Jinchuan (Baijiazuizi) Ni-Cu-(PGE) deposit, Jinchuan District, Jinchang Prefecture, Gansu (Ganzu) Province, China

The Proterozoic Jinchuan intrusion is located at the margin of the Sino-Korean massif. It intruded into late Archean metasedimentary rocks consisting of various gneisses, chlorite-quartz schists, banded marbles and migmatites. The intrusion occurs as a NW oriented lens, over 6000 m long, approximately 200–300 m wide and more than 1100 m thick. The primary magma was a high-MgO basalt.
The intrusion is divided into four segments by E–W to NE–SW trending strike-slip faults. Four mines are located within each of these segments and are referred to as mines III, I, II and IV, from west to east. Most of the intrusion (I and II mines) is exposed, except for the two ends (Mines III and IV) which are separated by faults and form two isolated parts that are covered by Quaternary alluvium. The intrusion consists of five dominant rock types. In order of decreasing abundance these are, lherzolite, dunite, plagioclase lherzolite, olivine websterite and websterite. These rock types subdivide the intrusion into an upper layer, a lower layer and a marginal layer consisting respectively of ultramafic cumulate (dunite and olivine-rich lherzolite), olivine-poor lherzolite, plagioclase lherzolite and websterite, and websterite and chlorite-tremolite schists. The dominant rocktype in the intrusion is lherzolite.
The sulfide ore bodies are situated in the middle and lower regions of the intrusion, with the major orebodies of Mines I and II accounting for more than 90% of the known Ni–Cu reserves in the deposit. Sulfide minerals generally increase in abundance towards the base of the complex. The dominant Ni sulfide ore is dissemi-nated to net-textured, with sulfide ranging from 1-40% by volume. Massive sulfide ore is rare.

World's largest Ni deposit.

Ref.:
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- Chusi Li, Zhanghua Xu, de Waal, S.A., Ripley, E.M., and Maier, W.D. (2004): Compositional variations of olivine from the Jinchuan Ni–Cu sulfide deposit, western China: implications for ore genesis. Mineralium Deposita 39, 159-172.
- Li Xianhua, Su Li, Song Biao, and Liu Dunyi (2004): SHRIMP U-Pb zircon age of the Jinchuan ultramafic intrusion and its geological significance. Chinese Science Bulletin 49(4), 420-422.
- Ripley, E.M., Sarkar, A., and Chusi Li (2005): Mineralogic and Stable Isotope Studies of Hydrothermal Alteration at the Jinchuan Ni-Cu Deposit, China. Economic Geology 100(7), 1349-1361.
- Yang, X.-Z., Ishihara, S., and Zhao, D.-H. (2006): Genesis of the Jinchuan PGE deposit, China: evidence from fluid inclusions, mineralogy and geochemistry of precious elements. Mineralogy and Petrology 86 (1/2), 109-128.
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