Geochemical, Geochronological, and Sr-Nd Isotopic Constraintson the Origin of the Mafic Dikes from the Pozanti-Karsanti

Ophiolite: Implications for Tectonic Evolution

Dongyang Lian,1,2 Jingsui Yang,1,2,3,* Yildirim Dilek,2,3

Fei Liu,2 Weiwei Wu,1,2 and Fahui Xiong2

1. Faculty of Earth Sciences, China University of Geosciences (Wuhan), Wuhan 430074, China; 2. CARMA,State Key Laboratory for Continental Tectonics and Dynamics, Institute of Geology, Chinese Academy

of Geological Sciences, Beijing 100037, China; 3. Department of Geology and EnvironmentalEarth Science, Miami University, Oxford, Ohio 45056, USA

AB STRACT

The Pozanti-Karsanti ophiolite is situated in the eastern segment of the Tauride belt. This ophiolite is composed ofmantle peridotites, ultramafic to mafic layered cumulates, hornblende gabbros, plagiogranite withminor sheeted dikesand pillow lavas. Metamorphic sole and the Aladag mélange were accreted beneath the base of the Pozanti-Karsantiophiolite. Gabbroic and doleritic dikes intrude the Pozanti-Karsanti ophiolite and the metamorphic sole around LateCretaceous, as determined by the zircon U-Pb ages (86.95 3.1 Ma) of the dikes, but no dikes have been observed in theunderlying Aladag mélange. The Pozanti-Karsanti dikes show light rare earth element–depleted chondrite-normalizedrare earth element patterns and high field strength element–depleted (Nb, Ta, and Ti) but large ion lithophile element–enriched (Rb, Ba, and U) primitive mantle–normalized trace element patterns. These dikes have Th/Nb ratios andoxygen fugacity higher than those of mid-ocean ridge basalt (MORB) but lower than island arc basalt. The Pozanti-Karsanti mafic dikes have (87Sr/88Sr)t ratios of 0.70433–0.70489 and εNd(t) of11.8 to12.4, indicating a depletedmantlesource and mixing of crustal or sedimentary components. Combining the characteristics of both trace elements andradiogenic isotopes, we conclude that these dikes are derived from Sp or Sp 1 Grt facies (Sp 1 Grt) depleted MORBmantle, with some addition of a subduction component in a forearc setting. On the basis of previous studies and ournew work on the Pozanti-Karsanti ophiolite, we conclude that this ophiolite formed during the subduction initiationof an intraoceanic subduction zone in the Late Cretaceous.

Online enhancements: supplemental tables.

Introduction

Ophiolites are on-land remnants of ancient oceaniccrust and uppermantle that have been incorporatedinto orogenic belts (American Geological Institute1972; Pearce et al. 1984; Dilek et al. 1999; Wakaba-yashi et al. 2010; Whattam and Stern 2011). Ophi-olitic rocks—especially the mafic rocks—can pro-vide critical geochemical and geochronological cluesfor understanding the evolution of oceanic litho-sphere (Pearce and Norry 1979; Lytwyn and Casey

1995; Parlak and Delaloye 1996; Parlak et al. 2000,2004; Pearce 2014; Liu et al. 2015).Turkey (Anatolia) consists of a series of terranes

joined together into a single landmass as a result ofthe closure of Paleo- and Neo-Tethyan oceanic basinsduring the Late Cretaceous–Early Cenozoic period(Ketin 1966; Sengör and Yilmaz 1981; Robertson andDixon 1984; Moix et al. 2008; Okay 2008; Robert-son et al. 2012). Ketin (1966) classified Turkey intofourmajor tectonic units, including the Pontides, theAnatolides, the Taurides, and the Border folds (fig. 1).These four tectonic units are separated from northto the south by four suture zones: the Intra-Pontidesuture zone, the Izmir-Ankara-Erzincan suture zone,

Manuscript received June 8, 2016; accepted October 25,2016; electronically published January 23, 2017.

* Author for correspondence; e-mail: yangjsui@163.com.

223

[The Journal of Geology, 2017, volume 125, p. 223–239] q 2017 by The University of Chicago.All rights reserved. 0022-1376/2017/12502-0007$15.00. DOI: 10.1086/690222

the Inner Tauride suture zone, and the Bitlis-Zagrossuture zone (Okay 2008; Robertson et al. 2012; Parlaket al. 2013). Ophiolitic massifs distributed along theInner Tauride suture zone are generally interpreted tobe the remnants of the Inner Tauride oceanic litho-sphere (part of the Neo-Tethyan Ocean) between theTaurus terrane and the Anatolian terrane (Dilek et al.1999; Andrew and Robertson 2002; Parlak and Rob-ertson 2004; Robertson et al. 2009, 2012; Parlak et al.2013).

Ophioliticmassifswithin theTauride tectonic beltare commonly intruded by mafic dikes at differentstructural levels from the metamorphic sole under-lying the ophiolitic sequence to the cumulate rocksin the ophiolite (Lytwyn and Casey 1995; Polat andCasey 1995; Parlak and Delaloye 1996, 1999; Dileket al. 1999; Çelik 2007, 2008). Thesemafic dikes canhelp to constrain the age of intraoceanic subductionand the tectonomagmatic evolution of the ophiolites.The Izu-Bonin-Mariana (IBM) region of the western

Pacific has long been an ideal place for understandingthe evolution of arc-basin systems in a modern intra-oceanic suprasubduction zone (Pearce et al. 1999,2005; Reagan et al. 2010). Detailed studies on theforearc, arc, and backarc magmatic rocks have pro-vided the opportunity to study the tectonic evolutionof the Pozanti-Karsanti ophiolite (PKO) by comparingthe magmatic rocks from this ophiolite with thosefrom the IBM arc-basin system.

Parlak and Delaloye (1996) reported whole-rock40Ar/39Ar ages ranging from 63.8 to 89.6 Ma for thetime of dike emplacement in the Mersin ophiolitenext to the PKO.Dilek et al. (1999) dated hornblendefrommafic dikes and themetamorphic sole rocks bythe 40Ar/39Ar method and obtained ages of 90–91Ma(dike swarms) and 92–90 Ma (metamorphic sole),respectively. White mica from mica schist of thePozanti-Karsanti metamorphic sole analyzed by the40Ar/39Armethodyieldedaplateauageof 92.451.3Ma(Çelik et al. 2006).

Figure 1. Main tectonic units and distribution of ophiolitic massifs in Turkey, after Robertson et al. (2012). IAESZ pIzmir-Ankara-Erzincan suture zone; ITS p Inner Tauride suture; PKO p Pozanti-Karsanti ophiolite. A color versionof this figure is available online.

224 D . L I AN E T A L .

In this article, we report new zirconU-Pb age dataobtainedby laser ablation inductively coupledplasmamass spectrometry (LA-ICP-MS) andwhole-rock com-position of major oxides, trace elements, and Sr-Ndisotopes of themafic dikes from the PKO. These newdata—combined with previous published data of themafic rocks from the PKO and the IBM arc-basinsystem—provide insights into themantle source andthemagmatic origin of thesemafic dikes and also thetectonic evolution of ophioliticmassifs in theTauridetectonic belt.

