Tectonic evolution and paleogeography of the Kirşehir Block and the Central Anatolian Ophiolites

33 Pages·2017·7.59 MB·English

Tectonic evolution and paleogeography of the Kirşehir
Block and the Central Anatolian Ophiolites, Turkey
Douwe J van Hinsbergen, Marco M Maffione, Alexis Plunder, Nuretdin M
Kaymakci, Morgan M Ganerød, Bart W H Hendriks, Fernando Corfu, Derya
Gürer, Giovanni I.N.O. de Gelder, Kalijn Peters, et al.
To cite this version:
Douwe J van Hinsbergen, Marco M Maffione, Alexis Plunder, Nuretdin M Kaymakci, Morgan M Gan-
erød, et al.. Tectonic evolution and paleogeography of the Kirşehir Block and the Central Anatolian
Ophiolites, Turkey. Tectonics, 2016, 35 (4), pp.983-1014. ￿10.1002/2015TC004018￿. ￿insu-01470256￿
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PUBLICATIONS
Tectonics
ı ş
RESEARCH ARTICLE Tectonic evolution and paleogeography of the K r ehir
10.1002/2015TC004018 Block and the Central Anatolian Ophiolites, Turkey
KeyPoints: DouweJ.J.vanHinsbergen1,MarcoMaffione1,AlexisPlunder1,2,NuretdinKaymakcı3,
• CentralAnatoliaformeddueto MorganGanerød4,BartW.H.Hendriks4,5,FernandoCorfu6,DeryaGürer1,GiovanniI.N.O.deGelder1,7,
interplayoftwosimultaneous
subductionzones KalijnPeters1,PeterJ.McPhee1,FraukjeM.Brouwer8,EldertL.Advokaat1,9,andReinoudL.M.Vissers1
• TheAnatolianthrustbeltformedby
foreland-propagatingnappestacking 1DepartmentofEarthSciences,UniversityofUtrecht,Utrecht,Netherlands,2UniversitéPierreetMarieCurie,Paris,France,
• Strongvariationsinsubduction 3DepartmentofGeologicalEngineering,MiddleEastTechnicalUniversity,Ankara,Turkey,4GeologicalSurveyofNorway,
obliquitymayexplaincontrasting CenterofGeodynamics,Trondheim,Norway,5StatoilASA,Rotvoll,Norway,6DepartmentofGeosciencesandCenterfor
metamorphichistories
EarthEvolutionandDynamics,UniversityofOslo,Oslo,Norway,7InstitutdePhysiqueduGlobedeParis,UniversitéParis
Diderot,UMRF-7154CNRS,Paris,France,8FacultyofEarthandLifeSciences,VrijeUniversiteitAmsterdam,Amsterdam,
SupportingInformation: Netherlands,9SEAsiaResearchGroup,DepartmentofEarthSciences,RoyalHollowayUniversityofLondon,Egham,
• SupportingInformationS1
UnitedKingdom
Correspondenceto:
D.J.J.vanHinsbergen, AbstractInCentralandWesternAnatoliatwocontinent-derivedmassifssimultaneouslyunderthrustedan
[email protected]
oceaniclithosphereintheCretaceousandendedupwithverycontrastingmetamorphicgrades:high
pressure,lowtemperatureintheTavşanlızoneandthelowpressure,hightemperatureintheKırşehirBlock.
Citation: Toassesswhy,wereconstructtheCretaceouspaleogeographyandplateconfigurationofCentralAnatolia
vanHinsbergen,D.J.J.,etal.(2016),
usingstructural,metamorphic,andgeochronologicalconstraintsandAfrica-Europeplatereconstructions.
Tectonicevolutionandpaleogeography
oftheKırşehirBlockandtheCentral Wereviewandprovidenew40Ar/39ArandU/PbagesfromCentralAnatolianmetamorphicandmagmatic
AnatolianOphiolites,Turkey,Tectonics, rocksandophiolitesandshownewpaleomagneticdataonthepaleo-ridgeorientationinaCentralAnatolian
35,983–1014,doi:10.1002/
Ophiolite.IntraoceanicsubductionthatformedwithintheNeotethysaround100–90Maalongconnected
2015TC004018.
N-SandE-Wstrikingsegmentswasfollowedbyoverridingoceanicplateextension.Alreadyduring
Received26AUG2015 suprasubductionzoneoceanspreading,continentalsubductionstarted.Weshowthatthecomplexgeology
Accepted15MAR2016 ofcentralandsouthernTurkeycanatfirstorderbeexplainedbyaforeland-propagatingthrustingofupper
Acceptedarticleonline23MAR2016
crustalnappesderivedfromadowngoing,dominantlycontinentallithosphere:theKırşehirBlockand
Publishedonline27APR2016
Tavşanlızoneaccretedaround85Ma,theAfyonzonearound65Ma,andTauridesaccretioncontinued
untilafterthemiddleEocene.WefindnoargumentforLateCretaceoussubductioninitiationwithina
conceptual“InnerTaurideOcean”betweentheKırşehirBlockandtheAfyonzoneaswidelyinferred.We
proposethatthemajorcontrastinmetamorphicgradebetweentheKırşehirBlockandtheTavşanlızone
primarilyresultsfromamajorcontrastinsubductionobliquityandtheassociatedburialrates,higher
temperaturebeingreacheduponhighersubductionobliquity.
