In this section geological, petrological and geochronological data on ophiolites from the western to eastern Taurides will be presented together with recent unpublished observations. A summary of the Tauride ophiolites is given in Table 1.
Ophiolites Radiometric age Protolith of metamorphic sole Mantle rocks Cr# Crustal rocks Proposed tectonic setting References Lycian ophiolites (Köyceğiz & Yeşilova) 93-90 Ma Ar-Ar metamorphic sole;
90-63 Ma K-Ar isolated dyke
N-MORB, WPA and IAT basalts Serpentinized harzburgite, dunite with chromite pods and pyroxenite Low Cr# (13-22)
High Cr# (33-83)
Ultramafic to mafic cumulates, isolated dykes Suprasubduction zone (SSZ) Uysal et al., 2012; Aldanmaz et al., 2009; Çelik and Chiaradia, 2008; Çelik et al., 2006 Tekirova (Antalya) 93 Ma Ar-Ar metamorphic sole IAT basalts Serpentinized harzburgite, dunite with chromite pods and pyroxenite Low Cr# (18-39.6)
High Cr# (33.2-77.8)
Ultramafic to mafic cumulates, isotropic gabbro, sheeted dykes, isolated dykes and volcanic rocks Suprasubduction zone (SSZ) Caran et al., 2010; Bağcı and Parlak, 2009, Bağcı et al., 2006; Çelik et al., 2006 Beyşehir-Hoyran ophiolites (Şarkikaraağaç, Madenli & Gencek) 91 Ma Ar-Ar metamorphic sole WPA and IAT basalts Serpentinized harzburgite, dunite with chromite pods and pyroxenite High Cr# (40-90) Isolated dykes Suprasubduction zone (SSZ) Elitok and Drüppel, 2008; Çelik and Delaloye, 2006; Çelik et al., 2006; Andrew and Robertson, 2002 Mersin ophiolite 96-91 Ma Ar-Ar metamorphic sole;
91-63 Ma Ar-Ar post-metamorphic isolated dyke;
83 Ma zircon U-Pb gabbro
N-MORB, WPA and IAT basalts Serpentinized harzburgite, dunite with chromite pods and pyroxenite High Cr# (60-80) Ultramafic to mafic cumulates, volcanics rocks and isolated dykes Suprasubduction zone (SSZ) Parlak et al., 2013, 1996; Çelik, 2008; Parlak and Robertson, 2004; Parlak and Delaloye, 1999, 1996; Dilek et al., 1999 Alihoca (Bolkardağ) ophiolite 90 Ma Ar-Ar metamorphic sole;
90 Ma, Ar-Ar post-metamorphic isolated dyke
- Serpentinized harzburgite, pyroxenite - Ultramafic to mafic cumulates, isotropic gabbro, volcanic rocks and isolated dykes Suprasubduction zone (SSZ) Dilek et al., 1999; Dilek and Whitney, 1997 Pozantı-Karsantı (Aladağ) ophiolite 92-90 Ma Ar-Ar metamorphic sole;
69 Ma zircon U-Pb gabbro
N-MORB, WPA and IAT basalts Serpentinized harzburgite, dunite with chromite pods and pyroxenite High Cr# (44-70) Ultramafic-mafic cumulates, isotropic gabbros with plagiogranite and isolated dykes Suprasubduction zone (SSZ) Saka et al., 2014; Parlak et al., 2013, 2002, 2000; Çelik, 2007; Çelik et al., 2006; Dilek et al., 1999; Lytwyn and Casey, 1995 Pınarbaşı (Kayseri) ophiolite 65 Ma zircon U-Pb isolated dyke WPA and IAT basalts Serpentinized harzburgite, dunite with chromite pods and pyroxenite - Ultramafic to mafic cumulates, isolated dykes Suprasubduction zone (SSZ) Parlak et al., 2013; Vergili and Parlak, 2005 Divriği (Sivas) ophiolite 89-87 Ma Ar-Ar metamorphic sole;
76 Ma Ar-Ar post-metamorphic isolated dyke;
89 Ma zircon U-Pb gabbro
WPA and IAT basalts Serpentinized harzburgite, dunite with chromite pods and lherzolite - Ultramafic-mafic cumulates, isotropic gabbros, sheeted dykes and isolated dykes Suprasubduction zone (SSZ) Parlak et al., 2013, 2006, 2005 Cr#=100×Cr/(Cr+Al); IAT. Island arc tholeiite; WPA. within plate alkali; N-MORB. normal mid-ocean-ridge-basalt.
Table 1. Summary of the characteristics of the Tauride belt ophiolites
The well-known Lycian nappes are an important part of the Tethyan orogenic belt in southwest Turkey and have been the focus of research since the early 1970's (Collins and Robertson, 1999, 1997; Okay, 1989; Şenel et al., 1989; Poisson, 1977; De Graciansky, 1972). Five major tectonostratigraphic units have been defined in ascending order as: (1) the autochthonous basement (Menderes metamorphic complex and Beydağları Platform), (2) the carbonate-dominated Lycian thrust sheet, (3) the Lycian mélange, (4) the Lycian ophiolites and (5) a Paleogene transgressive unit above the Lycian mélange (Collins and Robertson, 1999, 1997).
