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 -yOs values from 15. 3 to 40. 3. Massive sulfide ores and disseminated sulfide ores have similar yOs values that range up to about 260. Net-structured sulfide ores have the highest -yOs values up to about 1000. The study shows that the Qingkuangshan Ni-Cu-PCE 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 PCE depleted magma; (2) sulfides in the net-structured sulfide ores originated from a second stage of contamination and sulfide segregation at an R = 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?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.%青矿山Ni-Cu-PGE矿床位于四川会理县小关河地区,是峨眉山大火成岩省中典型含铂岩浆硫化物矿床之一.本文对该矿床开展了Re-Os同位素组成的分析研究.分析结果表明,不同类型岩矿石的初始Os同位素组成具有明显的不均一性,主要区分出三种不同Os同位素组成的岩矿石类型:不含硫化物的橄辉岩具低γOs,变化范围从15.3到40.3；致密块状和浸染状硫化物矿石相近,γOs值在260左右；海绵陨铁状矿石具有最高的放射性Os同位素组成,γOs值在1000左右.分析认为,青矿山Ni-Cu-PGE矿床是多级岩浆房演化的结果,原始岩浆具有苦橄质岩浆的性质,成矿岩体中不含硫化物的橄辉岩具有低的放射性Os同位素组成,其母岩浆不是矿石硫化物的直接母体；致密块状和浸染状硫化物矿石与海绵陨铁状矿石也具有不同的放射性Os同住素组成,是成矿岩浆演化过程中不同期次岩浆硫化物熔离形成的.模式分析认为:(1)原始岩浆在深部岩浆房受到下地壳混染(约1.8％),造成少量Cu、Ni及PGE元素进入熔离硫化物形成PGE适度亏损的成矿母岩浆；(2)海绵陨铁状矿石硫化物是PGE适度亏损的成矿母岩浆受下地壳二次混染形成的具有很高放射性Os同位素组成的岩浆(γOs(t＝260Ma)高达1000)经二次硫化物熔离(R≈1000)所形成；(3)PGE适度亏损的成矿母岩浆受上地壳二次混染(约6.7％),形成具有较高放射性Os同位素组成的岩浆(γOs(t =260Ma)在260左右)并发生二次硫化物熔离(R-5000),部分熔离硫化物积聚成矿浆形成块状硫化物矿石,未得到充分积聚的熔离硫化物形成浸染状硫化物矿石.Os同位素组成的不均一性表明青矿山Ni-Cu-PGE矿床为岩浆通道系统成矿,是多级岩浆房演化过程中不同期次含矿岩浆在岩浆通道系统中复合的结果.
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