Experimental Study of Amphibole Interaction with H2O–HCl Fluid at 650–750°C, 5–7 Kbar: Implications for High-Temperature Metasomatism of Metabasites

Abstract

Interaction between amphibole and H2O–HCl fluid was experimentally studied in an internally heated pressure vessel (IHPV) 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) 50 100 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.