The Lycian ophiolites in SW Turkey are mainly exposed in the Köyceğiz (Muğla) and Yeşilova (Burdur) regions (Figs. 2, 3). In both regions, the Lycian ophiolites display similar tectonostratigraphy to other ophiolites along the Taurides (Fig. 4). The Lycian mélange consists of two intergradational subunits, a layered tectonic mélange and an ophiolitic mélange (Collins and Robertson, 1997). The mélange sub-units are unconformably overlain by Paleocene to Eocene shallow water limestones (Şenel et al., 1989; Poisson, 1977). The mélange unit and the overlying limestones interleaved due to Eocene thrusting (Collins and Robertson, 1997). The layered tectonic mélange is mainly composed of thrust sheets of pelagic limestones that are separated by fragmented radiolarian cherts, black metalliferous cherts and litharenites set in a greenish clay matrix, with top to the southeast shear sense indicators (Collins and Robertson, 1999). The layered tectonic mélange is tectonically overlain by an ophiolitic mélange that consists of blocks of siliceous marble, basalt, gabbro, radiolarian chert and peridotite in a highly-deformed matrix of conglomerate, siltstone, claystone and sandstone (Collins and Robertson, 1999, 1997). A semi-coherent sheet of Mesozoic neritic limestone unit is also enclosed within the ophiolitic mélange. Blocks of basaltic volcanics within the ophiolitic mélange have mid-ocean-ridge (MOR) to within plate geochemical affinities (Collins and Robertson, 1997; Sarp, 1976). The Lycian mélange has been interpreted as an accretionary complex emplaced in the Late Cretaceous (Collins and Robertson, 1997).
Figure 2. Geological map of the western part of the Lycian ophiolites in the Köyceğiz area (De Graciansky, 1972).
Figure 3. Geological map of the eastern part of the Lycian ophiolites in Yeşilova region (Sarp, 1976).
Metamorphic sole rocks in the Yeşilova (Burdur) region are exposed beneath mantle tectonites northwest of Salda Lake, where they generally strike N-S and dip E/W (Fig. 3). They display granoblastic to lepidoblastic textures and are characterized by amphibolite, plagioclase amphibolite, amphibole schist, epidote-plagioclase amphibolite, calcschist, quartz-mica schist and marble (Sarp, 1976). The metamorphic sole is cut by 1.5–3 m isolated thick diabase dykes in the Değirmendere valley (Fig. 3). In the Köyceğiz (Muğla) region, a tectonic contact between the metamorphic sole and mantle tectonites is intruded by a post-metamorphic diabase dyke (Figs. 5a, 5b). The metamorphic sole beneath the mantle tectonites exhibits well developed foliation, dipping northwards (090°/40°N) (Fig. 5a). It is composed of garnet amphibolite, amphibolite, plagioclase amphibolite, epidote amphibolite, epidosite, micaschist, calcschist and marble (Figs. 5c, 5d, 5e). The metamorphic sole is highly deformed, folded and faulted, and up to 350 m thick (Çelik and Delaloye, 2003). Micaschists and calcschists are tectonically intercalated with amphibolites. Individual post-metamorphic dykes cut the metamorphic sole at different structural levels.
Figure 5. (a) Cross section showing the field relations of mantle tectonites and their underlying metamorphic sole in the Köyceğiz area. Field views of (b) the isolated dyke cutting the intraoceanic decoupling surface between mantle peridotite and the metamorphic sole, (c) deformed alternations of calcschist and epidote-amphibolite, (d) foliated amphibolites, and (e) calcschist and amphibolite.
The Lycian ophiolites above the metamorphic sole consist exclusively of mantle tectonites enclosing enclaves of cumulates. The mantle tectonites predominantly comprise harzburgites (up to 95%), dunites (5%–10%) and pyroxenites (~1%) (Sarp, 1976). They are variably serpentinized and display plastic deformation indicated by alternations of harzburgite-pyroxenite-dunite-chromitite bands (Sarp, 1976). Orthopyroxenite, diallagite and websterite are rare in the mantle tectonites and occur either as discordant dykes or bands (Juteau, 1980; Sarp, 1976), usually exhibiting granoblastic and porphyroclastic textures. The cumulate enclaves in the tectonites consist of pyroxenite, olivine gabbro, gabbro, gabbronorite, anorthositic gabbro and anorthosite (Sarp, 1976). The whole peridotite body is crosscut at different structural levels by isolated dykes of gabbro and diabase with chilled margins (Fig. 4). A number of dykes in the severely serpantinized mantle tectonites have been affected by Ca-metasomatism (rodingitization) (Sarp, 1976).
