TurkishJournalofEarthSciences (TurkishJ.EarthSci.),Vol.12, 2003,pp.175-198. Copyright©TÜB‹TAK GeologyandHydrothermalAlterationoftheAyd›n- Salavatl›GeothermalField,WesternAnatolia,Turkey ‹SMA‹LHAKKIKARAMANDERES‹1&CAH‹THELVACI2 1MadenTetkikveAramaGenelMüdürlü¤ü(MTA),EgeBölgeMüdürlü¤ü, TR-35042Bornova,‹zmir-Turkey 2DokuzEylülÜniversitesi,MühendislikFakültesi,JeolojiMühendisli¤iBölümü, TR-35100Bornova,‹zmir-Turkey(e-mail:[email protected]) Abstract: TheAyd›n-Salavatl›geothermalfieldislocatedinthemiddlepartoftheBüyükMenderesGraben,andis characterizedbynormal-faultstructures.ThestratigraphicsequenceoftheAyd›n-Salavatl›geothermalfield consistsofmetamorphicrocksoftheMenderesMassifandsedimentaryrocksdepositedduringtheriftingperiod oftheMenderesMassifintheMiocene.Geologicaldatasuggestthatthereisaconnectionbetweentectonic developmentandperiodsofhydrothermalalteration. HydrothermalalterationintheAyd›n-Salavatl›geothermalfieldoccurredinfivedistinctperiods,andallare relatedtodifferentstagesoffaultingsystems,fromtheMiddleMioceneuptothepresent.Thefirstperiodof hydrothermalalterationwascharacterizedbymercuryandantimonymineralizationrelatedtoacidicintrusions,and bytheoccurrenceofrutilemineralizationwithinquartzveins.Gabbrosandassociateddykesdevelopedinthe secondperiod.Inthisperiod,gneissesweresubjectedtohydrothermalalteration.Thethirdperiodwas characterizedbygraniteintrusions.Specularite,talc,calcite,quartz,andaragonitemineralizationandtravertine formedalongthemarginsoftheseintrusions.Thefourthperiodwasmarkedbyalbiteandchloritemineralization thatdevelopedduringN–Sfaulting.Hydrothermalalterationzoneswhichdevelopedinthelastperiodare associatedwithactivefaultsalongwhichhotfluidiscirculating.Thesefaultshavemorethan100mofdownthrow, andformedduringthefinalperiodofgrabenformation.Hydrothermalalterationproductscausedbythe circulationofgeothermalfluidswithinthesefaultsinUpperMiocenesedimentsincludekaolinite,illite, montmorillonite,dickite,vermiculite,calcite,pyrite,dolomiteandhydrobiotite.Thesemineralsarestill precipitating/forminginactivecirculationzones.ThermalwatersoftheAyd›n-Salavatl›geothermalfieldareaNa- HCO3 typewithhighCO2 andBcontentsthatareassociatedwithmetamorphicrocksoftheMenderesMassifand hydrothermalalterationwhichdevelopedviawater-rockinteractions.Geophysicalstudieswereusedtooutline tectonicstructuresandframesoftheSalavatl›geothermalfield. KeyWords: geothermalfield,hydrothermalalteration,BüyükMenderesGraben,Salavatl›,westernAnatolia, Turkey Ayd›n-Salavatl›JeotermalSahas›n›nJeolojisiveHidrotermal Alterasyonu,Bat›Anadolu,Türkiye Özet: Ayd›n-Salavatl›jeotermalsahas›BüyükMenderesvadisiortabölümündeyeral›rvenormalfayl›biryap›ile temsiledilir.Ayd›n-Salavatl›jeotermalsahas›stratigrafikkesitiMenderesMasifimetamorfikkayalar›vebunun üzerineMiyosen’dengünümüzekadardevamedendönemdeçökelmiflsedimanterkayatopluluklar›ndan oluflmaktad›r.JeolojikverilerMenderesMasifi’ndekitektonikgeliflimveevreleriilehidrotermalalterasyonlar›n iliflkilioldu¤unugöstermifltir. Ayd›n-Salavatl›jeotermalsahas›ndakihidrotermalalterasyonbeflfarkl›evreyeayr›lm›flt›r.Buevrelergenleflme tektoni¤ifaylar›ilebelirlenmiflolupOrtaMiyosen’denitibarengünümüzekadardevametmifltir.