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新疆阿奇山岩体LA ICP MS锆石U Pb年龄、Sr—Nd—Pb同位素特征及其成因探讨
投稿时间:2019-01-17  修订日期:2019-09-30  点此下载全文
引用本文:田明明,何建国,张松,高红雷,孔维豪,李平.2020.新疆阿奇山岩体LA ICP MS锆石U Pb年龄、Sr—Nd—Pb同位素特征及其成因探讨[J].地质论评,66(1):141-156,[DOI]:.
TIAN Mingming,HE Jianguo,ZHANG Song,GAO Honglei,KONG Weihao,LI Ping.2020.LA ICP MS zircon U Pb Age,Sr—Nd—Pb isotopic compositions of Aqishan pluton in Xinjiang and their petrogensis significance[J].Geological Review,66(1):141-156.
DOI:10.16509/j.georeview.2020.01.009
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作者单位E-mail
田明明 核工业北京地质研究院中核铀资源勘查与评价技术重点实验室北京100029 Email:tian_ming_ming@126.com 
何建国 核工业北京地质研究院中核铀资源勘查与评价技术重点实验室北京100029  
张松 核工业北京地质研究院中核铀资源勘查与评价技术重点实验室北京100029 Email: zhangsong1891@163.com 
高红雷 核工业北京地质研究院中核铀资源勘查与评价技术重点实验室北京100029  
孔维豪 核工业北京地质研究院中核铀资源勘查与评价技术重点实验室北京100029  
李平 核工业北京地质研究院中核铀资源勘查与评价技术重点实验室北京100029  
基金项目:注: 本文为“高放废物处置库新疆预选区阿奇山地段候选场址筛选与评价研究”项目资助的成果
中文摘要:本文运用LA ICP MS锆石U Pb定年法对新疆阿奇山岩体进行了测定,获得年龄为2695±16 Ma~2721±13 Ma,表明阿奇山岩体为晚二叠世。岩石的Sr、Nd、Pb同位素分析表明,该岩体有较低的锶同位素初始比值\[n(87Sr)/ n(86Sr)\]i(07044~07055)、正εNd(t)值(048~366)及较为年轻的Nd同位素两阶段模式年龄t2CDM(741~1090 Ma),表明其源岩与亏损地幔有关,而在Pb同位素n(207Pb)/ n(204Pb)— n(206Pb)/ n(204Pb)构造模式演化图解中,又显示其物质来源与壳幔相互作用有关。综合岩体岩石地球化学特征、前人研究成果及该区大地构造背景,分析认为阿奇山岩体的形成是地幔柱活动背景下壳幔相互作用过程的产物。阿奇山岩体位于新疆北部,属于中亚造山带的一部分,在晚二叠世,整个新疆北部已经进入后造山阶段,且晚古生代时期板块俯冲已经结束。但后造山岩浆形成必然需要新的动力及热源,而幔源岩浆的底侵不仅可以为后造山岩浆活动提供热源,还提供了大量物源。因此在区域性伸展构造环境下,由于壳幔相互作用强烈,来自深部的地幔柱幔源岩浆底侵,带来的热源诱发较年轻的地壳物质部分熔融,同时有部分幔源物质的混染,从而使阿奇山岩体花岗岩物源具有地幔和地壳双重特征。
中文关键词:LA ICP MS锆石U Pb年龄  Sr、Nd、Pb同位素  岩石成因  阿奇山岩体
 
LA ICP MS zircon U Pb Age,Sr—Nd—Pb isotopic compositions of Aqishan pluton in Xinjiang and their petrogensis significance
NameInstitution
TIAN MingmingBeijing Research Institute of Uranium Geology,Key laboratory of Uranium Resource Exploration and Evaluation Technology, CNNC, Beijing, 100029
HE JianguoBeijing Research Institute of Uranium Geology,Key laboratory of Uranium Resource Exploration and Evaluation Technology, CNNC, Beijing, 100029
ZHANG SongBeijing Research Institute of Uranium Geology,Key laboratory of Uranium Resource Exploration and Evaluation Technology, CNNC, Beijing, 100029
GAO HongleiBeijing Research Institute of Uranium Geology,Key laboratory of Uranium Resource Exploration and Evaluation Technology, CNNC, Beijing, 100029
KONG WeihaoBeijing Research Institute of Uranium Geology,Key laboratory of Uranium Resource Exploration and Evaluation Technology, CNNC, Beijing, 100029
LI PingBeijing Research Institute of Uranium Geology,Key laboratory of Uranium Resource Exploration and Evaluation Technology, CNNC, Beijing, 100029
Abstract:Objectives: Aqishan pluton is located in Shanshan county, Turpan region, Xinjiang province. In geotectonic position, It is located near the boundary between the Kazakh—Zhunge plate and the Tarim plate, and is inclined to the Tarim plate. By collecting the data from previous studies, some profiles have been performed systematically to reveal the characteristics of mineralogy, petrology and lithogeochemistry of Aqishan pluton. While very fewer work on high precision isotopic age have been done, and the study on Sr, Nd, Pb isotopes have not been carried out. Methods: We use the methods of high precision isotopic age dating which called LA ICP MS Zircon U Pb age dating to determine the formation age of Aqishan pluton; On the other hand, we use Sr—Nd—Pb isotope geochemical tracer technique to synthetical analyse the genesis of Aqishan pluton.Results:The result of LA ICP MS zircon U Pb dating shows that the age of Aqishan Pluton is 269.5±1.6 Ma~272.1±1.3 Ma, indicating that the Aqishan pluton formed in Late Permian. As for the Sr—Nd—Pb isotope compositions, the rocks have low initial ratio of strontium isotope\[n(87Sr)/n(86Sr)\]i (0.70442 ~ 0.70553), positive εNd(t)values (0.48 ~ 3.66) and relatively juvenile t2CDM(741 ~ 1090 Ma) . The Sr—Nd isotope compositions suggest that their primitive magma was most possibly derived from juvenile crust with variable involvement of depleted mantle derived magma, while in the Pb tectonic framework diagram, the material source is also related to the crust—mantle interaction. In combination with the characteristics of lithogeochemistry, previous research results and tectonic background, we analyzed that Aqishan pluton is the product of crust—mantle interaction under the background of mantle plume activity. Aqishan pluton is located in the northern Xinjiang, belongs to the part of the Central Asian orogenic belt, in Late Permian, the entire northern Xinjiang has entered to post orogenic satge, and the late Paleozoic plate subduction dynamics system has ended, while the formation of post orogenic magma requires new dynamics and heat source. The underplating of mantle magmas not only provide heat source for post orogenic magmatic activity, also supply a large number of material. Therefore, under the tectonic background of regional stretch, due to intensely crust—mantle interaction, the heat source, which resulted from the underplating of deep mantle plume magmas, induced partial melting of younger crust, accompanied with the contamination of a portion of the mantle material, all of this reasulted in the Aqishan pluton possesses the doubly characteristics of mantle and crust. Conclusions:The age of Aqishan pluton is 269.5±1.6 Ma~272.1±1.3 Ma, which formed in Late Permian. The isotopic characteristics of Sr—Nd—Pb and the previous research results show that Aqishan pluton is the product of crust—mantle interaction under the background of mantle plume activity.
keywords:LA ICP MS zircon U Pb dating  Sr, Nd, Pb isotopes  Petrogensis  Aqishan pluton
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