The mantle peridotites in the Köyceğiz (Muğla) area are composed of Cpx-bearing harzburgite, depleted harzburgite and dunite (Uysal et al., 2012; Aldanmaz et al., 2009). Uysal et al. (2012) reported that the Cpx-harzburgites contain high CaO (2.27 wt.%) and Al2O3 (2.07 wt.%) together with low Cr contents in coexisting spinels (Cr#=100×Cr/(Cr/Al): 13–22). In contrast, the depleted harzburgites and dunites have low CaO (0.58 wt.%) and Al2O3 (0.42 wt.%) with high-Cr spinels (Cr#: 33–83). They concluded that the Cpx-harzburgites were derived from the first-stage of melting and low-degrees of melt-rock interaction that occurred in a mid-ocean ridge (MOR) environment during the opening stage of the Neotethyan oceanic basin, but the depleted harzburgites and dunites were the products of second-stage melting and related refertilization in a suprasubduction zone (SSZ) environment. The geochemistry of the amphibolites from the metamorphic sole in Yeşilova area suggests that they are alkaline in character and exclusively derived from ocean island alkaline basalts (Çelik and Delaloye, 2003), while in contrast, the amphibolites from the metamorphic sole in the Köyceğiz area exhibit tholeiitic to alkaline magma types and were derived from mid-ocean ridge basalts (MORB), within plate basalts and island arc basalts (Çelik and Delaloye, 2003). The isolated diabase/dolerite dykes intruding the metamorphic sole and mantle tectonites in the Köyceğiz (Muğla) and Yeşilova (Burdur) regions display pronounced Nb-depletion, indicating a subduction-related setting for their magma genesis (Çelik and Delaloye, 2003). Pressure-temperature conditions (P/T) under which the metamorphic sole rocks in the Köyceğiz and Yeşilova regions formed were ~550 ℃/~5 kbar and ~600 ℃/~5 kbar, respectively (Çelik, 2002).
Thuizat et al. (1981) reported varied K-Ar ages for different mineral separates from three samples from the metamorphic sole at the base of the Lycian ophiolites. These are 102±4 to 98±4 Ma for hornblende separates, 88±4 to 83±3 Ma for plagioclase separates and 93±3 Ma for muscovite separates (Thuizat et al., 1981). Çelik and Chiaradia (2008) also reported K-Ar ages ranging from 90 to 63 Ma for the dyke intrusions in the Yeşilova region. The new 40Ar/39Ar ages for the metamorphic sole rocks beneath the Lycian ophiolites (Köyceğiz and Yeşilova) tightly constrain the timing of intraoceanic thrusting as Late Cretaceous (Çelik et al., 2006). Hornblende separates of the amphibolites in the Köyceğiz area yielded ages of 93.1±0.9 to 93.0±0.9 Ma, similar to the white mica ages (93.6±0.8 to 91.7±0.7 Ma). The hornblende separates of the amphibolites in the Yeşilova area yielded 91.3±0.9 to 90.7±0.5 Ma ages and white mica yielded an age of 91.2±2.3 Ma (Çelik et al., 2006). The age dating in both areas indicates a rapid cooling history.
The Antalya complex in Southwest Turkey comprises a number of autochthonous (the Beydağları Platform) and allochthonous (e.g., Kumluca unit, Alakırçay mélange, Tekeli-Tahtalı Dağ unit and Tekirova ophiolite) sedimentary, magmatic and metamorphic rock assemblages, that originated from oceanic, oceanic to continental margin and continental settings (Yılmaz, 1984; Robertson and Woodcock, 1981a, b, c, 1980; Delaune-Mayere et al., 1977; Marcoux, 1976; Juteau, 1975; Brunn et al., 1971, 1970). The allochthonous units of the Antalya complex were emplaced onto the Mesozoic Beydağları Platform during the Late Cretaceous (Fig. 6).
Figure 6. Geological map of the Tekirova (Antalya) ophiolite (Juteau and Whitechurch, 1980).
The Tekirova ophiolite comprises, from bottom to top, mantle tectonites, ultramafic-mafic cumulates, isotropic gabbros, sheeted dykes, plagiogranite, mafic volcanic rocks and associated sediments (Fig. 7). Contacts between these units are tectonic. The mantle tectonites, ultramafic to mafic cumulates and isotropic gabbros are intruded by isolated diabase dykes (Fig. 7). Metamorphic sole rocks in Tekirova ophiolite are observed as isolated blocks.Mantle tectonites are observed in Adrasan, Çıralı, and Kemer as well as in an N-S trending tectonic zone between the Kumluca and Doyran regions (Fig. 6). The mantle tectonites display porphyroclastic to mylonitic textures and are predominantly harzburgites (> 80%) with lesser amounts of dunite, orthopyroxenite, and chromitite (Juteau et al., 1977). Although the mantle tectonites are variably serpentinized they present good foliation patterns in the field defined by spinel and orthopyroxene aspect ratios (Juteau et al., 1977). Dunites with chromite pods are common and penetratively deformed. The harzburgitic tectonites also include veinlets of pyroxenite and two-pyroxene gabbro (Juteau et al., 1977). Irregular lenses of gabbro and clinopyroxenite due to rock-melt interaction in the harzburgitic mantle are also present. The well-preserved ultramafic to mafic cumulate rocks in the Tekirova ophiolites crop out mainly along the coastal section at Çıralı-Tekirova and at Doyran to the north. Small outcrops of mafic cumulate rocks are tectonically dispersed in places such as Gödene, Kuzdere, Kemer, Kuvvettaş Dere and Ziyaret Tepe within the Gödene zone (Fig. 6). The undeformed ultramafic to mafic cumulates in the Çıralı-Tekirova section are strongly layered and exhibit structures such as slumping, cross-bedding, phase and mineral ratio layering and mineral graded layers indicative of cumulate processes in a magma chamber (Bağcı et al., 2006; Juteau et al., 1977). They consist of dunite, clinopyroxenite, and wehrlite at the base, followed upwards by olivine gabbro, olivine gabbronorite and gabbro at the top. Four magmatic cycles were recognized with a total thickness of 3 to 4 km (Juteau and Whitechurch, 1980; Juteau et al., 1977). The dunite layers at the bottom also contain chromitite bands (Juteau et al., 1977). The isotropic gabbros crop out in the Kuzdere and Kemer regions (Fig. 6) and are represented by gabbro, diorite and quartz diorite. Small-scale plagiogranitic intrusions cut the isotropic gabbros at the Kemer junction. The mantle tectonites, ultramafic to mafic cumulates and isotropic gabbros are intruded by isolated dykes. Sheeted dykes are exposed locally north of Kemer and represented by panels of more or less brecciated diabase dykes, hosted by isotropic gabbros (Juteau, 1975). Volcanic rocks of the ophiolite suite are observed within the Gödene zone. Pelagic chalks interbedded with the volcanic rocks yielded a Late Cretaceous age (Robertson and Woodcock, 1982). A volcanic unit composed of mafic pillow lava interbedded with Late Triassic and Late Jurassic–Early Cretaceous pelagic sediments of the Alakırçay mélange is present (Robertson and Waldron, 1990; Marcoux, 1970).