‹lkevre hidrotermalalterasyoncivaveantimuanmineralleflmesivebunlarlailiflkiliasidikintrüzyonlar›nyerleflmesidir.Bu evrefosiljeotermalsistemlerdegözlenenmineralparajenezleri,rutilmineralizasyonlar›vekuvarsçatlakdolgular› ilekarakterizeedilmektedir.Gabroveonlaraefllikedendayklarikincievreyioluflturur.Buevredegnayslar›n hidrotermalalterasyonau¤rad›¤›belirlenmifltir.Üçüncüevredeisegranitintrüzyonlar›yerleflmifltir.Bu intrüzyonlar›nyankayalar›ndaspekülarit,talk,kalsit,kuvars,vearagonitmineralleriileüstboflal›mbölgelerinde travertenoluflumlar›görülür.Dördüncüevrealbit-kloritmineralizasyonuilekuzey–güneyuzan›ml›fayhatlar›nda belirlenmifltir.Sonevreiseyükseks›cakl›kl›jeotermalak›flkan›ndolaflt›¤›fayzonlar›ndabelirlenmifltir.Bufay zonlar›ndakihareket100metredenfazlad›rvegrabenoluflumunubelirleyensonhareketlerdir.ÜstMiyosen 175 AYDIN-SALAVATLIGEOTHERMALFIELD,WESTERNANATOLIA tortullar›içindedolaflanjeotermalak›flkanlarbufayzonlar›ndahidrotermalalterasyonasebepolmufllard›r.Aktif hidrotermalalterasyonmineralojisikaolinit,illit,montmorillonit,dikit,vermikülit,kalsit,pirit,dolomitve hidrobiyotitminerallerindenoluflmaktad›r.Buminerallerinvarl›¤›aktifjeotermalak›flkandolafl›m›n›nhalen sürdü¤ünügöstermektedir.Ayd›n-Salavatl›jeotermalsahas›n›nsular›,MenderesMasifikayalar›n›nsu-kaya etkileflimiilegeliflenhidrotermalalterasyonaba¤l›olarakyüksekCO 2 veBiçerikliNa-HCO 3 tipindedir.Jeofizik çal›flmalar›Salavatl›jeotermalsahas›n›ntektonikyap›s›n›vekonumunubelirlemekiçinkullan›lm›flt›r. AnahtarSözcükler: jeotermalsaha,hidrotermalalterasyon,BüyükMenderesGrabeni,Salavatl›,bat›Anadolu, Türkiye Introduction islocatedalongfaultsystemsnearthetownsofSalavatl› Extensivetectonicactivity,especiallytheformationof andSultanhisar. east–westgrabens,hasdictatedtheshapeofwestern AcoupleofdeepwellsweredrilledbyGeneral Anatolia(Figure1).Ofthese,BüyükMenderesandGediz DirectorateofMineralResearchandExploration(MTA) grabenshostthemainandthemostimportant (AS-1,1510mbelowgroundlevel;andAS-2,962m, geothermalfieldsofTurkey.Thedistributionof Figure2)withinalowresistivityzone(5–10ohmm) geothermalfieldsinTurkeycloselyfollowsthetectonic outlinedbyresistivity-depthsoundingstudies.Cuttings patterns.Allofthehotspringswithtemperaturesabove fromtheAS-1andAS-2wellsnearSalavatl›werestudied 50–100ºCineasternandwesternAnatoliaareclearly bypetrographicmicroscopyandXRDmethods,andthe relatedtoyoungvolcanicactivityandblockfaulting.Post- natureanddistributionoftheirmineralparageneseswere collisionalvolcanicactivity,lastingfromtheLateMiocene determined.Thedataobtainedfromthedrillcoresof topresent,hasbeenresponsibleforheatingthe thesewellsarethesubjectofthispaper,andareusedto geothermalfields(fiimflek1997;Y›lmaz1997;Demirel& explainamodelforthegeothermalsystemoftheAyd›n- fientürk1996).Thehighthermalactivitiesarereflected Salavatl›field. inwidespreadacidicvolcanicactivitywithmuch hydrothermalalteration,fumaroles,andmorethan600 hotspringswithtemperaturesupto100ºC(Ça¤lar MaterialsandMethods 1961). Relativelydetailedcuttinganalysesalongwithvarious TheAyd›n-Salavatl›geothermalfieldislocatedinthe otherboreholelogswereusedtoassessthegeothermal middlepartoftheBüyükMenderesGraben,andis systemintowhichwellsAS-1andAS-2weredrilled. characterizedbyE–W-trendingnormalfaults(Figure1). Duringdrilling,rockcuttingsweretakenevery2mand