The Qingkuangshan Ni-Cu-PGE deposit, located in the Xiaoguanhe area of Huili County, Sichuan Province, is one of the typical Ni-Cu-PGE deposits in the Emeishan Large Igneous Province (ELIP). In this paper, the Re and Os concentrations and Os isotopic compositions of the sulfide ores and associated ultramafic rocks in the Qingkuangshan deposit are studied in detail. The analyses indicate that the sulfide ores and associated ultramafic rocks can be divided into three types on the base of their Os compositions. Olivine websterites have low gamma Os values from 15. 3 to 40. 3. Massive sulfide ores and disseminated sulfide ores have similar gamma Os values that range up to about 260. Net-structured sulfide ores have the highest gamma Os values up to about 1000. The study shows that the Qingkuangshan Ni-Cu-PGE deposit is formed by multi-stage magma evolution, and that the primary magma was picritic. By model analyzing, the ore-forming mechanism can be concluded as follows; (1) primary magma has undergone lower crustal contamination in a deep magma chamber in the lower crust, and that the segregation of a small quantity of sulfide led to the formation of moderately PGE depleted magma; (2) sulfides in the net-structured sulfide ores originated from a second stage of contamination and sulfide segregation at an R approximate to 1000 in the lower crust from the moderately PGE depleted magma; (3) the moderately PGE depleted magma underwent the further contamination (on average about 6. 7%) and further sulfide segregation (R approximate to 5000) in the upper crust. The massive sulfide ores represent a higher degree of concentration, while the disseminated sulfide ores represent a lower degree of concentration. The marked observed variations in Os isotopic compositions indicate that the Qingkuangshan Ni-Cu-PGE deposit was formed in a magma conduit system, and that multiple pulses of magma with variable crustal contamination and sulfide segregation were involved in the development of the ore-bearing intrusion.

Publication name	ACTA PETROLOGICA SINICA　Volume:27 　Issue:9 　Pages:2655-2664 　Published:SEP 2011
Author(s)	Zhu FeiLin; Tao Yan; Hu RuiZhong; Yu SongYue; Qu WenJun; Du AnDao
Corresponding author	ZHU Feilin  zhufeilin2000@163.com,taoyan@vip.gyig.ac.cn   Chinese Acad Sci, Inst Geochem, State Key Lab Ore Deposit Geochem, Guiyang 550002, Peoples R China

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