苏鲁造山带中胡家林超镁铁质岩岩石地球化学特征.pdf

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1、矿物岩石地球化学通报·研究成果·BulletinofMineralogy，PetrologyandGeochemistryVo1．34No．3，May，2015苏鲁造山带中胡家林超镁铁质岩岩石地球化学特征高天山，陈江峰2，谢智21．南京地质矿产研究所，南京210016；2．中国科学技术大学地球和空间科学学院，合肥230026摘要：苏鲁造山带中胡家林超镁铁质岩地块主要由两部分组成：南部滑石山以蛇纹岩和蛇纹石化橄榄岩为主，夹薄层状石榴橄辉岩一(石榴)单斜辉石岩；北部胡家林主要由(石榴)单斜辉石岩组成，夹厚层状蛇纹岩。蛇纹岩．蛇

2、纹石化橄榄岩低A12O3、低CaO和高MgO，REE含量低，但LREE稍富集。石榴橄辉岩和(石榴)单斜辉石岩低MgO和CaO，高REE含量高，其稀土配分曲线均表现出单斜辉石单矿物的配分特征。这些超镁铁岩块中不同岩石的微量元素均具有Pb的正异常，弱的Nb、Ta的负异常，显示地壳流体交代信息。Nd、Sr、Pb同位素特征显示存在亏损地幔与地壳之间的混合作用。亲石元素含量最低的蛇纹石化石榴橄辉岩的Sr、Nd、Pb同位素组成受交代流体控制明显，而石榴橄辉岩和(石榴)单斜辉石岩不明显。胡家林和滑石山超镁铁岩中所含的交代地壳成分不同，胡

3、家林样品受到含水熔体和富水流体的双重交代，滑石山样品主要受富水流体的交代。关键词：元素地球化学；放射成因同位素；超镁铁质岩；苏鲁造山带中图分类号：P588．242文章编号：1007—2802(2015)03-0601—18doi：10．3969／j．issn．1007．2802．2015．03．017PetrologyandGeochemistryofUltramaficRocksatHujialin，SuluOrogenGAOTian．shan．_，CHENJiang．feng，XIEZhi1．NanjingInstit

4、uteofGeologyandMineralResources，Nanjing210016，China；2．SchoolofEarthandSpaceSciences，UniversityofScienceandTechnologyofChina，Hefei230026，ChinaAbstract：TheuhramaficbodyatHujialinconsistsoftwoparts．Thesouthernpart，whichistheHuashishanbody，con—sistsmainlyofserpentinit

5、eandserpentinizedperidotitewiththinlayersofgarnetolivinepyroxeniteand(garnet)clinopy-roxenite．Thenorthernpartconsistsmainlyofclinopyroxenitewiththicklayerofserpentinite．SerpentiniteandserpentinizedperidotitearelowinA1203andCaOandhighinMgO．TheserocksarelowinREE，but

6、slightlyenrichinLREE．Thegarnetolivinepyroxeniteand(garnet)clinopyroxenitearelowinMgOandhighinCaOandtotalREEcon-tents．Primitivemantle—normalizedtraceelementpatternsforalltypesofmafic-uhramaficrocksshowpositivePbanomalyandweaknegativeNbandTaanomalies，suggestingmetas

7、omatismofcrustallyderivedfluid／meh．TheSr，NdandPbiso—topiccompositionsoftheseuhramaficrockscanbeexplainedbymixingbetweenthedepletedmantleandthecrustat216Ma．Theserpentinizedgarnetolivinepyroxeniteexhibitsthelowestconcentrationsoflithophileelements，suggestingsignific

8、antcontributionsfromthemetasomaticfluid／melt．Thegarnetolivinepyroxeniteand(garnet)clin0pyroxeniteweremetasomatisedbyhydrousmelt．Therefore，theuhramaficro