The compositional variations and rhythmicity of the positive anomalous natural gamma(GR)layers developed in the Upper Permian of West Guizhou are not clear.In this paper,it analyzed the lithological characteristics,geochemical characteristics and periodicity of positive anomalous GR layers.Al2O3/TiO2,REE patterns,REE-La/Yb,La/Sc-Co/Th,Zr/TiO2-Al2O3/TiO2 and Nb/Ta-Zr/Hf diagrams indicate that the sources of highly radioactive layers include Emeishan basalt,volcanic ash originates from the Emeishan large igneous province during its waning phase and South China volcanic ash.The positive anomalous GR layers were formed during a period of relatively hot and low sea level,with long and short eccentricity cycles.The hot climate change caused rapid sea level rise and ice volume drop,and the rapid change of stress state on the region triggered volcanic activity to form periodic positive anomalous GR formations.Precise identification of positive anomalous GR layers can be used to compare and delineate the regional stratigraphic framework,and to analyze the magmatic evolution and critical element enrichment of the late Emeishan large igneous province.
关键词
黔西/晚二叠世/物质来源/火山活动/周期/地球化学
Key words
West Guizhou/Late Permian/provenance/volcanic activity/periodicity/geochemistry
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