Mineralogical Characteristics and Genesis of Garnet in the Jiama(Gyama) Copper-Polymetallic Deposit of Tibet
西藏甲玛铜多金属矿石榴子石矿物学特征及成因意义

The ore bodies of the Jiama(Gyama) copper polymetallic deposit are mainly hosted in skarn. Garnet skarn is the main skarn type, and it is therefore significant to study the mineralogical characteristics and genesis of the garnet. Based on previous studies, the authors used electron microprobe to analyze the garnets collected from different depths of drill holes at the mine center and the edge of the Jiama(Gyama) deposit, with a detailed comparative study of mineralogical characteristics. The analytical results of 18 garnet points and other electron microprobe analyses show that all the garnets are of calcium series. They are composed of Ti-poor andradite and Ti-, Mg- and Mn-rich grossular. Constrained by the fluid oxygen fugacity, garnets at the mining center are mainly composed of andradite, while those on the edge of the mining area are composed of grossular. The content of the andradite decreases from the depth to the shallow part, whereas the grossular content increases. In addition, the zigzag zonation composition of the garnet indicates that the fluid process had multi-phase and multi-stage characteristics.