Figure 7. Reconstructed column section of the Tekirova (Antalya) ophiolite (Juteau, 1975)
Geochemical data for the mantle peridotites of the Tekirova ophiolite exhibit a fertile to ultra-refractory character reflected by a progressive decrease in bulk rock contents of Al2O3, CaO, SiO2, TiO2, Sc, V, Y and an increase in magnesium numbers (Mg#=100×Mg/(Mg+Fe+2)) and spinel chromium numbers (Cr#: 18.0–39.6 in spinel lherzolites, 33.2–77.8 in harzburgites, and 68.7–72.2 in dunites) (Caran et al., 2010). The chondrite-normalized REE patterns of the spinel lherzolites are compatible with a residue of a low degree of partial melting of N-MOR mantle (Caran et al., 2010) the harzburgites although show 'V-shaped' REE distribution patterns similar to those of forearc harzburgites. The harzburgites could be residues from interaction of a previously melted mantle source with an ascending LREE-enriched melt in a suprasubduction zone environment. The dunites and the most refractory peridotites formed by dissolution of pyroxene from the host harzburgites during melt-mantle interaction (Caran et al., 2010). The podiform chromitites are composed of a very refractory olivine-spinel assemblage (Fo: 94.8 and 96.1 and Cr#: 72.2–81.2), suggesting formation from a boninitic magma (Caran et al., 2010). The ultramafic and mafic cumulate rocks in the Tekirova ophiolite are wehrlite, lherzolite, olivine clinopyroxenite, olivine gabbronorite, olivine gabbro, gabbronorite and gabbro (Bağcı et al., 2006). The order of crystallization in the cumulates is olivine (Fo88–76)±chromian spinel±clinopyroxene (Mg#92–76)± orthopyroxene (Mg#86–70)±plagioclase (An97–84). The whole-rock mineral chemistry, crystallization order of mineral phases, and high-An content of plagioclase in the cumulate rocks indicate that the Tekirova (Antalya) ophiolite formed in a suprasubduction zone environment (Bağcı et al., 2006). Limited cryptic variation through the cumulate rocks of the Tekirova ophiolite suggests that they crystallized from a compositionally uniform magma (Bağcı et al., 2006). The isotropic gabbros and the isolated dykes cutting the mantle tectonites and the crustal rocks exhibit tholeiitic to alkaline compositions. Three main types of parental basic magmas formed the oceanic crustal rocks of the Tekirova (Antalya) ophiolite: (1) island arc tholeiites (IAT), (2) low-Ti boninites and (3) ocean island basalts (OIB) (Bağcı and Parlak, 2009). The geochemical evidence suggests that the crustal rocks of the Tekirova (Antalya) ophiolite were generated by progressive source depletion from island arc tholeiites (IAT) to boninites and therefore, a fore-arc tectonic setting seems likely for the generation of the crustal rocks (Bağcı and Parlak, 2009). The OIB-type alkaline isotropic gabbros are thought to have resulted from either; (1) late-stage magmatic activity fed by melts that originated from an asthenospheric window created by slab break-off or (2) subduction of a ridge system which generated an OIB source across the asthenospheric window (Bağcı and Parlak, 2009). Robertson and Waldron (1990) reported occurences of Late Triassic and Late Jurassic–Early Cretaceous basaltic extrusives in the Antalya complex. The Late Triassic lavas are associated with radiolarites, pelagic limestones, turbidites and patch reefs, and range from within plate to transitional and MORB-type basalts (Robertson and Waldron, 1990) whereas the Late Jurassic–Early Cretaceous basalts exhibit a MORB-type geochemical character and may reflect renewed spreading within a pre-existing Antalya ocean basin (Robertson and Waldron, 1990).
The magmatic and the metamorphic rocks associated with the Tekirova (Antalya) ophiolites have been dated by K-Ar and 40Ar/39Ar geochronology. The magmatic rocks (gabbro, diabase, plagiogranite) and the metamorphic rocks from the Alakırçay mélange as well as the Tekirova ophiolite yielded very scattered (130 to 60 Ma) K-Ar cooling ages (Yılmaz, 1984). Thuizat et al. (1981) reported 94±4 Ma hornblende and 102±7 Ma plagioclase K-Ar ages for garnet amphibolites from the metamorphic sole in the Antalya complex. Recent 40Ar/39Ar dating of hornblende separates from the metamorphic sole within the Alakırçay mélange have yielded more reliable Late Cretaceous ages (93.8±1.7 and 93.0±1.0 Ma) (Çelik et al., 2006).
