Crystallization of high-Ca chromium garnet upon interaction of serpentine, chromite, and Ca-bearing hydrous fluid

Abstract

The results of experimental modeling of the conditions of crystallization of high-Ca chromium garnets in the system serpentine–chromite–Ca-Cr-bearing hydrous fluid at a pressure of 5 GPa and temperature of 1300°С are reported. The mineral association including quantitatively predominant high-Mg olivine and diopside-rich clinopyroxene, bright-green garnet, and newly formed chrome spinel was formed. Garnet mostly crystallized around primary chromite grains and was characterized by a high concentration of CaO and Cr₂O₃. According to the chemical composition, garnets obtained are close to the uvarovite–pyrope varieties, which enter the composition of relatively rare natural paragenesis of garnet wehrlite. The experimental data obtained clearly show that high-Ca chromium garnets are formed in the reaction of chromite-bearing peridotite and Ca-rich fluid at high P–T parameters.