简介：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.