The Beyşehir-Hoyran Nappes include Mesozoic carbonate platform deposits, deep sea sediments and ophiolite-related units (ophiolitic mélange, metamorphic sole and ophiolite) and crop out extensively on the western limb of the Isparta Angle of the central Taurides (Andrew and Robertson, 2002; Özgül, 1984; Monod, 1977; Özgül and Arpat, 1973). The ophiolite-related rock assemblages are well exposed both to the north and south of Lake Beyşehir (Fig. 1).
In the northern part of the Lake Beyşehir area, the ophiolitic rocks are seen at two localities, namely Madenli and Şarkikaraağaç (Figs. 8, 9). The ophiolitic rocks in the Şarkikaraağaç area tectonically overlie the Anamas-Akseki Platform in the west and Sultandağ Platform in the east. The contact relations between the two sides are not clear because the area is covered by Neogene sediments (Fig. 8). On the Anamasdağ side, the ophiolite-related rocks are represented by harzburgitic mantle tectonites at the top, underlain downwards by a subophiolitic metamorphic sole and mélange (Fig. 10). The harzburgites exhibit medium-grained granoblastic texture and are characterized by forsteritic olivine (Mg#92–93), orthopyroxene and minor chromian spinel and diplay mylonitic textures at the basal thrust contact (Elitok and Drüppel, 2008). Isolated diabase dykes intrude the mantle tectonites. A thin sheet of highly-deformed metamorphic sole rocks, up to 140 m thick, tectonically underlies the harzburgitic mantle tectonites (Elitok and Drüppel, 2008). These rocks directly beneath the mantle tectonites mainly exhibit granoblastic to nematoblastic textures and are composed of pyroxene amphibolite and amphibolite, followed by epidote amphibolite, plagioclase amphibolite, calcschist and quartzite towards the bottom (Elitok and Drüppel, 2008). The metamorphic sole is cut by isolated post-metamorphic diabase dykes as in the other Tauride ophiolites. On the Sultandağ side, relatively fresh harzburgitic mantle tectonites with minor pyroxenite veins rest tectonically on an ophiolitic mélange. The harzburgites are intruded by isolated diabase dykes at different structural levels (Elitok and Drüppel, 2008). In both regions, the ophiolites are tectonically underlain by ophiolitic mélanges that contain blocks of recrystallized limestone, gabbro, isolated diabase, radiolarite, cherts, and silicaclastic rocks set in a strongly sheared serpentinite matrix (Elitok and Drüppel, 2008). The ophiolite-related units in both areas are overthrust by Upper Triassic massive neritic limestones and wildflysch deposits. The limestone unit in the Central Taurides is known as the Gencek unit (Monod, 1977) or Boyalı Tepe unit (Andrew and Robertson, 2002). Both the Gencek and the Boyalı Tepe units consist of blocks and dismembered thrust sheets in a sandy wildflysch matrix (Andrew and Robertson, 2002). Allochthonous units, namely metamorphic sole rocks, mantle tectonites, the Gencek unit and wildflysch are exposed In the Madenli area (Fig. 9). The metamorphic sole rocks beneath the mantle tectonites are highly deformed and characterized by amphibolites and epidote amphibolites and are intruded by isolated diabase dykes (Figs. 11a, 11b, 11c). The strongly sheared serpentinized harzburgites rest tectonically on the metamorphic sole and are followed upward by thrust slices of Upper Triassic massive neritic limestones (Fig. 11a) of the Gencek or Boyalı Tepe units and wildflysch deposits (Andrew and Robertson, 2002; Monod, 1977), as in the Şarkikaraağaç area.
Figure 8. Geological map of the Şarkikaraağaç area (Elitok and Drüppel, 2008).
Figure 9. Geological map of the Madenli area (Elitok and Drüppel, 2008).
Figure 11. (a) Cross section showing the field relations of the mantle tectonites, underlying metamorphic sole and the limestone thrust sheet in Madenli area. Field views of (b) the foliated amphibolite and (c) isolated dyke in the metamorphic sole in Madenli.
In the southern part of the Lake Beyşehir area, the ophiolite-related rock assemblages are exposed as thrust slices between the Hadim nappe and the Gencek unit around Gencek Village (Figs. 12, 13). The ophiolitic mélange unit consists mainly of blocks and fragments of radiolarian cherts, serpentinite, limestone, volcanic rocks, volcaniclastic sediments, serpentinized peridotite, and amphibolites set in a sandstone and mudstone matrix (Andrew and Robertson, 2002). The age of the units within the mélange ranges from Triassic to Upper Cretaceous. The metamorphic sole rocks exhibit granoblastic to nematoblastic textures and are represented by garnet amphibolite, pyroxene amphibolite, plagioclase amphibolite and epidote amphibolite (Fig. 13c) (Çelik and Delaloye, 2006). A peridotite body in the mélange is represented by serpentinized harzburgite and intruded by numerous isolated diabase dykes (Figs. 13a, 13b).
Figure 12. Geological map of the Gencek region south of Beyşehir Lake (Monod, 1977).
