东昆仑东段到木提岩体成因及构造意义:来自年代学及地球化学的约束  

Petrogenesis and Tectonic Implications of Daomuti Intrusive Rocks in East Kunlun Orogen:Constraints from the Geochronology and Geochemistry

作　　者：韩建军 李红刚 何俊[4] 赵明福 韩旭 张新远[2,3] 柴云 HAN Jianjun;LI Honggang;HE Jun;ZHAO Mingfu;HAN Xu;ZHANG Xinyuan;CHAI Yun(Qinghai Geological Survey,Xining 810001,Qinghai,China;Qinghai Provincial Key Laboratory of Geological Processes and Mineral Resources of Northern Qinghai-Tibetan Plateau,Xining 810012,Qinghai,China;Qinghai Geological Survey Institute,Xining 810012,Qinghai,China;School of Earth and Space Sciences,University of Science and Technology of China,Hefei 230026,Anhui,China;School of Resources and Environmental Engineering,Hefei University of Technology,Hefei 230009,Anhui,China)

机构地区：[1]青海省地质调查局,青海西宁810001 [2]青海省青藏高原北部地质过程与矿产资源重点实验室,青海西宁810012 [3]青海省地质调查院,青海西宁810012 [4]中国科学技术大学地球和空间科学学院,安徽合肥230026 [5]合肥工业大学资源与环境工程学院,安徽合肥230009

出　　处：《西北地质》2023年第6期140-154,共15页Northwestern Geology

基　　金：青海省地质勘查项目“青海省都兰县昂日塔地区1∶25000万区域地质矿产调查”(2017042034jc015)资助。

摘　　要：到木提岩体位于东昆仑造山带东段,主要岩性有二长花岗岩、花岗闪长岩及闪长岩。笔者对新发现的闪长岩进行了锆石U–Pb测年和岩石地球化学测试,以确定其形成时代及岩石成因,结合二长花岗岩和花岗闪长岩的岩石地球化学特征,综合探讨到木提岩体的侵位时代、岩石成因及构造演化程。LA–ICP–MS锆石U–Pb测年获得的闪长岩206Pb/238U年龄为(244.6±1.8)Ma,到木提闪长岩体结晶时代为早三叠世。二长花岗岩和花岗闪长岩的地球化学特征显示:里特曼指数小于3.3,具钙碱性–高钾钙碱性特征;铝饱和指数A/CNK值均小于1.1;岩石中P2O5含量普遍较低,且与SiO2含量呈负相关性;富集K、Rb、La等LILE,亏损Nb、Ta、Ti、P等HFSE。地球化学特征表明,到木提岩体属于Ⅰ型花岗岩。综合分析认为,东昆仑东段到木提岩体是下地壳岩石发生部分熔融形成的火山弧花岗岩,阿尼玛卿洋俯冲作用可以持续到早-中三叠世,俯冲过程中形成区域性的地幔岩浆底侵就是导致下地壳熔融的热源,且幔源岩浆不同程度混入到到木提岩浆演化中,岩浆演化中伴有一定的结晶分异发生。The Daomuti intrusive rocks is located in the eastern section of the East Kunlun orogenic belt,and mainly includes monzogranite,granodiorite and diorite.In this paper,zircon U-Pb dating and petrogeochemical tests are performed on newly discovered diorite to determine its crystalline age and petrogenesis.Comprehensively analyse the petrogeochemical characteristics of monzogranite and granodiorite,and discuss the emplace-ment age,rock genesis and tectonic evolution of the Daomuti intrusive rocks.LA-ICP-MS zircon U-Pb dating analysis shows that the 206Pb/238U weighted average age of diorite is(244.6±1.8)Ma,and the crystallization age of the diorite is Early Triassic.The geochemical characteristics of the monzogranite and granodiorite show that the Ritman index is greater than 3.3 and has the characteristics of calcium alkalinity-high potassium calcium alkalinity;the aluminum saturation index A/CNK values are less than 1.1;the P2O5 content in the rocks is low,and its has a negative correlation with SiO2 content;It is enriched with LILE such as K,Rb,La,and loses HFSE such as Nb,Ta,Ti and P.The above characteristics indicate that the Daomuti intrusive rocks belongs to type I granite.Based on the research results of this paper,it can be considered that the Daomuti intrusive rocks is a volcanic arc granite,its formed by partial melting of the lower crust rocks,and the Animaqing Ocean subduction continued to the Early-Middle Triassic The mantle magma underplating during the subduction process is the heat source that causes the melting of the lower crust,and the mantle source magma is mixed into the Daomuti intrusive rocks’magma evolution,and during the Daomuti intrusive rocks’magma evolution occurred fractional crystallization.

关 键 词：闪长岩 花岗闪长岩 二长花岗岩 地球化学 锆石U-Pb年龄 构造环境 东昆仑东段 

分 类 号：P595[天文地球—地球化学] P597.1[天文地球—地质学]