扬子板块西缘下志留统龙马溪组底部斑脱岩研究——锆石U-Pb测年、微量元素特征及地质意义  

BENTONITES IN THE BOTTOM OF LOWER SILURIAN LONGMAXI FORMATION ON THE WESTERN MARGIN OF YANGTZE PLATE:Zircon U-Pb Age,Trace Element Characteristics and Geological Implication

作　　者：王万能 庞占基 王浩宇 王东晖 于一帆 WANG Wan-neng;PANG Zhan-ji;WANG Hao-yu;WANG Dong-hui;YU Yi-fan(Kunming Natural Resources Comprehensive Survey Center,CGS,Kunming 650000,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650000

出　　处：《地质与资源》2023年第6期691-698,共8页Geology and Resources

基　　金：中国地质调查局项目“滇中楚雄云龙镇等4幅1∶5万区域地质调查”(DD20220987).

摘　　要：奥陶系—志留系之交斑脱岩分布广泛,且发育数层,是研究该时期地层年代学、地层对比、事件地层及生物大灭绝的良好载体.通过对扬子板块西缘永善地区上奥陶统—下志留统龙马溪组底部地层中的斑脱岩进行锆石U-Pb测年,获得年龄加权平均值443.5±1.7 Ma,限定了地层的沉积年龄,为扬子板块西缘奥陶系—志留系火山喷发事件及地层年代学研究提供了较可靠的依据,也为扬子板块周缘奥陶系—志留系高分辨率地层格架的建立提供基础信息.锆石微量元素特征显示其具有I型花岗岩类特征,形成于岩浆弧或造山带.晚奥陶世—早志留世多期次、高频率的火山活动可能是造成生物大灭绝的主导因素.Bentonites are widely distributed and developed in several layers in the Ordovician-Silurian boundary,which is of great significance for the study of stratigraphic chronology,stratigraphic correlation,event stratigraphy and mass extinction in the period.The zircon U-Pb dating of bentonites in the bottom of Upper Ordovician-Lower Silurian Longmaxi Formation in Yongshan area on the western margin of Yangtze Plate yields the weighted average age of 443.5±1.7 Ma,which defines the sedimentary age of the strata and provides a reliable basis for the study of Ordovician-Silurian volcanic eruption event and stratigraphic chronology on the western margin of Yangtze Plate,as well as basic information for the establishment of Ordovician-Silurian high-resolution stratigraphic framework on the periphery of Yangtze Plate.The trace element characteristics of zircon show the features of I-type granite formed in magmatic arc or orogenic belt.The multi-stage and high-frequency volcanic activity in the Late Ordovician-Early Silurian is possibly the dominant factor causing the mass extinction.

关 键 词：扬子板块 斑脱岩 锆石U-Pb年龄 微量元素 生物大灭绝 

分 类 号：P597[天文地球—地球化学]