Whole rock geochemistry of fresh peridotites (mainly harzburgite) in the Beyşehir-Hoyran ophiolite reveals Cr and Ti contents akin to those inferred to be suprasubduction zone ophiolites (Andrew and Robertson, 2002). High chromium numbers (Cr#: 40–90) confirm their SSZ origin. Whole rock analyses of the isolated dykes cutting the peridotites also suggest a subduction related setting because they show marked Nb-depletion when normalized to N-MORB (Andrew and Robertson, 2002). Elitok and Drüppel (2008) reported that the dykes cutting the peridotites and the metamorphic sole in Şarkikaraağaç area exhibit depleted- to enriched-LREE geochemistry, also suggesting a subduction-related setting for their genesis. The amphibolites from the metamorphic sole of the Gencek area of the Beyşehir-Hoyran ophiolites to the south of Beyşehir Lake have alkaline to subalkaline compositions (Çelik and Delaloye, 2006). Trace element geochemistry suggests that they were derived from within plate alkaline basalt (WPA). In contrast the amphibolites from the metamorphic sole of the Şarkikaraağaç area of the Beyşehir-Hoyran ophiolites to the north of Beyşehir Lake display two different geochemical affinities, namely alkaline and tholeiitic. Their trace element geochemistry suggests derivation from within-plate alkali basalts and tholeiitic island arc basalts (Elitok and Drüppel, 2008). The pressure-temperature conditions (P/T) under which the metamorphic sole rocks in Gencek area formed were 550–600 ℃ and ~5 kbar (Çelik and Delaloye, 2006).
The first geochronological study on the amphibolites of the metamorphic sole rocks from the Beyşehir-Hoyran ophiolite by K-Ar yielded cooling ages of 93±3 Ma for hornblende and 84±3 Ma for plagioclase separates (Thuizat et al., 1981). More precise 40Ar/39Ar cooling ages of 91.5±1.9 to 90.9±1.3 Ma were obtained by Çelik et al. (2006).
The Mersin ophiolite is located in the southern flank of the Tauride calcareous axis in southern Turkey and offset from the Pozantı-Karsantı ophiolite by the sinistral Ecemiş fault (Fig. 14) (Juteau, 1980). The overall tectono-stratigraphy, from bottom to top, is: (1) Mersin mélange, (2) metamorphic sole, and (3) Mersin ophiolite (Fig. 15) (Parlak, 1996; Pampal, 1987, 1984).
Figure 14. Simplified geological map of the Bolkardağ region, showing the relationships of the Mersin, Alihoca and Pozantı-Karsantı ophiolites (MTA, 2002).
Figure 15. (a) Geological map and (b) a column section of the Mersin ophiolite (Parlak et al., 1996).
The Mersin mélange is exposed along an SW-NE trending tectonic zone at the top of the Tauride Platform and has an exposure area of around 600 m2 (Parlak and Robertson, 2004). It directly overlies Upper Cretaceous pelagic carbonates (the Yavça Formation) that form the highest stratigraphic levels of the Tauride carbonate platform. The Mersin mélange unit consists of both variable-sized blocks of limestone and locally coherent stratigraphic successions tens to hundreds of meters thick that have been interpreted as parts of broken formations. They mainly strike NE-SW and dip southward beneath the Mersin ophiolite (Fig. 15) (Parlak and Robertson, 2004). The tectonic contact between the mélange and the ophiolite dips towards N70E/71SE in the Sorgun valley. Four distinct assemblages are documented, namely; (1) a shallow-water carbonate association, ranging in age from Permian to Late Cretaceous; (2) a volcanogenic-terrigenous-pelagic association, ranging in age from Late Triassic to Late Cretaceous; (3) a seamount type alkaline basalt-radiolarite-pelagic limestone association, ranging in age from Upper Jurassic–Lower Cretaceous and (4) an ophiolite-derived association of Late Cretaceous Age (Parlak and Robertson, 2004). The matrix of the mélange formed by a combination of tectonic and sedimentary processes during latest Cretaceous time (Parlak and Robertson, 2004). As a whole, the Mersin mélange documents a number of events including Triassic rifting of the Tauride continent, Jurassic–Cretaceous passive margin subsidence, oceanic seamount genesis, and Cretaceous oceanic crust genesis (Parlak and Robertson, 2004).
The Mersin mélange is structurally overlain by the Mersin ophiolite, with a preserved metamorphic sole at three localities (Fig. 15). Thin units of ophiolite-related metamorphic rocks at three localities occupy a constant stratigraphic position at the base of a thick ultramafic unit (Fig. 15). At Fındıkpınarı Village, the metamorphic rocks crop out between the hazburgitic tectonite and the mélange unit. The metamorphic sole rocks display granoblastic to nematoblastic textures and are represented by amphibolites, amphibole schists, epidote-amphibole schists, quartz-epidote-amphibole schists, quartzites and marble lenses. Foliation surfaces in the metamorphic sole generally strike NE and dip variably toward the SW. The structural thickness of the metamorphic sole is ~200–250 m. The rocks are folded, imbricated and cut by post-metamorphic diabase dykes (Figs. 16a, 16c) with thicknesses ranging from 0.4 to 4 m whose attitudes vary from N60E to E-W. The dykes do not intrude the tectonic contact with the overlying harzburgite in a similar manner to the Pozantı-Karsantı and Lycian ophiolites, suggesting that some primary features were obliterated due to intensive deformation. The metamorphic sole rocks rest tectonically on the volcanic (pillow lava) and sedimentary (pelagic limestone, mudstone and manganese-rich cherts) rock assemblages of the mélange unit. The second outcrop of the metamorphic sole crops out at the base of the serpentinized mantle tectonites in a deep valley at Şahna Village where there are ductily deformed and folded amphibolites in turn intruded by a thin diabase dyke (Fig. 16b). A small tectonic inclusion of coarse-grained amphibolite is exposed beneath the harzburgitic mantle tectonites on the road to Gözne-Arslanköy, as a third outcrop of the metamorphic sole (Fig. 15).