1. Introduction
ConvergencebetweentheAfrican/ArabianandEurasianplatessinceCretaceoustimehasformedaninten-
selydeformedandinplacesmetamorphiccollageofophioliticandcontinentalrocks.Althoughthesehave
beenintenselydeformedinahighlynoncylindricalfoldandthrustbelt,thegeologyofTurkeyisatfirstorder
whatmaybeexpectedinasubduction-collisionzone:itcomprisesathin-skinnedfoldandthrustbeltthatin
places became subjected to high-pressure, low-temperature blueschist to eclogite facies metamorphism.
OnestrikingexceptionistheKırşehirBlockintheheartofAnatolia,a200×200×200kmtriangularcrystalline
massifofcontinentalorigin(Figure1).Itcontainshigh-temperaturemetamorphicrocksandigneousintru-
sionsofLateCretaceousage.Theserocksexperiencedregionalhigh-grademetamorphismwithconditions
upto6–8kbarand700–800°C[WhitneyandDilek,2001;Lefebvre,2011;Lefebvreetal.,2015]atmuchhigher
temperaturesandmuchlowerpressuresthanrecordedbycontemporaneouseclogitetoblueschistfaciescon-
©2016.TheAuthors.
tinentalmetamorphicrocksoftheTavşanlızone(upto24kbarandonly500°C)onlytensofkilometerstothe
Thisisanopenaccessarticleunderthe
termsoftheCreativeCommons west[Sherlocketal.,1999;DavisandWhitney,2008;Whitneyetal.,2010;Plunderetal.,2013,2015](Figure1).
Attribution-NonCommercial-NoDerivs ThispaperexploresapossibleexplanationforthehighgeothermalgradientthatexistedduringtheCretaceous
License,whichpermitsuseanddistri-
metamorphismoftheKırşehirBlock.
butioninanymedium,providedthe
originalworkisproperlycited,theuseis Tothisend,weattemptatconstrainingtheplatekinematiccontextwithinwhichtheKırşehirBlockmeta-
non-commercialandnomodifications
oradaptationsaremade. morphism occurred. Paleogeographic reconstructions invariably suggest that the complex deformation
HINSBERGENETAL. TECTONICEVOLUTIONOFCENTRALANATOLIA 983
Tectonics 10.1002/2015TC004018
Figure 1.Tectonic map of Turkey, modified after Advokaat et al. [2014]. BO=Beyşehir Ophiolite; ÇkB=Çankırı Basin;
HB=HaymanaBasin,SO=Sarıkaramanophiolite;TB=TuzgölüBasin;andUB=UlukışlaBasin.
patternofAnatoliaiscausedbysubductionofoceaniclithosphereoftheNeotethyanOceanaswellasof
continentallithosphereoftheAnatolide-TauridefragmentthatborderedtheNeotethystothesouth[e.g.,
DeweyandSengör,1979;SengörandYilmaz,1981;Okay,1986;Robertson,2004;BarrierandVrielynck,2008;
Moixetal.,2008;Robertsonetal.,2009;Pourteauetal.,2010;Lefebvreetal.,2013].Thesereconstructions
show that a minimum of two subduction zones must have existed during the metamorphism of the
Tavşanlı zone and the Kırşehir Block. In a northern one, Neotethyan oceanic lithosphere has subducted
below the Pontides—the southern Eurasian margin in northern Turkey—since at least Early Cretaceous
time[Okayetal.,2006,2013].
SouthofthePontides,theİzmir-Ankarasuturezonemarkstheformersubductionzone.Tothesouthliesa
foldandthrustbeltofophiolitesandAnatolide-Tauridederivedunits.Detailedstudiesoftheseophiolites
have led workers to interpret that at least one more subduction zone must have formed south of the
Pontides within the Neotethyan oceanic domain in Late Cretaceous time as attested by widespread circa
95–90Ma ages of metamorphic soles [Sengör and Yilmaz, 1981; Okay, 1986; Robertson, 2002; Çelik et al.,
2006; Dilek et al., 2007; Aldanmaz et al., 2009; Dilek and Furnes, 2011; Parlak et al., 2013]. The Anatolide-
Taurideunits,originallylocatedonthedowngoingplateofthisintraoceanicsubductionzone,wereunder-
thrust below and accreted to Neotethyan oceanic lithosphere since Late Cretaceous time [Sengör and
Yilmaz, 1981; Robertson et al., 2009; Pourteau et al., 2010;van Hinsbergen et al., 2010; Plunder et al., 2013].
Relicsoftheoverridingoceaniclithospherearepreservedasophioliteklippenthatformthehigheststructural
unit above a roof thrust bringing ophiolites in contact with all but the deepest major thrust units of the
Anatolide-Taurides.CollisionoftheAnatolide-Tauridefoldandthrustbeltandoverlyingophioliteswiththe
Pontidesformed theIzmir-Ankara suture zonein latest Cretaceous-Paleogenetime [Kaymakci etal.,2009;
Meijersetal.,2010].
