Third largest copper mining area in China, extending on about 660 km2 around Dongchuan city, about 120 km north of Kunming. The host rocks belong to the Proterozoic Kunyang Group which is divided into three sub-groups with eleven formations. Most of the copper deposits are located within the middle Kunyang sub-group, and a different type of copper deposit occurs in each of its three lower formations:
- XIKUANGSHAN-type Fe-Cu deposit (Yinmin formation): There is an iron ore layer (hematite and magnetite, oolitic or blocky structures) in the middle of the Yinmin formation. The fine copper veins (chalcopyrite and chalcocite) distribute in the iron ore layer and form an impregnation structure iron-copper ore deposit.
- DONGCHUAN-type copper deposit (Luoxue formation): This is the most important copper ore type in Dongchuan. The chalcocite-chalcopyrite layers interbed or interlace with the dolomitites to form layered ores. Chalcocite and chalcopyrite fill along the algal layers in the algal dolomitites, which are deformed to form the so-called "maweisi" (horse-tail like) ores.
- TAOYUAN-type copper deposit (Heishan formation): The chalcopyrite-calcite veins interpenetrate in the carbon slates.
The area includes the Tangdan, Luoxue, Yinmin, Xintang, Baixila, Lanniping and Shijiangjun copper mines, of which the Tangdan and Luoxue mines are the largest. The tonnage of the Tangdan mine alone nearly reaches that of a super-large copper ore deposit.
Ref.:
- Wan Kenan (1984): Geochemical characteristics of sedimentation and metamorphism of the Dongchuan copper deposit, Yunnan Province, China. Precambrian Research 25(1-3), 135-136.
- Yang Weihua (1996): Geochemistry of Strata-Bound Copper Deposits. In: Tu Guangzhi and Xu Zhonglun, eds.: Geochemistry of Strata-Bound Deposits in China. Science Press, Beijing (1996), pp. 470-507.
- Huaning Qiu (1998): Petrogenetic chronologic framework and ore-forming ages of the Dongchuan Copper Deposits, Yunnan, SW China. PhD Dissertation, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences (in Chinese with English Abstract).
- Qin Dexian and Liu Chunxue (2000): Emanation-Sedimentary Metallogenic Series and Models of the Proterozoic Rift in the Kangdian Axis. Acta Geologica Sinica 74(3), 466-472.
- Huaning Qiu, Bingquan Zhu, and Dazhong Sun (2002): Age significance interpreted from 40Ar-39Ar dating of quartz samples from the Dongchuan Copper Deposits, Yunnan, SW China, by crushing and heating. Geochemical Journal 36, 475-491.
