青海赛什腾山早古生代花岗岩地球化学特征及意义.pdf

《青海赛什腾山早古生代花岗岩地球化学特征及意义.pdf》由会员上传分享，免费在线阅读，更多相关内容在行业资料-天天文库。

1、矿物岩石地球化学通报·研究成果·BulletinofMineralogy，PetrologyandGeochemistryVo1．35No．5，Sep．，2016青海赛什腾山早古生代花岗岩地球化学特征及意义辛存林，谢庆豪，董凯2，廖建栋1．西北师范大学地理与环境科学学院，兰州730070；2．中国地质大学(武汉)地理科学与资源学院，武汉430074摘要：为揭示柴北缘复杂的构造演化特征，用x射线荧光光谱(XPF)、电感耦合等离子质谱(ICP-MS)等方法对赛什腾山花岗闪长岩、花岗岩和二长花岗岩进行了系统的全岩地球化学与微量元素研究。结果表明，赛什腾山岩体富含Si

2、O(64．23％一71．56％)、A1O。(14．03％～18．36％)；KO／NaO值平均为0．48，具准铝质一弱过铝质、钙碱性特征；岩石相对富集Th、u、sr，亏损Ta—Nb、Ti、Pb；稀土总量变化幅度较大(74．29x10一～169．11×10)，轻重稀土分馏明显，弱Eu负异常特征；主微量元素图解及对比分析显示出I型花岗岩特点。结合其他资料，可以认为赛什腾山岩体形成于岛弧环境，是地幔上侵混染了大陆地壳形成的产物，该花岗岩侵位时南祁连洋尚未闭合。关键词：I型花岗岩；地球化学；岛弧；赛什腾山中图分类号：588．121文章编号：1007—2802(2016)

3、05—0908—09doi：10．3969／j．issn．1007。2802．2016．05．O11GeochemicalCharacteristicsofEarlyPaleozoicGranitesintheSaishitengMountain，QinghaiProvinceandTheirSignificanceXINCun。lin，XIEQing．hao，DONGKai，LIAOJian．dongl-CollegeofGeographyandEnvironmentalScience，NorthwestNormalUniversity，Lanzhou730

4、070，China2．CollegeofGeographyandResources，ChinaUniversityofGeosciences(Wuhan)，Wuhan430074，ChinaAbstract：InordertorevealcomplicatedtectonicevolutioncharacteristicsofnorthernmarginoftheQaidamBasin，XPFandICP—MSwereusedtostudymajorandtraceelementgeochemistryoftheSaishitenggraniticdiorit

5、e，graniteandmonzograniteinthispaper．TheresultsindicatethatthosegranitoidscontainhighcontentsofSiO2(64．23％一71．56％)andA12O3(14．03％一18．36％)withtheaverageK2O／Na20ratioof0．48，suggestingthatthegranitoidshavemetaluminous—weakperaluminousandcalc—alkalinecharacteristics．ItcanbeseenOiltheprim

6、itivemantle-normalizedtraceelementspi·dergramsthattheyarerelativelyrichinTh，U，andSr，relativelydepletedinTa，Nb，Ti，andPb．TheirZREEcontentsvarylargelyfrom74．29x10一to169．11x10一，withobviousfractionationbetweenLREEandHREE，andweaknegativeEuanomaliesonthechondrite—normalizedREEpatterns．Both

7、oftheirmajorandtraceelementsshowcharacteristicsoftheI-typegranite．Withthecombinationofpreviousdata，itisbelievedthattheSaishitengintrusivebodywasformedintheis—landarcenvironmentbytheemplacementofthemagmaderivedmainlyfromthemantlewithcontaminationoftheeontinen·talcrustwhentheSouthQili

8、anOceanwasnotclosed