东天山地区中天山地块内中元古代花岗岩的特征及地质意义  

Characteristics of Mesoproterozoic Granites and Their Geological Significances from Middle Tianshan Block,East Tianshan District,NW China

作　　者：施文翔[1,2] 廖群安[3] 胡远清[1,4] 杨再峰 

机构地区：[1]中国地质大学研究生院,武汉430074 [2]新疆维吾尔自治区第一区域地质调查大队,乌鲁木齐830011 [3]中国地质大学地球科学学院,武汉430074 [4]鄂东北地质大队,湖北孝感432000 [5]新疆维吾尔自治区地质调查院,乌鲁木齐830011

出　　处：《地质科技情报》2010年第1期29-37,共9页Geological Science and Technology Information

基　　金：新疆维吾尔自治区项目"新疆哈密市路白山一带1:5万区域地质矿产调查"(XJQDW2003-13)

摘　　要：在天山造山带觉罗塔格山系东段的中天山地块内,新识别出一套侵位于长城系星星峡群变质岩中的片麻状花岗质岩体,岩石组合为片麻状闪长岩+片麻状花岗闪长岩+片麻状二长花岗岩+片麻状钾长花岗岩,锆石SHRIM PU-Pb测年表明这套侵入岩的结晶年龄为(1 453±15)^(1 458±40)Ma(207Pb/206Pb表面年龄),是中元古代晚期的产物。岩石学及地球化学特征显示为高钾钙碱性系列,具I型花岗岩组合特征,形成于板块汇聚的环境。这套花岗质侵入岩的厘定,对于可能存在于元古宙的天山洋的闭合事件,从岩浆作用上提供了重要信息,同时对中天山星星峡群的地层时代提供了一个很好的上限。另外,还发现了一颗形成年龄为(2 991±22)Ma的残留锆石,指示该区可能存在太古宙的古老基底。A suit of pluton is identified, consisting of the typical rock association： gneissic diorite, gneissic granodiorite, gneissic monzonite granite, gneissic K-feldspar granite, from metamorphic rocks of the Xingxingxia Group, Middle Tianshan Block, Tianshan Orogenic Belt, NW China. 16 zircons from Middle Tianshan gneissic granodiorites were dated using SHRIMP U-Pb method. A weighted average apparent age of （1 453 ± 15）-- （1 458 ± 40） Ma （^207 Pb/^206 Pb） attained, is equal to the late Mesoproterozoic era, which represents the crystal age of the source rocks of gneissic granodiorite. The petrochemical and geochemical characteristics of the intrusive rocks shows a high-K calc-alkaline and I type granites, formed in convergent environment. It is a magmatism evidence for the existence and the closing event of the Proterozoic Tianshan Ocean according to the results of the SHRIMP U-Pb, which gives a good minimum ceiling of the age of Xingxingxia Group. Besides, the discovery of a residual zircon SHRIMP U-Pb age of （2 991±22） Ma indicates the basement time of the Middle Tianshan may cast back to the Archaean era.

关 键 词：中天山 中元古代 花岗岩 岩石地球化学 

分 类 号：P588.121[天文地球—岩石学]