Anderson et al.，2007-Omphacite breakdown reactions and relation to eclogite exhumation rates.pdf

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1、ContribMineralPetrol(2007)154:253277DOI10.1007/s00410-007-0192-xORIGINALPAPEROmphacitebreakdownreactionsandrelationtoeclogiteexhumationratesEricD.AndersonÆDavidP.MoecherReceived:12December2006/Accepted:26February2007/Publishedonline:3April2007ÓSpringer-Verlag2

2、007AbstractClinopyroxene+plagioclase(±Hbl±Qtz)withslow/lowoverstepping;fine-grained,grainboundarysymplectitesafteromphacitearewidelycitedasevidencesymplectite:rapid,tectonicexhumationwithrapid/highforprioreclogite-faciesorhigh-pressure(HP)metamor-overstepping).

3、VariationsinXCaEs,Xjd,andXCaTsofpre-phism.PrecursoromphacitecompositionsofretrogradecursorHPomphacitearerelatedtothesymplecticmineraleclogites,usedforreconstructingretrogradePTpaths,areassemblagesthatresultfromdecompression.Quartz-nor-commonlyestimatedbyreinte

4、gratingsymplectitephasesmativesymplectitiesindicatequartz-producingretrogradewiththeassumptionthatthesymplectite-formingreactionsreactions(e.g.,breakdownofprecursorCaEs);quartz-freewereisochemical.Comparisonsofbroadbeamsymplectitesymplectities(e.g.,diopside+pl

5、agioclaseafteromphacite)compositionstoadjacentunreactedpyroxenefromvariousindicatequartz-consumingreactions(jd,CaTsbreakdown)symplectitesafterclinopyroxenefromtheAppalachianoutpacedquartz-producingreactions.BlueRidge(ABR)andWesternGneissRegion(WGR)suggestthatt

6、hesymplectiteformingreactionsarelargelyKeywordsSymplectite
Omphacite
Eclogite
isochemical.Endmembercalculationsbasedonreinte-EasternBlueRidge
WesternGneissRegion
PTpath
gratedsymplectitecompositionsfromtheABRandWGRRetrograde
Isothermaldecompression
Reintegrati

7、on
suggestthataminorCa-Eskola(CaEs)componentHornblendequartzexsolution
Ca-Eskola(XCaEs=0.040.15)waspresentinprecursorHPclinopy-roxene.WGRsymplectitesconsistoffine-grained(~1lm-scale),vermicularintergrowthsofPl+CpxII±HblthatIntroductionoccuratgrainboundariesorin

8、ternally.ABRsymplectitescontaincoarser(~10lm-scale)planarlamellaeandrodsofClinopyroxene+plagioclasesymplectitesafteromphacitePl+CpxII+Qtz+Hblwithinclinopyroxenecores.Theareacommonf