摘要
幔源岩浆活动的成因研究,对约束区域构造演化历史具有重要意义.东昆仑祁漫塔格鹰爪沟镁铁-超镁铁质层状岩体由橄榄辉长苏长岩、含长橄榄二辉岩及橄榄二辉岩组成.获得橄榄辉长苏长岩的LA-ICP-MS锆石U-Pb年龄为263±4Ma,指示岩体形成于中二叠世晚期.岩石地球化学特征显示,鹰爪沟岩体具有低SiO2、高MgO、FeOt含量,富集LREE、LILE,亏损HREE以及Th、U、Nb、Ta、Ti等不相容元素等特征.全岩εNd(t)=0.73~0.92,锆石εHf(t)=8.33~13.50.综合区域地质背景资料,认为其形成于古特提斯洋俯冲作用下的活动大陆边缘裂谷,源自于受软流圈熔体和俯冲流体交代的岩石圈地幔.结合同期具有壳幔混源特征的花岗岩资料,认为东昆仑地区在中二叠世已有幔源岩浆底侵活动,主要形成于古特提斯洋俯冲体制下局部的伸展背景.
The study of the origin of mantle-derived magmatism is of great significance to the tectonic evolution history.Located in the Yingzhuagou area of Qimantag,East Kunlun,the mafic-ultramafic layered intrusion consists of olivine gabbro-norite,feldspar-olivine websterite and olivine websterite.The LA-ICP-MS zircon U-Pb dating results suggest that the olivine gabbronorite intruded at 263±4 Ma,belonging to late Middle Permian.All the rocks are characterized by low SiO2,high MgO and FeOt,enrichment of LREE and LILE,depletion of HREE and incompatible elements(e.g.Th,U,Nb,Ta,Ti).εNd(t)=0.73-0.92,εHf(t)=8.33-13.50.Based on the regional geological background,it is suggested that the rocks were formed in an active continental margin rift setting with the subduction of Paleo-Tethys Ocean.The magma came from the lithospheric mantle metasomatized by subduction fluid and asthenosphere melt.Combining the data of granite that originated from mixing of crustal and mantle materials in the same period,it is concluded that underplating of mantle-derived magmas should have started before Middle Permian in East Kunlun area and should have been controlled by the regional extensional setting in the subduction ofPaleo-Tethys Ocean.
作者
胡朝斌
李猛
查显锋
高晓峰
李婷
Hu Chaobin;Li Meng;Zha Xianfeng;Gao Xiaofeng;Li Ting(Xi'an Center of Geological Survey,Orogen Research Center,China Geological Survey,Xi'an 710054,China;Key Laboratory for the Study of Focused Magmatism and Giant Ore Deposits ,Ministry of Natural Resources ,Xi'an 710054,China;Institute of Mineral Resources,Chinese Academy of Geological Sciences,Beijing 100037,China)
出处
《地球科学》
EI
CAS
CSCD
北大核心
2018年第12期4334-4349,共16页
Earth Science
基金
中国地质调查局项目(No.DD20160002)
国家科技支撑专题(No.2015BAB05B01-01)
国家自然科学基金项目(No.41602005)
关键词
祁漫塔格
中二叠世
镁铁-超镁铁质岩
交代岩石圈地幔
幔源岩浆底侵
地球化学
Qimantag
Middle Permian
mafic-ultramafic rock
lithospheric mantle metasomatism
underplating of mantle-derived-magma
geochemistry
