Abstract

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Title:: Geochemical Characteristics and Their Significance of Garnets from Gejiu Sn Polymetallic Deposit of Yunnan

Author(s):: JIA Run-xing; FANG Wei-xuan; 1. China Non-ferrous Metals Resource Geological Survey, Beijing 100012, China;2. Beijing Institute of Geology for Mineral Resources, Beijing 100012, China

Keywords:: garnet; zonal structure; mineral geochemistry; electron microprobe analysis; skarn; infiltration metasomatism; Sn deposit; Yunnan

Abstract:: The electron microprobe analysis results show that the garnets in the contact zones between granite and carbonate from Gejiu Sn polymetallic deposit of Yunnan are mainly grossularite, andradite and a few of pyrope and spessartite. From the inner to outer contact zones, the content of Fe of garnet has the decreasing trend, but the contents of Al and Mn have the obviously increasing trend, and the content of Sn has the weakly increasing trend. The trend is mainly related to the decrease of andradite in the inner side and the increase of spessartite in the outer side. The content of Sn of garnet with ring growth lines in the inner contact zone is less than 0.03%; the content of Sn of garnet with zonal structure in the outer contact zone is 0.50%-0.55%. The ring growth lines and zonal structure of garnet imply the chemical composition volatility of metallogenic fluid. It is related to the periodicity change of physical and chemical conditions in post-magmatic hydrothermal infiltration metasomatism between granite and surrounding rocks. Compared with the inner contact zone, the outer contact zone is more favorable to the enrichment and precipitation of Sn.