印度-欧亚大陆侧向碰撞带的地壳组成:始-渐新世岩浆岩继承锆石U-Pb年龄及Hf同位素空间变化的启示  

Crustal architecture of the oblique collision belt: Insights of the spatial variation in U-Pb ages and Hf isotope of inherited zircons from the Eocene to Oligocene magmatic rocks

作　　者：董猛猛 杨天南[1] 信迪[1] 梁明娟 DONG MengMeng;YANG TianNan;XIN Di;LIANG MingJuan(Key Laboratory of Deep-Earth Dynamics of Ministry of Natural Resources,Institute of Geology,Chinese Academy of Geological Sciences,Beijing 100037,China;School of Earth and Space Sciences,Peking University,Beijing 100871,China;Geological Museum of Guizhou,Guiyang 550081,China)

机构地区：[1]自然资源部深地动力学重点实验室,中国地质科学院地质研究所,北京100037 [2]北京大学地球与空间科学学院,北京100871 [3]贵州省地质博物馆,贵阳550081

出　　处：《岩石学报》2022年第11期3484-3502,I0017-I0019,共22页Acta Petrologica Sinica

基　　金：自然资源部深地动力学重点实验室自主研究课题(J1901-4);国家自然科学基金项目(92055206、42163007);国家重点研发计划项目(2016YFC0600306-4、2015CB452601)联合资助.

摘　　要：在通过锆石U-Pb方法测定岩浆活动时代的过程中总会获取或多或少的继承锆石年龄数据,这些数据对于揭示岩浆岩所处构造单元的构造-岩浆事件序列具有独特优势。本文选择印度-欧亚大陆侧向碰撞带内NEE走向的始-渐新世岩浆岩带作为研究对象,详细收集、梳理该岩浆岩带内现有测年结果中的继承锆石U-Pb年代学和Hf同位素数据,采用统计分析方法,尝试探讨被该岩浆岩带穿越的扬子、印支、保山、腾冲地块的构造-岩浆事件及其序列,对比分析其大地构造亲缘性和地块拼贴历史。继承锆石U-Pb年龄频率分布和Hf同位素数据统计结果显示,扬子与印支地块记录了相同的晋宁期、加里东期、印支期构造-岩浆事件,而腾冲与保山地块则记录了相同的加里东期、印支期构造-岩浆事件。结合现有地层学、古生物和古地磁等方面数据,我们提出扬子-印支与腾冲-保山地块作为两个具有不同结晶基底的独立地块,分别就位于古生代-早中生代古大洋(原、古特提斯洋)的两侧,该大洋板块双向俯冲于这两个地块之下,在两个地块内留下了可高度对比的构造-岩浆事件。由此提出,正向碰撞带班公湖-怒江缝合带内完备的地质记录与侧向碰撞带之间的关联、哀牢山洋的构造属性等是值得深入探究的重大问题。Most igneous rocks contain some inherited zircons whose age-data are valuable to reveal tectonothermal history of the continental block with these igneous rocks as a by-product of them.A huge NEE-trending Eocene to Oligocene magmatic zone developed in the oblique collision belt in southeastern Tibetan Plateau,where numerous magmatic rocks occurred in the Yangtze,Indochina,Baoshan and Tengchong blocks.This paper collected the available U-Pb dating results and Hf isotopic data of the inherited zircons from the igneous rocks of this magmatic zone.Statistics of these data revealed three tectonothermal events happened in the Yangtze and Indochina blocks during the Neoproterozoic,the Early Paleozoic,and the Late Plaeozoic to Early Mesozoic,respectively;while only two tectonothermal events of the Early Paleozoic and the Late Paleozoic to Early Mesozoic occurred in the Baoshan and Tengchong blocks.These data,combined with the previously published stratigraphic,paleontological and paleomagnetic data,suggest that the Yangtze and Indochina blocks are likely a single block,while the Tengchong and Baoshan blocks belong to another single block.Between them,a long-lived paleo-ocean should exist from the Early Paleozoic to the Early Mesozoic.Two directions subduction of the plaeo-oceanic plate under the Yangtze-Indochina and Tengchong-Baoshan blocks resulted in the highly comparable magmatism histories of the two blocks.Therefore,the geological relationships of the Bangong-Nujiang suture between the orthogonal and oblique collision belts,and the tectonic properties of the Ailaoshan ocean are major issues worthy further studying.

关 键 词：统计分析 继承锆石 U-PB年龄 HF同位素 构造-岩浆事件 青藏高原东南缘 

分 类 号：P542[天文地球—构造地质学] P597.3[天文地球—地质学]