Figure 16. (a) Cross-section showing the structural relationships of subophiolitic metamorphic rocks of the Mersin ophiolite in the Fındıkpınarı area. Field views of post-metamorphic dykes emplaced into ductily (b) and brittly (c) deformed metamorphic sole rocks.
The Mersin ophiolite is well exposed in several NW-SE-trending deep valleys dissecting Miocene carbonates on the southern flank of the Tauride Platform (Parlak, 1996). It has an ~6-km-thick complete oceanic lithospheric section except for sheeted dykes (Fig. 15). From bottom to top, it is characterized by harzburgitic mantle tectonites, ultramafic to mafic cumulates and volcanics. The best exposures are observed along the Sorgun valley in the western part of the massif. Mantle tectonites rest tectonically on a mélange unit to the south of Sorgun Village along the Sorgun valley in the west (Fig. 15). Although the mantle tectonites are highly sheared and serpentinized along the contact, they exhibit good foliation patterns characterized by alternations of dunite, harzburgite and orthopyroxenite banding in several places. A number of isolated dykes intersect at different structural levels. A dunitic zone with bands and pods of chromitite within the Moho-transition zone is observed below the ultramafic cumulates about 1-km thick, that start with dunite and are followed upward by dunite and wehrlite alternations (Parlak et al., 1996), in turn covered by clinopyroxenites towards the south. A succeeding zone of alternating wehrlite and olivine gabbroic cumulates is seen before the mafic cumulates. The ultramafic cumulates exhibit adcumulate textures and display structures such as igneous lamination, size grading and rhytmic layering (Fig. 15). The mafic cumulates, ~2 km thick, are dominated by olivine gabbro, leucogabbro, gabbro and anorthosite (Parlak et al., 1996). The mafic cumulates show rhythmic to graded layering and are characterized by adcumulate, mesocumulate and orthocumulate textures. Two distinct series of volcanic rocks are present. The first outcrop of the volcanics is seen in the Sorgun valley where it is intercalated with radiolarites and pelagic limestones of Late Jurassic to Early Cretaceous Age. The second outcrop of the volcanic rocks is located in the Fındıkpınarı region and is represented by pillow lavas and lava flows probably of Late Cretaceous Age. The pillows are approximately 50 cm in diameter and their vesicles are filled by pyrite, calcite and quartz (Parlak et al., 1997).
Major and trace element geochemistry of the ultramafic to mafic cumulates suggest that they formed within the Inner Tauride Ocean in a supra-subduction zone tectonic setting (Parlak et al., 1996). The crystallization order of the cumulates is: olivine±chromian spinel+ clinopyroxene+plagioclase and orthopyroxene. The presence of highly magnesian olivine (Fo91–80) and clinopyroxene (Mg#95–77), as well as Ca-rich plagioclase (An95–91) in the cumulate rocks suggests a subduction-related setting (Parlak et al., 1996). The geochemistry of the isolated diabase dykes cutting the mantle tectonites and the cumulates of the Mersin ophiolite, suggests their derivation from an island arc tholeiitic magma (Parlak et al., 1997; Parlak and Delaloye, 1996). Basaltic rocks associated with deep marine sediments show an alkaline affinity and are more akin to seamount-type alkaline basalt formed in a within plate setting, whereas the major and trace element chemistry of the second group of volcanic rocks suggests a subduction-related setting (Parlak et al., 1997). Zircon separates from the cumulate gabbroic rocks, dated by LA-MC-ICP-MS, yielded a crystallization age of 82.8±4.0 Ma (Parlak et al., 2013). Isolated dykes cutting the Mersin ophiolite were also dated by 40Ar/39Ar techniques (Dilek et al., 1999; Parlak and Delaloye, 1996). Diabase dykes cutting the metamorphic sole yielded whole-rock ages of 89.8±0.3 to 86.3±0.3 Ma (Parlak and Delaloye, 1996), whereas the dykes in the mantle tectonites yielded a hornblende cooling age of 91.0±0.8 Ma (Dilek et al., 1999). Çelik (2008) reported whole-rock K-Ar cooling ages of 88.4±3 to 88.8±2 Ma for the dykes cutting the metamorphic sole.
The geochemistry of the amphibolites from the metamorphic sole suggests a derivation from alkali ocean island alkali basalts, mid-ocean ridge and island arc tholeiitic basalts (Çelik, 2008; Parlak et al., 1997). Thuizat et al. (1981) reported Late Cretaceous (94±4 and 98±4 Ma) K-Ar ages on hornblende separates. Parlak et al. (1995b) reported a 93.4±2.2 Ma K-Ar isochron age for hornblendes from the metamorphic sole and Çelik (2008) also reported a 93.8±3 Ma cooling age for hornblende separates. Similar Late Cretaceous cooling ages (96 to 91 Ma) by the 40Ar/39Ar technique on hornblende separates have also been documented (Dilek et al., 1999; Parlak and Delaloye, 1999). Pressure-temperature conditions (P/T) under which the metamorphic sole rocks formed were 522±15 ℃ and ~5 kbar (Çelik, 2008).
