Aoyitake plagiogranite in western Tarim Block, NW China: Age, geochemistry, petrogenesis and its tectonic implications  

作　　者：ZHANG Chuanlin1,2, YU Haifeng3, YE Haimin2, ZHAO Yu2 & ZHANG Dongsheng4 1. Key Laboratory of Isotope Geochronology and Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China 2. Nanjing Institute of Geology and Mineral Resources, Nanjing 210016, China 3. Tianjin Institute of Geology and Mineral Resources, Tianjin 300170, China 4. The 2nd Regional Geological Investigation Party, Xinjiang Bureau of Geology and Mineral Resources, Changji 831100, China 

出　　处：《Science China Earth Sciences》2006年第11期1121-1134,共14页中国科学（地球科学英文版）

基　　金：This study was supported by the National Natural Science Foundation of China (Grant Nos. 40303007 and 40421303).

摘　　要：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 (δ Eu=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 positive εNd(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.SHRIMPP U-Pb zircon age and geochemical and Nd isotopic data are reported forthe Aoyitake plagiogranite in western Tarim Block, NW China. The plagiogranite intruded the MiddlePro-terozoic and Lower Carboniferous with an exposure area of ca. 60 km^2 and crystallized at330.7±4.8 Ma. Rock types mainly include tonalite, trondhjemite and minor amounts of diorite andquartz-diorite. Feldspars in the rocks are dominated by oligoclase-andesine, and minor perthiteobserved 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 SiO_2. There is no LRRE/HREE fractionation(La_N/Yb_N=0.5-1.5), medium negative Eu anomalies (δEu=0.3-0.6), high Y content and low Sr/Y ratio(～1.0). These granites exhibit relatively juvenile Nd T_(2DM) model ages of 470 to 580 Ma andpositive ε_(Nd)(331 Ma) values of 6.23 to 7.65. The aforementioned characteristics are similar tothose of ocean island or ocean ridge plagiogranites. However, the regional geology, especially itsscale, precludes that the plagiogranite pluton was derived directly from fractionationalcrystallization of mantle-derived basaltic magma. We interpreted that the primary magma of thepluton might be tonalitic in composition generated by ca. 50% partial melting of the juvenilebasaltic crust. The primary magma experienced intensive fractionational crystallization, andintruded into the middle to upper crusts to form the granite pluton. In combination with theprevious regional geological data, it is concluded that the plagiogranite pluton was emplaced withinthe Tarim Block in respond to the Carboniferous continental rifting along the Tianshan orogenicbelt.

关 键 词：WESTERN Tarim  Aoyitake plagiogranite  age  geochemistry  TECTONIC implications. 

分 类 号：P548[天文地球—构造地质学]