Zircon U-Pb geochronology and geochemistry of the Permian-Triassic granitic intrusions in the Huade area,Inner Mongolia,NE China:Constraints on the tectonic evolution of the Paleo-Asian Ocean
This paper presents detailed petrological,zircon U-Pb chronological,whole-rock geochemical and Sr-Nd-Hf isotopic studies on the Permian-Triassic granitic intrusions in Huade County,Inner Mongolia.The geochemical and isotopic features indicate that the studied intrusions were derived from a Paleo-to Mesoproterozoic crustal source of the North China craton.The Bayinchahan intrusions experienced magma mixing during the magma upwelling.The Baiyintla intrusions were S-type granite formed by partial melting of metamorphic greywacke during crustal thickening,the Maohuqing intrusions were Ⅰ-type granite,the Kangjiadi and the Zhangwanliang intrusions were A-type granite.Zircon dating results indicate that the Bayinchahan,Baiyintela,Maohuqing,Zhangwanliang and Kangjiadi plutons were formed in the Early Permian(276±1 Ma),the Middle Permian(270±1 Ma),the Late Permian(254±1 Ma),the Early Triassic(248±1 Ma)and the Late Triassic(229±1 Ma),respectively.Combined with previous studies,we conclude that the study area experienced subduction,subduction-collision,continuous collision and post-orogenic extension during the Early Permian to Late Triassic.The closing time of the eastern part of the Paleo-Asian Ocean in the study area should be the late Middle Permian.
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