西藏唐加地区早侏罗世高镁安山岩U-Pb年代学、岩石地球化学及地质意义  

U-Pb GEOCHRONOLOGY,PETROGEOCHEMISTRY AND GEOLOGICAL SIGNIFICANCE OF EARLY JURASSIC HIGH MAGNESIUM ANDESITE IN TANGJIA AREA,TIBET

作　　者：杨珍 杨文光[2] 朱利东[2] 李博[1] 郝金月 Yang Zhen;Yang Wenguang;Zhu Lidong;Li Bo;Hao Jinyue(Chongqing Vocational Institute of Engineering,Chongqing 402260,China;Institute of Sedimentary Geology,Chengdu University of Technology,Chengchi,Sichuan 610059,China;College of Earth Sciences,Chengdu University of Technology,Chengdu,Sichuan 610059,China)

机构地区：[1]重庆工程职业技术学院,重庆402260 [2]成都理工大学沉积地质研究院,四川成都610059 [3]成都理工大学地球科学学院,四川成都610059

出　　处：《矿物岩石》2021年第3期61-71,共11页Mineralogy and Petrology

基　　金：国家自然科学基金项目(No.41002055);中国地质调查局地调项目(No.DD20160015);重庆工程职业技术学院科研课题(KJB202106)。

摘　　要：西藏唐加地区甲拉浦组中发育高镁安山岩,通过对其样品U-Pb年代学和地球化学特征分析结果显示,唐加地区甲拉浦组高镁安山岩U-Pb年龄为197.1±2.9 Ma,时代为早侏罗世。地球化学特征显示,甲拉浦组高镁安山岩属于钾钙碱性系列,w(SiO_(2))在53.04%-54.53%之间,w(MgO)为4.98%-6.18%,w(Al_(2)O_(3))为17.17%-17.54%,w(CaO)为7.00%-11.34%,FeO^(T)/MgO为1.26-1.48,平均值为1.33,Mg^(#)值为58.7-62.5,平均值为61.2。样品显示轻稀土元素富集,Eu微负异常,大离子亲石元素Rb,Ba,Pb富集,Nb,Ta,Ti等高场强元素亏损。由此可知,唐加地区早侏罗世甲拉浦组高镁安山岩形成于与俯冲消减有关的构造背景,是新特提斯洋北向俯冲洋壳部分熔融的产物。The dating of the high magnesium andesite developed in the Jialapu Formation in Tangjia area,Tibet has obtained the age of 197.1±2.9 Ma(early Jurassic)by means of LA-ICP-MS zircon U-Pb age analysis.The geochemical analysis of the high magnesium andesite shows that it belongs to the potassium-calc-alkaline series,with the contents of w(SiO_(2))ranging from 53.04%to 54.53%,w(MgO)from 4.98%to 6.18%,w(Al_(2)O_(3))from 17.17%to 17.54%,w(CaO)from 7.00%to 11.34%.FeO^(T)/MgO ranges from 1.26 to 1.48,with an average of 1.33 and Mg^(#)ranges from 58.7 to 62.5,with an average of 61.2.The high magnesium andesite samples shows enrichment of light rare earth elements,slight negative anomaly of Eu,enrichment of large ion lithophile elements such as Rb,Ba,Pb,and depletion of high field strength elements such as,Nb,Ta,Ti.Through the chronology and geochemical analysis of Early Jurassic Jialapu Formation high magnesium andesites,it is proposed that the high magnesium andesites in Tangjia area were formed in the tectonic setting related to plate subduction,and resulted from partial melting of the Neo-Tethys Ocean crust during the northward subduction process.

关 键 词：高镁安山岩 新特提斯洋 唐加地区 锆石U-PB年龄 地球化学 

分 类 号：P597.2[天文地球—地球化学]