藏东八宿地区朱村组火山岩地球化学、同位素年代学及其构造意义
Geochemical, geochronological features and tectonic significance of volcanic rocks of Zhucun Formation in Baxoi area, eastern Tibet, China
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摘要: 藏东八宿县城西南出露一套由中酸性火山碎屑岩及熔岩组成的火山岩地层体，研究程度不高，报道较少，时代争论较大，构造意义不明确，称之为朱村组。在朱村组获得角闪英安岩锆石SHRIMP U－Pb年龄为128Ma±2Ma，将朱村组的时代厘定为早白垩世。地球化学特征反映朱村组火山岩形成于怒江洋壳向冈底斯－念青唐古拉板块俯冲、消减的火山弧环境，是伯舒拉岭火山岩浆弧的组成部分，与伯舒拉岭早白垩世花岗闪长岩应为同源不同相的产物，并认为藏东地区班公湖－怒江缝合带的闭合在早白垩世晚期已经完成。Abstract: There are volcanic rocks which are made up of intermediate-acid volcanic－clastic rocks and lavas in the northwest Baxoi County， eastern Tibet. So far, the genesis of these rocks are poorly studied, including their formation age and tectonic significance. They were refered as Zhucun formation. The authors have obtained zircon U－Pb dating age of 128±2Ma of the amphibole dacite of Zhucun formation so the age of the Zhucun formation is defined as Early Cretaceous. The geochemical characteristics of the Zhucun formation reflect that the volcanic rocks formed in the volcanic arc setting of the Nujiang oceanic subduction to Gangdis－Nyainqentanglha plate which is part of the Boshula mountains volcanic arc. Compared to Boshulaling Early Crateceous granodiorite, they have the same magma resources but show different facies. The authors also think that the closing of the Bangong Co－Nujiang suture belt in eastern Tibet was finished during early cretaceous.
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Keywords:
- eastern Tibet /
- Baxiu area /
- Zhucun Formation /
- volcanic rock /
- tectonic significance
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