Geological Setting

The PKO is one of the largest Late Cretaceous oce-anic lithospheric remnants, situated in the easternpart of the Tauride tectonic belt (fig. 1; Juteau 1980;Robertson andDixon 1984; Lytwyn andCasey 1995;Dilek et al. 1999; Parlak et al. 2000; Robertson 2002;Çelik 2007). The Tauride belt is bounded in thesouth-southeast by the Border folds of the Arabianplatform and in the north by the Anatolide terrane(Ketin 1966; Dilek et al. 1999). The Tauride belt con-sists of Precambrian basement and a series of nappesystems, including the Paleozoic and Early Mesozoicplatform carbonates, volcanosedimentary and epiclas-tic rocks, Triassic to Cretaceous ophiolite complexes,and Late Cretaceous and younger postcollisional sed-imentary and volcanic rocks (Özgül 1976). The Tau-ride belt in the Aladag region is characterized by animbricated thrust structure developed during late-stage emplacement of the PKO onto the Menderes-Taurus block in the LateCretaceous (Polat andCasey1995). The lower thrust sheets are composed of para-autochthonous units including Late Devonian to EarlyCretaceous platform-type carbonates, while the up-per thrust sheets consist of the Aladag mélange, theTuronian-Santonian dynamothermal metamorphicsole, and the overlying Early toMid-Cretaceous PKO(Polat and Casey 1995; Polat et al. 1996). The Aladagmélange complex at the bottom of the upper thrustsheet is composed of three tectonostratigraphicunits.From the bottom to the top, these tectonic units are(1) brittlely deformed lower tectonic slice composedof blocks of limestones, cherts, and volcanic rockswith a matrix of cataclasite (resulted from brittle dis-aggregation of limestone, dolomite, chert, and vol-canic blocks) at the base and turbiditic shales andsandstones at the top; (2) ductilely deformed middletectonic slice of red pelitic matrix with ophioliticblocks at the top and limestoneblocks at the bottom;and (3) ductilely deformed upper tectonic slice com-posed of serpentiniticmatrix with ophiolitic andmeta-morphic blocks (Polat et al. 1996). The dynamo-

thermal metamorphic sole overlying the Aladagmélange and underlying the mantle section of thePKO shows an invertedmetamorphic sequencewiththe greenschist facies rock at the base and the am-phibolite facies rock at the top (Thuizat et al. 1981;Polat andCasey1995).This highly folded and faultedmetamorphic sole is about 400–500 m thick (Çelik2007). Geochemical studies on themetamorphic solesuggest that the amphibolite facies volcanic rocks havealkali ocean island basalt (OIB) protoliths, whereasthe greenschist facies metavolcanic rocks show nor-mal mid-ocean ridge basalt (N-MORB) characteris-tics (Lytwyn andCasey 1995; Polat et al. 1996; Çelikand Michel 2003; Çelik et al. 2006). The contacts be-tween the metamorphic sole and the overlying ophio-lite are defined by a 3–5-m-thick, strongly shearedserpentinized mantle tectonite (Çelik 2007).The PKO is about 100 km long and 30 km wide,

covering an area of approximately 1300 km2 (fig. 2)and offset from theMersin ophiolite by the sinistralEcemis Fault in the southwest (Polat and Casey1995). It is bounded to the north and east by thePaleozoic Tauride carbonate rocks, on the west byOligocene and Neogene deposits within the left-lateral strike-slip Ecemis Fault Zone and Tertiaryandesites, and on the south by Neogene sedimentsof the Adana Basin.

Petrography

The PKO has a relatively complete ophiolitic se-quence comprising (from bottom to top) peridotites,ultramafic and mafic cumulate rocks, isotropic gab-bros, sheeted dikes, and pillow lavas (fig. 3; Polat andCasey 1995; Dilek et al. 1999; Parlak et al. 2000,2002). However, most of the crustal rocks of thisophiolite have been eroded during and after its em-placement onto the Menderes-Taurus block (White-church et al. 1984). The mantle peridotites are dom-inated by harzburgites, with minor dunite occurringas lenses or patches within them (fig. 4A).Mafic dikes are very common in the PKO and also

in other ophiolitic massifs within the Tauride belt.These dikes generally show gabbroic or doleritic tex-tures cutting both the metamorphic sole and mantleperidotites (figs. 3, 4); however, no dikes have beenobserved in the underlying mélange. Dike intrusionsare about 0.3–10 m thick with a common north-northeast strike (Polat et al. 1996; Dilek et al. 1999).The sampled mafic dikes from the PKO have fine-grained textures mainly composed of green-brownto green hornblende, plagioclase, and alteration min-erals (e.g., albite, chlorite, talc; fig. 4C, 4D). Relicts ofaugitic clinopyroxene are surroundedby reaction rimsof amphiboles (fig. 4D). The alteration of clinopy-

Journal of Geology 225O R I G I N O F MA F I C D I K E S

roxene to amphibole was suggested to happen at atemperature of 6757 to more than 10007C (LytwynandCasey 1995). Amphiboles in the Pozanti-Karsantidikes compositionally range from tschermakitic horn-blende to actinolite, with most being magnesio-hornblendes (Lytwyn and Casey 1995). Plagioclasescommonly have a turbid surface because of serici-tization or saussuritization.

Analytical Method

BulkMajor and Trace Elements. We have analyzedeight mafic dike samples from the PKO for major

and trace element geochemistry at the NationalResearch Center for Geoanalysis in Beijing. Whole-rock samples were trimmed to remove the alteredsurfaces and cleanedwith deionizedwater. Then thesamples were crushed and powdered with an agatemill to pass a 200-mesh screen.Major elementsweredetermined on fused glass by X-ray fluorescence spec-trometry. The analytical accuracy is estimated to be1% relative for SiO2 and 2% relative for the otheroxides. Trace elements were determined by ICP-MS.Three national standards (GBW07105, GBW07103,and GBW07111) were measured simultaneously toensure consistency of the analytical results. Water

Figure 2. Simplified geological map of the Pozanti-Karsanti ophiolite in the Aladag region, after Polat et al. (1996).

226 D . L I AN E T A L .

andCO2were determined by gravimetric techniquesin which the sample is heated in a closed containerand the water vapor is collected in a separate tube,condensed, and then weighed. The detection limitfor H2O and CO2 is 0.01 wt%. In our geochemicalplots, oxides are reported as wt% and were recal-culated and plotted on anhydrous (volatile-free) ba-sis, where the oxide sum is normalized to 100%.

Sr and Nd Isotope Analyses. Sr and Nd isotopicanalyses were carried out on a VG 354 mass spec-trometer with five collectors at the Center of Mod-ern Analysis at Nanjing University. Rb, Sr, Sm, andNd were separated and purified through standard

ion exchange techniques. The Sr and Nd isotopicratios were normalized against 86Sr/88Sr p 0.11938and 146Nd/144Nd p 0.7219, respectively. Sr standardNBS-987 yielded 86Sr/88Sr p 0.710233 5 0.000006(2j), and Nd standard La Jolla gave 146Nd/144Nd p0.511863 5 0.000006 (2j). The detailed analyticalprocedures for Nd and Sr measurements have beendescribed by Wang et al. (2007).