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Toobtainafirst-orderkinematicreconstructionofCentralAnatolia,wetakethefollowingapproach:(i)we
review structural geological and paleomagnetic constraints on the burial, exhumation, and subsequent
deformationhistoryoftheKırşehirBlocksinceCretaceoustime,aswellasfromophiolitesthatoverliethe
KırşehirBlock;(ii)weassesstheplatekinematiccontextinwhichtheKırşehirBlockaswellastheadjacent
Tavşanlızonewereburiedbelowtheophiolitesandbecamemetamorphosed;(iii)weassessthekinematic
historybyreviewingthecomplexgeologyof CentralTurkeyandassessingthemomentof onsetof intra-
Neotethyansubductionbyreviewingageconstraintsonthecrystallizationofophiolitesandthecoolingof
theirmetamorphicsoles;(iv)weprovidenewU/PbagesonplagiogranitesoftheSarıkaramanophiolitethat
overliestheKırşehirBlock(SOinFigure1)anddetermineapaleospreadingdirectionthroughapaleomag-
neticanalysisofsheeteddikesofthisophiolite,tobeabletotakeintoaccountinourplatemodeltheorienta-
tion of the plate boundary at which the ophiolite formed; (v) we infer the moment of accretion and
subsequent exhumation of the metamorphic massifs of Central Anatolia by reviewing geochronological
constraintsandbyaddingnewU/Pband40Ar/39AragesforrocksoftheKırşehirBlock.Together,thesecon-
straintsdefinethetimewindowbetweentheonsetofintraoceanicsubductionandtheaccretionofthemeta-
morphic domains to the overriding Neotethyan oceanic plate lithosphere represented by the ophiolite
klippen;and(vi)weassessthenetarealossduringthistimeperiodfromcontemporaneousAfrica-Europe
convergenceusingAtlanticoceanreconstructions[Setonetal.,2012;Torsviketal.,2012].Thecombinedana-
lysisdeterminestherateanddirectionatwhichtheTavşanlızoneandKırşehirBlockwereunderthrustand
metamorphosed.Apossibleexplanationforthemetamorphiccontrastbetweenthetwodomainsisoffered.
2. Geological Setting
2.1. Cretaceous-CenozoicTectonicHistoryofCentralAnatolia
AnatoliaevolvedbetweentheEurasianandAfricanplates(Figure1)thathavebeenconvergingsinceEarly
Cretaceoustime[e.g.,Torsviketal.,2012].Atpresent,mostofAnatoliaandtheAegeanregioncanbeapproxi-
matedasamicroplatethatmoveswestwardrelativetoEurasiaandAfrica/ArabiaalongtheNorthAnatolian
transformfaulttothenorth,theHellenicandCyprustrenchesinthesouth,andtheEastAnatolianfaultinthe
east[e.g.,Reilingeretal.,2010](Figure1).Itsplateboundaryisdiffuseinseveralplacesandpoorlyconstrained
[e.g.,Biryoletal.,2011;vanHinsbergenandSchmid,2012;Özbakıretal.,2013],andthe“microplate”isinternally
deforminginmanyplaces[Reilingeretal.,2010;Koçetal.,2012,2016b].Theformationofthemicroplateis
believedtorelatetotheindentationofArabiaintoeasternAnatolialeadingtoawestwardescape[Dewey
andSengör,1979;SengörandKidd,1979]andtoslabretreat[Faccennaetal.,2006;Sternaietal.,2014]since
theLateMiocene[Keskin,2003;Sengöretal.,2003;Faccennaetal.,2006;Hüsingetal.,2009;Okayetal.,2010].
Priortothattime,Anatoliawasnotacoherentplate,butinsteadunderwentdistributed,majorinternaldefor-
mation in the wider Africa-Europe plate boundary zone. At first order, Anatolia is subdivided into two
continent-derived fold and thrust belts and an intervening “İzmir-Ankara” suture zone. The Pontide fold
andthrustbeltinnorthernTurkeycontainsrocksthathadbeenpartofthesouthernEurasianmarginsince
atleastthemid-Mesozoic[SengörandYilmaz,1981;OkayandNikishin,2015].TheAnatolide-Tauridedomain
incentralandsouthernTurkeywasderivedfromcontinentallithospherethatriftedanddriftedawayfrom
Gondwana since Triassic time [Sengör and Yilmaz, 1981; Altiner et al., 1999; Frizon de Lamotte et al., 2011]
andsubsequentlybecamepartoftheAfricanplate.TheAnatolidesarecomprisedofmetamorphosedand
exhumedmassifsinTurkey(KırşehirBlock,Tavşanlızone,Afyonzone,andMenderesmassif;Figure1)and
theTauridesrefertoabeltofnon-metamorphosedsedimentaryrocks(includinglargeplatformcarbonates)
insouthernTurkey.TheTauridesareathin-skinnedfoldandthrustbeltformedbelowophiolitesfromLate
CretaceousuntilatleastEocenetime[Özgül,1984],andtheirCretaceousnappesarelikelythenonmetamor-
phosedequivalentsofsomeofthemetamorphosed“Anatolide”massifs.
