南秦岭勉略构造带高压基性麻粒岩变质作用及其锆石U-Pb年龄.pdf

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1、1000-0569／2013／029(05)一1657~4ActaPetrologicaSinica岩石学报南秦岭勉略构造带高压基性麻粒岩变质作用及其锆石U·Pb年龄梁莎刘良张成立杨永成杨文强康磊曹玉亭LIANGSha，LIULiang，ZHANGChengLi，YANGY0ngCheng，YANGWenQiang，KANGLeiandCAOYuTing1．大陆动力学国家重点实验室，西北大学地质学系，西安7100692．陕西省地矿局区域地质矿产研究院，咸阳7120001．StateKeyLaboratoryofContinentalD

2、ynamics，DepartmentofGeology，Northw~tUniversity，Xi'an710069，China2．ShaanxiInstituteofRegionalGeologyandMineralResources，Xianyang712000，China2013-02-09收稿．2013-04—15改回．LiangS，LiuL，ZhangCL，YangYC，YangWQ，KangLandCaoYT．2013．MetamorphismandzirconU-Pbageofhigh·pressuremaficgran

3、ulitesininMian-Lfiesuturezone。SouthQinlingorogen．ActaPetrologicaSinica，29(5)：1657—1674AbstractMianxian—LfieyangareaisarepresentativeofMJan—Lnetectonicmrlangebelt．TwotypesofHPmaficgranuliteswererecognizedinXujiapingregionintheno．hemMianxianCounty．Accordingtopetrographics

4、tudyandP—TpseudosectionscalculatedbyTHERM0CALC3．33，thepeakmetamorphicmineralassemblageofthefirsttypegranuliteisassociateswithGrtl+Cpx+P11+QzattheconditionsofT=800～860℃．P=12．4—14．6kbar。andtheretrogradeassemblageischaracterizedbyGrt，+Hbl+P1，+Qz．Thesecondtypegranuliteischa

5、racterizedbytypical“whiteeye—socket”texturewithalbiteoroligoclase，indicatingthatOmpwasonceexistedintherock．Therefore，thepeakmetamorphicmineralassemblageofthesecondgranulitemightbeGrtl+Omp(?)+QzorGrt1+Cpx(?)+P1+Oz，andtheconditionisestimatedtobeT=775—900℃，P>19．2kbarandT=7

6、50～850oC，P=16．5～19．8kbar，respectively．rherockwassubsequentlysufferedtwostagesretrogradedmetamorphism．agranulitefaciesstagewithmineralassemblageofGrt2+Opx+Hb1l+Pl1+QzandanamphibolitefaciesstagewithGrt3+Hbl2+P12+Qz．Thediversityinitialcompositionmightbethemainfactorthatcau

7、sedthedifierentpeakmetamorphicmineralassemblagesandconditionsbetweenthetwotypesofthegranulites．LA—ICP—MSzirconU—Pbdatingobtainedthemetamorphicageof214±11Maandtheprotolithageof477Maforthesecondtypegranulite，andthecrystallizationageof215±5Mafortheleucosomecrossingthegranu

8、lite，respectively．Combinedwithcharacteristicsoftraceelements．theageof214±11Mamightrepresentstheamphibolitefaci