Zircon U-Pb Dating. Zircon grainswere recoveredfrom themafic dikes in the PKO.These zirconswereseparated from the crushed samples using heavy-liquid andmagneticmethods. Theywere handpickedunder a binocular microscope and later mounted ina rounded epoxy resin. The epoxy resinmounts werepolished to expose the grain center of zircons. Catho-doluminescence and transmitted light images wereobtained to check themicrostructures and inclusiondistributions of each zircon and also to choose thebest positions for analyses. Zircon U-Pb dating wascarried out by LA-ICP-MS at the University of Sci-ence and Technology of China. Laser analyses wereperformed using a Geolas2005 and a 193-nm ArFexcimer laser ablation system. During our analyses,the diameter of the laser ablation spot was 24 mm.Element and isotope ion signal intensities were ac-quired by an Agilent 7500 ICP-MS instrument. In-ternational standard zircon 91500 was used as theexternal standard for thematrix-matched calibrationof U-Pb dating. References glass of NIST SRM 610was analyzed as an external standard, and 29Si wasused as an internal standard for the trace elementcalibration. Offline isotope ratios were processed bythe LaDating@Zrn program. Common Pb correctionand ages of the samples were calibrated and calcu-lated using ComPvCorr#3-18 (Andersen 2002). U-Pbconcordia diagrams andweightedmean calculationswere made using ISOPLOT (Ludwig 2003).

Results

Major and Trace Elements. Whole-rock major andtrace elements contents of the mafic dike rocksfrom the PKO are listed in table S1 (tables S1–S3 areavailable online). These mafic dikes have relativelylow volatile oxides (H2O 1 CO2) contents rangingfrom 2.10 to 2.99 wt%. Whole-rock SiO2 contentsrange from 52.53 to 54.21 wt%, consistent withbasaltic to andesitic composition (fig. 5A, 5B). ThePozanti-Karsanti mafic dikes generally have low al-kaline contents (with K2O ranging from 0.23 to 0.39wt%) and belong to the tholeiitic series (fig. 5C).Mg# values of the PKO mafic dikes vary between0.56 and 0.60, within the range of 0.45–0.64 formafic dikes in theTauride ophiolitic belt (Dilek et al.

Figure 3. Simplified geological column of the Pozanti-Karsanti ophiolite, modified after Parlak et al. (2000). Acolor version of this figure is available online.

Journal of Geology 227O R I G I N O F MA F I C D I K E S

1999). Combined with the existing data and our dataof the PKO mafic dikes, negative or positive corre-lations can be observed between SiO2, CaO, TiO2,and MgO (fig. 6).

In the Zr/Ti versus Nb/Yb diagram, the PKOmafic dikes also fall in the field of basaltic andesite(fig. 5B), in accordance with the characteristics ofmajor oxides. Chondrite-normalized rare earth el-ement (REE) patterns for the dikes are marked bymoderate light REE (LREE)-depleted patterns sim-ilar to those of N-MORBs (fig. 7A). These dikesshow slightly negative to no Eu anomalies, with dEu(Eu=Eu�) values of 0.90–0.99 indicating weak or noplagioclase crystallization. In the primitive mantle–normalized trace element diagrams, these rocks showenrichments in large ion lithophile elements (LILEs;i.e., Rb, Pb, U, and Sr) but depletion in high fieldstrengthelements (HFSEs; i.e.,Nb,Ta, andTi;fig. 7B).

Zircon U-Pb Ages. The U-Pb age data of zirconsfrom mafic dike samples in the PKO are shown in

table S2 (fig. 8). Twelve zircons—including threeinherited zircons—have been analyzed. These threeinherited zircons (with ages of 1387, 395 [core], and336 Ma, respectively) display prism textures withclear oscillatory zonation. One of the three inher-ited zircons contains core rimmedby ametamorphiczone (fig. 8). The other analyzed zircons have a longprism shape with no or very weak oscillatory zona-tion. In the 206Pb/238Uversus 207Pb/235Udiagram, thesezircons (except the inherited ones) give an intercep-tion age of 86.25 4.1 Ma, which is identical to theirweighted mean 206Pb/238U age of 86.9 5 3.1 Mawithin the uncertainties (fig. 9).

Sr-Nd Isotopes. The Sr-Nd isotopic data of thePozanti-Karsanti mafic dikes are listed in table S3.143Nd/144Nd ratios of these mafic dikes ranging from0.512734 to 0.512773 are lower than those of de-pletedMORBmantle (DMM) and IBM forearc basalts,whereas 87Sr/88Sr ratios varying between 0.704418and 0.704956 are higher than those of DMM (fig. 10).

Figure 4. A, Field photograph for harzburgite with dunite lens. Dashed line represents the contact between duniteand harzburgite. B, Outcrop of mafic dikes in the Pozanti-Karsanti ophiolite. Dashed line represents the contactbetween mafic dike and strongly serpentinized peridotite. C, Characteristics of the Pozanti-Karsanti dikes undermicroscope. D, Relict of clinopyroxene rimmed by amphibole. amp p amphibole; pl p plagioclase; px p pyroxene.

228 D . L I AN E T A L .

Figure 5. A, B, Classification of the Pozanti-Karsantimafic dikes using total alkali silica diagram (A) of LeBaset al. (1986) and Zr/Ti-Nb/Y diagram (B) from Pearce(2014). C, K2O-SiO2 diagram. Triangles indicate previ-ously published data of the Pozanti-Karsanti dikes fromLytwyn and Casey (1995) and Dilek et al. (1999). BA pbasaltic andesite; BTA p basaltic trachyandesite; Ir pIrvine dividing line between alkaline and subalkaline com-positions, after Irvine and Baragar (1971). A color versionof this figure is available online.

The 143Nd/144Nd and 87Sr/88Sr ratios are very close tothe bulk silicate earth and somemafic rocks from theYarlung Zangbo ophiolitic belt (YZO) of the easternTethys. The initial 87Sr/88Sr ratios and εNd(t) valueswere calculated using the new age data (87 Ma) re-ported in this article. The Pozanti-Karsanti maficdikes have (87Sr/88Sr)t ratios of 0.70433–0.70489 andεNd(t) values of11.8 to12.4. These ratios are close tothose of the basalts from the Southwest Indian Ridgeand some basaltic rocks from the YZO.

