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榴辉岩相峰期流体活动来自东昆仑榴辉岩石英脉的证据.PDF

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10000569/2014/030(08)233950 ActaPetrologicaSinica 岩石学报 榴辉岩相峰期流体活动:来自东昆仑榴辉岩石英脉的 证据 1,2 2 1,2 贾丽辉  孟繁聪  冯惠彬 1,2 2 1,2 JIALiHui ,MENGFanCong andFENGHuiBin 1中国地质大学,北京 100083 2中国地质科学院地质研究所,大陆构造与动力学国家重点实验室,北京 100037 1ChinaUniversityofGeosciences,Beijing100083,China 2StateKeyLaboratoryforContinentalTectonicsandDynamics,InstituteofGeology,ChineseAcademyofGeologicalSciences,Beijing100037,China 20140210收稿,20140512改回 JiaLH,MengFCandFengHB2014Fluidactivityduringeclogitefaciespeakmetamorphism:Evidencefromaquartz veinineclogiteintheEastKunlun,NW ChinaActaPetrologicaSinica,30(8):2339-2350 Abstract  ThispaperreportsaquartzveinineclogitefromWenquanareaintheEastKunlun,andthroughacomprehensive researchinUPbageandLuHfisotope,whichprovidessomeevidenceaboutfluidactivityinpeakeclogitefaciesmetamorphicstage ThezircongrainsinWenquanquartzveinhaveperfecteuhedralhabitandshowsectororweakzoning,whichprecludesthepossibility thatthezirconcrystalswerephysicallyintroducedintothequartzveinfromthecountryrockZircongrainsfromquartzveinandeclogite 206 238 yieldweightedmean Pb/ Udateof450±2Maand451±2Ma,respectively,whichdescribesthattheformingageofzirconin quartzveinandthepeakeclogitefaciesmetamorphicstageareconsistentThesimilarityofHfisotopecompositioninthetwostylesof zirconprovestheaqueousfluid/meltthatformedveinsisinternalsource,whichmaybederivedfromthefusedquartzineclogite,but wecannotprecludetheexsolusionofstructuralhydroxylinomphaciteandgarnetQuartzveinformedmorelikelyinaqueousfluid ratherthanmeltbecauseofthelowU,ThcontentsandTh/Uratiosinzircons Keywords  Zircon;Quartzvein;Eclogite;UPb;LuHf;EastKunlun 摘 要  本文通过对东昆仑温泉地区榴辉岩中石英脉的锆石UPb定年和LuHf同位素的综合研究,为榴辉岩相峰期变质 阶段的流体活动提供了一定的证据。石英脉中的锆石晶型较好,具有振荡环带或弱分带,排除了从寄主榴辉岩中捕获锆石的 可能性。石英脉和寄主榴辉岩中锆石UPb年龄的加权平均值分别为450±2Ma和451±2Ma,说明石英脉中锆石的形成年龄 与榴辉岩相的峰期变质阶段一致。两种锆石Hf同位素组成的相似性说明形成石英脉的流体/熔体为内部来源,推测可能为榴 辉岩中石英发生溶解以及绿辉石和石榴石分子结构中羟基的出溶作用形成。锆石
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