南阿尔金早古生代后碰撞花岗岩的成因及地质意义
Genesis and Geological Significance of Post-Collision Granites in South Altun
徐楠 1吴才来 2赵苗苗 3刘畅4
作者信息
- 1. 安徽理工大学深部煤矿采动响应与灾害防控国家重点实验室,安徽淮南 232001;中国地质科学院地质研究所,北京 100037
- 2. 中国地质科学院地质研究所,北京 100037
- 3. 河南省公平竞争审查事务中心,河南郑州 450000
- 4. 核工业北京地质研究院,中核集团铀资源勘查与评价技术重点实验室,北京 100029
- 折叠
摘要
南阿尔金早古生代洋陆转换作用的极性是近年来的研究热点之一,但深俯冲陆壳的折返作用缺少详实的岩石学证据.本文对茫崖北杂岩体开展岩石学、地球化学、锆石U-Pb年代学和Lu-Hf同位素研究,探讨其物质来源及成岩时的构造环境,揭示造山带早古生代构造演化的岩浆活动响应.研究表明,南阿尔金458～420 Ma花岗岩的εHf(t)和tDM2具有相似的变化范围,显示高碱、富钾、低钛、贫铁等钾玄质岩石特征,指示其相似的物质来源和岩浆源区.458～453 Ma花岗岩是深俯冲陆壳断离并折返至上地壳后经历减压熔融的产物,451～420 Ma花岗岩是后碰撞伸展环境下幔源岩浆底侵下地壳的产物.因此,南阿尔金深俯冲陆壳的折返作用在<453 Ma已经完成,造山带在<451 Ma进入造山晚期的后碰撞环境.
Abstract
The polarity of Early Paleozoic ocean-continent transformation in South Altun has been an issue recently.However,detailed petrological evidence for the exhumation of the deep subducted continental crust is still lacking.In this paper,it researches petrological,geochemical,zircon U-Pb chronological and Lu-Hf isotopic characteristics of the northern Manya complex,to discuss its source and tectonic environment,and reveal magmatic response to the Early Paleozoic tectonic evolution.The 458-420 Ma granites have similar material source and magmatic source,resulting from the similar ranges of ε Hf(t)and tDM2 values,and shoshonitic characteristics such as rich in alkali and K,and lack of Ti and Fe.The 458-453 Ma granites were formed by decompression melting of deep-subducted continental crust,which were transported to the upper crust by exhumation.The 451-420 Ma granites were product of partial melting of lower crustal materials triggered by underplating of mantle-derived magma in a post-collisional extensional environment.Thus,exhumation of the deep-subducted continental crust completed at<453 Ma,and the orogenic belt were in late orogenic post-collisional environment at<451 Ma.
关键词
南阿尔金/早古生代/折返/后碰撞/岩石学/地球化学Key words
South Altyn/Early Paleozoic/exhumation/post-collisional/petrology/geochemistry引用本文复制引用
出版年
2024
NETL
NSTL
万方数据