Discussion

Petrogenesis of the Pozanti-Karsanti Mafic Dikes.The selected Pozanti-Karsanti mafic dikes in thisarticle have low volatile oxide contents, indicat-ing a relatively low degree of alteration effect. Inthese mafic rocks, relicts of clinopyroxene rimmedby amphibole are commonly observed, which hasbeen attributed to the reaction CPX 1 OPX 1PLAG 1 Ol 1 ILM 1 H2O p HBD at a temperatureof possibly 19007C (Lytwyn and Casey 1995). ThePozanti-Karsanti mafic dikes also experienced low-temperature (!4507C) hydrothermal alteration, asindicated by the existence of epidote, chlorite, andactinolite (Lytwyn and Casey 1995).In the Na2O 1 K2O versus SiO2 diagram, the

Pozanti-Karsanti dikes have basaltic to basaltic-andesitic compositions, which is consistent withthose determined by fluid-immobile elements (i.e.,Zr, Ti, Nb andY; Pearce 2014). The Pozanti-Karsantimafic dikes have relatively lower Mg# values (Mg/Mg1 Fetotal p 0.56–0.60) and Cr (116–150 ppm) andNi (45–52 ppm) contents than primary melts in equi-librium with peridotites (e.g., Cr p 300–500 ppm,Ni 1 300 ppm; Frey et al. 1978), indicating that thesedikes are crystallization differentiation products ofthe primary melts (Lytwyn and Casey 1995; Dileket al. 1999). The negative correlation of SiO2, TiO2,andV againstMgO and the positive correlation ofNiagainstMgOsuggest crystallization of olivine (fig. 6).Besides, the positive correlation between CaO andMgO indicates the crystallization of clinopyroxene(fig. 6B). Some mafic dikes show slightly negativeEu anomalies (Eu=Eu� p 0.90–1.00), indicatingweakfractional crystallization of plagioclase (fig. 7A).The Pozanti-Karsanti mafic dikes exhibit LREE-

depleted, chondrite-normalized REE patterns with(La/Yb)N varying between 0.63 and 0.78, similar tothose of the N-MORB (fig. 7A; Sun andMcDonough1989). In the primitive mantle–normalized trace el-ement diagram, these rocks display enrichments ofLILEs (Rb, Ba, andSr) anddepletion ofHFSEs (Nb,Ta,and Ti;fig. 7B). The LREE-depleted characteristics—

Journal of Geology 229O R I G I N O F MA F I C D I K E S

Figure 6. Plots of major elements and Cr and V for the Pozanti-Karsanti mafic dikes. Triangles indicate previouspublished data of the Pozanti-Karsanti dikes from Lytwyn and Casey (1995) and Dilek et al. (1999). Izu-Bonin-Mariana(IBM) forearc basalt data are from Reagan et al. (2010); IBM arc and backarc rock data are from Pearce et al. (2005).

combined with the negative anomalies of Nb, Ta,and Ti—indicate that the melts from which thesemafic dikeswerederivedwere fromadepletedmantlesource (Pearce and Parkinson 1993). Aldanmaz et al.(2000) used nonmodal batch melting equations tomodel REE concentration variations during the melt-ing of the DMM (McKenzie and O’Nions 1991), theprimitive mantle (Sun and McDonough 1989), and aspeculated enriched mantle source (Aldanmaz et al.2000). La and Sm are both incompatible elements,thus these two elements are not significantly affectedby variations in the source mineralogy (e.g., spinel orgarnet) during partial melting processes (Aldanmazet al. 2000). In the La/Sm versus La diagram, mostPozanti-Karsantimafic dikes plot close to themeltingtrend of the DMM source with the melting degree of8%–15% (fig. 11A). BecauseYb is stronglycompatiblewith garnet but not with other normal minerals (e.g.,spinel, clinopyroxene, and olivine), the existence ofgarnet in the mantle source will significantly controlthe Yb contents in mantle-derived melts (Aldanmazet al. 2000; Pearce 2008). In the Sm/Yb versus Smdiagram, these mafic dikes plot close but a littlehigher than the expectedmelting trend of the spinel-lherzolite facies DMM source, with melting degreesaround 10% consistent with those determined bythe La/Sm versus La plot (fig. 11B). In the Sm/Ybversus La/Sm diagram, the Pozanti-Karsanti dikesdistribute along the melting trend of the spinel-lherzolite facies DMM source (fig. 11C). In thesethree diagrams, the Pozanti-Karsantimafic dikes plotall around N-MORB, suggesting that these maficdikes may have a similar mantle source to that ofN-MORB and also that these dikes are closer to thecomposition of forearc volcanic rocks from the IBM

arc-basin system (Reagan et al. 2010). Thus, thePozanti-Karsanti mafic dikes may have originatedfromanSp or Sp1Grt facies depletedmantle source.Sr-Nd isotopic systematics are also of great im-

portance in constraining the characteristics of themantle source (Hart 1984; Zindler and Hart 1986;Mahoney et al. 1998; Xu and Castillo 2004). ThePozanti-Karsanti mafic dikes have 143Nd/144Nd valueslower than those of DMM and most mafic rocksfrom the YZO of the eastern Tethys (Zindler andHart 1986; Xu andCastillo 2004; Liu et al. 2015). εNd(t) of the Pozanti-Karsanti dikes range from 1.9 to2.6 and fall close to the field of modern SouthwestIndian Ridge. Sr isotopic compositions of these dikesare more radiogenic than the DMM and Pacific–North Atlantic MORB. The positive εNd(t) valuessuggest that these dikeswere derived fromadepletedmantle source, but the low εNd(t) values and high87Sr/86Sr ratios may suggest mixing of other compo-nents (e.g., fluids or melts from the crustal materialor sediments; Zindler and Hart 1986; Elliott et al.1997).Nb and Th are both highly incompatible elements

during mantle melting processes; however, they be-have differently in the subduction zone because oftheir different properties (Pearce 2014). BecauseTh issubduction mobile and Nb is subduction immobile,they can provide constraints on the subduction/crustal input. In the Th/Yb versus Nb/Yb diagram,the Pozanti-Karsanti dikes plot above the MORB–OIB array and around the boundary of oceanic arcrocks (fig. 12A; Pearce 2008, 2014), indicating thatsubduction components (fluids/melts) contributed tothe formation of these dikes. These subduction com-ponents may be derived from both subducted sedi-

Figure 7. Chondrite-normalized rare earth element patterns and primitive mantle–normalized trace element dia-gram for the Pozanti-Karsanti mafic dikes. Data of mafic dikes (triangles), forearc, arc, and backarc rocks are from thesame references as in figure 6. E-MORB p enriched mid-ocean ridge basalt; N-MORB p normal mid-ocean ridgebasalt; OIB p ocean island basalt.

Journal of Geology 231O R I G I N O F MA F I C D I K E S

ments and altered crust, resulting in the enrichmentof some LILEs, higher Th/Nb ratios, and more radio-genic Sr isotopic compositions, as explained by El-liott et al. (1997).

In general, magma of the Pozanti-Karsanti maficdikes derived from the Sp or Sp 1 Grt (Sp 1 Grt)facies DMM source. This magma experienced as-similation of subduction component and crystal-lization differentiation processes.

Tectonic Evolution of the Pozanti-Karsanti Ophiolite.The PKO in the eastern Tauride belt consists ofmantle peridotites, ultramafic to mafic layered cu-mulates, hornblende gabbros, plagiogranites withmi-nor sheeted dikes, and pillow lavas (Cakir 1978;Tekeli et al. 1984; Lytwyn and Casey 1995; Dilek

et al. 1999; Parlak et al. 2000, 2002; Saka et al. 2014).The mantle peridotites are dominated by the re-fractory harzburgites, with some dunite lenses orpatches. The constituent minerals of harzburgitesmainly fall within the field of forearc peridotites, asshown by Saka et al. (2014), indicating a relativelyhigh degree of partialmelting in the suprasubductionzone environment. The LREE-enriched chondrite-normalized REE patterns combined with the lowheavy REE contents of the peridotites indicate thatthese harzburgites have been modified by fluids/melts from the subduction zone (Saka et al. 2014).Ultramafic cumulate rocks in the basal part of thePKO mainly consist of dunite, wehrlite, olivine cli-nopyroxenite, clinopyroxenite, and olivine webster-

Figure 8. Cathodoluminescence images of representative zircons from the Pozanti-Karsanti dikes. Circles indicatethe position of analyzing spot by laser ablation inductively coupled plasma mass spectrometry. U-Pb ages are listedfor the individual zircon grains. The diameter of the laser ablation spot was 24 mm.