OneormoreNeotethyanoceanicbasin(s)onceseparatedthePontidesandAnatolide-Taurides.Relicsofthis
oceanarefoundoffscrapedinmélanges,aswellasinophiolites.Theoldestknownradiolarianchertsfoundin
mélangealongtheİzmir-Ankarasuturehaveamid-TriassicageshowingaminimumagefortheNeotethys
OceaninTurkey[Tekinetal.,2002;TekinandGöncüoğlu,2007].Theophiolitesthatarewidespreadsouthof
theIzmir-Ankarasuturehaveasanaddedplatekinematiccomplexity,asuprasubductionzone(SSZ)geo-
chemicalsignature[Yalınızetal.,2000b;Parlaketal.,2002;Dileketal.,2007;Yalınız,2008;Aldanmazetal.,
2009] suggesting that they formed by spreading above a subduction zone [Pearce et al., 1984]. Based on
HINSBERGENETAL. TECTONICEVOLUTIONOFCENTRALANATOLIA 985
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008],hrustğ
şıdafterGautieretal.[2002,2008],Iketal.[2dLefebvreetal.[2011,2015].LocationsoftışB=Ayhan-BüyükklaBasin;BG=BaranadaıOphiolite;KyG=KaracayrGranitoid;detailsandreferencesoftheages.
fiesimplie[2011],an[2014].ABı=Karsantovidethe
ışficmapoftheKrehirBlockmodiedafterMTA[2002].Stretchinglineationorientationsandshearsensesarefebvreetal.[2011,2015].LocationsofextensionaldetachmentscomefromGautieretal.[2008],Lefebvreşıüoglu[1997],MTA[2002],YürürandGenç[2006],Gülyüzetal.[2013],Advokaatetal.[2014],andIketal.ğığııÇG=ÇiçekdaGranitoid;ÇO=ÇiçekdaOphiolite;KD=KamanDetachment;KG=KurancalGabbro;KOııSavclThrust;andYB=YozgatBatholith.NumbersbehindagesrefertolistingsinTable1,whichalsopr
Figure2.GeologicalandtectonişıIk[2009],Lefebvre[2011],andLfaultsbasedonKöksalandGöncğıgranitoid;ÇB=ÇiçekdaBasin;ıSO=Sarkaramanophiolite;ST=
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geochemical and metamorphicdata SSZ ophiolites are widely interpreted to formshortly (<10Myr) after
subduction initiation [Casey and Dewey, 1984; Stern and Bloomer, 1992; Stern et al., 2012; Dewey and Casey,
2013;Maffioneetal.,2015a;vanHinsbergenetal.,2015].Afterinitiationofsubduction,atleastonespreadingcenter
mustthereforehaveexistedwithintheNeotethyandomainbetweenthesubductionzonebelowthePontides
andtheintra-Neotethyansubductionzone(s),closetotheintraoceanictrench.Thisspreadingproducedoceanic
crust, and the amount of lithosphere that subducted in the Anatolian subduction zones in Late Cretaceous
timemustthereforehavebeenhigherthantheamountofcontemporaneousAfrica-Eurasiaconvergence.
2.2. UpperCretaceousCrystallineUnits
The metamorphic units of western and central Anatolia are subdivided into three massifs based on their
metamorphicgradeandstructuralposition:theKırşehirBlockinthenortheast,theTavşanlızoneinthenorth-
west,andtheAfyonzonefringingbothzonestothesouth(Figure1).
2.2.1. KırşehirBlockandCentralAnatolianOphiolites
TheKırşehirBlockoccupiestheheartofAnatoliaandcurrentlyformsatriangularmassifalsoknownasthe
CentralAnatolianCrystallineComplex[Göncüoğluetal.,1991;Lefebvre,2011](Figure2).Itissubdividedinto
threesubmassifs,onthebasisofcommontrendsofstretchinglineations,plutonicbelts,andpaleomagnetic
declinations,boundedbyfaults:theAkdaǧ,Kırşehir,andNiǧde-Aǧaçören-Hırkadağmassifs[Lefebvre,2011;
Lefebvre et al., 2013] (Figure 2). These are composed of Paleozoic to Mesozoic metasedimentary rocks,
intrudedbyabeltofgranitoids[Kadıoğluetal.,2006].Themetamorphicrocksareinplacesoverlainbyultra-
maficandmaficrocksofanophiolitesuitedefinedastheCentralAnatolianOphiolites,wherebyallelements
ofthePenrosesequence[Anonymous,1972]canbefound.Theyare,however,severelydismemberedand
scatteredacrosstheKırşehirBlock:ophioliteblocksvaryinsizefromhundredsofmeterstotensofkilometers
andareonlyafewhundredmeters thick[Yaliniz etal.,1996,2000a,2000b,2000c;YalınızandGöncüoğlu,
1998;Floydetal.,2000;Toksoy-KöksalandGöncüoğlu,2001;Yalınız,2008].Itisgenerallyassumedthatthese
ophiolite fragments are the remains of a once coherent oceanic lithosphere below which the Kırşehir
Blockbecameunderthrustandmetamorphosed[SengörandYilmaz,1981;Yalinizetal.,1996;Boztuğetal.,
2009c].Theseophioliteblocksincludewell-studiedoccurrencesofultramaficandmaficbodiessuchasthe
Sarıkaramanophiolite,theÇiçekdağıophiolite,andtheKurancalımetagabbro(Figure2).Thesearethebest
studiedandmostcompleteophioliticsequencesintheregion,andwereviewtheirstructureandcomposi-
tiontoinferthenatureandevolutionofthelithospherebelowwhichtheKırşehirBlockwasunderthrust.
