新疆天格尔地区碱长花岗岩的地球化学、年代学及其地质意义  

Geochemistry, geochronology and geological significance of alkali-feldspar granite from Tianger area, Xingjiang.

作　　者：王居里[1] 王守敬[1] 柳小明[1] 

机构地区：[1]大陆动力学国家重点实验室,西北大学地质学系,西安710069

出　　处：《岩石学报》2009年第4期925-933,共9页Acta Petrologica Sinica

基　　金：国家科技支撑计划重点项目(2006BAB07B04 -05);国家科技攻关计划项目(2003BA612A-06-10-01)资助

摘　　要：新疆天格尔地区的碱长花岗岩出露于中天山与北天山构造带的结合部位,主要由石英和条纹长石组成,含少量斜长石和黑云母。对该岩体进行了全岩主量、微量元素分析和锆石LA-ICP-MS U-Pb定年。主量和微量元素分析结果表明,岩石具有高的SiO_2、K_2O+Na_2O(K_2O>Na_2O)、Rb、Th、U和∑REE(除Eu外)含量,低的CaO、TiO_2、Ba、Sr、P和Eu含量,属于富钾钙碱性花岗岩,具有向A型花岗岩过渡的后碰撞富钾钙碱性花岗岩的特征,形成于天山后碰撞由挤压向拉张构造体制转变的过渡时期。锆石LA-ICP-MS U-Pb定年研究获得269.7±0.7Ma的岩体侵位年龄,表明北天山古洋盆于晚石炭世闭合,天山与准噶尔、塔里木联结成统一的大陆后,石炭纪末期-中二叠世天山造山带处于挤压向拉张构造体制转变的过渡时期,在中天山北缘以发生大规模右行走滑剪切为标志,形成冰达坂韧性剪切带,同时发生强烈的韧性剪切成岩成矿作用,形成天格尔金矿带及其中的诸多金矿床和矿点,并引起壳、幔物质部分重熔产生岩浆。The alkali-feldspar granitic pluton occurred in Tianger area, between central Tianshan and northern Tianshan, Xinjiang, which is mainly composed of quartz and perthite, with a little plagioclase and biotite. The granite is characterized by the high SiO(2), K(2)O + Na(2)O(K(2)O > Na(2)O), low CaO, TiO(2), and moderately peraluminous features, and is relatively enriched in Rb, Th, U, Sigma REE (excep Eu), poor in Ba, Sr, P, Ti and Eu. It belongs to post-collisional K-rich cale-alkline granitoids (KCG), showing the transitional features between K-rich calc-alkline granitoids and A-type granitoids, and formed in the transitional period from compresion to extension of post-collision of Tianshan orogenic belt. Zircon LA-ICP-MS U-Pb dating for the granite yielded an age of the 269.7 +/- 0.7Ma, representing the emplacement age of the pluton, indicating that after the closure of the northern Tiansban plaeo-ocean basin in the late Carboniferous, the Tianshan orogenic belt get into post-collisional period during the latest stage of Carboniferous to the Middle Permian, signed by large scale dextral strike-slip shear along the northern margin of the central Tianshan, as well as intense ductile shear diagenesis and ore-forming process, and formed gold deposits and ore spots in Tianger gold ore belt. Meanwhile the magma originated from partial melting of crust and mantle material, emplaced along the weak zone between central Tianshan and northern Tianshan.

关 键 词：后碰撞花岗岩 锆石U-PB年代学 构造环境 天格尔 新疆天山 

分 类 号：P588.121[天文地球—岩石学] P597.3[天文地球—地质学]