232 D . L I AN E T A L .

ite (Parlak et al. 2002), and the mafic cumulates arecomposed of gabbronorite (Parlak et al. 2000). Thecumulate sequence in the PKO indicates a mineralcrystallization sequence of Ol→Cpx→Opx→ Pl ina suprasubduction zone setting, which might be dueto the high CaO/Al2O3 ratios in the suprasubductionzone magmas (Pearce and Parkinson 1993). Miner-alogical and geochemical data of the cumulate rockssuggest that the ultramafic cumulate rocks crystal-lized in amedium- to high-pressure environment andthe mafic cumulate rocks crystallized in the low-pressure environment, but both of them formed inthe suprasubduction tectonic setting (Parlak et al.2000, 2002).Elements such as Nb, Ta, Zr, Hf, Ti, V, and Y are

generally unaffected by the alteration processes,and thus they are effective indicators in discrimi-

nating the tectonic settings of themafic rocks (Woodet al. 1979; Pearce and Parkinson 1993; Pearce 2008,2014). In the Th/Yb diagrams, the Pozanti-Karsantidikes have Th/Yb ratios lower than most oceanicarc basalts but higher than MORB rocks, implyinga weaker addition of subduction components thanthose of oceanic arc rocks (fig. 12A; Pearce 2008,2014).MORBmagmas are thought to be generated atrelatively reducing conditions (e.g., quartz-fayalite-magnetite [QFM]-1), while oceanic arc magma gen-

Figure 9. Concordia plots (A) and weighted average agediagram (B) of representative zircon grains from thePozanti-Karsanti mafic dike.

Figure 10. Plots of 143Nd/144Nd versus 87Sr/88Sr (A) andεNd(t) versus (87Sr/88Sr)t (B) for the Pozanti-Karsanti maficdikes. Field of island arc basalt (IAB) is from White andPatchett (1984); field of mid-ocean ridge basalt (MORB),ocean island basalt (OIB), depletedMORBmantle (DMM),highmu (HIMU), bulk silicate earth (BSE), enrichedmantle1 (EMI), and enrichedmantle 2 (EMII) are fromZindler andHart (1986). Data of rocks from mafic rocks from YarlungZangbo ophiolite (YZO) are from Xu and Castillo (2004)and Liu et al. (2015); Izu-Bonin-Mariana (IBM) forearc ba-salt data are from Reagan et al. (2010); field of Pacific–NorthAtlanticMORB,most IndianMORB,Reunion-Crozethotspot, and Southwest Indian Ridge are from Mahoneyet al. (1998); data ofmafic dikes (triangles), forearc, arc, andbackarc rocks are from the same references as in figure 6.PKO p Pozanti-Karsanti ophiolite.

Journal of Geology 233O R I G I N O F MA F I C D I K E S

esis is thought to take place at an oxygen fugacity ofQFM1 1 (Pearce andParkinson1993). V is amediumincompatible element that is very sensitive to thevariation of oxygen fugacity (Pearce and Parkinson1993). At high oxygen fugacity, V31/(V41 1 V51) andthe partition coefficients are low, but at low oxygenfugacity, V31/(V411V51) and the partition coefficientare high (Parkinson and Pearce 1998). In the V-Tidiagram, the Pozanti-Karsanti dikes plot around theboundary ofMORB and island arc tholeiite (fig. 12B).In the V-Yb diagram, these rocks show oxygen fu-gacities close to QFM transitional between thoseof MORB and island arc tholeiite (fig. 12C; Pearceand Parkinson 1993). In the Hf/3-Th-Ta triangulardiagram, the Zr/Y-Zr diagram, and the Cr-Y dia-gram, most dikes plot near the boundary or withinthe overlapping field of MORB and island arc basalt(fig. 13). In the Zr/Y diagram, these rocks also form atrend from MORB to island arc basalt (fig. 13A).

The Pozanti-Karsanti dikes show transitional char-acteristics fromMORB to suprasubduction zonemag-matic rocks. To better constrain the exact tectonicsetting of these dikes, we have collected the geo-chemical data of forearc, arc, and backarc volcanicrocks from the IBM arc-basin system (Pearce et al.2005; Reagan et al. 2010) and also plot them in theabove-mentioned diagrams. It can be seen that thesedikes are more consistent with the forearc basalts.Because the metamorphic sole underlying the ophi-olitic sequence is also intruded by these dikes, thesedikes may have originated from a ridge-subductionevent in a forearc environment, as proposed by Lyt-wyn and Casey (1995) and Dilek et al. (1999).

According to the suprasubduction zone charac-teristics of the PKO rocks (from mantle peridotitesto the cumulate rocks and also themafic dikes), herewe put forward another possiblemodel that the PKOmayhave formed during subduction initiation (Stern2004; Wakabayashi et al. 2010; Whattam and Stern2011) and then been intruded by the mafic dikesforming in the forearc environment (Lytwyn andCasey 1995; Dilek et al. 1999). The mantle part ofthe PKO may represent the melting residue of theupwelling fertile asthenosphere due to the incipienttrench rollback in the intraoceanic subducting pro-cess, as depicted byWhattamand Stern (2011). Fluidsfrom the subducting slab induced a high degree ofpartial melting of the mantle peridotites, generatingthe highCaO/Al2O3melts for the cumulate sequenceof this ophiolite.

Age of Intraoceanic Subduction. The metamor-phic sole underlying the ophiolite can provide cru-cial information regarding the evolution of the over-lying ophiolite, especially about its emplacementover an intraoceanic subduction zone or over a pas-

Figure 11. Plots of La/Sm versus La (A), Sm/Yb versusSm (B), and Sm/Yb versus La/Sm (C) for the Pozanti-Karsanti dikes. The modeled melting curves are fromAldanmaz et al. (2000); depleted mid-ocean ridge basalt(MORB) mantle (DMM) is from the compilation of Mc-Kenzie and O’Nions (1991, 1995); primitive mantle (PM),normalMORB (N-MORB), and enrichedMORB (E-MORB)compositions are from Sun and McDonough (1989). En-riched mantle (EM) is the speculated EM source of theWesternAnatolianMantle byAldanmaz et al. (2000). Dataof mafic dikes (triangles), forearc, arc, and backarc rocksare from the same references as in figure 6. IBM p Izu-Bonin-Mariana.