ThemostprominentandbeststudiedophioliteontheKırşehirBlockistheSarıkaramanophiolite(Figure2).It
is composed of a crustal sequence of isotropic gabbros intruded by late stage plagiogranites that likely
resulted from fractional crystallization of basaltic magmas [Floyd et al., 1998; Yalınız et al., 2000c; Toksoy-
Köksaletal.,2001].Thissequenceisoverlainbysheeteddikesandpillowlavas,plagiogranite-relatedrhyolites
andTuronian-Santoniancherts[Floydetal.,1998;Yalınız,2008].Theophioliteisintrudedbyaquartzmonzo-
nite pluton that also cuts the underlying high-grade metamorphic rocks of the Kırşehir Block [Yalınız and
Güncüoglu,1999;Yalınızetal.,1999].
The Çiçekdağı Ophiolite retains a fairly complete crustal sequence with gabbros, dikes, extrusives, and a
Turonian-Santonian epi-ophiolitic cover. The Sarıkaraman and Çiçekdağı ophiolites have geochemical
compositions consistent with formation at a suprasubduction zone spreading center [Yaliniz et al., 1996,
2000a;YalınızandGüncüoglu,1999].Maficblocksinthesubophioliticmélanges,however,havemid-oceanic
ridgebasaltor,toalesserdegree,oceanislandbasaltgeochemicalsignatures[Floydetal.,2000]reflecting
derivationfromtheoriginalNeotethyanoceaniccrust.
TheKurancalımetagabbro(Figure2)isakilometerscale,isolatedgabbrobodydescribedindetailbyToksoy-
Köksal and Göncüoğlu [2001] that is interpreted to be a remnant of the severely dismembered Central
Anatolianophiolitesequence[YalınızandGöncüoğlu,1998;İlbeyli,2008].Itisanisolatedbodyofcompo-
sitionally layered pyroxene and hornblende gabbro with a calc-alkaline geochemical composition that
was interpreted to have formed in an incipient island arc above an intraoceanic subduction zone
[Toksoy-Köksal and Göncüoğlu, 2001]. The gabbro body measures ~1km across and is separated from
thehigh-grademetamorphicrocksoftheKırşehirBlockbyanintenselyshearedmélangezonewithmetao-
phioliticandmetacarbonaterocks.Thegabbros,mélanges,andtheKırşehirBlockmetamorphicrocksare
allintrudedbyfelsicdikeslikelyrelatedtothenearbyBaranadaǧgranitoid[Toksoy-KöksalandGöncüoğlu,
2001](Figure2).
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ThemetamorphicrocksoftheKırşehirBlockweresubjectedtoregionalhigh-temperature,medium-pressure
(HT-MP)conditionsandconsistofgreenschisttoupperamphibolite-faciesmarbles,calcsilicates,metapelites,and
quartzites.PeakP-T(Pressure-Temperature)estimatesthroughoutthemassifareratheruniform.IntheAkdaǧ
massif peak metamorphic conditions were estimated around 5–8kbar/550–675°C [Whitney et al., 2001] and
3.5–6.5kbar/400–700°C [Şahin and Erkan, 1999]. The P-T estimates in the Kırşehir massif reach 6.5–7.5kbar/
700–770°C[Whitneyetal.,2001].Paragenesesassociatedwith7–8kbar/700°CintheHırkadağmassifareover-
printedat3–4kbar/800°Cduringgraniteintrusion[WhitneyandDilek,2001;Lefebvre,2011;Lefebvreetal.,2015].
AnalysesofschistsoftheNiǧdemassifhaveyieldedmetamorphicconditionsvaryingfrom5–6kbar/>700°Cto
3–4kbar/640–650°C,ofwhichthelatterconditionslikelyprevailedduringsyn-decompressionalgranitoidintrusion
[WhitneyandDilek,1998,2001].Similarpressuresbelow4kbarweredeterminedforrareschistsintheAǧaçören
massifclosetothegranitoidintrusions[Whitneyetal.,2001].Regionalpeakmetamorphismhenceoccurredunder
conditionsupto~8kbar/700°C,withlocaloverprintsatevenhighertemperaturesupto800°Cbutlowerpressures
of3–4kbarduringgranitoidintrusion.Theregionalpeakmetamorphicmineralparagenesesarefoundinaregion-
allypervasive,flatlying,andmildlyundulatingfoliation[Seymen,1983;Lefebvre,2011].
