沉积与特提斯地质2018，Vol.38Issue(1)：11-22,12.
西藏仁布县帕夏始新世埃达克质岩的发现及其意义
The discovery and geological significance of the Eocene adakitic rocks in Paxia,Renbu,Xizang
摘要
Abstract
The emphasis in the present paper is placed on LA-ICP-MS zircon U-Pb dating and whole-rock lithogeochemical analysis of quartz diorite cropped out in the middle part of the Gangdise tectonic belt. The sampled quartz diorite yields a weighted average age of 49. 5 ± 1. 7 Ma (n = 9,MSWD = 2. 0)dated by using LA-ICP-MS zircon U-Pb dating method. Geochemical data suggest that the quartz diorite belongs to the metaluminous high-K cala-alkaline series rocks,with the total REE contents (ΣREE)ranging from 110. 14 × 10-6 to 143. 36 × 10-6 , LREE / HREE ratios ranging from 7. 09 to 10. 23,and δEu values ranging from 0. 93 to 1. 14. These rocks are characteric of the enrichment of the large ion lithophile elements (LILE)U,Th,K,Ba and Rb,depletion of the high field strength elements (HFSE)Ta,Nb and Ti,and high Sr contents and low Y contents,which represent typical features of adakitic rocks. The authors in the present paper contend that the adakitic quartz diorite in the study area may originate from a mixed magmatic origin including the lower crust and mantle wedge,with the residual phases of rutile and hornblende and without the plagioclase phase,and with the fractional crystallization during the emplacement of the magmas. The quartz diorite pluton may record the mixed crust-mantle magmatic origin associated with the mantle upwelling triggered by the broken subducting plate in the middle part of the Gangdise tectonic belt at about 50 Ma.关键词
冈底斯岩基/埃达克质岩/构造背景/西藏仁布Key words
Gangdise batholith/adakitic rock/tectonic setting/Renbu in Xizang分类
天文与地球科学引用本文复制引用
宋旭波,李应栩,李光明,刘洪,向安平..西藏仁布县帕夏始新世埃达克质岩的发现及其意义[J].沉积与特提斯地质,2018,38(1):11-22,12.基金项目
国家重点研发计划课题(编号:2016YFC0600308)和中国地质调查局地质调查项目(编号:20160015)资助 （编号:2016YFC0600308）
