新疆库鲁克塔格西段奥陶纪花岗岩体地质特征及构造意义  

Geological characteristics and tectonic significance of Ordovician granite intrusions in the western segment of Quruqtagh,Xinjiang

作　　者：郭瑞清[1] 秦切[1] 木合塔尔.扎日 赵亮亮[1] 孙敏佳[1] 魏震[1] 

机构地区：[1]新疆大学地质与矿业工程学院,新疆乌鲁木齐830047

出　　处：《地学前缘》2013年第4期251-263,共13页Earth Science Frontiers

基　　金：中国地质调查局项目"天山-兴蒙造山带基本构造格局综合调查和研究"(1212011058476);"天山成矿带地质矿产调查评价"(1212011120477);国家自然科学基金项目(41162006)

摘　　要：塔里木盆地北缘是塔里木克拉通与南天山造山带结合部位,发育近东西展布的古生代花岗质侵入岩带,该侵入岩带对探究塔里木北缘构造背景及属性乃至南天山洋演化至关重要。文中研究岩体位于库鲁克塔格西段的博斯腾湖南岸,主要岩性为二长花岗岩,LA-ICP-MS U-Pb锆石年龄分别为(458±3)Ma和(454.6±4.6)Ma,代表花岗岩结晶年龄。地球化学特征显示,花岗岩的SiO2质量分数为71.03%～74.39%,K2O质量分数为4.14%～5.07%,A/CNK=1.03～1.08,属弱过铝质高钾钙碱性I型花岗岩;(La/Yb)N为16.41～37.59,δEu=0.44～0.79,具轻稀土富集、重稀土相对亏损的特征;在原始地幔标准化蛛网图上,样品均明显富集K、Rb、Ba、Th等大离子亲石元素,亏损Ta、Nb、P、Ti等高场强元素。花岗岩岩浆源于下地壳的部分熔融,在熔融过程中源区残留石榴子石和斜长石。综合区域地质资料及前人成果,认为花岗岩形成的动力和热力来源与南天山洋向南俯冲有关,推测在早古生代南天山洋存在双向俯冲,并从奥陶纪开始向南俯冲消减,一直延续到早石炭世,到晚石炭世闭合。Located at the junction between the southern Tianshan and the Tarim Craton,the northern Tarim Craton that developed a nearly east-westward belt of Paleozoic granitic intrusive rocks is a key area to the study of the northern Tarim tectonic setting and attribute and the evolution of the South Tianshan Ocean.This study presents the ages and geochemical data of the monzonitic intrusions in the western segment of Quruqtagh.The LA-ICP-MS U-Pb dating of zircons for two samples from two intrusions yield age of（458±3） Ma and（454.6±4.6） Ma,respectively.Geochemically,the granites have the concentrations of SiO2（71.03%-74.39%）,of K2O（4.14%-5.07%） and of A/CNK（1.03-1.08）,which fall into the range of slightly peraluminous high potassic calc-alkaline I-type granite;the granites are of the characteristics of light REE enrichment and heavy REE deficiency with（La/Yb）N（16.41-37.59） and δEu（0.44-0.79）;in the PM-normalized trace element diagram,all samples are distinctly enriched in K,Rb,Ba,and Th and depleted in Ta,Nb,P,and Ti.The granites were probably derived from partially melting of the lower crust with plagioclase and grarnet in the residual.Based on the regional magmatism and previous studies,it is suggested that these monzonitic granites may result from southward subduction of the southern Tianshan oceanic plate.It is proposed that the South Tianshan Ocean underwent double-direction subduction during the early Paleozoic and the southward subduction-reduction that started during the late Ordovician,continued to the early Carboniferous and ended in the late Carboniferous.

关 键 词：花岗岩 LA-ICP-MS锆石U-PB定年 塔里木北缘 南天山 

分 类 号：P588.121[天文地球—岩石学] P542[天文地球—地质学]