地质通报2016，Vol.35Issue(5)：648-666,19.
班公湖-怒江缝合带中段东巧地区早白垩世岩浆作用--对大洋演化和地壳增厚的指示
Early Cretaceous magmatism in Dongqiao, Tibet：Implications for the evolution of the Bangong-Nujiang Ocean and crustal growth in a continent-continent collision zone
摘要
Abstract
The Dongqiao area is located across Bangong Co-Nujiang River suture zone (BNSZ) and the southern Qiangtang ter⁃rane. The study area has widely exposed diverse rock types such as diabases, rhyolites and granodiorites. In this paper, the authors re⁃port the LA-ICP-MS zircon U-Pb age and whole-rock major and trace element composition data of the diverse Early Cretaceous magmatic rocks from Dongqiao. The diabase sample yielded a zircon U-Pb age of 138.7±1.0Ma, and the zircons from rhyolite yield⁃ed an age of 110.4±0.4Ma, indicating that the magmatic rocks in Dongqiao formed in two periods of magmatism. According to geo⁃chemical characteristics of the rocks, the diabases were produced by partial melting of the mantle, and the granodiorites by partial melting of ancient lithospheric mantle that had been modified by subduction-related components. In addition, the geochemical data indicate that rhyolites can be divided into two types of high Sr and low Sr rhyolites. Low Sr rhyolites were formed by partial melting of ancient lithospheric mantle, and the melt subsequently underwent intense fractional crystallization. High Sr rhyolites had an affinity with adakites, which were derived from partial melting of thickened lower crust. The new data obtained by the authors, together with recently published data, led the authors to develop a model of bidirectional subduction and subsequent slab break-off of the lith⁃ osphere of the Bangong-Nujiang Ocean which can explain the two magmatic events in the region from BNSZ to the southern Qiangtang terrane. Research on high Sr rhyolites indicates that the extensive magmatism and continent-continent collision contribut⁃ed significantly to the crustal growth after the closure of Bangong-Nujiang Ocean in Early Cretaceous.关键词
班公湖-怒江缝合带/早白垩世/双向俯冲/板片断离/地壳增厚Key words
Bangong Co-Nujiang River suture zone/Early Cretaceous/bidirectional subduction/slab break-off/crustal growth分类
天文与地球科学引用本文复制引用
强巴扎西,吴浩,格桑旺堆,次仁欧珠,巴桑顿珠,琼达,女达娃..班公湖-怒江缝合带中段东巧地区早白垩世岩浆作用--对大洋演化和地壳增厚的指示[J].地质通报,2016,35(5):648-666,19.基金项目
中国地质调查局项目（编号1212011086060）和吉林大学研究生创新基金资助项目 （）
