北阿尔金喀腊大湾地区4337高地北花岗闪长岩SHRIMP U-Pb定年及其构造意义  

SHRIMP Zircon U-Pb Geochronology of Northern Highland4337Granodiorite in Kaladawan Area of Northern Altun Mountains and Its Tectonic Implications

作　　者：孟令通[1] 陈柏林[1] 罗迪柯 王永[1] 孙岳[1,3] 吴玉[1] 张昊[3] 王铜 

机构地区：[1]中国地质科学院地质力学研究所,北京100081 [2]中信建设有限责任公司能源矿产工程部,北京100027 [3]中国地质大学(北京)地球科学与资源学院,北京100083

出　　处：《吉林大学学报（地球科学版）》2015年第6期1757-1771,共15页Journal of Jilin University：Earth Science Edition

基　　金："十一.五";十二.五"国家科技支撑计划重点项目(2006BAB07B02-04;2011BAB06B08-04);中国地质调查局地质调查项目(1212011085043)

摘　　要：喀腊大湾位于北阿尔金中东段,为北东向阿尔金断裂与东西向阿尔金北缘断裂所夹持,区内遍布中酸性侵入岩。笔者选取喀腊大湾地区4337高地北花岗闪长岩岩体为研究对象来反演喀腊大湾地区构造演化。岩石地球化学数据表明,岩体为高钾钙碱性I型花岗岩,可能是下地壳中钾和高钾变质玄武岩在高压条件下部分熔融形成的。4337高地北花岗闪长岩岩体锆石SHRIMP U-Pb年龄为(494.4±5.5)Ma,表明其为晚寒武世岩浆活动的产物。结合岩体的地球化学、微量元素构造环境判别图解、年代学和区域地质背景的特征,判定其形成于与俯冲有关的活动陆缘(大陆弧)构造环境。同时,结合前人对喀腊大湾地区岩浆岩的研究,认为该区在早古生代发育一条活动陆缘(大陆弧)岩浆岩带,指示北阿尔金局限洋盆在晚寒武世—早中奥陶世向南俯冲在中阿尔金地块之下。通过对比北阿尔金东西段报道的中酸性侵入岩年龄数据,认为北阿尔金局限洋盆西段经历了更长时间的俯冲,整体呈东早西晚的剪刀状闭合。Kaladawan area of the eastern Altun Mountains of Xinjiang is tectonically located between the NE‐trending Altyn Tagh strike‐slip fault and the EW‐trending northern Altyn Tagh fault ,where the intermediate‐acid intrusive rocks are wildly distributed .The granodiorite in the north of Highland 4337 is selected to study the tectonic evolution of the Kaladawan area .The geochemical data of the intrusion suggests that it is high‐K calc‐alkaline I‐type granitic rock which was likely derived from a partial melting of the intermediate‐ to high‐K meta‐andesitic‐basaltic rocks under high pressure .Zircon U Pb age obtained by SHRIM P from the granodiorite is (494 .4 ± 5 .5) Ma ,implying that it was emplaced in the Late Cambrian period .Integrated with geochemistry ,trace element discrimination ,geochronology , and regional background ,it is inferred that the granodiorite was formed in a subduction‐related active continental margin (continental arc) .In combination with the previous studies of magmatic activity in Kaladawan area ,we suggest that the central Altun block were developed in Early Paleozoic into an active continental margin (continental arc) ,and a magmatic belt were caused by the southward subduction of an oceanic crust to central Altun block during Late Cambrian to Early‐Middle Ordovician .Compared to the ages of the intermediate‐acid intrusive rocks of north Altyn Tagh area ,the evolution of western and eastern parts is different .The west of north Altyn Ocean subduction lasted relatively longer than the east ,and the syn‐collision stage in the east was earlier than in the west .

关 键 词：阿尔金 喀腊大湾地区 岩石地球化学 锆石SHRIMP U-PB定年 部分熔融 活动大陆边缘 

分 类 号：P588.12[天文地球—岩石学] P597.3[天文地球—地质学]