昌都-思茅构造带晚三叠世构造环境的火山岩地球化学判别  

Geochemistry Discrimination of Late Triassic Volcanic Rocks in Changdu-Simao Tectonic Zone

作　　者：寇林林[1] 钟康惠[1] 唐菊兴[2] 刘肇昌[1] 董树义[1,3] 解波[1] 

机构地区：[1]成都理工大学,四川成都610059 [2]中国地质科学院,北京100037 [3]中国地质大学,北京100081

出　　处：《西北地质》2009年第1期79-87,共9页Northwestern Geology

基　　金：973项目(No.2002CB412607);中国地质调查局项目(70401154020);中国地质调查局综合研究项目(200110200010)、(200420190004);四川省矿物学、岩石学、矿物学重点学科基金

摘　　要：青藏东缘昌都-思茅带构造环境的研究对其所蕴含的找矿潜力具有重要意义,中三叠世末,三江联合地体形成,昌都-思茅构造带进入陆内演化阶段。通过对昌都-思茅构造带晚三叠世火山岩地球化学特征及地层学的研究,指出本区晚三叠世火山岩具有堑垒相间的古地貌、双峰式火山岩的火山-沉积组合及显伸展因子的岩浆作用等特点。火山活动主要是沿着乡城形成了所谓滞后形的岛弧岩浆,但很多地质事实表明,这之后并不是挤压的,而是在短暂的挤压后的伸展。对此问题,我们搜集了大量的数据,分析发现火山岩具有双峰特征。并通过岩石地球化学图解投图,指出昌都-思茅构造带在晚三叠世属于伸展构造环境,综合得出本区为陆内裂谷环境。The study of geological structural setting of Changdu-Simao Tectonic zone （CSTZ） located in East Margin of Qinghai-Tibet, southwest China, is of vital significance for determining the favorable area of ore deposits. By the end of Middle Triassic, the Three-river Composite Terrane had been formed, making the Changdu-Simao Tectonic Zone （CSTZ） go into an intra-continental evolution stage. Our research on geochemical and stratigraphic characteristics of Late Triassic volcanic rocks in the Changdu- Simao Tectonic Zone shows that the volcanic rocks are characterized by a graben-horst ancient landform, a bimodal volcanic-sedimentary assemblage, and a magmatism with extension factors. Volcanic activities are mostly seen along Xiangcheng, forming the so-called lag-arc magma. However, lots of geological facts indicate that, after these activities, this is not an extrusive process all the time but a stretching process after a short period of extrusion. Aiming at this problem, we collected and analyzed a large number of data and found that the volcanic rocks had a bimodal feature. Based on the geochemistry diagram, we believe that the Changdu-Simao structure was in a stretching environment in late Triassic period. So this area belongs to an intra-continental rift environment.

关 键 词：昌都-思茅构造带 晚三叠世火山岩 地球化学 构造环境 陆内裂谷 

分 类 号：P588.1[天文地球—岩石学] P591[天文地球—地质学]