东昆仑五龙沟金矿田平台岩体岩相学、年代学、地球化学特征及其构造意义  

Petrography,Geochronology,Geochemical Characteristics of Pingtai Pluton in Wulonggou Gold Orefield,East Kunlun Orogen,China and Their Tectonic Significance

作　　者：李君阳 薛春纪[1] 王斌 赵晓波[1] 赵伟策 刘洋涛 李鹏 韩玉 LI Jun-yang;XUE Chun-ji;WANG Bin;ZHAO Xiao-bo;ZHAO Wei-ce;LIU Yang-tao;LI Peng;HAN Yu(School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China;The First Geological Exploration Institute of Qinghai Province,Haidong 810699,Qinghai,China;Deep Exploration Technology Innovation Engineering Technology Center of Large and Super Large Dold Deposits Around Qaidam of Qinghai Province,Haidong 810699,Qinghai,China;Beijing Institute of Geology for Mineral Resources Co.,Ltd.,Beijing 100012,China)

机构地区：[1]中国地质大学(北京)地球科学与资源学院,北京100083 [2]青海省第一地质矿产勘查院,青海海东810699 [3]青海省柴达木周缘大型超大型金矿深部探测技术创新工程技术中心,青海海东810699 [4]北京矿产地质研究院有限责任公司,北京100012

出　　处：《地球科学与环境学报》2023年第5期1176-1191,共16页Journal of Earth Sciences and Environment

基　　金：青海省重点研发与转化计划项目(2021-SF-155);国家重点研发计划项目(2017YFC0601202)。

摘　　要：东昆仑五龙沟金矿田东南部出露中三叠世侵入体——平台岩体,为探究古特提斯洋俯冲演化过程提供了新的线索。对平台岩体内的花岗闪长岩开展了详细的岩相学、LA-ICP-MS锆石U-Pb年代学、岩石地球化学和Hf同位素研究。结果表明:平台岩体内的花岗闪长岩主要由斜长石(体积分数为45%~50%)、石英(20%~25%)、钾长石(20%~25%)、角闪石(5%)、黑云母(5%)组成;花岗闪长岩锆石U-Pb加权平均年龄为(247±1)Ma,侵位于中三叠世;主量元素特征显示SiO_(2)含量(质量分数)为64.88%~65.90%,FeO^(T)/MgO平均值为3.70,Fe_(2)O_(3)/FeO平均值为1.48,锆石饱和温度平均值为770℃,因此,花岗闪长岩属于I型花岗岩;球粒陨石标准化稀土元素配分模式表现为轻稀土元素富集、重稀土元素亏损的特征,并具有弱负Eu异常;原始地幔标准化微量元素蛛网图具有富集大离子亲石元素(Cs、Rb、Ba)、亏损高场强元素(Nb、Ta等)的特征;花岗闪长岩的锆石ε_(Hf)(t)值为-4.51~0.64,Hf二阶段模式年龄为1.54~1.22 Ga。综合地球化学特征和区域构造演化,东昆仑五龙沟金矿田平台岩体内的花岗闪长岩源区为陆壳物质,形成于与古特提斯洋俯冲有关的活动大陆边缘环境,进一步表明古特提斯洋在中三叠世时仍处于北向俯冲阶段。The Middle Triassic Pingtai pluton,which occurs in the southeastern part of Wulonggou gold orefield,East Kunlun orogen,provides new insights into the subduction history of the Paleo-Tethyan ocean.The detailed petrology,whole-rock geochemistry,zircon U-Pb age and Hf isotopic data of granodiorite from Pingtai pluton were conducted.The results show that the granodiorite of Pingtai pluton mainly comprises plagioclase(the volume fraction is 45%-50%),quartz(20%-25%),K-feldspar(20%-25%),hornblende(5%),and biotite(5%),and it yields a zircon U-Pb weighted mean age of(247±1)Ma,suggesting an emplacement age of Middle Triassic;whole-rock geochemistry characteristics show that SiO_(2) content varies from 64.88% to 65.90%,average ratios of FeO~T/MgO and Fe_(2)O_(3)/FeO are 3.70 and 1.48,respectively,and average saturation temperature for zircon is calculated to be 770 ℃.Therefore,it is suggested that the granodiorite belongs to strong peraluminous and high-potassium calcium alkaline series,which is similar to typical I-type granite.Chondrite-normalized REE pattern shows that the granodiorite is enriched in LREEs and depleted in HREEs with weak negative Eu anomaly.The ε_(Hf)(t) values range from-4.51 to 0.64,and the Hf model age is 1.54-1.22 Ga.In combination with regional geological data,it is suggested that the granodiorite of Pingtai pluton is generated in a continental magmatic arc setting,which is related to the northward subduction of the Paleo-Tethyan ocean,and its parental magma is derived from meta-sandstone of continental crust.It is further indicated that the subduction of the Paleo-Tethyan ocean might have lasted until the late Middle Triassic.

关 键 词：花岗闪长岩 地球化学 锆石U-Pb年龄 中三叠世 构造演化 东昆仑造山带 古特提斯洋 

分 类 号：P597[天文地球—地球化学]