Attribution of Neoproterozoic Meta-Volcanic Series in Gengji-Banqiao Area,Northern Hubei Province:Evidence from Zircon U-Pb Dating and Hf Isotopes
There are two sets of meta-volcanic series scattered among the Sinian-Ordovician in Gengji and Banqiao area of Zaoyang City,northern Hubei Province,Northern Yangtze craton.Their attribution is disputed by the Wudang Group and Huashan Group,and has lacked in-depth research for a long time.Through systematic field investigation,LA-ICP-MS zircon U-Pb dating and Lu-Hf isotopic analysis,we propose that the meta-volcanic series in the Gengji area were mainly light gray and grayish white metamorphic acidic pebbly pyroclastic tuff,crystalline tuff,vitroclastic tuff and siltstone,associated with the siliceous striated stromatolite dolomite of the Dagushi Group.The zircon age for the metamorphic pyroclastic tuff from Gengji is 821.7 Ma with zircon εHf(t)values of-2.44-9.70,indicating that they may be part of the Huashan Group in the Northern Yangtze craton.However,the meta-volcanic series in the Banqiao area were mainly composed of grainy and white metamorphic acid clastic rock tuff,volcanic tuff,acid volcanic rock and siltstone,and associated with a large number of basic intrusive rocks.The zircon age of the metamorphic acid volcanic rocks from Banqiao is 741.2 Ma with zircon εHf(t)values of 4.62-9.56,indicating they belong to the Wudang Group in the South Qinling orogen,and may be a remnant of the thrust nappe during Indosinian.
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