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Petrogenesis and significance of the Hongshan syenitic pluton,South Taihang zircon SHRIMP U-Pb age,chemical compositions and Sr-Nd isotopes [查看] ZhouLing、ChenBin

The Hongshan syenitic pluton(South Taihang)is mainly made up of hornblende syenite and minor granite.SHRIMP zircon dating yields a U-Pb age of 135±2.7Ma for the emplacement of the pluton,while biotite Rb-Sr isotopic data give an isochron of 120.3±2.4Ma.Hongshan syenites show low silica,hig alkalis and LILE such as Sr,and exhibit negligible Eu anomalies or slightly positive anomalies in the REE patterns.The syenites show quite enriched isotopic compositions with Isr from 0.7052 to 0.7102 and Nd(t)from -7.5 to -11.1.Petrogenesis of the pluton can be that partial melting of an enriched lithospheric mantle gave birth to an alkali basaltic magma,whcih subsequently underplated in the lower crust and experienced a coupled factionation of ferromagnesian phases like pyroxene and hornblende and minor(＜10%)contamination of lower continental crust,producing the Hongshan syenites that partially evolved into granite through combined fractionation of hornblende and feldspar.Our data are not in agreement with a previours model that the syenites originated melting of lower crust in a thickened crust circumstance,and thus do not support the speculation of "East China Plateau"in the Mesozoic

Petrogenesis and significance of the Hongshan syenitic pluton,South Taihangzircon SHRIMP U-Pb age,chemical compositions and Sr-Nd isotopes [查看] ZHOULing、CHENBin

The Hongshan syenitic pluton(South Taihang)is mainly made up of hornblemde syenite and minor granite.SHRIMP zircon dating yields a U-Pb age of 135±2.7Ma for the emplacement of the pluton,while biotite Rb-Sr isotopic data give an isochron of 120.3±2.4Ma.Hongshan syenites show low silica,high alkalis and LILE such as Sr,and exhibit negligible Eu anomalies or slightly positive anomalies in the REE patterns.The syenites show quite enriched isotopic compositions with Isr from 0.7052 to 0.7102 andεNd(t)from -7.5 to -11.1.Petrogenesis of the pluton can be that partial melting of an enriched lithospheric mantle gave birth to an alkali basaltic magma,which subsequently underplated in the lower crust and experienced a coupled fractionation of ferromagnesian phases like pytoxene and hornblende and minor(〈10%)contamination of lower continental crust,producing the Hongshan syenites that partially evolved into granite through combined fractionation of hornblende and feldspar.our data are not in agreement with a previous model that the syenites originated from melting of lower crust in a thickened crust circumstance,and thus do not support the speculation of "East China Plateau"in the Mesozoic