The Early Cretaceous aluminous A-type granites in the Lower Yangtze River belt(LYRB)can provide important insights into the Mesozoic magmatism in eastern China,but their origin remains highly controversial.In this stu...The Early Cretaceous aluminous A-type granites in the Lower Yangtze River belt(LYRB)can provide important insights into the Mesozoic magmatism in eastern China,but their origin remains highly controversial.In this study,radiogenic Ca-Nd isotopic analysis was performed for syenite porphyry and alkali-feldspar granite porphyry of the Yangshan pluton,a typical aluminous A-type granitic intrusion in the LYRB,to constrain its source and geodynamic setting.The results show thatε_(Ca)(126 Ma),ε_(Nd)(126 Ma)and K/Ca_(source) of the syenite porphyry range from-0.24 to+0.96,-7.2 to-6.0,and 0.31 to 1.26,respectively.The corresponding values for the alkali-feldspar granite porphyry range from 0.26 to 0.84,-8.0 to-6.1,and 0.79 to 1.08,respectively.Binary mixing modeling indicates that they were originated from the same sources with different proportion,namely,a mixing of 50%to 75%Neoproterozoic crust and 50%to 25%asthenospheric mantle.Together with previous works,we propose that the Early Cretaceous subduction of the ridge between the Pacific and Izanagi plates was responsible for the formation of the aluminous A-type granites in the LYRB.展开更多
Some Au deposits in southern Anhui Province have recently been found to be closely associated with Late Mesozoic intrusions. Typical examples include the Huashan Au(Sb) deposit and Au deposits at Zhaojialing, Wuxi,and...Some Au deposits in southern Anhui Province have recently been found to be closely associated with Late Mesozoic intrusions. Typical examples include the Huashan Au(Sb) deposit and Au deposits at Zhaojialing, Wuxi,and Liaojia. In order to understand the mechanisms that led the formation of these Au deposits, we make detailed reviews on the geological characteristics of these Au deposits. Specifically, we present new LA-ICP-MS zircon U–Pb dating, along with elemental and Hf isotopic data from the Huashan Au(Sb) deposit. Our data suggests that the Huashan ore-related intrusions were emplaced during the Late Jurassic and Early Cretaceous periods(144–148 Ma). They are characterized by arc-magma features and high oxygen fugacity and are rich in inherited zircons. Zircon U–Pb ages and Lu–Hf isotopes from intrusions suggest that Proterozoic juvenile lithosphere is the main source of these intrusions. The regional geological history implies that lithosphere beneath southern Anhui was produced during a Proterozoic subduction and was fertilized with Au(Cu) in the process. Integrated with theresults of previous studies, we inferred that Late Mesozoic intrusions formed by the remelting of the lithosphere could provide the metal endowment for the Au-rich deposits in southern Anhui.展开更多
基金the State Key Laboratory of Nuclear Resources and Environment,East China University of Technology,Nanchang(No.2020Z03)the National Key R&D Program of China(Nos.2016YFC0600408,2019YFA0708400)the Strategic Priority Research Program of the Chinese Academy of Sciences(No.XDB41020102)。
文摘The Early Cretaceous aluminous A-type granites in the Lower Yangtze River belt(LYRB)can provide important insights into the Mesozoic magmatism in eastern China,but their origin remains highly controversial.In this study,radiogenic Ca-Nd isotopic analysis was performed for syenite porphyry and alkali-feldspar granite porphyry of the Yangshan pluton,a typical aluminous A-type granitic intrusion in the LYRB,to constrain its source and geodynamic setting.The results show thatε_(Ca)(126 Ma),ε_(Nd)(126 Ma)and K/Ca_(source) of the syenite porphyry range from-0.24 to+0.96,-7.2 to-6.0,and 0.31 to 1.26,respectively.The corresponding values for the alkali-feldspar granite porphyry range from 0.26 to 0.84,-8.0 to-6.1,and 0.79 to 1.08,respectively.Binary mixing modeling indicates that they were originated from the same sources with different proportion,namely,a mixing of 50%to 75%Neoproterozoic crust and 50%to 25%asthenospheric mantle.Together with previous works,we propose that the Early Cretaceous subduction of the ridge between the Pacific and Izanagi plates was responsible for the formation of the aluminous A-type granites in the LYRB.
基金supported by the National Key R&D Program of China(No.2016YFC0600404)the National Natural Science Foundation of China(Nos.41372087,41673040,41174043)the Project of Geological Science and Technology of Anhui Province(2014-K-04,2016-K-1)
文摘Some Au deposits in southern Anhui Province have recently been found to be closely associated with Late Mesozoic intrusions. Typical examples include the Huashan Au(Sb) deposit and Au deposits at Zhaojialing, Wuxi,and Liaojia. In order to understand the mechanisms that led the formation of these Au deposits, we make detailed reviews on the geological characteristics of these Au deposits. Specifically, we present new LA-ICP-MS zircon U–Pb dating, along with elemental and Hf isotopic data from the Huashan Au(Sb) deposit. Our data suggests that the Huashan ore-related intrusions were emplaced during the Late Jurassic and Early Cretaceous periods(144–148 Ma). They are characterized by arc-magma features and high oxygen fugacity and are rich in inherited zircons. Zircon U–Pb ages and Lu–Hf isotopes from intrusions suggest that Proterozoic juvenile lithosphere is the main source of these intrusions. The regional geological history implies that lithosphere beneath southern Anhui was produced during a Proterozoic subduction and was fertilized with Au(Cu) in the process. Integrated with theresults of previous studies, we inferred that Late Mesozoic intrusions formed by the remelting of the lithosphere could provide the metal endowment for the Au-rich deposits in southern Anhui.
