ni sulfide liquids at a magmatic stage. The character of relationships between Pd, Pt, Te, Cu, and S in the rocks led us to distinguish two groups of genetic trends: the first group combines samples from the chilled zone, plagioperidotites, and olivine gabbronorites that compose underlying sills in the central part of the intrusion, and the second one comprises poor and high-grade ores in the northeastern termination of the intrusion (Ozernyi Prospect). We put forward the hypothesis that the first-group trends reflect different degrees of accumulation of crystallization products of the most primitive sulfide liquids, whereas the trends of the second group pertain to sulfide matter significantly depleted in Cu, Te, and PGE. New data on Fe, Ni, Cu, Co, Se, Te, Zn, Mo, Ag, Cd, Sb, Pb, Rh, PGE, and Au concentrations in sulfides from the chilled gabbronorite and ores of the Baikalskoe deposit are presented. Results of thermodynamic modeling (with the COMAGMAT-5 program package) of sulfide saturation in the intercumulus of a primitive orthocumulate are used to reproduce the composition (Cu, Pd, Pt, Au, and Te) of the parental sulfide liquid. The model concentrations of noble metals in the sulfide are demonstrated to be one to two orders of magnitude higher than the concentrations in the "average sulfide" estimated by LA-ICP-MS. More realistic estimates for the composition of the parental sulfide liquids can be obtained by normalizing the bulk concentrations of these elements to 100% sulfide mass. These estimates are in good agreement with results from thermodynamic simulations. [ABSTRACT FROM AUTHOR]

Abstract: Modern seafloor hydrothermal systems are unique environments in which many of the Earth's reservoirs, including the hydrosphere, biosphere, and geosphere, dynamically interact. Analysis of spatially constrained sulfur isotope compositions from fluids and hydrothermal precipitates within the discharge zone of a volcanogenic system can be used to trace the interactions between the various isotopically distinct sulfur reservoirs that result in the formation of hydrothermal massive sulfide deposits. Here we present in situ sulfur isotope results from laterally and vertically constrained euhedral hydrothermal pyrite from the Iheya North hydrothermal system in the Okinawa Trough, which was investigated during the Integrated Ocean Drilling Program Expedition 331. Hydrothermal pyrite at the North Big Chimney yields δ34S values of ~+11.9 ± 1.1‰ (1σ), which are near identical to the δ34S composition of the vent fluid. Outward, ~150 and ~450 m from North Big Chimney, hydrothermal pyrite within drill core yields δ34S equal to +10.9 ± 1.3‰ (1σ) and +7.0 ± 3.8‰ (1σ), respectively, showing a shift in isotopic composition away from the main vent site. This evolution to a lighter and more scattered isotopic signature of hydrothermal pyrite (which is easily identifiable from biogenic pyrite) is interpreted to indicate that the hydrothermal fluid leached sulfides (formed previously by biogenic processes) from the surrounding sedimentary strata. As the most significant metal enrichments (Fe, Zn, Cu, Bi, Tl, and Cd) are associated with samples that contain average hydrothermal pyrite δ34S values similar to δ34S of the vent fluid, we demonstrate that sulfur isotopes can vector toward metals in seafloor massive sulfide deposits. [ABSTRACT FROM AUTHOR]

This study tests the application of chalcophile elements such as nickel, copper and the platinum-group elements as indicators of nickel-sulphide prospectivity in komatiites from terranes of the Karelian Craton in northern Finland and Norway. Major element abundances reflect volcanic processes associated with the emplacement dynamics of ultramafic lavas, whereas the variable chalcophile element concentrations record the ore-forming process, mainly as an anomalous metal depletion and enrichment relative to the calculated background. Geochemical data from this study indicate that Paleoproterozoic komatiites in the Pulju Greenstone Belts and Archean komatiites in the Enontekiö area are prospective for nickel-sulphide mineralisation. Conversely, on the basis of the present dataset, ultramafic rocks from the Palaeoproterozoic Karasjok Greenstone Belt display lower prospectivity for nickel-sulphides, although potential exists if high-volume flow conduits and channels within the large volcanic flow field could be identified. [ABSTRACT FROM AUTHOR]