塔里木东北缘罗东镁铁-超镁铁质岩体地质、地球化学特征对岩石成因和镍成矿作用的指示

Geology and Geochemistry of the Luodong Mafic-Ultramafic Intrusion,Northeast Margin of Tarim Indicate Its Petrogenesis and Ni Mineralization

罗东岩体位于塔里木东北缘,主要岩相有橄榄岩、橄辉岩和辉长岩,矿化多以浸染状硫化物产于橄榄岩相中。岩石具高镁、低硅、低碱,具平坦的稀土分布模式和明显的Ba,Nb负异常和Pb,Sr正异常。母岩浆来源于受俯冲流体交代改造的亏损地幔发生的高程度部分熔融,具高温高镁含水和氧化特征。结晶分异是主要的岩浆作用,岩体同时经历了显著的地壳混染。早期深部熔离造成了铂族元素亏损,浸染状硫化物是晚期熔离的产物。据地质、地球化学和地球物理信息,罗东岩体具有良好的铜镍矿找矿前景,高品位富矿是下一步找矿重点。

The Luodong intrusion,located in the northeast margin of Tarim Basin.The intrusion mainly consists of peridotite,oolite and gabbro,and the mineralization as disseminated sulfide occurs in peridotite facies.Theses rocks are characterized by high magnesium,low silicon and low alkali,and they have flat rare earth partition mode,obvious Ba,Nb negative anomaly and Pb、Sr positive anomaly.The parental magma is derived from the high degree partial melting of depleted mantle which is modified by subduction fluid,and it has the characteristics of high temperature,high magnesium and hydrous and oxidized nature.Fractional crystallization is the main magmatism,while the intrusion had experienced significant crustal assimilation.The depleted of platinum group elements is caused by early sulfide segregation at depth,and disseminated sulfide is the product of late segregation.According to geological,geochemical and geophysical information,the Luodong intrusion has a good prospecting prospect of Cu-Ni ore,and high grade rich ore is the key point of the future prospecting.