中亚造山带南缘中—新元古代地壳的揭示——来自北山—阿拉善北部钻遇碱性花岗岩的年代学和Hf同位素示踪研究  

Revelation of the Meso-Neoproterozoic Crust on the Southern Margin of the Central Asian Orogenic Belt:Chronology and Hf Isotope Tracer from Drilling-intersected Alkaline Granites,Northern Beishan-Alxa

作　　者：宋博 张慧元[2,3] 魏东涛[2,3] 李渭 赵飞 李文明[2,3] SONG Bo;ZHANG Hui-yuan;WEI Dong-tao;LI Wei;ZHAO Fei;LI Wen-ming(College of Earth and Planetary Sciences,University of Chinese Academy of Sciences,Beijing 100049;Xi’an Center of China Geological Survey,Xi’an,Shaanxi 710054;Key Laboratory of Paleozoic Oil and Gas Geology in North China,China Geological Survey,Xi’an,Shaanxi 710054)

机构地区：[1]中国科学院大学地球与行星科学学院,北京100049 [2]中国地质调查局西安地质调查中心,陕西西安710054 [3]中国地质调查局北方古生界油气地质重点实验室,陕西西安710054

出　　处：《地球学报》2021年第1期9-20,I0001-I0005,共17页Acta Geoscientica Sinica

基　　金：中国地质调查局地质调查项目(编号:DD20190092,DD20190113)资助。

摘　　要：前寒武纪微陆块是北山—阿拉善北部增生造山带的重要组分,旱山、雅干和珠斯楞—杭乌拉地区的前寒武纪基底是否存在学界尚存争议。居延海介于北山造山带北部和阿拉善地块北缘的构造衔接部位,受限于巴丹吉林沙漠覆盖,岩石露头极少,我们通过钻井工程,钻遇一套晚石炭世碱性花岗岩,锆石U-Pb年龄和Hf同位素特征揭示,该花岗质岩浆锆石结晶年龄为(312±1)Ma(MSDW=0.46,n=18)和(315±2)Ma(MSWD=0.93,n=15),具有正的εHf(t)值,介于+0.8~+4.4之间,平均值为+2.2,对应二阶段模式年龄TDM2为1048~1267 Ma,平均值为1183 Ma,具有古老地壳的源区属性。通过与旱山构造带、雀儿山构造带、雅干构造带和珠斯楞—杭乌拉构造带的晚石炭世花岗质岩浆对比分析,结合旱山构造带、雅干构造带和珠斯楞—杭乌拉构造带0.9 Ga花岗质岩石的出露以及区域上的重磁资料解译,我们认为旱山、雅干和珠斯楞—杭乌拉构造带存在中—新元古代地壳,且可开展进一步的衔接关系研究。The Precambrian microcontinent is an important component of the northern Beishan–Alxa accretionary orogenic belt.Much controversy exists regarding the Precambrian basement of the Hanshan,Yagan and Zhusileng–Hangwula.Juyanhai is located between the northern part of the Beishan Orogenic Belt and the northern margin of the Alxa block.It is restricted by the Badain Jaran Desert and has very few rock outcrops.The authors drilled a set of Late Carboniferous alkaline granites.The zircon LA-ICP-MS U-Pb chronology and Hf isotope characteristics reveal that the granitic magma has zircon crystallization ages of(312±1)Ma and(315±2)Ma,and has positiveεHf(t)values between+0.8 and+4.4,+2.2 on average,corresponding to the two-stage model age(TDM2)of 1048~1267 Ma,with average value being 1183 Ma.The ancient crust contributed the granitic magma.Based on comparing the Late Carboniferous granitoids with the Hanshan tectonic Belt,Queershan tectonic Belt,Yagan tectonic Belt,and Zhusleng–Hangwula tectonic Belt,the authors analyzed the Meso–Neoproterozoic crust in northern Beishan–Alxa.Additionally,based on the outcrops of 0.9 Ga granitic rocks and the regional interpretation of gravity and magnetic data,the authors infer that the Hanshan,Yagan and Zhusileng–Hangwula tectonic belts assembled together,and further conjunction can be carried out.

关 键 词：微陆块 北山 阿拉善 碱性花岗岩 晚石炭世 锆石U-PB LA-ICP-MS LU-HF 

分 类 号：P597.2[天文地球—地球化学] P586[天文地球—地质学]