YANG Huan-huan1, TANG Ju-xing1, ZHANG Zhong2, WANG Qin3, ZHANG Zhi4, SONG Yang1, YANG Chao5, WANG Yi-yun3, DING Shuai3, FANG Xiang1, LIN Bin1, GAO Ke3, YUAN Hua-shan6
(1. MLR Key Laboratory of Metallogeny and Mineral Resource Assessment, Institute of Mineral Resources, Beijing 100037, China;
2. Tianyuan Minerals Exploration Ltd, Shigatse 857000, China；
3. College of Earth Sciences, Chengdu University of Technology, Chengdu 610059, China;
4. Chengdu Center, China Geological Survey, Chengdu 610081, China;
5. Département de géologie et de génie géologique, Université Laval, Quebec QC G1V0A6, Canada; 6. Golden Dragon Mining Co., Ltd., Lhasa, Tibet 850000, China)
Abstract: Tiegelongnan copper (gold-silver) deposit in Duolong ore-concentrated area is the first discovered epithermal deposits in Tibet, China. Pyrites in deposit develops extensively with obvious characteristics. Pyrites which are located in shallower parts of drillings develop band structure and they are relative rarity in other deposits. This paper studies the mineralogical characteristics, trace elements and unique band structure of pyrites in the ore area by using field drilling geological record, microscopic identification, electron microprobe analysis and so on. At the same time, the paper explains the origin of banded pyrites and the geological implications of banded pyrites. Result show that banded pyrites in Tiegelongnan ore area is the result of discontinuous growth. The Co/Ni and element contents of Au, Cu and Se show rhythm changes from core to edge of banded pyrite. Temperature of fluid during formation of the external band is higher than that of formation of the internal band. Contents of Au, Cu and Se in the liquid during formation of the external band are higher than those during of the internal band. Au in the banded pyrite gets into pyrite crystal lattice via Au+ replacing Fe2+. While part of Cu gets into pyrite crystal lattice via Cu2+ replacing Fe2+ to form CuS2 and part of Cu gets into pyrite via copper sulfide inclusions. The banded pyrite developed in the shallow of orebody, which is approach to the strong copper mineralization and Au, Ag and Cu grades in the position that banded pyrite developed are high. Therefore, the banded pyrite is the indication for concentrating Au, Ag and Cu elements in Tiegelongnan ore area.
Keywords: pyrite; band structure; occurrence of Au and Cu; origin of banded pyrite; Tiegelongnan; Tibet
Email: zggyhh@163.com
ACTA MINERALOGICA SINICA Vol. 36, No. 1, 2016, Page 70-79
