扬子地块西缘乌蒙山地区早白垩世橄榄玄武玢岩的发现及其对陆缘碰撞造山事件陆内响应的启示  

The discovery of the Early Cretaceous olive basaltic porphyrite in the Wumengshan area on the western margin of the Yangtze block and its implications for the intracontinental response to the continental margin collision orogenic event

作　　者：张宏辉 袁永盛 李致伟 谢财富[3] 张七道 陈贵仁 吴亮 朱利东[4] 潘江涛 李仕忠 胡关云 张沥元 ZHANG Honghui;YUAN Yongsheng;LI Zhiwei;XIE Caifu;ZHANG Qidao;CHEN Guiren;WU Liang;ZHU Lidong;PAN Jiangtao;LI Shizhong;HU Guanyun;ZHANG Liyuan(Kunming General Survey of Natural Resources Center of China Geological Survey,Kunming 650111,Yunnan,China;Technology Innovation Center for Natural Ecosystem Carbon Sink,Ministry of Natural Resources,Kunming 650111,Yunnan,China;School of Earth Sciences,East China University of Technology,Nanchang 330013,Jiangxi,China;Institute of Sedmentary,Chengdu University of Technology,Chengdu 610059,Sichuan,Chian;Geophysical Investigation Center of 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]东华理工大学地球科学学院,江西南昌330013 [4]成都理工大学沉积地质研究院,四川成都610059 [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》2025年第2期477-492,共16页Geological Bulletin of China

基　　金：自然资源综合调查指挥中心科创基金《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);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)。

摘　　要：【研究目的】扬子板块西缘燕山期岩浆活动的缺失致使该时期的构造运动缺乏精确的时间记录,本次工作首次在滇东北乌蒙山地区发现了早白垩世的基性侵入岩,探讨其成因及地质意义对于探索扬子西缘燕山期构造活动具有重要意义。【研究方法】通过详细的野外地质观测、镜下鉴定、锆石U-Pb测年和岩石地球化学方法对新发现的侵入岩进行研究。【研究结果】早白垩世基性侵入岩的岩性为橄榄玄武玢岩,呈斑状结构,杏仁状构造,斑晶以斜长石及橄榄石为主;其31个锆石测点的U-Pb谐和年龄为134.0±0.4 Ma,形成时代为早白垩世早期。岩石地球化学特征显示其具有富碱、高Ti、高Al、低SiO_(2)的特征,稀土元素总量较高,重稀土元素亏损,轻、重稀土元素分馏明显,与研究区二叠纪峨眉山玄武岩具有高度相似的地球化学特征,二者应同源,可能是二叠纪形成的峨眉地幔柱尾部交代富集地幔,在班公湖-怒江结合带俯冲-碰撞作用的远程挤压效应下引起软流圈部分熔融,上升侵位过程中与地壳发生轻度混染,形成的基性—超基性侵入岩。【结论】早白垩世橄榄玄武岩玢岩的地球化学特征表明,特提斯构造域与扬子板块西缘的陆缘碰撞造山运动具有巨大的远程效应,其发现也将滇西地区燕山期岩浆活动的研究扩展到了小江断裂带以东的乌蒙山区一带,填补了四川盆地周缘燕山期岩浆活动的空白,同时,橄榄玄武玢岩的形成也表明,扬子板块西缘大规模陆内挤压造山达到高峰,134 Ma左右是扬子板块西缘陆内造山温压达到高峰的时间记录。[Objective]The absence of Yanshanian magmatic activities in the western margin of the Yangtze block has led to a lack of precise time records of tectonic movements during this period.In this study,Early Cretaceous basic intrusive rocks were discovered for the first time in the Wumengshan area of northeastern Yunnan.This discovery is of great significance for exploring the Yanshanian tectonic activities in the western margin of the Yangtze block.[Methods]This paper conducts research on the newly discovered intrusive rocks through detailed field geological observations,microscopic identification,zircon U-Pb dating,and petrogeochemical methods,and explores their genesis and geological significance.[Results]The lithology of the Early Cretaceous basic intrusive rocks is olivine basaltic porphyrite,which has a porphyritic texture and amygdaloidal structure.The phenocrysts are mainly plagioclase and olivine.The U-Pb concordia age of 31 zircon measurement points is 134.0±0.4 Ma,indicating that the formation age is the early stage of the Early Cretaceous.Petrogeochemical characteristics show that these rocks are rich in alkalis,high in Ti and Al,and low in SiO_(2).They have a relatively high total rare earth content,depleted heavy rare earths,and obvious fractionation between light and heavy rare earths elements.These characteristics are highly similar to those of the Permian Emeishan basalts in the study area,suggesting that they are the same origin.They may be the metasomatized and enriched mantle at the tail of the Emeishan mantle plume formed in the Permian.Under the long-range extrusion effect of the subduction-collision in the Bangonghu-Nujiang suture zone,partial melting of the asthenosphere occurred.During the ascending and emplacement process,they underwent mild contamination with the crust,forming basic-ultrabasic intrusive rocks.[Conclusions]The Early Cretaceous olivine basaltic porphyrite indicates that the continental-margin collision orogeny between the Tethys tectonic domain and the western margin of the Y

关 键 词：基性侵入岩 碰撞造山 扬子板块西缘 燕山期 峨眉山地幔柱 

分 类 号：P534.53[天文地球—古生物学与地层学] P588.12[天文地球—地质学]