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1、成都理工大学硕士学位论文isbetween1.03~1.12,beingacalciumbaseofrocks.Inthe(K2O+Na2O)-SiO2(TAS)diagram,SiO2-Nb/Ydiagram,Zr/TiO2-Nb/YdiagramandSiO2-AR(alkalinityratio)diagram,Xumaiultramaficrockmostlybehaveasthecalc-alkalinerockseries.Rockm/fisbetween7.06～13.4,beingamagnesiumultramaficrock.IntheFMCdiagram,allsa
2、mplesofXumaiultramaficrockfallinthemaficpoorareaofcalcium.(3)ThetransitionelementsTiandVofXumaiultramaficrockaresignificantlylowerthanthecorrespondingvalueoftheprimitivemantle,whileCr,Co,Niaresimilartotheoriginalmantle,theprimitivemantlenormalizedelementdistributionpatternsistheasymmetric"W"type,
3、TiandCuformtwodistinctnegativeanomaly"valley",thepartitioncharacteristicsoftheresidualmantle.Thelargeionlithophileelements(LILE)Rb,Sr,Ba,Uareobviouslyenrichedandhighfield-strengthelments(HFSE)Nb,Ta,Zrarerelativeloss.Theappearanceofenrichment,Sr,Rbandotherofelements,inparticularthelossofNb,showsso
4、medifferenceswithatypicalmid-oceanridgeN-MORB,whichreflectsthegeochemicalcharacteristicsofislandarcenviromentfigure.(4)TheREEcontentsofXumaiultramaficrockarelow,comparedwiththeheavylossesofmantle.ChondritestandardcurveofrareearthelementsrevealsLREEenrichment,HREEheavylosses,andslightlyright-wingt
5、ype.LREEhasobviousinternalfractionation,HREEhasrelativelyweakfractionationandsignificantpositiveEuanomalies.TheLREEofXumaiultramaficrockisenrichment,probablymantleperidotitemetasomatismwhichhasbeenlateandalteration.MantleperidotiteREEabundanceisverylow,subductionofoceaniccrustduringthereleaseofLR
6、EEandLILE-richplasmainthewaterflowbyaddingalargeextentchangedthenatureofrareearthelementsofrock,resultinginLREEenrichment.(5)Throughtheuseofabundanceratiosoftraceelementsandmajorelements,traceelementsandmorepatternsynthesismethod,theformationofigneousrockXumaiislandarearccalc-alkalinemagma,result
7、ingfromthereductionontotheedgeoftheplateclosed.KeyWords:UltramaficrocksGeochemistryTectonicenvironmentXumaiOphioliticmelangesoftheJinshajiangzoneIVPDF文件使用"pdfFactoryPro"试用版本创建www.fineprint.cn独创性声明本人声明所呈交的学位论文是本人在导师指导下进
