新疆阿尔泰南缘萨尔布拉克铁矿区花岗岩年代学及地球化学研究  

The Chronology and Geochemistry of the Granite from the Serbulak Iron Deposit in the Southern Margin of Altay,Xingjiang

作　　者：刘锋[1] 杨富全[1] 李延河[1] 郭正林 柴凤梅[1,3] 耿新霞[1] 张志欣[1] 

机构地区：[1]中国地质科学院矿产资源研究所,北京100037 [2]新疆维吾尔自治区有色地质勘查局706队,新疆阿尔泰836500 [3]新疆大学资源与环境学院,乌鲁木齐830046

出　　处：《地质学报》2010年第2期195-205,共11页Acta Geologica Sinica

基　　金：国家重点基础研究发展计划项目(编号2007CB411302);中央级公益性科研院所基本科研业务费专项资金项目(编号K0811);国家自然科学基金项目(编号40672065);"十一五"国家科技支撑计划项目(编号2006BAB07B02-01;05);国土资源大调查项目(编号1212010786006)资助成果

摘　　要：本文对新疆阿尔泰南缘萨尔布拉克铁矿区花岗岩体进行了锆石SHRIMP U-Pb年龄测定,获得岩体形成时代为410±4Ma(MSDW=0.88),是晚志留世—早泥盆世岩浆活动产物。岩体的年龄限定它侵入的地层时代大于410Ma,为前泥盆系而不是前人认为的中泥盆统;同时限定萨尔布拉克矽卡岩型铁矿的形成时代略晚于410Ma,为晚志留世末期—早泥盆世早期成矿。萨尔布拉克花岗岩具有富硅、偏碱性,LREE富集且分馏明显,HREE亏损且分馏不明显,中等负铕异常(δEu=0.35～0.47),微量元素Th、U、La、Ce、Nd、Zr、Hf相对富集,Nb、Ta、Sr、P、Ti相对亏损,具明显负异常的特点。Na2O/K2O集中于1附近,属于钙碱性—高钾钙碱性系列。铝过饱和指数变化于1.07～1.14,为过铝质。其微量元素地球化学特征与蒙库岩体(400～404Ma)具有很好的相似性,表明萨尔布拉克花岗岩形成于与板块俯冲有关的活动大陆边缘的陆缘弧环境中,可能是洋壳铁镁质岩石在板块俯冲过程中熔融形成,且加入了陆壳物质。SHRIMP U-Pb zircon dating on the granite from the Serbulak iron deposit district in the southern margin of Altay in Xinxiang shows that it formed at 4104 Ma （MSDW=0.88） equivalent to late Silurian or early Devonian. This age defines that the stratum intruded by the granitic pluton was formed at pre Devonian more than 410 Ma, rather than previously considered middle-Devonian and the Serbulak skarn iron deposit was formed at the end of late Silurian or the beginning of early Devonian appreciably late than 410 Ma. Geochemically, the Serbulak granite is relatively enriched in silica, alkaline, Th, U, La, Ce, Nd, Zr, Hf and markedly fractionated LREE, is predominantly depleted in Nb, Ta, Sr, P, Ti, weakly fractionated HREE and contains moderate Eu negative anomaly （δEu=0. 3540.47）. All of the Na2O/K2O ratios are around 1, indicating calc-alkaline to high K calc-alkaline series. The A/CNK ratios range from 1.07 to 1. 14, indicating perahminous granite. The apparent similarity of geochemical features on trace elements to the Mengku pluton （400-404 Ma） implies that the Serbulak pluton formed in a continental arc setting of active continental margin setting related to the subduction of plate where the mafic rocks from the oceanic crust may melt and the crust material may be trapped.

关 键 词：花岗岩 锆石SHRIMP U—Pb年龄 地球化学 萨尔布拉克 阿尔泰南缘 

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