阿拉善地块北缘达伦乌苏中酸性侵入岩锆石U-Pb 年龄、岩石地球化学特征及其构造演化意义  

Zircon U-Pb ages,whole-rock geochemical characteristics and their tectonic significances of the Dalunwusu intermediate-acidic intrusive rocks in the northern margin of the Alxa Block

作　　者：雷聪聪 李卫星 张超[2] 王文宝 马军 LEI Cong-cong;LI Wei-xing;ZHANG Chao;WANG Wen-bao;MA Jun(Hohhot General Survey of Natural Resources Center,China Geological Survey,Hohhot 010020,China;School of Resources and Environmental Engineering,Shandong University of Technology,Zibo,Shandong 255049,China)

机构地区：[1]中国地质调查局呼和浩特自然资源综合调查中心,呼和浩特010020 [2]山东理工大学资源与环境工程学院,山东淄博255049

出　　处：《矿物岩石地球化学通报》2023年第4期860-872,共13页Bulletin of Mineralogy, Petrology and Geochemistry

基　　金：中国地质调查局地质调查项目(ZD20220503)。

摘　　要：花岗岩的形成时代和岩石地球化学特征在揭示岩浆源区、形成环境和构造演化方面具有重要作用。本文对位于雅干断裂北侧的达伦乌苏中酸性侵入岩体开展了系统的岩相学、岩石地球化学及锆石U-Pb年代学研究。结果显示,达伦乌苏中酸性侵入体由石英闪长岩和花岗闪长岩组成,其加权平均年龄分别为(300.4±2.6)Ma和(303.6±2.5)Ma,表明其形成时代为晚石炭世。岩石地球化学特征显示,达伦乌苏中酸性侵入岩具有较低的SiO_(2)含量(57.27%~67.37%)和(K_(2)O+Na_(2)O)含量(4.74%~6.77%),整体相对富钠(Na_(2)O/K_(2)O>1),具有典型I型花岗岩特征;富集Rb、Th、K、Hf等大离子亲石元素,亏损Nb、Ta、P、Ti、Sr等高场强元素,显示轻稀土元素富集、重稀土元素亏损的右倾稀土元素配分模式,具有弧火山岩特点;同位素示踪结果显示石英闪长岩的[(87Sr/86Sr)_(i)=0.7051~0.7053],暗示其可能来源于年轻的地壳源区。岩石学及地球化学特征表明,达伦乌苏中酸性侵入岩体具有岛弧岩浆岩的地球化学属性,为古亚洲洋于晚石炭世在阿拉善地块北缘俯冲消减的产物。结合区域岩浆、地质和构造研究数据,本文认为阿拉善地块北缘在晚石炭世晚期仍处于俯冲消减构造环境。The formation age and petrogeochemical characteristics of the granite play important roles for revealing the magma source,forming environment and tectonic setting evolution.In this paper,we have carried out a systematic study on the petrography,petrogeochemistry,zircon U-Pb geochronology of the Dalunwusu intermediate-acidic intrusive rocks,which are located in the north side of the Yagan Fault.The Dalunwusu intermediate-acid intrusive rocks mainly consist of quartz diorite and granodiorite,whose weighted mean ages,based on the zircon LA-ICP-MS U-Pb dating results,are of(300.4±2.6)Ma and(303.6±2.5)Ma,respectively,indicating that they were formed in the Late Carboniferous.Petroeochemical characteristics show that the Dalunwusu intermediate-acidic intrusive rocks have relatively low contents of SiO_(2)(57.27%~67.37%)and(K_(2)O+Na_(2)O)(4.74%~6.77%),relatively rich in Na(Na_(2)O/K_(2)O1),and have the geochemical characteristics of typical I-type granite.The Dalunwusu intermediate-acidic intrusive rocks are relatively enriched in large ion lithophile elements,such as Rb,Th,K and Hf,and depleted in high field strength elements,such as Nb,Ta,P,Ti and Sr,withright-inclined chondrite-normalized REE distribution patterns,which means that they are enriched in LREE and depleted in HREE.They have the characteristics of arc volcanic rocks.Isotope tracing results show the quartz diorite samples have(87Sr/86Sr)_(i) values varying from 0.7051 to 0.7053,indicating that the quartz diorite was sourced from the juvenile crust.The petrological and geochemical characteristics show that the Dalunwusu intermediate-acidic intrusive rocks have the characteristics of arc magmatic rocks,and they were products of the Paleo-Asian ocean subduction in northern margin of the Alxa Block during Late Carboniferous.Combined with regional magmatic,geological and tectonic data,we have suggested that the northern margin of the Alxa Block was still in the subduction tectonic enviroument during the Late period of Late Carboniferous.

关 键 词：阿拉善地块北缘 雅干构造带 LA-ICP-MS锆石U-PB年龄 岛弧环境 晚石炭世晚期 

分 类 号：P597[天文地球—地球化学]