乌蒙山地区茅口组中上部火山物质的发现:峨眉地幔柱早期活动的证据  

Discovery of volcanic matter in the Upper Maokou Formation of the Wumengshan area:Evidence of early activity of the Emeishan mantle plume

作　　者：张宏辉 杨朝 李致伟 陈贵仁 余杨忠 袁永盛 李锁明 张耀堂 张沥元 赵见波 吴亮 潘江涛 ZHANG Honghui;YANG Zhao;LI Zhiwei;CHEN Guiren;YU Yangzhong;YUAN Yongsheng;LI Suoming;ZHANG Yaotang;ZHANG Liyuan;ZHAO Jianbo;WU Liang;PAN Jiangtao(Kunming General Survey of Natural Resources Center,China Geological Survey,Kunming 650111,Yunnan,China;Technology Innovation Center for Natural Ecosystem Carbon Sink,Ministry of Natural Resources,Kunming 650111,Yunnan,China;State Key Laboratory of Geological Processes and Mineral Resources,China University of Geosciences,Wuhan 430074,Hubei,China;State Key Laboratory of Lithospheric Evolution,Institute of Geology and Geophysics,Chinese Academy of Sciences,Beijing 100029,China;Geophysical Investigation Center,China Geological Survey,Langfang 065000,Hebei,China)

机构地区：[1]中国地质调查局昆明自然资源综合调查中心,云南昆明650111 [2]自然资源部自然生态系统碳汇工程技术创新中心,云南昆明650111 [3]中国地质大学(武汉)地质过程与矿产资源国家重点实验室,湖北武汉430074 [4]中国科学院地质与地球物理研究所岩石圈演化国家重点实验室,北京100029 [5]中国地质调查局地球物理调查中心,河北廊坊065000

出　　处：《地质通报》2024年第7期1207-1220,共14页Geological Bulletin of China

基　　金：中国地质调查局项目《滇中楚雄地区云龙镇等4幅1/5万区域地质调查》(编号:DD20220987)、《云南乌蒙山区1/5万瓦岗等9幅区域地质调查》(编号:DD20191012-01)、《滇东-黔西黄葛树等4幅1/5万矿产地质调查》(编号:DD20220967)、《自然资源综合调查标准化与标准制修订》(编号:DD20230532);自然资源综合调查指挥中心科创基金项目《滇东北峨眉山地幔柱活动与地表系统响应之间的耦合关系》(编号:KC20230020)。

摘　　要：峨眉地幔柱活动是显生宙重要的地质事件,为了加深对滇东北乌蒙山地区峨眉地幔柱活动演化的认识,对该区茅口组中上部凝灰岩的同位素年龄、锆石微量元素、锆石Lu-Hf同位素、牙形石生物地层等进行了研究。研究区茅口组中上部的凝灰岩为滇东北乌蒙山地区峨眉地幔柱活动演化增加了新的岩石学证据,其最底层凝灰岩的锆石U-Pb年龄为268.7±1.7 Ma(MSWD=0.89,n=8);发现的牙形石为Jinogondolella aserrata,是二叠系瓜德鲁普统沃德阶的典型分子,与锆石U-Pb年龄对应。茅口组凝灰岩锆石微量元素特征显示其为基性岩浆锆石,具有大陆弧型构造背景及较高的Th/Nb值,可能代表峨眉山大火成岩省大规模喷发之前的火山活动。茅口组凝灰岩锆石Hf同位素特征显示,εHf(t)值为-6.7~11.6,大部分为负值,少量正值,具不均一性,反映该时期的火山活动除地幔柱物质参与外还有较多地壳物质的加入。茅口组凝灰岩的发现表明,峨眉地幔柱在乌蒙山地区于瓜德鲁普统沃德期已经发生小规模的岩浆喷发活动,该时期地幔柱的作用主要表现为对岩石圈热量的传导及部分地幔物质参与的熔融作用,为峨眉地幔柱模型的建立增加了新的证据。The Emeishan mantle plume activity is an important geological event in Phanerozoic.To deepen our understanding on the evolution of the Emeishan mantle plume activity in the Wumengshan area of northeastern Yunnan,the isotopic chronology,zircon trace element,zircon Lu-Hf isotopes and dental spines of the middle and upper tuffs of the Maokou Formation in this area were investigated,which is a new direct petrology evidence for the evolution of Emeishan mantle plume activity in the Wumengshan area of northeast Yunnan Province,and the result shows that the zircon U-Pb age of the uppermost tuffs of the Maokou Formation is 268.7±1.7 Ma(MSWD=0.89,n=8),consisting with the Jinogondolella aserrata,which is a typical molecule of the Permian Guadalupian Wordian.The zircon trace element characteristics of the uppermost tuffs of the Maokou Formation show affinities of basalt magma origin and continental arc-type tectonic setting,together with a high Th/Nb value,indicating a volcanic activity pre the large-scale eruption of the Emeishan Large Igneous Province.TheεHf(t)value of the zircons of the Maokou Formation is-6.7~11.6,indicating that the volcanic activity pre the Emeishan mantle plume was strongly influenced by the mantle plume materials and more crustal materials.The discovery of tuff in Maokou Formation shows that the Emeishan mantle plume has undergone a small-scale magmatic eruption in the Wumengshan area during the in the Permian Guadalupian Wordian.During this period,the mantle plume mainly played the role of conducting heat to the lithosphere and melting some mantle materials,which added new evidence for the establishment of Emeishan mantle plume model.

关 键 词：地幔柱 峨眉山玄武岩 火山活动 茅口组 牙形石 锆石U-Pb年龄 LU-HF同位素 地质调查工程 

分 类 号：P597.3[天文地球—地球化学] P588.12[天文地球—地质学]