The regional foliation was cut by a prominent belt of granitoids currently exposed along the western
and northern perimeter of the Kırşehir Block [Yalınız et al., 1999; Kadıoğlu et al., 2003, 2006; Köksal et al.,
2013](Figure2).Thesegranitoidscanbesubdividedintobeltswithincreasingalkalinityfromwesttoeast
[İlbeyli, 2004a, 2005]. In the Ağaçören massif felsic intrusions occur together with gabbro intrusions that
shouldnotbeconfusedwithophiolite-relatedgabbros[Kadıoğluetal.,2003].Thegranitoids’geochemistry
showsthattheywerederivedfromamantlesourceenrichedbysubduction-relatedfluids,furthercontami-
natedbypartialmeltsofcontinentalcrust[Kadıoğluetal.,2003;İlbeyli,2004a,2005;İlbeylietal.,2009;Delibaş
andGenç,2012a;Köksaletal.,2013].Geochemicalstudiesinterpretedthatmeltingwastriggeredbyexten-
sionofanalreadyhotKırşehirBlockandthedecompressionofanunderlying,metasomatizedmantlewedge
[İlbeyli,2005;Köksaletal.,2013].Processessuchaslithosphericdelaminationorslabbreakoffhavebeenpro-
posedtoexplainthehightemperaturesandgranitoidintrusionsoftheKırşehirBlock[İlbeyli,2004a,2004b,
2005;Kadıoğluetal.,2006;İlbeylietal.,2009;Köksaletal.,2012].
Thegranitoidsarelargelyundeformed,clearlypostdatingthepervasiveregionalfoliation,andintrudedat
pressuresvaryingfrom2.6to5.3kbar[İlbeyli,2005].Inplaces,theyaredeformedbygreenschistfaciesshear
zones,interpretedtobesyn-exhumational[Işıketal.,2008;Işık,2009].Moreover,thegranitoidsintrudenot
onlytheKırşehirBlockbutalsotheoverlyingophiolitesandophioliticmélange(Figure2)[e.g.,Yalınızetal.,
1999; İlbeyli, 2005]. A detachment fault in marbles near Kaman that accommodated exhumation of the
Kırşehirmassifrelativetoanchimetamorphicophioliticmélangewasintrudedbyandrecrystallizedaround
the Baranadaǧ granitoid [Lefebvre et al., 2011]. These crosscutting relationships show that the Kırşehir
Blockwasburiedbelowoceaniclithosphererepresentedbytheophioliteremnantsandwasthenintensely
deformedandmetamorphosed.Theblockwassubsequentlyintrudedbythegranitoidbelt.Thesegranitoids
wereaffectedbyandintrudeexhumation-relatedretrogradeshearzones.Theythusappeartohaveformed
duringregionalextensionandexhumationoftheKırşehirBlock[seealsoWhitneyandDilek,1998;Whitney
etal.,2003].
Pervasive stretching lineation orientations were mapped in detail by Lefebvre [2011] and Lefebvre et al.
[2011,2015]fortheAkdaǧ,Kırşehir,andHırkadaǧmassifsandbyGautieretal.[2008]andIşık[2009]for
the Niǧde and Aǧaçören massifs, respectively (Figure 2). The lineations demonstrate that the pervasive
regionalfoliationisassociatedwithatop-to-the-SWsenseofshearinthecenteroftheAkdaǧmassif,a
top-to-the-S sense of shear in the center of the Kırşehir massif, and a top-to-the-SSE sense of shear in
thecenteroftheNiǧdemassif.Towardtheedgesofeachmassif,however,shearsensesinlowergrade
metamorphicrocksarenearlyorthogonaltothesyn-regionalmetamorphicstretchinglineationsandpoint
fromthecoreofthemassifsoutward:top-to-the-Ninthenorthandtop-to-the-SinthesouthoftheAkdaǧ
massif; top-to-the-NW in the northwest; top-to-the-SE in the southeast of the Kırşehir massif [Işık et al.,
2008;Lefebvre,2011;Lefebvreetal.,2011];top-to-the-SWintheAǧaçörenmassif[Işık,2009];andtop-to-
the-ENE in the Hırkadaǧ andNiǧde massifs [Whitney and Dilek, 2000; Gautier et al., 2008; Lefebvre et al.,
2015].Thelowergradeandoutwardpointingshearsensesareincontrastwiththemainstructuraltrend
definedbytheKırşehirBlock’sgranitoidbeltsandtop-to-the-SWlineationsthatcharacterizethedeeper,
centralpartoftheBlockandcoincidewiththoseonsyn-exhumationalshearzonesandextensionaldetach-
ments [Gautier et al., 2008; Işık et al., 2008; Işık, 2009; Lefebvre et al., 2011, 2015]. They formed during a
HINSBERGENETAL. TECTONICEVOLUTIONOFCENTRALANATOLIA 988
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HINSBERGENETAL. TECTONICEVOLUTIONOFCENTRALANATOLIA 989
Tectonics 10.1002/2015TC004018
second phase of deformation postdating formation of the main regional metamorphism and synchro-
nouslywithgranitoidintrusion.
