新疆北山启鑫基性-超基性岩体地球化学特征及地质意义  

Geochemical Characteristics of Qixin Mafic-ultramafic Pluton in Beishan,Xinjiang Province and Its Geological Significance

作　　者：黄敏[1] 刘洋旭[1] 蔡永丰 Huang Min;Liu Yangxu;Cai Yongfeng(No.6 Geological Team,Xinjiang Bureau of Geological Exploration and Mineral resources,Hami,Xinjiang,839000,China;Collaborative Innovation Center for Exploration of Hidden Nonferrous Metal Deposits and Development of New Materials in Guangxi&Guangxi Key Laboratory of Hidden Metallic Ore Deposits Exploration,Guilin University of Technology,Guilin,Guangxi,541004,China)

机构地区：[1]新疆维吾尔自治区地质矿产勘查开发局第六地质大队,新疆哈密839000 [2]桂林理工大学广西有色金属隐伏矿床勘查及材料开发协同创新中心&广西隐伏金属矿产勘查重点实验室,广西桂林541004

出　　处：《新疆地质》2018年第1期44-50,共7页Xinjiang Geology

基　　金：2015年度中央返还两权价款资金项目<新疆若羌县黑海-启鑫一带铜镍矿调查评价>(K15-2-LQ17);国家自然科学基金项目(41502180)联合资助

摘　　要：岩石学分析表明,新疆北山一带启鑫岩体的岩石类型主要有蛇纹石化橄榄岩、二辉橄榄岩、斜方辉橄岩、辉橄岩、辉石岩、橄长岩、橄榄辉长岩、辉长岩和闪长岩,岩体铜镍矿化明显。元素地球化学分析结果显示,启鑫岩体具富铁镁,贫钾钠特征,MgO含量为8.42%~34.37%,Mg#为0.77~0.85,SiO_2含量为36.31%~51.50%,属基性-超基性岩类。岩石相对富集大离子亲石元素Rb,Sr等,亏损高场强元素Nb等,部分样品Zr,Hf,Ta呈一定程度的正异常,表明启鑫岩体起源于高镁拉斑玄武质岩浆,在成岩过程中分离结晶相主要是橄榄石和单斜辉石,并存在斜长石的堆晶作用,同时发生了一定程度的同化混染作用,推测启鑫岩体可能形成于岛弧向板内环境转换的构造背景。Petrological and element geochemical analyses have been carried out on Qixin pluton intruded in Beishan Rift Belt in West Xinjiang in order to reveal the distribution of mafic-ultramafic magmatism and its tectonic significance in northeastern Tarim plate.Petrological analyses suggest that the Qixin pluton is composed of olivinite,lherzolite,harzburgite,augite peridotite,pyroxenite,allivalite,olivine-gabbro,gabbro and diorite with obvious Cu-Ni mineralization.Analysis results of geochemistry show that the Qixin pluton is characterized by high FeOT,MgO(Mg#=0.77~0.85)and low total alkali contents.Their SiO2 contents are in range of 36.31%to 51.50%.The pluton shows enrichment in LILEs(Rb,Sr)and HFSEs(Zr,Hf,Ta),and depletion in Nb.Integrated with regional geological data,it could be inferred that the Qixin pluton originated from high-Mg tholeiitic basaltic magma,and the main mechanism controlling the magmatic evolution was fractional crystallization of olivine and clinopyroxene,accumulation of plagioclase and minor assimilate contamination.The change from arc to intraplate environment would be a major tectonic setting to form the Qixin pluton.

关 键 词：新疆北山 基性-超基性岩 地球化学 岩石学 启鑫岩体 

分 类 号：P595[天文地球—地球化学] P57[天文地球—地质学]