柴北缘陶吐尕恩乌苏辉绿玢岩的年代学、地球化学及其构造意义  

Chronology,geochemistry and tectonic significance of the Taotugaenwusu diabase porphyrite in the northern margin of the Qaidam Basin

作　　者：汪周鑫 刘光莲 刘智刚 李建兵 WANG Zhouxin;LIU Guanglian;LIU Zhigang;LI Jianbing(Qinghai Geological Survey Institute,Key Laboratory of the Northern Qinghai-Tibet Plateau Geological Processes and Mineral Resources,Engineering and Technology Center of Remote Sensing Big Data in Qinghai Province,Xining Qinghai 810012,China;The Third Geological Exploration Institution of Qinghai Province,Xining Qinghai 810029,China;Zhongcheng Mining Ltd.of Sichuan Province,Chengdu Sichuan 610047,China)

机构地区：[1]青海省地质调查院青藏高原北部地质过程与矿产资源重点实验室、青海省遥感大数据工程技术研究中学,青海西宁810012 [2]青海省第三地质勘查院,青海西宁810029 [3]四川省众成矿业有限公司,四川成都610047

出　　处：《矿物学报》2024年第6期856-869,共14页Acta Mineralogica Sinica

基　　金：青海省“高端创新创业人才”计划项目(编号:青地矿科[2021]16号);中国地质调查局西安地质调查中心“青海省都兰县阿木尼区地区1꞉5万区域矿产地质调查”项目(编号:12120114018222)。

摘　　要：柴北缘中东部怀头他拉地区出露的早古生代陶吐尕恩乌苏辉绿玢岩,侵位于寒武至奥陶纪的滩间山群(Є-O),蕴含着柴北缘洋盆演化的重要信息,对研究早古生代增生造山作用具有重要意义。本文对该岩体开展了岩石学、地球化学和同位素年代学研究,通过岩体主、微量及稀土元素的特征分析,探讨了岩浆源区、岩石成因及构造环境。结果表明,辉绿玢岩锆石^(206)Pb/^(238)U年龄为447 Ma。岩石相对贫碱,里特曼(组合)指数均值(1.785)<3.3,属钙碱性岩。岩石相对富集大离子亲石元素(LILE),亏损高场强元素(HFSE),稀土元素配分曲线总体右倾,铕(Eu)异常不明显,岩浆分异程度不高。(Th/Nb)_(N)均值(2.485)>1,Nb/La均值(0.555)<1,La/Ta均值(31.06)>25、Sm/Nd均值(0.215)<0.3、Rb/Sr均值(0.145)介于上地幔(0.034)和地壳(0.35)之间,指示其岩浆起源于岩石圈地幔,并具有壳幔混染的特点。综合区域背景,表明该岩体形成于晚奥陶世洋壳俯冲消减的增生造山构造环境。The early Paleozoic Taotugaenwusu diabase-prophyrite,outcroped in the Huaitoutala area in the northern margin of the Qaidam Basin,intruded into the Cambrian-Ordovician Tanjianshan Group.It contains important information about the evolution of the northern Qaidam oceanic basin and is of great significance for studying the early Paleozoic accretionary orogeny.In this paper,the petrology,geochemistry and isotopic chronology of the diabase-prophyrite have been studied.Its magma source,petrogenesis and tectonic environment have been discussed by analyzing characteristics of major,trace and rare earth elements of the rock samples The results show that the diabase-prophyrite has zircon^(206)Pb/^(238)U age of 447 Ma.The rock is relatively alkaline,with average value of the Ritman index of 1.785 which is<3.3.It belongs to the calc-alkaline rock.The rock samples are relatively enriched in LILE,depleted in HFSE,with generally right-declined REE distribution patterns and not obvious Eu anormalies,indicating that its magma was not very highly differentiated.The(Th/Nb)_(N)mean of 2.485(>1),Nb/La mean of 0.555(<1),La/Ta mean of 31.06(>25),Sm/Nd mean of 0.215(<0.3),and Rb/Sr mean of 0.145(which is between the upper mantle(0.034)and the earth's crust(0.35))indicate that the magma was originated from the lithospheric mantle and has characteristics of the mixture of crust and mantle materials.Combined with the regional geological background,it is believed that the diabase-prophyrite was formed in the accretionary orogenic tectonic environment of the Late Ordovician oceanic crust subduction.

关 键 词：辉绿玢岩 地球化学 U-Pb锆石测年 岛弧玄武岩 柴北缘构造带 

分 类 号：P588.124[天文地球—岩石学]