Sulfide Formation as a Result of Sulfate Subduction into Silicate Mantle (Experimental Modeling under High P,T-Parameters)

Abstract

Ca,Mg-sulfates are subduction-related sources of oxidized S-rich fluid under lithospheric mantle P,T-parameters. Experimental study, aimed at the modeling of scenarios of S-rich fluid generation as a result of desulfation and subsequent sulfide formation, was performed using a multi-anvil high-pressure apparatus. Experiments were carried out in the Fe,Ni-olivine–anhydrite–C and Fe,Ni-olivine–Mg-sulfate–C systems (P = 6.3 GPa, T of 1050 and 1450 °C, t = 23–60 h). At 1050 °C, the interaction in the olivine–anhydrite–C system leads to the formation of olivine + diopside + pyrrhotite assemblage and at 1450 °C leads to the generation of immiscible silicate-oxide and sulfide melts. Desulfation of this system results in the formation of S-rich reduced fluid via the reaction olivine + anhydrite + C → diopside + S0 + CO2. This fluid is found to be a medium for the recrystallization of olivine, extraction of Fe and Ni, and subsequent crystallization of Fe,Ni-sulfides (i.e., olivine sulfidation). At 1450 °C in the Ca-free system, the generation of carbonate-silicate and Fe,Ni-sulfide melts occurs. Formation of the carbonate component of the melt occurs via the reaction Mg-sulfate + C → magnesite + S0. It is experimentally shown that the olivine-sulfate interaction can result in mantle sulfide formation and generation of potential mantle metasomatic agents—S- and CO2-dominated fluids, silicate-oxide melt, or carbonate-silicate melt.

Experimental Modeling of Silicate and Carbonate Sulfidation under Lithospheric Mantle P,T-Parameters

“…To date, experimental studies simulating sulfidation of olivine, pyroxene, and garnet at crustal pressures have been performed [33,34]. High-pressure experiments on simulation of sulfidation processes in the silicate mantle with involvement of S-bearing fluids or melts and on identification of a potential mechanism of sulfide formation under deep subduction conditions have been performed in olivine-sulfur and olivine-pyrite [35], olivine-Fe,Ni-sulfide [36], and olivine-sulfate-carbon [37] systems. Experiments simulating the behavior of carbon-and sulfur-bearing phases in subduction processes have become topical in recent years; however, these are single studies on the interaction of carbonates and sulfur (a simplified model of subducted marine sediments) with silicate phases at mantle pressures and temperatures.…”

High S and high CO2 contents in haplokimberlite: An experimental and Raman spectroscopic study

“…This approach is not incompatible to the observed sulfides in natural kimberlites (Boctor and Meyer, 1982;Griffin et al, 2002;Katayama et al, 2017). As demonstrated by Bataleva et al (2018), transformation from sulfates to sulfides is possible under mantle conditions and could take place into kimberlitic melts. The reactions proposed by Bataleva et al (2018) involves several chemical reactions desulfation and sulfidation with olivine and carbon (i.e.…”

“…As demonstrated by Bataleva et al (2018), transformation from sulfates to sulfides is possible under mantle conditions and could take place into kimberlitic melts. The reactions proposed by Bataleva et al (2018) involves several chemical reactions desulfation and sulfidation with olivine and carbon (i.e. diamond) to form pyroxenes and sulfides.…”

Editorial for the Special Issue: Experimental and Thermodynamic Modeling of Ore-Forming Processes in Magmatic and Hydrothermal Systems

“…The reconstruction of the sources of ore components and fluids, physicochemical parameters, and the mechanisms of accumulation and separation of elements during the formation of ore deposits is an important task in addressing the fundamental problems of ore-forming processes. Some of the papers in this issue deal with experimental and thermodynamic modeling [19][20][21][22][23][24][25], while the others are devoted to the analytical geochemistry, geochronology, and genesis of some ore occurrences [26][27][28].…”

“…Bataleva and coauthors [21] report the results of the experimental modelling of interactions of Mg, Fe, and Ni-olivine with anhydrite and Mg-sulfate, which are possible sources of oxidized S-rich fluid under lithospheric mantle P-T parameters. An experimental study was performed in the olivine-CaSO 4 (MgSO 4 )-C systems at 6.3 GPa and temperatures of 1050 and 1450 • C using a multianvil high-pressure apparatus.…”