234 D . L I AN E T A L .

sivemargin (Parlak andDelaloye 1999;Wakabayashiand Dilek 2000; Guilmette et al. 2009). Metamor-phic soles are commonly foundunderlying ophioliticmassifs within the Tauride belt and have been inter-preted to form during the intraoceanic subduction ofthe Neo-Tethyan Ocean (Thuizat et al. 1981; DilekandThy1992; Polat andCasey 1995; Polat et al. 1996;Parlak and Delaloye 1999). The ages of these meta-morphic soles have been dated through K-Ar and40Ar/39Ar methods and summarized by different au-thors (Dilek et al. 1999; Parlak and Delaloye 1999;Çelik et al. 2006, 2008). Ages of these metamorphicsoles range from 71 to 140 Ma, showing a relativelarge time span (Parlak and Delaloye 1999). Thuizatet al. (1981) report the K-Ar hornblende ages around94 Ma of the amphibolites from the PKO metamor-phic sole. Dilek et al. (1999) reported another two40Ar/39Ar hornblende ages of 91.7 and 90.4 Ma. Çeliket al. (2006) published 40Ar/39Ar ages of 92.4 Ma forwhite mica from the PKO mica schist in the PKO.The ages of the PKO metamorphic sole are close totheweightedmean age (92.6Ma) of themetamorphicsole from the Mersin ophiolite (Parlak and Delaloye1999).Because the metamorphic sole underlying the

PKO is intruded by the mafic dikes, these dikes canalso provide constraints on the age of intraoceanicsubduction. Dilek andThy (1992) reported 40Ar/39Arages of 140 5 6 Ma for the mafic dikes from thePKO. However, Parlak and Delaloye (1996) pub-lished younger 40Ar/39Ar ages ranging from 89.6 50.7 to 63.95 0.9Ma for themafic dikes cutting boththe mantle tectonites and metamorphic sole. Thus,there is still a large time span for these dikes. ZirconU-Pb dating of one of these mafic dikes describedabove yields amean 206Pb/238U age of 86.95 3.1Ma,supporting the age results of the metamorphic solereported by Thuizat et al. (1981) and Dilek et al.(1999). Thus, intraoceanic subduction of the Neo-Tethyan Ocean of the eastern Tauride part musthave taken place at least before 90 Ma.

Summary and Conclusions

Mafic dikes with gabbroic and doleritic textures in-trude the PKOand theunderlyingmetamorphic sole,and no dikes have been observed in the Aladag mé-lange. Thesemafic dikes have basaltic-andesitic com-position and LREE-depleted chondrite-normalizedFigure 12. Plots of Th/Yb versus Nb/Yb (A), V versus

Ti/1000 (B), and V versus Yb (C) for the Pozanti-Karsantidike rocks. A and B are after Pearce (2014); C is afterPearce and Parkinson (1993). Data of mafic dikes (tri-angles), forearc, arc, and backarc rocks are from the samereferences as in figure 6. BABBp backarc basin basalt; E-MORBp enrichedmid-ocean ridge basalt; FABp forearcbasalt; IAT p island arc tholeiite; IBM p Izu-Bonin-

Mariana; N-MORBp normalMORB;OIBp ocean islandbasalt; QFM p quartz-fayalite-magnetite; SZ p supra-subduction zone.

Journal of Geology 235O R I G I N O F MA F I C D I K E S

REE patterns. In the primitive mantle–normalizedtrace element diagram, the Pozanti-Karsanti dikesshow negative anomalies in HFSE (such as Nb, Ta,and Ti) and variable enrichments in LILEs (such asRb, Ba, and U). These dikes have less radiogenicNd isotopes but more radiogenic Sr isotopes thanthe DMM mantle source. On the basis of meltingmodels ofmantle sources of different facies using La,Sm, and Yb, we conclude that these dikes originatedfrom Sp or Sp 1 Grt facies (Sp 1 Grt) mantle. TheLREE and HFSE depleted characteristic combinedwith positive εNd(t) values suggest that these dikeswere derived from a depleted mantle source similarto those of MORB. However, the relatively higherTh/Nb ratios than MORB imply the addition of asubduction component in the Pozanti-Karsanti dikes.The oxygen fugacities of the Pozanti-Karsanti dikesare aroundQFMhigher than those ofMORB (QFM-1)but lower than IAB (QFM1 1). Through comparisonstudies of the Pozanti-Karsanti dikes with volcanicrocks from the IBM arc-basin system, we proposethat the Pozanti-Karsanti dikes formed in the fore-arc environment during intraoceanic subduction. Zir-conU-Pb ages suggest that the emplacement of thesedikes occurred at 86.9 5 3.1 Ma.

On the basis of previous studies and our newworkon the PKO, we conclude that this ophiolite formedduring the subduction initiation of the intraoceanicsubduction. The mantle part of the PKO may repre-sent the melting residue of the upwelling fertile as-thenosphere due to the incipient trench rollback.Fluids from the subducting slab induced a high de-gree of partial melting of the mantle peridotites,generating the high CaO/Al2O3 melts for the cumu-late sequence of this ophiolite. Continued subduc-tion resulted in the formation of the metamorphicsole and the emplacement of mafic dikes in the LateCretaceous.

ACKNOWL EDGMENT S

We thank W. Zhou from the China University ofGeosciences (Wuhan) and Turkish geologists forassistance in the fieldwork and the China NationalResearch Center for the geochemical analyses. Weappreciate B. Shi from the Chinese Academy ofGeological Sciences for the cathodoluminescenceimaging of the zircons. We would also like to thankM.Wiedenbeck,A.Rocholl, P. T.Robinson, and J.A.Pearce for their valuable suggestions in modifyingthis manuscript. Two reviewers and the editors aregreatly appreciated for their critical and constructivecomments and suggestions that greatly improvedthe manuscript. This research was funded by grants

Figure 13. Tectonic discrimination diagrams for rocksof the Pozanti-Karsanti mafic dikes. A, Hf/3-Th-Ta dia-gram, after Wood et al. (1979). B, Zr/Y versus Zr diagram,after Pearce andNorry (1979).C, Cr-Y diagram, after Pearceet al. (1984). Data ofmafic dikes (triangles), forearc, arc, andbackarc rocks are from the same references as in figure 6.IAT p island arc tholeiite; IBM p Izu-Bonin-Mariana;MORB p mid-ocean ridge basalt; VAB p volcanic arc ba-salt; WPB p within-plate basalt.

236 D . L I AN E T A L .

from the China Scholarship Council, the Ministry ofScience and Technology of China (2014DFR21270),the China Geological Survey (121201102000150069,12120115027201, DD20160023-01, and 201511022),

the InternationalGeoscience Programme (IGCP-649),and the Fund from the State Key Laboratory of Con-tinental Tectonics and Dynamics (Z1301-a20 andZ1301-a22).

R E F E R E NC E S C I T E D

Aldanmaz, E.; Pearce, J. A.; Thirlwall,M. F.; andMitchell,J. G. 2000. Petrogenetic evolution of late Cenozoic,post-collision volcanism in western Anatolia, Turkey.J. Volcanol. Geotherm. Res. 102:67–95.

American Geological Institute. 1972. Penrose field con-ference on ophiolites. Geotimes 17:24–25.

Andersen, T. 2002. Correction of common lead in U-Pbanalyses that do not report 204Pb. Chem. Geol. 192:59–79.

