柴达木西北缘大通沟南山基性-超基性岩地球化学特征及找矿前景分析

Geochemistry and Prospecting Potential of Datonggou South Mountain Basic-ultrabasic Rocks in Northwest Qaidam Basin

大通沟南山地区基性-超基性岩体位于柴达木地块西北缘,侵位于新元古代地层。岩体多呈北东向展布,脉状、透镜状产出,岩石类型主要为橄榄辉石岩、辉石角闪石岩、辉石橄榄岩、橄榄二辉岩等,铜镍矿化主要赋存于橄榄辉石岩、辉石角闪石岩中。岩石表现出低硅、中镁、高钛、高钙等特征,富集轻稀土元素和大离子亲石元素(Th、U、Rb),相对亏损高场强元素(Nb、Ta、Ti)。岩石学及岩石地球化学研究表明岩浆在演化过程中发生了一定程度的结晶分异和同化混染,显示出良好的铜镍矿成矿条件。岩石MgO含量、m/f值等指标显示岩体具有良好的铜镍矿含矿性。通过对岩体形成环境、岩石地球化学、物化探特征综合研究,表明大通沟南山地区基性-超基性岩具有良好的铜镍硫化物矿床形成条件和找矿前景。

The Datongnanshan basic-ultrabasic rocks are located at the northwest margin of Qaidam block,which were intruded into the Neoproterozoic formation.These rocks are distributed in the northeast direction,which are mainly occurred as vein and lens.The rocks are composed of olivine pyroxenite,pyroxene amphibolite,pyroxene peridotite and olivine websterite,The Cu-Ni mineralization is primarily occurred in olivine pyroxenite and pyroxene amphibolite.These rocks are characterized by low silicon,middle magnesium,high titanium and high calcium,which are enriched in light rare earth elements and large ion lithopile elements（Th,U,Rb）,and relatively depleted in high field strength elements（Nb,Ta,Ti）.Petrological and geochemical studies indicate that the crystallization differentiation and crustal contamination were occurred during the process of magma evolution,showing agood potential for forming copper and nickel deposits.The MgO content and m/f ratios of these rocks indicate that they have a good property of bearing copper and nickel.After studying the formation environment,petrogeochemistry,geophysical and geochemical characteristics of these rocks comprehensively,the results show that the Datonggounanshan basic-ultrabasic rocks have good prospecting prospect and forming conditions of CuNi sulfide deposits.