Experimental Study of Amphibole Interaction with H2O–HCl Fluid at 650–750oC, 5–7 Kbar: Implications for High-Temperature Metasomatism of Metabasitesстатья
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Дата последнего поиска статьи во внешних источниках: 2 сентября 2020 г.
Аннотация:Interaction between amphibole and H2O–HCl fluid was experimentally studied in an internally heated pressure vessel at 650–800°C and 5–7 kbar. The stability of the anorthite–amphibole association was approved to be constrained at T = 650–800°C, (P = 5–7 kbar) within a range of HCl fugacity (fHCl) 50 < fHCl < 400 bar. At higher fHCl, the amphibole is replaced by gedrite (or cordierite at 800°C) + chlorite. Concentrations of major components in the equilibrium solutions were measured. It is demonstrated that Ca and Fe are more significantly than Mg removed from the amphibole, whereas Al and Si weakly pass into the fluid phase and mostly form an aluminosilicate matrix consisting of small spherical and clastic quartz grains, phases like Al2SiOn × mH2O, and fibrous sillimanite. The aluminosilicate matrix locally hosts large (>100 μm), corundum and quartz crystals. Based on experimental data, it is demonstrated that interaction between metabasite with acidified fluid resulted in Ca, Fe, and no so much Mg removal from the metabasite (as inferred for rocks cropping out on Kii Island in the White Sea). The HCl fugacity in the metasomatizing fluid was approximately 50–200 bar at T = 650 – 800°C, P = 5–7 kbar. Rock depletion in bases led to that the residual matrix enriched in Al2O3 and SiO2, and this was favorable for the origin of corundum, on the one hand, and highly silicic rocks, like quartzite, on the other.