东昆仑石头坑德镁铁-超镁铁质岩体矿物学特征及成矿指示  

Mineralogical Characteristics of the Shitoukengde Mafic-Ultramafic Intrusions in East Kunlun Orogenic Belt and the Ore-Forming Indication

作　　者：张照伟[1] 王亚磊[1] 钱兵[1] 刘月高[1] 祁昌炜 董俊[3] 尹建华[3] 

机构地区：[1]国土资源部岩浆作用成矿与找矿重点实验室中国地质调查局西安地质调查中心,陕西西安710054 [2]青海省地质调查局,青海西宁810001 [3]四川省地质矿产勘查开发局一八地质队,四川崇州611200

出　　处：《地质与勘探》2017年第5期825-837,共13页Geology and Exploration

基　　金：国土资源部公益性行业科研专项"拉陵灶火镍成矿赋矿机理及勘查技术研究示范"(201511020);中国地质调查局"东昆仑铜镍多金属资源基地调查"二级项目(DD20160013)共同资助

摘　　要：石头坑德镁铁-超镁铁质岩体位于东昆仑造山带东段五龙沟地区,邻近昆中大断裂,主要岩性为辉石岩、橄辉岩、橄榄岩、辉长岩等,铜镍矿体主要赋存于Ⅰ号岩体的辉石岩、橄辉岩和橄榄岩中。岩石地球化学特征表明,其镁铁比值(m/f)变化范围在2.77~6.01之间,属铁质系列的镁铁-超镁铁岩,有利于成铜镍矿。稀土总量总体较低,轻稀土元素之间分馏强,重稀土元素之间分馏弱。岩石总体富集LILE(Rb、Ba、Th、U),贫HFSE(Nb、Ta、Zr、Y),具有明显的Rb、U正异常及Nb、Ta的负异常。超镁铁岩类橄榄石中的Ni普遍亏损,指示深部存在硫化物的熔离作用,在橄榄石结晶之前,大量的Ni进入到硫化物中,极有利于形成富矿岩浆或矿浆。可见,伴随同化混染作用的发生,岩浆中S达到过饱和,进而硫化物发生不混溶作用,富含硫化物的岩浆运移至东昆仑造山带邻近昆中断裂构造薄弱的部位成岩成矿。铜镍矿体多赋存在含橄榄石的超镁铁质岩体内,指示石头坑德岩体深部存在高度富集铜镍的部位,是下一步的找矿方向。The Shitoukengde mafic-ultramafic intrusions,adjacent to the middle-Kunlun fault,lie in the Wulonggou area in the eastern section of the East Kunlun orogenic belt.It is composed of pyroxenite,olivine pyroxenite,peridotite and gabbro.The Ni-Cu orebodies mainly occur in the pyroxenite,olivine pyroxenite and peridotite of the No.I intrusion.Petrogeochemical characteristics of rocks show that the m/f values of these rocks range from2.77 to 6.01,and the ore-bearing rocks belong to ferruginous series mafic-ultramafic intrusions that are favorable for the formation of magmatic NiCu sulfide ore bodies.These rocks have low total rare earth element values,showing obvious fractionation between LREE and HREE,with intense LREE fractionation but weak HREE fractionation.They are enriched in LILE（Rb,Ba,Th and U）while depleted in HFSE（Nb,Ta,Zr and Y）,and generally show obvious positive Rb and U anomalies,as well as negative Nb and Ta anomalies.The olivines of ultramafic rocks are depleted in Ni content,revealing the immiscibility of the sulfides occurred at depth.It is very favorable for formation of sulfide-enriched magma,with massive Ni entering the sulfides before olivine crystallization.During the upwelling process of mantle-derived magma,the S was supersaturated in the magma due to the addition of crustal materials accompanied with the occurrence of assimilation and contamination,followed by the immiscibility of the sulfides.Analysis suggests that the sulfide-enriched magma migrated to the weak structural portation of the middle-Kunlun fault nearby the East Kunlun orogenic belt to form mineral deposits.Magmatic Ni-Cu sulfide ore bodies are mostly hosted in the ultramafic rocks containing plenty of olivines,suggesting that the deep part of the Shitoukengde intrusions is the locality with highly enriched Ni-Cu sulfide bodies,thus the target of further ore prospecting.

关 键 词：矿物学特征 镁铁-超镁铁质岩 岩浆铜镍矿床 成矿指示 石头坑德 东昆仑 

分 类 号：P588.1[天文地球—岩石学] P595[天文地球—地质学]