阿尔泰造山带阿巴宫花岗岩体年代学及地球化学研究

Study on chronology and geochemistry for Abagong granite in Altay orogen

花岗岩的成因和演化一直是颇受关注的科学问题。新疆阿尔泰阿巴宫岩体位于北阿尔泰喀纳斯-可可托海古生代岩浆弧南界;利用锆石SHRIMP U-Pb法测得该岩体的形成年龄为462.5±3.6Ma(MSDW=1.4),即侵入时代为奥陶纪中期。岩石地球化学特征显示高硅、富钾,Rb、Th、U、La等富集,Ba、Sr、P、Ti、Nb强烈亏损,LREE富集、HREE分馏不明显,较强负铕异常以及铝过饱和特征;铝过饱和指数1.09～1.39,属于高钾钙碱性强过铝质花岗岩(SP)。综合前人有关阿尔泰造山带发展、演化的研究成果,认为阿巴宫岩体形成于大陆岩浆弧环境,是陆壳物质部分熔融的结果。

Genesis and evolution of granitoids have always been the scientific issue studied widely. Abagong granite pluton in Allay, Xinjiang is located in the southern boundary of Paleozoic magmas are in Kanas-Keketuohai tectonic unit. Its age of 462. 5 +/- 3. 6 Ma (MSDW = 1.4) obtained by SHRIMP U-Pb zircon dating means that Abagong pluton was formed (luring Middle Ordovician. Its petrology and geochemistry show that Abagong granite enrichs silica, K, Rb, Th, U, La etc and LREE, depletes Ba, Sr, P, Ti, Nb, takes on prominent Eu negative anomaly, not obvious fractionation for HREE and peraluminous characteristics. The A/CNK ratios range from 1. 09 to 1. 39, shared by high-K and calc-alkaline strong peraluminous granite. Based on former research related to the evolution of Allay Orogen, we concluded that Abagong pluton was formed in continental are setting and resulted from partial melting of old crustal material.