Geochronology,geochemistry and zircon Hf isotopes of the volcanic rocks from the Dashizhai formation in the Shabulengshan area,west Ujimqin Banner,Inner Mongolia,China
In order to reveal the diagenetic age and petrogenesis of rhyolitic rocks from the Permian Dashizai Formation exposed in the Shabulengshan area,West Ujimqin Banner,Inner Mongolia,we conducted a comprehensive study of zircon U-Pb chronology,Hf isotope and whole-rock geochemistry of the rhyolitic rocks in this paper.The results show that the lower intercept age on the Tera-Wasserburg plot is(263±3)Ma(MSWD=1.4),which is consistent with the weighted average 206Pb/238U age(262Ma).The rhyolitic rocks are characterized with rich in K and Si,with obviously negative Eu anomalies.Meanwhile,they are enriched in elements such as Rb,Ba and U,and depleted in elements such as Nb,Ta and Ti,implying the characteristics of A type granite.Zircons of these rocks have εHf(t)values of 8.7～11.1 and two-stage Hf model ages(tDM2)of 577～729 Ma,implying the rock-forming materials were derived from the partial melting of the Neoproterozoic juvenile lower crust.Combined with previously published research results,we conclude that the volcanic rocks from the Dashizhai Formation in the Shabulengshan area could be formed in a regional extension setting after the closure of Paleo Asian Ocean.
Central Asian orogenic beltShabulengsharhyolitic rocks from the Dashizhai Formationpetrogeochemistryzircon U-Pb datingHf isotope
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