Home – Home – Jornals – Russian Geology and Geophysics 2018 number Неопубликованное

Experimental researches focusing on modeling of interaction between eclogitic and lherzolitic garnets with reduced and oxidized sulfur-rich fluids are conducted using multianvil high-pressure apparatus of “split-sphere” type (BARS). Experiments are carried out in garnet-sulfur-carbon and garnet-anhydrite-carbon systems at the pressure of 6.3 GPa and the temperatures of 1150, 1300, and 1450 °С in graphite ampules, as well as in Pt-ampules with hematite buffering container. It is experimentally demonstrated that interaction of both reduced and oxidized sulfur-rich fluids with mantle garnets leads to their partial dissolution and recrystallization, and to the formation of zoned crystals with decreased iron content in rims. Apart from that, this interaction also results in (1) garnet carbonatisation accompanied by formation of the magnesite±dolomite+kyanite+coesite assemblage, and (2) garnet sulfidation with formation of pyrite (1150-1300 °С) or sulfide melt (1450 °С) as inclusions in garnets and in interstitial space. As a result of conducted experimental researches it is established that indicatory characteristics of mantle garnets that underwent metasomatism by sulfur-rich agents, are decreased FeO content in peripheral crystal zones relatively to their centers, and formation of sulfide inclusion in the zones borders. In this paper we also present the first data on diamond dissolution in the silicate-sulfur-carbon systems under lithospheric mantle P,T-parameters that simulate mantle metasomatism of garnet-bearing lithologies by sulfur-rich fluids. It is found that under such conditions diamond crystals undergo partial dissolution resulting in formation of characteristic etching pits (negative trigons on {111} and rectangles on {100}).