wereproperlylabelled.Circulationlossesandratesof Thestratigraphicsequenceofthefieldiscomposedof penetrationwererecordedforeachdrillpipesunk. metamorphicrocksoftheMenderesMassifandoverlying theMiocenesedimentaryrocksdepositedduringthe Temperaturelogswerecarriedoutduringdrillingto Mioceneexhumationofthemassif.Fielddatasuggest locateaquifersandassesstheconditionofthewells.The thatthereisaconnectionbetweentectonicdevelopment temperature-loggingequipmentcomprisedAmerada andperiodsofhydrothermalalteration.Severaldeep loggingtools.Theselogsprovideimportantinformation wellsweredrilled(AS-1,1510mandAS-2,962m)and ontemperatureconditions,flowpathsandfeed-zonesin revealedlowresistivityzones(Karamanderesi1997). geothermalsystems.Temperaturelogshavealsobeen preparedafterdrillingandproduction. Preliminarystudieswereconductedonaregional scalebyKaramanderesi(1972).Geochemicalanalysisof Thewell-testingmethodwascontrolledbylip- waterfromhotspringsnearSalavatl›villageindicated pressuremeasurementsthatgivetotalmass-flowrate thattheareahashot-water-dominatedgeothermal andtheheatcontent(enthalpy)ofatwo-phase potential,andgeophysicalstudiesoutlinedthestructural geothermalfluidfromadischargepipe. situationofthegeothermalfield.Geophysicalstudies Samplesinthewellordrillboxesarewettenedby usinggravity(Gülay1988)andelectricalresistivity pouringwaterontothem.Wettingthecuttingsis methods(fiahin1985)indicatedthatthegeothermalfield necessarytoenhancethevisibilityofthesamplesor 176 ‹.H.KARAMANDERES‹&C.HELVACI N ÝZMÝR study area 0 500 km Edremit graben Bakýrçay graben Simav graben Gördes graben Soma graben Turgutlu ÝZMÝR Gediz graben M E ND Küçük Menderes graben ER E S Kýzýldere Salavatlý M A S S AYDIN I F DENÝZLÝ Büyük Menderes 0 50 km graben Geothermal field fault (unspecified and/or vergence unknown) Gökova graben normal fault AEGEAN SEA fault (inferred) neotectonic fault-bounded basin Figure1. MaintectonicfeaturesofwesternAnatoliaandlocationmapoftheAyd›n-Salavatl›geothermalfield. certainfeaturessuchasfinelydisseminatedsulphides weremadeinordertoexpandorconfirmpreliminary (e.g.,pyrite).Thewetsampleswerethenplacedontothe findingsfromthecuttings.However,thismethodintends mountingstageofthemicroscopeforinvestigation. tocomplementratherthanreplacecarefulbinocular Cuttingexaminationwasdoneusingbinocularmicroscope microscopicstudiesandaddsunderstandingwithregard witha5x10magnificationofthefieldofstudy.Initial torock-mineraldepositionandalteration.Selectedthin- informationobtainedincludesstratigraphic/ sectionsampleswereanalysedusingthepetrographic sedimentologicalfeatures,alterationmineralogyand microscope. evidenceofpermeabilities.Inadditiontobinocular X-raydiffractometricanalysesweredoneonthe~4 microscopicstudy,thinsectionsforpetrographicstudy µmfractionsofparticularsamplesfromthecuttingsin 177 AYDIN-SALAVATLIGEOTHERMALFIELD,WESTERNANATOLIA 10 Q Q Bey Daðý N 09 Ovacýk Plateau Overthrust Bozdað 0 1 2km Q DEMÝRHAN Kabaklýdere MALGAÇEMÝR A Bozköy overthrust Q GÜVENDÝK Kara T. AZAPDERESÝ ESKÝHÝSAR SALAVATLI AS-1 SULTANHÝSAR ATÇA AS-2 Hamam (mevkii) YAVUZKÖY B. Menderes River A KÖÞK Geoelectric profil line 2040 86 1680 YENÝPAZAR alluvium