Andrew, T., and Robertson, A. H. 2002. The Beyşehir-Hoyran-Hadim Nappes: genesis and emplacement ofMesozoic marginal and oceanic units of the northernNeotethys in southern Turkey. J. Geol. Soc. Lond.159:529–543.

Cakir,U. 1978. Pétrologie dumassif ophiolitiquedePozanti-Karsanti (Taurus Cilicien, Turquie): étude de la partiecentrale. PhD dissertation, Université de Strasbourg.

Çelik, O. F. 2007.Metamorphic sole rocks and theirmaficdykes in the eastern Tauride belt ophiolites (southernTurkey): implications for OIB-type magma generationfollowing slab break-off. Geol. Mag. 144:849–866.

———. 2008. Detailed geochemistry and K-Ar geochro-nology of the metamorphic sole rocks and their maficdykes from the Mersin ophiolite, southern Turkey.Turk. J. Earth Sci. 17:685–708.

Çelik, Ö. F., andMichel, D. 2003. Origin of metamorphicsoles and their post-kinematic mafic dyke swarms inthe Antalya and Lycian ophiolites, SWTurkey. Geol. J.3/4:235–256.

Çelik, Ö. F.; Michel, D.; and Gilbert, F. 2006. Precise40Ar–39Ar ages from the metamorphic sole rocks of theTauride Belt Ophiolites, southern Turkey: implica-tions for the rapid cooling history. Geol. Mag. 2:213–227.

Dilek, Y., and Thy, P. 1992. Structure, petrology andgeochronology of mafic dike intrusions in the Tauridebelt (S. Turkey) and implications for the Neotethyanpaleogeography. EOS: Trans. Am. Geophys. Union73:546.

Dilek, Y.; Thy, P.; Hacker, B.; and Grundvig, S. 1999.Structure and petrology of Tauride ophiolites andmaficdike intrusions (Turkey): implications for the Neoteth-yan ocean. Geol. Soc. Am. Bull. 111:1192–1216.

Elliott, T.; Plank, T.; Zindler, A.;White,W.; and Bourdon,B. 1997. Element transport from slab to volcanic frontat theMariana arc. J. Geophys. Res. 102:14,991–15,019.

Frey, F. A.; Green, D. H.; and Roy, S. D. 1978. Integratedmodels of basalt petrogenesis: a study of quartz tholei-ites to olivine melilitites from south eastern Australiautilizing geochemical and experimental petrologicaldata. J. Petrol. 19:463–513.

Guilmette, C.; Hébert, R.; Wang, C.; and Villeneuve, M.2009. Geochemistry and geochronology of the meta-morphic sole underlying the Xigaze ophiolite, YarlungZangbo Suture Zone, south Tibet. Lithos 112: 149–162.

Hart, S. R. 1984. A large-scale isotope anomaly in theSouthern Hemisphere mantle. Nature 309:753–757.

Irvine, T., and Baragar, W. 1971. A guide to the chemicalclassification of the common volcanic rocks. Can. J.Earth Sci. 8:523–548.

Juteau, T. 1980. Ophiolites of Turkey. Ofioliti 2:199–237.Ketin, I. 1966. Tectonic units of Anatolia (Asia Mi-

nor). MTA Bull 66:23–34.Le Bas, M. J.; Le Maitre, R. W.; Streckeisen, A.; and Za-

nettin, B. 1986. A chemical classification of volcanicrocks based on the total alkali-silica diagram. J. Petrol.27:745–750.

Liu, F.; Yang, J.; Dilek, Y.; Xu, Z.; Xu, X.; Liang, F.; Chen,S.; and Lian, D. 2015. Geochronology and geochemis-try of basaltic lavas in the Dongbo and Purang ophio-lites of the Yarlung-Zangbo Suture zone: plume-influenced continentalmargin-type oceanic lithospherein southern Tibet. Gondwana Res. 27:701–718.

Ludwig, K. R. 2003. User’s manual for Isoplot 3.00: a geo-chronological toolkit for Microsoft Excel. Berkeley,Berkeley Geochronology Center.

Lytwyn, J. N., and Casey, J. F. 1995. The geochemistry ofpostkinematic mafic dike swarms and subophioliticmetabasites,Pozanti-Karsanti ophiolite,Turkey: evidencefor ridge subduction. Geol. Soc. Am. Bull. 107: 830–850.

Mahoney, J. J.; Frei, R.; Tejada, M.; Mo, X. X.; Leat, P. T.;and Nägler, T. F. 1998. Tracing the Indian Oceanmantle domain through time: isotopic results from oldWest Indian, East Tethyan, and South Pacific seafloor.J. Petrol. 39:1285–1306.

McKenzie, D. P., and O’Nions, R. K. 1991. Partial meltdistributions from inversion of rare earth element con-centrations. J. Petrol. 32:1021–1091.

———. 1995. The source regions of ocean island basalts.J. Petrol. 36:133–159.

Moix, P.; Beccaletto, L.; Kozur, H. W.; Hochard, C.;Rosselet, F.; and Stampfli, G. M. 2008. A new classi-fication of the Turkish terranes and sutures and itsimplication for the paleotectonic history of the region.Tectonophysics. 451:7–39.

Okay, A. I. 2008. Geology of Turkey: a synopsis. Ansch-nitt 21:19–42.

Özgül, N. 1976. Toroslar’in bazi temel jeoloji özellikleri.Bull. Geol. Soc. Turkey 19:65–78.

Parkinson, I. J., and Pearce, J. A. 1998. Peridotites from theIzu-Bonin-Mariana forearc (ODP Leg 125): evidence for

Journal of Geology 237O R I G I N O F MA F I C D I K E S

mantle melting and melt-mantle interaction in a supra-subduction zone setting. J. Petrol. 39:1577–1618.

Parlak, O., and Delaloye, M. 1996. Geochemistry andtiming of post-metamorphic dyke emplacement in theMersin ophiolite (southernTurkey): newage constraintsfrom 40Ar/39Ar geochronology. Terra Nova 8: 585–592.

———. 1999. Precise 40Ar/39Ar ages from the meta-morphic sole of the Mersin ophiolite (southern Tur-key). Tectonophysics 301:145–158.

Parlak, O.; Höck, V.; and Delaloye, M. 2000. Suprasub-duction zone origin of the Pozanti-Karsanti ophiolite(southern Turkey) deduced from whole-rock and min-eral chemistry of the gabbroic cumulates. Geol. Soc.Lond. Spec. Publ. 173:219–234.

———. 2002.The supra-subduction zonePozanti-Karsantiophiolite, southern Turkey: evidence for high-pressurecrystal fractionation of ultramafic cumulates. Lithos65:205–224.

Parlak, O.; Hoeck, V.; Kozlu, H.; and Delaloye, M. 2004.Oceanic crust generation in an island arc tectonicsetting, SE Anatolian orogenic belt (Turkey). Geol.Mag. 141:583–603.

Parlak, O.; Karaoğlan, F.; Rızaoğlu, T.; Klötzli, U.; Koller,F.; and Billor, Z. 2013. U–Pb and 40Ar–39Ar geochro-nology of the ophiolites and granitoids from the Tau-ride belt: implications for the evolution of the InnerTauride suture. J. Geodyn. 65:22–37.

