云南永平县水泄辉长岩锆石U-Pb年代学、地球化学及地质意义  

Zircon U-Pb dating,geochemistry and geological significance of the Shuixie gabbros in Yongping County,Yunnan Province

作　　者：李赛赛[1,2] 王洋 张洪瑞[4] 刘兴源 王秋宇 杨澍 LI Saisai;WANG Yang;ZHANG Hongrui;LIU Xingyuan;WANG Qiuyu;YANG Shu(Collaborative Innovation Center for Erploration of Nonferrous Metal Deposits and Efficient Utilization of Resources By the Province and Ministry,Guilin University of Technology,Guilin,Guangxi 541004,China;College of Earth Sciences,Guilin University of Technology,Guilin,Guangxi 541004,China;School of Earth Sciences,Hebei GEO University,Shijiazhuang,Hebei 050031,China;Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing 100083,China)

机构地区：[1]桂林理工大学有色金属矿产勘查与资源高效利用省部共建协同创新中心,广西桂林541004 [2]桂林理工大学地球科学学院,广西桂林541004 [3]河北地质大学地球科学学院,河北石家庄050031 [4]中国地质科学院地质研究所,北京100037 [5]中国地质大学地球科学与资源学院,北京100083

出　　处：《地质学报》2023年第4期1157-1177,共21页Acta Geologica Sinica

基　　金：国家自然科学基金项目(编号42261144669,42273073,42262026)资助的成果。

摘　　要：滇西地区二叠纪—三叠纪岩浆岩展布还不清楚,导致相关古特提斯构造演化模型还存在争议。本文对兰坪-思茅盆地西缘水泄地区的辉长岩开展了LA-ICP-MS锆石U-Pb定年、锆石Hf同位素、全岩主微量元素及Sr-Nd同位素分析,探讨了岩石成因及地质意义。水泄辉长岩2件样品的锆石U-Pb年龄分别为237.8±3.4 Ma和240.8±3.3 Ma,代表其结晶年龄,属于中三叠世。样品具有较高的Na2O/K2O(3.81~49.14),明显富集Ba、Rb、Th、U等大离子亲石元素,相对亏损Nb、Ta等高场强元素,稀土元素弱分馏,轻稀土弱富集,δEu值为0.87~1.07,无明显的Eu异常。锆石εHf(t)值全为正值,主要介于+5.67~+15.75,全岩初始87Sr/86Sr比值为0.70453~0.70776,ε_(Nd)(t)值全为正值,介于+4.9~+5.2。地球化学特征显示水泄辉长岩来源于亏损地幔的部分熔融,在岩浆演化过程中发生了镁铁质矿物和铁钛矿物的分离结晶作用。水泄辉长岩位于江达-维西弧和云县弧衔接部位,产出于陆缘弧环境。该岩脉与杂多弧、江达-维西弧和云县弧同属古特提斯主洋盆俯冲的产物,由此构成了一条上万千米长的弧岩浆岩带。The distribution of Permian-Triassic magmatic rocks in western Yunnan Province is still unclear,resulting in controversy regarding the Paleo-Tethyan tectonic evolution model.Here,we present new LA-ICP-MS zircon U-Pb,zircon Hf isotopes whole-rock major and trace element,and Sr-Nd isotopic data for the Shuixie grabbos of the western Langping-Simao basin in the Sanjiang Orogen,SW China.The zircon U-Pb ages of two samples from Shuixie gabbros are 237.8±3.4 Ma and 240.8±3.3 Ma respectively,representing their crystallization age and belonging to the Middle Triassic.The samples have high Na_2O/K_2O(3.81~49.14),and are enriched in LILEs(such as Ba,Rb,Th,U),depleted in HFSEs(such as Nb,Ta).The REEs are weakly fractionated,and the LREEs are weakly enriched.TheδEu values ranges from 0.87 to 1.07,without obvious Eu anomaly.Zirconε_(Hf)(t)values are all positive,mainly ranging from+5.67 to+15.75.The initial~(87)Sr/~(86)Sr ratio of the whole rock ranges from 0.70453~0.70776,andε_(Nd)(t)values are all positive,ranging from+4.9 to+5.2.Geochemical characteristics show that Shuixie gabbros originated from the partial melting of the depleted mantle,and the fractional crystallization of mafic minerals and Fe-Ti minerals occurred during the magmatic evolution.Shuixie gabbros are located at the junction of the Jiangda-Weixi arc and the Yunxian arc,and occurs in the continental margin arc environment.These dykes,together with the Zadoi arc,the Jiangda-Weixi arc and the Yunxian arc,are the products of the subduction of the Paleo-Tethys main ocean basin,thus forming an arc magmatic belt with a length of tens of thousands of kilometers.

关 键 词：辉长岩 三江造山带 古特提斯 地球化学 中三叠世 

分 类 号：P588.124[天文地球—岩石学] P597.3[天文地球—地质学]