内蒙古四子王旗小南山地区镁铁质-超镁铁质岩体岩石成因及含矿性评价  

Petrogenesis and mineralization potentials of mafic-ultramafic intrusions in the Xiaonanshan region,Siziwangqi,Inner Mongolia

作　　者：马云飞 焦建刚[1,2,3] 郭天牧 闫馨云 刘健 高超[1] 王静[5] 李峰 MA Yunfei;JIAO Jiangang;GUO Tianmu;YAN Xinyun;LIU Jian;GAO Chao;WANG Jing;LI Feng(School of Earth Science and Resources,Chang'an University,Xi'an,Shaanxi 710054,China;Key Laboratory of Western China's Mineral Resources and Geological Engineering,Ministry of Education,Xi'an,Shaanxi 710054,China;Xi'an Key Laboratory for Mineralization and Efficient Utilization of Critical Metals,Xi'an,Shaanxi 710054,China;Huanqing Oil Production Plant,Petro China Yumen Oilfield Company,Qingyang,Gansu 745700,China;Inner Mongolia Geologic Surveying and Mapping Institute,Hohhot,Inner Mongolia 010020,China)

机构地区：[1]长安大学地球科学与资源学院,陕西西安710054 [2]西部矿产资源与地质工程教育部重点实验室,陕西西安710054 [3]西安市关键金属成矿与高效利用重点实验室,陕西西安710054 [4]中国石油玉门油田分公司环庆采油厂,甘肃庆阳745700 [5]内蒙古自治区地质测绘院,内蒙古呼和浩特010020

出　　处：《地质学报》2022年第12期4312-4330,共19页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号92162213);内蒙古自治区地质勘查基金项目(编号2020-KY05)联合资助的成果。

摘　　要：内蒙古四子王旗小南山铜镍矿床及外围分布几处镁铁质-超镁铁质岩体,其成因联系及成矿潜力尚不清晰,制约了该地区铜镍硫化物矿床的找矿工作。本文对小南山、土脑包和白音敖包岩体开展了年代学、岩石学及地球化学研究,结果显示,小南山地区存在两类镁铁质-超镁铁质岩:小南山、土脑包含铜镍硫化物岩体由辉长岩、辉石岩组成,矿物组合以斜长石、单斜辉石为主,含少量斜方辉石和橄榄石,发育次闪石化、滑石化和绿泥石化;而白音敖包辉长岩不含铜镍硫化物,矿物组合以斜长石、单斜辉石为主,发育绿泥石化和钠黝帘石化,白音敖包辉长岩锆石U-Pb年龄为277.2±7.3Ma,与小南山岩体(272.7±2.9Ma)同期。此外,小南山和土脑包辉长岩Mg#值为0.56~0.67,m/f值为1.25~1.98,MgO与Ni、Co负相关,Ni与Cu/Zr值正相关,稀土元素配分曲线为右倾型;白音敖包辉长岩Mg#值为0.50~0.51,m/f值为0.97~1.02,MgO与Ni、Co相关性不明显,Cu/Zr值集中在1附近,稀土元素配分曲线为平坦型。岩石地球化学数据指示小南山和土脑包岩体是源自流体交代岩石圈地幔部分熔融,原生岩浆为高镁拉斑玄武质岩浆,岩浆上升过程受到10%~20%陆壳混染,外来硫的加入和分离结晶作用导致硫化物熔离成矿;白音敖包辉长岩由派生岩浆结晶形成,其岩浆源区受到交代作用不明显,岩浆上升过程仅受到5%左右的地壳物质混染,钻探验证没有发现矿体。The Xiaonanshan Cu-Ni sulfide deposit is located in Siziwangqi,Inner Mongolia and is associated with several regional mafic-ultramafic intrusions.Their genetic relationship and mineralization potentials are still questionable,which restricts the mineral prospecting of Cu-Ni sulfide deposits in this area.In this study,we investigated the Xiaonanshan,Tu'naobao and Baiyin'aobao intrusions in aspects of gechronology,petrology,and geochemistry to constrain their petrogenesis and ore-bearing evaluation.The results show that there are two types of mafic-ultramafic intrusions in Xiaonanshan area.The Xiaonanshan and Tu'naobao Cu-Ni sulfide-bearing intrusions consist of gabbro and pyroxenite,with mineral assemblages mainly of plagioclase and clinopyroxene,and minor orthopyroxene and olivine,as well as uralitization,talcum,and chlorite alteration.The Baiyin'aobao gabbro mineral assemblage is mainly composed of plagioclase and clinopyroxene,which have altered into chlorite and zoisite,and without Cu-Ni sulfide.The Baiyin'aobao intrusion has similar formation age of 277.2±7.3 Ma to the Xiaonanshan intrusion(272.7±2.9Ma).The Xiaonanshan and Tu'naobao gabbro have Mg#values of 0.56~0.67,with an m/f ratio of 1.25~1.98.Moreover,their MgO contents show negative relationships with Ni and Co,their Ni contents have positive correlations with Cu/Zr values,and they exhibit right inclined rare earth elements(REE)patterns.The Baiyin'aobao gabbro has Mg#values of 0.50~0.51,with an m/f ratio of 0.97~1.02.This intrusion shows unobvious relationships between its MgO contents with Ni and Co,has Cu/Zr values close to 1,and has flat REE patterns.The geochemical data indicate that the Xiaonanshan and Tu'naobao intrusions were sourced from lithosphere mantle modified by fluids.Their primary magma is high-MgO tholetiitic basaltic magma,with 10%~20%crustal contamination during ascent.The participation of external sulfur and fractional crystallization resulted in sulfide segregation to form the sulfide deposit.The Baiyin'aobao gabbro is formed by t

关 键 词：岩石成因 含矿性评价 铜镍硫化物矿床 镁铁质-超镁铁质岩 小南山 内蒙古 

分 类 号：P612[天文地球—矿床学] P581[天文地球—地质学]