首页> 外文期刊>Journal of the Geological Society >Palaeozoic metamorphism of the Neoproterozoic basement in NE Cathaysia: zircon U-Pb ages, Hf isotope and whole-rock geochemistry from the Chencai Group
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Palaeozoic metamorphism of the Neoproterozoic basement in NE Cathaysia: zircon U-Pb ages, Hf isotope and whole-rock geochemistry from the Chencai Group

机译:华夏东北部新元古代地下古生界变质作用:陈财集团的锆石U-Pb年龄,H同位素和全岩石地球化学

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The protoliths of the metamorphic suite of the Chencai Group in the northeastern margin of the Cathaysia Block in South China are composed of Neoproterozoic argillaceous-arenaceous rocks of turbidite facies, marine carbonates, gabbro and basalt. Here, we present zircon U-Pb ages, Hf isotopes, and whole-rock geochemical data on migmatites and metagabbros from the Chencai Group and the surrounding hornblende gneisses. The gabbroic enclaves in the migmatites and hornblende gneiss are characterized by subductionrelated geochemical characteristics, which differentiate them from the migmatites. Zircons from the hornblende gneiss, migmatite and gabbro yielded weighted mean ~(206)Pb/~(238)U ages of 879 ± 10 Ma, 438 ± 3 Ma and 453.2 ± 3.5 Ma, respectively. Hf isotopic analysis reveals εHf(t) values of +0.02 to -2.55 for zircons from the migmatite, whereas those from the hornblende gneisses and gabbros show positive εHf(t) values (+3.41 to +13.36 and +1.80 to +5.25, respectively). Our data correlate the protoliths of the hornblende gneiss and metagabbros to subduction-related magmatism prior to the assembly of the Yangtze and Cathaysia blocks. The migmatite and gabbro record a Palaeozoic tectonothermal event that led to migmatization and resetting of Neoproterozoic ages. Our results suggest that the Palaeozoic event was initiated before c. 453 Ma with metamorphism at c. 438 Ma.
机译:华南地区华夏地块东北边缘的晨彩群变质组的原岩由浊积岩相,海相碳酸盐岩,辉长岩和玄武岩的新元古代泥质-砂质岩组成。在这里,我们介绍了Chencai集团和周围的角闪长片麻岩的锆石U-Pb年龄,Hf同位素和全矿物地球化学数据。蒙脱石和角闪长片麻岩中的辉长岩飞地具有俯冲作用相关的地球化学特征,这使它们与蒙脱石区分开来。角闪闪片麻岩,辉锰矿和辉长岩中的锆石分别具有879±10 Ma,438±3 Ma和453.2±3.5 Ma的加权平均〜(206)Pb /〜(238)U年龄。 Hf同位素分析显示,从蒙脱石中得到的锆石的εHf(t)值在+0.02到-2.55之间,而角闪长片麻岩和长辉长岩的锆石的εHf(t)值分别为正值(分别为+3.41至+13.36和+1.80至+5.25。 )。我们的数据将角闪石片麻岩和变辉岩的原岩与俯冲作用相关的岩浆作用相关联,然后才组装扬子和华夏地块。蒙脱石和辉长岩记录了一个古生代构造热事件,该事件导致了新元古代的迁移和复位。我们的结果表明古生代事件是在c之前开始的。 453 Ma,在c处具有变质作用。 438毫

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