Finally,theHırkadaǧdetachmentwasassociatedwiththeformationofthesyn-kinematicAyhansedimentary
basin [Advokaat et al., 2014]. In the deepest, syn-extensional part of the stratigraphy a series of upper
Cretaceousvolcanicsyieldeda40Ar/39Arplagioclaseageof72.1±1.5Maandextensionalfaultsareuncon-
formablycoveredbyLutetianlimestones[Advokaatetal.,2014],whichprovidethebeststratigraphiccon-
straintontheextensionalexhumationhistoryoftheKırşehirBlock.
2.2.2. TavşanlıandAfyonZones
TheTavşanlızonewasdefinedbyOkay[1984]andformsan~EWtrending,300kmlongand50kmwide
belt of high-pressure, low-temperature metamorphic rocks. It contains continent-derived metasediments
ascribedtothenorthernmarginoftheAnatolide-Tauridecontinent.Tavşanlırocksweresubductedbelow
anoceanic lithosphere in theCretaceous. Dismemberedrelics of this lithosphere have beenpreserved as
ophiolites[OkayandTüysüz,1999;OkayandWhitney,2010].TheTavşanlızonesensustrictoisaPaleozoic
toMesozoicsedimentarysequence,composedofdetritalsedimentsatthebasegradingintoplatformcarbo-
nates.Theseweremetamorphosedunderblueschisttoeclogitefaciesconditions,upto24kbar/500°C[Okay,
2002;DavisandWhitney,2008;Whitneyetal.,2010;Plunderetal.,2013,2015]duringtheLateCretaceous
[Okay and Kelley, 1994; Sherlock et al., 1999; Sherlock and Kelley, 2002]. The continental unit that recorded
theseconditionsisalsoknownastheOrhanelisequenceorunit[Okay,1986;Plunderetal.,2013].
The Orhaneli sequence is overlain by an accretionary complex, derived from the Neotethyan Ocean. The
sequenceis mostlymade of basalt, tuff, and chertand was divided into threemain tectonometamorphic
units with increasing metamorphic grade at increasing structural depth from 4–8kbar/250–300°C to
17kbar/450°C[Okay,1980a,1980b,1982;Plunderetal.,2013,2015].Theseocean-derivedunitsarefrequently
includedintheTavşanlızone,butinFigure3theyareseparatelyindicated,astheydonotbelongtothe
passive margin sequence and are also found also atop the Afyon zone. The Tavşanlı and ocean-derived
high-pressure units are overlain by ophiolites, and in places they include a metamorphic sole [Lisenbee,
1972;ÖnenandHall,1993;Okayetal.,1998].
To the east, the Tavşanlı zone becomes poorly defined. Blueschist facies continent-derived rocks were
reportedinnumerousplacesinAnatolia[e.g.,vanderKaaden,1966;Okay,1986;Pourteauetal.,2010],but
these may also be part of the Afyon zone [van der Kaaden, 1966; Okay, 1986; Dilek and Whitney, 1997;
Pourteau et al., 2010]. The Orhaneli sequence has not been documented to the east or south of the
Sivrihisarmassif(Figure3).IntheregionofAltınekin,blueschisthasbeendescribedquestioningtheextent
of the Tavşanlı zone [Droop et al., 2005]. Most of the rocks described are similar to the oceanic complex
describedintheTavşanlıregionandsharesimilarP-Tconditionsat10.5kbar/440°C.TheHP-LTconditions
inthecontinentalrocksofthisareaat9.4kbar/400°C[Droopetal.,2005]areidenticaltosomedocumented
intheAfyonzone[Pourteauetal.,2014].Unfortunately,nopublisheddataregardingtheageofthoseblues-
chistsareavailable.
TheAfyonzone,partoftheBolkardağnappe,wasoriginallydefinedbyOkay[1984,1986]asapassivemargin
sequencemetamorphosedundergreenschistfaciesconditions.Itisa~800kmlongbeltwrappedaroundthe
KırşehirBlocktoitswestern,southern,andeasternside(Figure1).TheAfyonzoneisoverlyingtheMenderes
massif[Pourteauetal.,2010].TheTavşanlızonestructurallyoverliestheAfyonzone,whereastheexactstruc-
turalrelationshipsbetweentheKırşehirBlockandtheTavşanlıandAfyonzonescannotbedirectlyobserved
inthefieldastheyarecoveredbysedimentarybasins.TheTavşanlıandAfyonzonesarealsostructurally
overlain by Cretaceous SSZ ophiolites (Figure 3). The discovery of glaucophane in metagabbros of the
Pan-African basement units and of Fe-Mg carpholite in conglomerates of the metasedimentary cover
interpreted as Permo-Triassic in age constrain the burial history of the Afyon zone with peak pressure-
temperature conditions at 10kbar and 350–400°C [Rimmelé et al., 2003; Candan et al., 2005; Pourteau
etal.,2010,2014].
