青海东昆仑野牛沟早侏罗世花岗闪长岩岩石成因及构造背景  

Petrogenesis and geotectonic setting of Early Jurassicgranodiorites in Yeniugou,eastern Kunlun, Qinghai Province

作　　者：张万辉 曹守林 李小亮 严正平 杨乐 李正栋 杨德 党园园 李良[4] ZHANG Wanhui;CAO Shoulin;LI Xiaoliang;YAN Zhengping;YANG Le;LI Zhengdong;YANG De;DANG Yuanyuan;LI Liang(The First Nonferrous Geological Exploration Institute of Qinghai Province(Qinghai Provincial Nonferrous Geological Survey Institute),Xining 810000,China;Qinghai Key Laboratory of Concealed Mineral Exploration,The First Nonferrous Geological Exploration Institute of Qinghai Province,Xining 810000,China;Geological Science and Technology Branch,Qinghai Provincial Nonferrous Metal Geological and Minerals Exploration Bureau,Xining 810001,China;School of Earth Sciences,Yunnan University,Kunming 650500,China)

机构地区：[1]青海省有色第一地质勘查院(青海省有色地质调查院),西宁810000 [2]青海省有色第一地质勘查院青海省隐伏矿勘查重点实验室,西宁810000 [3]青海省有色地质矿产勘查局地质科技处,西宁810001 [4]云南大学地球科学学院,昆明650500

出　　处：《世界地质》2024年第4期479-495,共17页World Geology

基　　金：青海省有色地质矿产勘查局局管项目(青色地[2020]63号)。

摘　　要：为查明格尔木野牛沟地区早侏罗世花岗闪长岩的岩石成因、成岩构造背景及其与晚三叠世花岗岩的成因联系,笔者利用岩石地球化学、锆石U-Pb定年及Lu-Hf同位素等方法对上述问题展开研究。结果显示,野牛沟花岗闪长岩的锆石具有典型的岩浆锆石震荡环带与Th/U比值(0.25~1.28,>0.10),其加权平均年龄与εHf(t)值分别为(198.4±1.6)Ma和4.99~7.50。该岩石具有C型埃达克岩的特征,包括高Sr[(400.13×10^(-6))~(420.00×10^(-6))]和低Mg[w(MgO)=0.95%~1.19%]、Y[(6.93×10^(-6))~(7.87×10^(-6))]、Yb[(0.65×10^(-6))~(0.77×10^(-6))]与Na 2O/K 2O比值(1.12~1.34,<2),相对亏损重稀土元素和高场强元素。结合区域构造演化可知,野牛沟花岗闪长岩起源于拆沉至深部的新元古代下地壳角闪岩的部分熔融(T DM2=919~759 Ma),是印支晚期岩浆作用的延续,同形成于古特提斯洋闭合-造山后下地壳拆沉引起的强烈伸展背景。In order to ascertain the petrogenesis,geotectonic setting and genetic connection with Late Triassic granites of the Early Jurassic granodiorites in Yeniugou area of Golmud City,the authors systematically conducted whole-rock geochemical,zircon U-Pb dating and Lu-Hf isotopic studies on the above issues.The results show that the zircons of Yeniugou granodiorites exhibit typical magmatic zircon oscillatory zoning and Th/U values(0.25-1.28,>0.10),with weighted average age andεHf(t)value of(198.4±1.6)Ma and 4.99-7.50,respectively.In geochemistry,the Yeniugou granodiorites show the geochemical properties of C-type adakitic rock,including high Sr[(400×10^(-6))-(420×10^(-6))]but low Mg[w(MgO)=0.95%-1.19%],Y[(6.93×10^(-6))-(7.87×10^(-6))]and Yb[(0.65×10^(-6))-(0.77×10^(-6))]contents,with typical low Na 2O/K 2O ratios(1.12-1.34,<2),relative depletion of heavy rare earth elements and high field strength elements.Based on the geotectonic evolution,it can be inferred that the primary magma of Yeniugou granodiorites originated from the partial melting of Neopro-terozoic lower crustal amphibolite(T DM2=919-759 Ma).It is a continual magmatism of the Late Indosinian,and emplaced within the same geodynamic setting as the Late Triassic granitoids in a strong extensional background that was caused by the lower crustal delamination after the closure of Paleo-Tethys Ocean and orogeny.

关 键 词：早侏罗世 埃达克质岩石 造山后伸展 野牛沟花岗闪长岩 东昆仑 

分 类 号：P595[天文地球—地球化学] P597[天文地球—地质学]