西藏改则县多不扎地区上侏罗统对望山组的建立及意义

对望山组是发育在羌南板块南缘的一套岩石组合,以安山岩、流纹岩、玄武质凝灰岩为主,有少量的玄武安山岩夹层,具有明显的岩浆喷出相和沉积相韵律分布的特点。利用LA-ICP-MS同位素定年技术对对望山组安山岩中的锆石进行了U-Pb同位素测年,获得锆石的~(206)Pb/~(238)U年龄加权平均值为150.5±0.6Ma,表明对望山组的形成时代为晚侏罗世中晚期,在详细剖面测制和区域对比的基础上建立了对望山组。对望山组的建立对完善班公湖-怒江缝合带的地层系统、探讨班公湖-怒江洋的晚侏罗世构造演化具有重要的地质意义。

Establishment of Upper Jurassic Duiwangshan Formation in Duobuza area, Gerze County, Tibet, and its significance

The Duiwangshan Formation is a rock assemblage developed in the south of Qiangtang plate and consists of andesite, liparite, basaltic tuff and minor basaltic andesite interlayer. It has obvious rhythm distribution characteristics between extrusive facies and sedimentary facies of magma. Conducting LA-ICP-MS U-Pb dating, the authors obtained andesite average ²⁰⁶Pb/²³⁸U age of 150.5±0.6Ma, which indicates Duiwangshan Formation should have been formed in middle-late period of Late Jurassic. The Late Jurassic Duiwangshan Formation was established based on the detailed section measurement and regional correlation, which has important geological significance for the completion of the stratigraphic system in Bangong Co-Nujiang Suture Zone (BANSZ) and the study of tectonic evolution of Bangong Co-Nujiang Ocean in Late Jurassic.