塔里木板块东南缘敦煌地块内大敖包沟铜镍矿化镁铁-超镁铁质岩年代学、岩石地球化学研究  

Geochronology and geochemistry of Cu-Ni mineralized mafic-ultramafic rocks in the Daaobaogou deposit of the Dunhuang Block in the southeastern margin of the Tarim Plate

作　　者：康鸿杰 苏欣 王永豪 周超 张治国 景生鹏 宁娜 曾进 王东阳 严雨昕 KANG Hong-jie;SU Xin;WANG Yong-hao;ZHOU Chao;ZHANG Zhi-guo;JIN Sheng-peng;NING Na;ZENG Jin;WANG Dong-yang;YAN Yu-xin(Gansu Institute of Natural Resources Planning and Research,Lanzhou 730000,China)

机构地区：[1]甘肃省自然资源规划研究院,兰州730000

出　　处：《矿物岩石地球化学通报》2024年第6期1239-1254,共16页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：甘肃省科技计划项目(22JR5RA602);甘肃省自然资源厅科技项目(202210)。

摘　　要：大敖包沟铜镍矿化镁铁-超镁铁质岩产于塔里木板块东南缘敦煌地块内,研究其成岩年代和岩石地球化学特征对敦煌地块内铜镍硫化物成矿作用及找矿预测具有重要意义。本文对镁铁-超镁铁质岩锆石U-Pb年代学、Sr-Nd-Hf同位素以及主、微量元素进行了分析测试。结果显示,大敖包沟镁铁-超镁铁质岩锆石SHRIMP U-Pb年龄为(331.7±7.3)Ma(早石炭世),岩石具有较低Mg#(33.45~71.55),轻稀土LREE(La_(N)/Yb_(N)=6.23~15.19)和亲石元素(Rb、Th、U等)富集,高场强元素(Nb、Ta、Ti等)亏损,以及微弱的Eu负异常(δEu=0.66~1.08)特征;AFM和Ni/Cu-Pd/Ir图解显示岩石属于拉斑系列。结合区域地质特征研究,本文认为大敖包沟镁铁-超镁铁质岩形成于碰撞后伸展环境,其原生岩浆来源于部分熔融的岩石圈地幔,为高镁拉斑玄武岩浆,具有向钙碱性演化趋势,岩浆演化过程中发生过分离结晶、地壳物质混染和铜镍硫化物熔离作用。The copper-nickel mineralized mafic-ultramafic rocks in the Daaobaogou deposit of the Dunhuang Block are located in the southeastern margin of the Tarim Plate.It is of great significance to study the diagenetic age and geochemical characteristics of those rocks for understanding the Cu-Ni mineralization and predictive prospecting the Cu-Ni resources in the Dunhuang Block.In this study,we have carried out analyses of the zircon U-Pb chronology,Sr-Nd-Hf isotopes,major and trace elements of those maficultramafic rocks.The results show that the olivine pyroxenite of mafic-ultramafic rocks in the Daaobaogou deposit has zircon SHRIMP U-Pb age of(331.7±7.3)Ma(early Carboniferous epoch).The mafic-ultramafic rocks are characterized with relatively low Mg^(#) values(33.45–71.55),enriched LREE(La_(N)/Yb_(N)=6.23–15.19)and LILE(Rb,Th,U,etc.),depleted HFSE(Nb,Ta,Ti,etc.),and relatively weak negative Eu anomalies(δEu=0.66–1.08).Based on the AFM and Ni/Cu-Pd/Ir diagrams,they belong to the tholeiitic series.Combined with studies on characteristics of regional geology,it is believed that they were formed in the postcollision extensional environment by the evolved magmas through the evolution towards the calc-alkaline one from the original high magnesium tholeiitic basaltic magma which was originated from the partial melting of the lithosphere mantle.In the evolution process of original magma,the fractional crystallization,crustal material mixing and segregation of Cu-Ni sulfides had occurred in the magma.

关 键 词：镁铁-超镁铁质岩 地球化学 年代学 岩浆源区 敦煌地块 

分 类 号：P588.12[天文地球—岩石学] P624[天文地球—地质学] P597