新疆东准噶尔北部青格里河下游花岗岩类的时代及地质意义  

Dating of Granitic Plutons and Its Geological Implications in the Lower Reaches of the Qinggeli River in the Northern Part of East Junggar,Xinjiang

作　　者：周刚[1] 张招崇[2] 谷高中 杨文平 何斌 张小林 罗世宾 王祥 贺永康 

机构地区：[1]中国地质科学院地质研究所,北京100037 [2]中国地质大学地质过程与矿产资源国家重点实验室,北京100083 [3]新疆地质矿产局第四地质大队,新疆阿勒泰836500

出　　处：《现代地质》2006年第1期141-150,共10页Geoscience

基　　金：国家"305"项目(2001BA609A-07-02);国家自然科学基金项目(40572047);教育部新世纪优秀人才支持计划(NCET-04-0728);科技部"973"项目(2001CB409807);新疆维吾尔自治区1:5万区域地质矿产调查项目(XJQD2003-03)

摘　　要：选取新疆东准噶尔北部青格里河下游一带乌图布拉克、阿热勒托别和哈旦逊岩体等具一定规模的3个代表性岩体，通过全岩Rb-Sr等时线同位素定年，确定了研究区内玛音鄂博断裂南侧花岗岩类的形成时代分别为（334．1±9．5）Ma、（300±9）Ma和（280±12）Ma，其初始^87Sr／^86Sr比值分别为0．70433、0．70435和0．70384。结果表明研究区内花岗岩分别形成于华力西中晚期的不同阶段。乌图布拉克岩体形成于早石炭世，为碰撞造山作用晚期的钙碱性花岗岩，可能是早泥盆世富Nb玄武岩部分熔融的产物；结合前人厘定的板块俯冲时间（408—376Ma），推测西伯利亚板块与哈萨克斯坦-准噶尔板块的碰撞时限为376～334Ma。阿热勒托别岩体形成于后碰撞拉张环境，可能是形成于岛弧环境的中基性火山岩部分熔融的产物；哈旦逊岩体虽然也形成于后碰撞拉张环境，但拉张程度更高，属于与岩浆底侵作用有关的花岗岩类。Three representative plutons, Wutubulak, Areletuobie and Hadansun, in the lower reaches of the Qinggeli river in the northern part of East Junggar, Xinjiang were chosen for Rb-Sr isochron dating. The results show that the formation-ages of granitic plutons in the southern side of the Mayin＇ebo fault in the researched area are （334. 1±9. 5） Ma, （300 ±9） Ma and （280 ±12） Ma with the initial ^87Sr/^86Sr ratios of 0. 70433, 0. 70435 and 0. 70384, respectively, and that they were generated at different stages of middle -late Variscan Movement. The Wutubulak pluton, which formed at Early Carboniferous, belong to calc-alkaline series, was likely produced by partial melting of the Early Devonian Nb-enriched basalts during post-collisional event. In combination with the previously assumed plate subduction time （408 -376 Ma）, the collision of Siberian Plate with Kazakstan-Junggar Plate can be limited within the range of 376 -334 Ma. The Areletuobie subsequent to post-collision, and it is rocks that might form in an island arc ronment of post-collision, it might be inferred to be generated by partial pluton formed in an extensional setting melting of intermediate-basic volcanic setting. Although the Hadansun pluton also formed in an extensional envirelated to magma underplating under a strong extensional environment.

关 键 词：RB-SR等时线年龄 花岗岩类 碰撞 底侵 东准噶尔北部 新疆 

分 类 号：P588.121[天文地球—岩石学]