The Coexisting Clinopyroxene‐Garnet Acidometer and Acidity Facies of Skarn Deposits

Abstract On the basis of geological studies of skarn deposits in China and by using thermodynamic models of the solid solution, the coexisting clinopyroxene‐ garnet pair in skarn deposits has been analysed and a coexisting clinopyroxene‐garnet acidometer developed. They can be used to estimate the medium condition under which the skarn was formed. The research on the acidity for the formation of various metallic skarn deposits in China suggests that skarns endowed with dissimilar types of mineralization and occurring in diverse environments differ in the acidity conditions for their formation and in the trend of acidity variation of ore‐bearing fluid. This, coupled with the study of oxygen fugacity of coexisting minerals, makes it possible to establish the oxygen fugacity‐ acidity facies of skarn deposits, which reflect the close genetic relationship between the metallization and the formation of skarn.