SHRIMPP U-Pb zircon age and geochemical and Nd isotopic data are reported for the Aoyitake plagiogranite in western Tarim Block,NW China.The plagiogranite intruded the Middle Pro-terozoic and Lower Carboniferous with ...SHRIMPP U-Pb zircon age and geochemical and Nd isotopic data are reported for the Aoyitake plagiogranite in western Tarim Block,NW China.The plagiogranite intruded the Middle Pro-terozoic and Lower Carboniferous with an exposure area of ca.60 km2 and crystallized at 330.7±4.8 Ma.Rock types mainly include tonalite,trondhjemite and minor amounts of diorite and quartz-diorite.Feldspars in the rocks are dominated by oligoclase-andesine,and minor perthite observed locally.The granites are sodic with Na/K ratios(molar)between 4 and 87.Total REE(50-220 ppm)show a clear positive correlation with SiO2.There is no LRRE/HREE fractionation(LaN/YbN=0.5-1.5),me-dium negative Eu anomalies(δEu=0.3-0.6),high Y content and low Sr/Y ratio(~1.0).These granites exhibit relatively juvenile Nd T2DM model ages of 470 to 580 Ma and positiveεNd(331 Ma)values of 6.23 to 7.65.The aforementioned characteristics are similar to those of ocean island or ocean ridge plagiogranites.However,the regional geology,especially its scale,precludes that the plagiogranite pluton was derived directly from fractionational crystallization of mantle-derived basaltic magma.We interpreted that the primary magma of the pluton might be tonalitic in composition generated by ca.50%partial melting of the juvenile basaltic crust.The primary magma experienced intensive frac-tionational crystallization,and intruded into the middle to upper crusts to form the granite pluton.In combination with the previous regional geological data,it is concluded that the plagiogranite pluton was emplaced within the Tarim Block in respond to the Carboniferous continental rifting along the Tianshan orogenic belt.展开更多
基金This study was supported by the National Natural Science Foundation of China(Grant Nos.40303007 and 40421303).
文摘SHRIMPP U-Pb zircon age and geochemical and Nd isotopic data are reported for the Aoyitake plagiogranite in western Tarim Block,NW China.The plagiogranite intruded the Middle Pro-terozoic and Lower Carboniferous with an exposure area of ca.60 km2 and crystallized at 330.7±4.8 Ma.Rock types mainly include tonalite,trondhjemite and minor amounts of diorite and quartz-diorite.Feldspars in the rocks are dominated by oligoclase-andesine,and minor perthite observed locally.The granites are sodic with Na/K ratios(molar)between 4 and 87.Total REE(50-220 ppm)show a clear positive correlation with SiO2.There is no LRRE/HREE fractionation(LaN/YbN=0.5-1.5),me-dium negative Eu anomalies(δEu=0.3-0.6),high Y content and low Sr/Y ratio(~1.0).These granites exhibit relatively juvenile Nd T2DM model ages of 470 to 580 Ma and positiveεNd(331 Ma)values of 6.23 to 7.65.The aforementioned characteristics are similar to those of ocean island or ocean ridge plagiogranites.However,the regional geology,especially its scale,precludes that the plagiogranite pluton was derived directly from fractionational crystallization of mantle-derived basaltic magma.We interpreted that the primary magma of the pluton might be tonalitic in composition generated by ca.50%partial melting of the juvenile basaltic crust.The primary magma experienced intensive frac-tionational crystallization,and intruded into the middle to upper crusts to form the granite pluton.In combination with the previous regional geological data,it is concluded that the plagiogranite pluton was emplaced within the Tarim Block in respond to the Carboniferous continental rifting along the Tianshan orogenic belt.
