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.
Abstract:
The study of geological structural setting of Changdu 2 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-con tinental 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 agraben-horst ancient landform, abimodal volcanic-sedimentary assemblage, and amagmatism with extension factors. Volcanic activities are mostly seena long Xiangcheng, forming the so-called lag-arcmagma. However, lots of geological facts indicate that, after these activities, this is not an extrusive process all the time but a stretching process after ashort period of extrusion. Aiming at this problem, we collected and analyzed a large number of data and found that the volcan icrocks had a bimodal feature. Ba sed on the geochem istry diagram, we believe that the Changdu-Simao structure was in a stretching environment in late Triassic period. So this a reabelongs to an intra-continental riftenvironment.
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