2.2.3. PostCretaceousTectonicHistoryofCentralAnatolia
Afteritsexhumation,theKırşehirBlockwasbrokenintothreemassifsthatunderwentsignificantdifferential
vertical axis rotations as shown by paleomagnetic data from Upper Cretaceous granitoids [Lefebvre et al.,
2013].PostLutetiancontractionalfoldandthrustzoneswithpossiblestrike-slipcomponentsaccommodated
these rotations [Gülyüz et al., 2013; Lefebvre et al., 2013; Advokaat et al., 2014] and remained active until
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Table1. OverviewofAvailableGeochronologicalConstraintsFromAnatolianOphiolitesandTheirSoles,andtheKırşehirBlock,theTavşanlıandAfyonZones,and
theAlanyaNappesa
Number SampleCode RockType Mineral Method Age(Ma) Error Reference
OphioliteCrust
1 FEM093 gabbro hornblende Ar/Ar 150.5 1.5 a
2 FEM173 gabbro hornblende Ar/Ar 150.0 3.9 a
3 FK69 gabbro zircon U/Pb 69.1 2.1 b
4 FK57 gabbro zircon U/Pb 82.8 4.0 b
5 K27099J plagiogranite zircon U/Pb 90.5 0.2 c
6 K27099C plagiogranite zircon U/Pb 89.4 0.6 c
74 K05107J gabbro plagioclase Ar/Ar 83.5 5.7 c
MetamorphicSole
7 P349 amphibolite hornblende Ar/Ar 93.0 2.0 d
8 P534 garnetamphibolite hornblende Ar/Ar 90.0 3.0 e
9 YLK-228 amphibolite hornblende Ar/Ar 93.1 0.9 f
10 YLK229 amphibolite hornblende Ar/Ar 93.0 0.9 f
11 YLK253 metamorphicsoleschist muscovite Ar/Ar 93.0 1.0 f
12 YLK-255 metamorphicsoleschist muscovite Ar/Ar 91.7 0.7 f
13 YLK266 metamorphicsoleschist muscovite Ar/Ar 93.6 0.8 f
14 YL-103 amphibolite hornblende Ar/Ar 90.7 0.5 f
15 YL-134 amphibolite hornblende Ar/Ar 91.3 0.9 f
16 YL-106 amphibolite hornblende Ar/Ar 91.2 2.3 f
17 A-292 amphibolite hornblende Ar/Ar 93.0 1.0 f
18 A-295 amphibolite hornblende Ar/Ar 93.8 1.7 f
19 B-192 amphibolite hornblende Ar/Ar 90.9 1.3 f
20 B-194 amphibolite hornblende Ar/Ar 91.5 1.9 f
21 A2 amphibolite hornblende Ar/Ar 85.6 0.3 g
22 A8 amphibolite hornblende Ar/Ar 87.0 0.4 g
23 A12 amphibolite hornblende Ar/Ar 85.3 0.2 g
24 A13 amphibolite hornblende Ar/Ar 84.7 0.3 g
25 94-PO-65 amphibolite hornblende Ar/Ar 90.6 0.9 h
26 93-MO-5 amphibolite hornblende Ar/Ar 91.0 0.8 h
27 93-MO-22 amphibolite hornblende Ar/Ar 91.3 0.4 h
28 OP257 amphibolite hornblende Ar/Ar 93.7 0.3 j
29 OP256 amphibolite hornblende Ar/Ar 96.1 0.3 j
30 OP255 amphibolite hornblende Ar/Ar 93.6 0.4 j
31 OP254 amphibolite hornblende Ar/Ar 93.9 0.4 j
32 OP253 amphibolite hornblende Ar/Ar 91.8 0.3 j
33 OP132 amphibolite hornblende Ar/Ar 92.7 0.3 j
34 OP131 amphibolite hornblende Ar/Ar 91.9 0.3 j
35 PK-20 metamorphicsoleschist muscovite Ar/Ar 92.4 1.3 f
36 EY-92-2 amphibolite hornblende Ar/Ar 90.4 0.9 h
37 93-AO-3 amphibolite hornblende Ar/Ar 91.7 0.6 h
38 FEM-076 amphibolite hornblende Ar/Ar 166.9 1.1 k
39 FEM-068 amphibolite hornblende Ar/Ar 177.1 1.0 k
40 FEM-067 amphibolite hornblende Ar/Ar 174.1 0.9 k
41 FEM-084 amphibolite hornblende Ar/Ar 169.9 1.0 k
KırşehirBlock
42 BAL76 syenite biotite Ar/Ar 64.9 0.3 l,m
43 BAL78 syenite biotite Ar/Ar 66.6 0.2 l,m
44 BAL72 leucogranite biotite Ar/Ar 73.6 0.3 l
45 BAL69 leucogranite biotite Ar/Ar 71.5 0.3 l
46 BAL66 granitoid hornblende Ar/Ar 67.1 0.3 l
47 BAL66 granitoid biotite Ar/Ar 65.7 0.2 l
48 A22109C schist biotite Ar/Ar 75.2 0.5 c
49 A19109B schist biotite Ar/Ar 75.0 0.3 c
50 A19109B schist K-feldspar Ar/Ar 73.4 0.4 c
51 03V-34 mylonitizedgranite hornblende Ar/Ar 72.4 0.2 n
52 03V-34 mylonitizedgranite K-feldspar Ar/Ar 71.6 0.2 n
53 03V-56 granite hornblende Ar/Ar 81.2 0.5 n
54 03V-56 granite K-feldspar Ar/Ar 82.4 0.3 n
55 03V-47 mylonitizedgranite hornblende Ar/Ar 71.6 0.3 n
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