阿尔泰库尔干巴斯岩体LA-ICP-MS锆石U-Pb定年及地质意义

为探讨新疆福海县默色克奥依一带在阿尔泰南缘新发现的库尔干巴斯花岗岩体的岩石成因、形成时代以及构造环境,开展了LA-ICP-MS锆石U-Pb定年和岩石地球化学研究。结果显示:U-Pb锆石年龄为(391.4±4.0)Ma(MSWD=0.94),形成时代为中泥盆世,库尔干巴斯花岗岩体属于高钾钙碱性弱过铝质花岗岩、SiO2含量为(62.73%~74.75%),TiO2含量为(0.32%~0.90%),Na2O含量为(3.06%~5.02%),K2O含量为(3.37%~4.10%),P2O5含量为(0.01%~0.19%),Al2O3含量为(12.38%~16.00%)。具有高硅、高碱、富铝、低钛、低磷特征,微量元素显示LREE富集且分馏明显,HREE亏损,中等的Eu负异常(δEu=0.41~0.98),富集Rb、Th、K、La,亏损Ba、Nb、P、Ti的特征,认为库尔干巴斯岩体形成于俯冲消减有关的火山岛弧环境,是哈萨克斯坦-准噶尔板块再次向阿尔泰地块俯冲消减的产物,为该区域构造演化划分提供了新的证据。

LA-ICP-MS Zircon U-Pb Dating and Geological Significance of Altay Kurganbas Rock

In order to discuss the petrogenesis,formation age,and tectonic setting of the newly discovered Kurganbas granite in the southern margin of Altay in the Mosekeaoyi area of Fuhai county,Xinjiang,U-Pb dating of rocks and geochemical studies of LA-ICP-MS zirconium were developed to investigate.The results show that age of U-Pb zircon is(391.4±4.0)Ma(MSWD=0.94)and age of formation is Middle Devonian.The Kurganbas granite is a high-potassium calcium-alkali weak peraluminous granite with a SiO2 content of 62.73%-74.75%,TiO2 content of 0.32%-0.90%,Na2O content of 3.06%-5.02%,K2O content of 3.37%-4.0%,P2O5 content of 0.01%-0.19%,and Al2O3 content of 12.38%-16.00%.With high silicon,high alkali,aluminum-rich,low titanium,and low phosphorus characteristics,trace elements show LREE enrichment and obvious fractionation,HREE loss,moderate Eu negative anomaly(δEu=0.41-0.98),enrichment of Rb,Th,K,La,and the characteristic of loss of Ba,Nb,P,and Ti.It is supposed that the Kurganbass was formed in a volcanic island arc environment related to subduction and reduction,and is the product of the subduction of reduction of the Kazakhstan-Jungar plate to the Altay block.It provides new evidence for the tectonic evolution of the area.