Parlak, O., and Robertson, A. 2004. The ophiolite-relatedMersin Melange, southern Turkey: its role in thetectonic–sedimentary setting of Tethys in the EasternMediterranean region. Geol. Mag. 141:257–286.

Pearce, J. A. 2008. Geochemical fingerprinting of oceanicbasalts with applications to ophiolite classification andthe search forArcheanoceanic crust. Lithos100: 14–48.

———. 2014. Immobile element fingerprinting of ophio-lites. Elements 10:101–108.

Pearce, J. A.; Kempton, P. D.; Nowell, G. M.; and Noble,S. R. 1999. Hf-Nd element and isotope perspectiveon the nature and provenance of mantle and subduc-tion components in Western Pacific arc-basin sys-tems. J. Petrol. 40:1579–1611.

Pearce, J. A.; Lippard, S. J.; and Roberts, S. 1984. Charac-teristics and tectonic significance of supra-subductionzone ophiolites. Geol. Soc. Lond. Spec. Publ. 16:77–94.

Pearce, J. A., and Norry, M. J. 1979. Petrogenetic impli-cations of Ti, Zr, Y, and Nb variations in volcanicrocks. Contrib. Mineral. Petrol. 69:33–47.

Pearce, J. A., and Parkinson, I. J. 1993. Trace elementmodels for mantle melting: application to volcanic arcpetrogenesis. Geol. Soc. Lond. Spec. Publ. 76:373–403.

Pearce, J. A.; Stern, R. J.; Bloomer, S. H.; and Fryer, P. 2005.Geochemical mapping of the Mariana arc-basin system:implications for the nature and distribution of subduc-tioncomponents.Geochem.Geophys.Geosyst. 6:Q07006.

Polat, A., and Casey, J. F. 1995. A structural record of theemplacement of the Pozanti-Karsanti ophiolite onto theMenderes-Taurus block in the late Cretaceous, easternTaurides, Turkey. J. Struct. Geol. 17:1673–1688.

Polat, A.; Casey, J. F.; and Kerrich, R. 1996. Geochem-ical characteristics of accreted material beneath thePozanti-Karsanti ophiolite, Turkey: intra-oceanic de-tachment, assembly and obduction. Tectonophysics263:249–276.

Reagan, M. K.; Ishizuka, O.; Stern, R. J.; Kelley, K. A.;Ohara, Y.; Blichert Toft, J.; Bloomer, S. H.; Cash, J.;Fryer, P.; and Hanan, B. B. 2010. Fore-arc basalts andsubduction initiation in the Izu-Bonin-Mariana sys-tem. Geochem. Geophys. Geosyst. 11:Q03X12.

Robertson, A. H. F. 2002. Overview of the genesis andemplacement of Mesozoic ophiolites in the EasternMediterranean Tethyan region. Lithos 65:1–67.

Robertson, A. H. F., and Dixon, J. E. 1984. Introduction:aspects of the geological evolution of the EasternMediterranean. Geol. Soc. Lond. Spec. Publ. 17:1–74.

Robertson, A. H. F.; Parlak, O.; and Ustaömer, T. 2009.Melange genesis and ophiolite emplacement relatedto subduction of the northern margin of the Tauride–Anatolide continent, central andwesternTurkey.Geol.Soc. Lond. Spec. Publ. 311:9–66.

———. 2012. Overview of the Palaeozoic-Neogene evo-lution of Neotethys in the Eastern Mediterranean re-gion (southern Turkey, Cyprus, Syria). Petrol. Geosci.18:381–404.

Saka, S.; Uysal, I.; Akmaz, R. M.; Kaliwoda, M.; andHochleitner, R. 2014. The effects of partial melting,melt-mantle interaction and fractionation on ophio-lite generation: constraints from the late CretaceousPozantı-Karsantı ophiolite, southern Turkey. Lithos2014:300–316.

Sengör, A. M., and Yilmaz, Y. 1981. Tethyan evolution ofTurkey: a plate tectonic approach. Tectonophysics 75:181–241.

Stern, R. J. 2004. Subduction initiation: spontaneous andinduced. Earth Planet. Sci. Lett. 226:275–292.

Sun, S., and McDonough, W. F. 1989. Chemical and iso-topic systematics of oceanic basalts: implications formantle composition and processes. Geol. Soc. Lond.Spec. Publ. 42:313–345.

Tekeli, O.; Aksay, A.; Urgun, B. M.; and Isik, A. 1984.Geology of the Aladag mountains. In Tekeli, O., andGöncüoğlu, M. C., eds. The geology of the Taurus Belt.Ankara, MTA, p. 143–158.

Thuizat, R.; Whitechurch, H.; Montigny, R.; and Juteau,T. 1981. K-Ar dating of some infra-ophiolitic meta-morphic soles from the Eastern Mediterranean: newevidence for oceanic thrustings before obduction. EarthPlanet. Sci. Lett. 52:302–310.

Wakabayashi, J., and Dilek, Y. 2000. Spatial and temporalrelationships between ophiolites and their metamor-phic soles: a test of models of forearc ophiolite genesis.Geol. Soc. Am. Spec. Pap. 349, p. 53–64.

Wakabayashi, J.; Ghatak, A.; and Basu, A. R. 2010.Suprasubduction-zone ophiolite generation, emplace-ment, and initiation of subduction: a perspective fromgeochemistry, metamorphism, geochronology, and re-gional geology. Geol. Soc. Am. Bull. 122:1548–1568.

238 D . L I AN E T A L .

Wang, Y.; Yang, J.; Chen, J.; Zhang, K.; and Rao, W.2007. The Sr and Nd isotopic variations of the Chi-nese Loess Plateau during the past 7 Ma: implica-tions for the East Asian winter monsoon and sourceareas of loess. Palaeogeogr. Palaeoclimatol. Palaeo-ecol. 249:351–361.

Whattam, S. A., and Stern, R. J. 2011. The “subductioninitiation rule”: a key for linking ophiolites, intra-oceanic forearcs, and subduction initiation. Contrib.Mineral. Petrol. 162:1031–1045.

White, W. H., and Patchett, J. 1984. Hf-Nd-Sr isotopesand incompatible element abundances in island arcs:implications for magma origins and crust-mantle evo-lution. Earth Planet. Sci. Lett. 67:167–185.

Whitechurch, H.; Juteau, T.; andMontigny, R. 1984. Roleof the EasternMediterranean ophiolites (Turkey, Syria,Cyprus) in the history of the Neo-Tethys. Geol. Soc.Lond. Spec. Publ. 17:301–317.

Wood,D.A.; Joron, J. L.; andTreuil,M. 1979.A re-appraisalof the use of trace elements to classify and discriminatebetween magma series erupted in different tectonicsettings. Earth Planet. Sci. Lett. 45:326–336.

Xu, J., and Castillo, P. R. 2004. Geochemical and Nd-Pbisotopic characteristics of the Tethyan asthenosphere:implications for the origin of the Indian Ocean mantledomain. Tectonophysics 393:9–27.

Zindler, A., and Hart, S. 1986. Chemical geodynamics.Annu. Rev. Earth Planet. Sci. 14:493–571.

Journal of Geology 239O R I G I N O F MA F I C D I K E S