Geochemical Constraints of the Ediacaran Volcano-Sedimentary Succession of the Sa’al Metamorphic Complex at Wadi Zaghra,South Sinai,Egypt

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摘要 Thevolcano-sedimentarysuccessionaroundWadiZaghrainSinai,atthenorthernmostsegmentoftheArabianNubianShield,comprisesvolcanicrocksinterbeddedwithratherimmaturesediments.Thesuccessionisdominatedbyintermediatetosilicicvolcanicsofmedium-tohigh-Kcalc-alkalineaffinity.Itisdividedintotwounits,thelowerunitincludesintermediaterocksanddacitesinterbeddedwithgraywackes,semi-pelitesandpelitesandtoppedbypolymictconglomerates.Thisunitissubjectedtofoldingandregionalmetamorphism(uptogarnetzone)andisintrudedbyquartzdiorite-granodioriteinducing,locally,low-pressurecontactthermalmetamorphism.Theunmetamorphosedupperunitencompassesacidvolcanicsintercalatedwithlitharenite,sublithareniteandminorarenite.Therhyolitesofthisunitpertaintothehighlyfractionatedgranitesandarecharacterizedbyanagpaiticindex(NK/A)rangingfrom0.87to0.96.Theymayreflecteitherextensiveinteractionofsubduction-relatedmagmaswiththecontinentalcrustorachangeinthetectonicregime.Thepresentlithologicalandgeochemicalcharacteristicsofthestudiedsedimentstogetherwithavailablezirconagesindicateratherdistalprovenanceoftheirdetritus.Thisdetrituscomprisesfluvial-alluvialsedimentsaccumulatedintheintermontanebasins,whicharehalf-grabensortiltedfaultblocks.Thetectonicsettingofthedepositionalbasinsisactivecontinentalmarginandcontinentalislandarcs.GeochemicalpatternsoftheZaghravolcano-sedimentarysuccessionindicatetheircorrelationwiththeDokhanVolcanics-HammamatClasticssequenceoftheEasternDesertofEgypt.Also,theZaghravolcanicsdisplaygeochemicalsimilaritieswiththoseexposedinSinai,attheRutig,FeraniandIqnaShar’aareas.TheZaghrasuccessionisdatedasEdiacaranbutisnotrelatedeithertotheensimaticislandarcassemblageortotherift-relatedassemblageformedduringtheearlystagesofthebreak-upofRodiniaaspreviouslythought.
机构地区 不详
出处 《地质学报:英文版》 2019年1期
出版日期 2019年01月11日(中国期刊网平台首次上网日期,不代表论文的发表时间)
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