The northern margin of the Bolkardağ Platform is bounded by the east-west trending, deformed and dismembered Alihoca ophiolite (Fig. 14). The tectonic contact between the Bolkardağ Platform and the Alihoca ophiolite is marked by discontinuous exposures of blueschists (van der Kaaden, 1966; Blumenthal, 1955). Glaucophane-bearing HP rocks are present within the mafic volcanics of the Lower Triassic series of the Bolkar Platform (Pourteau et al., 2010) and within blocks of the ophiolitic mélange (van der Kaaden, 1966). Another locality of HP rocks is exposed beneath the Kızıltepe ophiolite, a klippe above the Mesozoic carbonate platform of the Bolkardağ Platform farther south relative to the Alihoca ophiolite (Fig. 14). A thin metamorphic sole beneath the Kızıltepe ophiolite was overprinted by blueschist-facies metamorphism during the Late Cretaceous (Dilek and Whitney, 1997).
The Alihoca ophiolite is represented by highly serpentinized peridotites, pyroxenite, ultramafic to mafic cumulates, isotropic gabbros and minor extrusive rocks. The mafic cumulates also include thin bands and lenses of wehrlite and pyroxenite (Dilek et al., 1999; Dilek and Whitney, 1997). Microgabbroic to diabasic dykes up to 2 m thick intrude all the units except volcanics. The Alihoca ophiolite and its related mélange unit are overlain by the Çiftehan Formation (Demirtaşlı et al., 1984) that has a basal conglomerate at the bottom gradually passing upwards into cherty limestone and red pelagic limestone of Campanian–Maastrichtian age.
Pyroxenes within ultramafic cumulates (clinopyroxenite and websterites) of the Alihoca ophiolite have restricted chemical compositions (e.g., diopside En48Fs6Wo46-En44Fs10Wo46; orthopyroxene En84Fs14Wo2-En75Fs23Wo2). These rocks have relatively high Mg olivine (Fo85) and highly calcic plagioclase (An98–96) (Dilek et al., 1999). This feature points to a highly refractory parental magma composition and possibly hydrous crystallization conditions (Dilek et al., 1999). The geochemistry of the isolated diabase dykes cutting the serpentinized mantle tectonites as well as the crustal rocks of the Alihoca ophiolite, suggests that they represent magma compositions typical of evolved island arc tholeiites from a depleted mantle source that underwent metasomatism introducing large-ion-lithophile (LIL) element and light rare earth element (LREE) enriched fluids (Dilek et al., 1999). Dilek and Whitney (1997) suggested the following history for the formation of the metamorphic sole and its blueschist overprint: (1) metamorphism of basaltic protoliths in the amphibolite facies during inception of an intra-oceanic subduction zone, (2) infiltration of amphibolite by fluid along fractures and grain boundaries at high P/T in this subduction zone, (3) cessation of pervasive deformation and continued, post-kinematic growth of high P/T minerals and (4) exhumation and greenschist-facies retrogressive metamorphism.
40Ar/39Ar hornblende dating of amphibolite from the metamorphic sole of the Kızıltepe ophiolite yielded a cooling age of 90.6±0.9 Ma and hornblendes separated from an isolated dyke cutting the layered gabbro-pyroxenite of the Alihoca ophiolite yielded a cooling age of 90.8±0.8 Ma (Dilek et al., 1999).
The Pozanti-Karsanti ophiolite is exposed in the eastern Aladağ region of the Tauride belt and covers an area of approximately 1 300 km2 to the east of the Ecemiş strike-slip fault of southern Turkey (Parlak et al., 2002, 2000; Parlak, 2000; Polat et al., 1996; Lytwyn and Casey, 1995; Çataklı, 1983; Tekeli et al., 1983; Juteau, 1980; Bingöl, 1978; Çakır, 1978) (Fig. 14). An imbricated stack of thrust sheets resting upon the eastern Taurus autochthon is exposed in the Aladağ region (Polat et al., 1996; Blumenthal, 1947). The upper thrust sheets are characterized by ophiolite-related rock assemblages, namely ophiolitic mélange, a dynamothermal metamorphic sole and oceanic lithospheric sections, whereas the lower thrust sheets consist of platform-type carbonates, ranging in age from Late Devonian to Early Cretaceous (Tekeli et al., 1983). We describe the rock units from the upper thrust sheets below.
A Campanian to Maastrichtian unmetamorphosed ophiolitic mélange is composed of a variety of igneous, metamorphic and sedimentary blocks structurally dispersed in a serpentinitic to pelitic matrix (Polat and Casey, 1995; Tekeli et al., 1983). The ophiolitic mélange was subdivided into three tectonic slices based on the origin of the blocks and the surrounding matrix, field relationships and deformation style (Polat et al., 1996). These are: (1) an upper tectonic slice characterized by a serpentinitic matrix with ophiolitic and metamorphic blocks, (2) a middle tectonic slice composed of a pelitic matrix with ophiolite blocks at the top and limestone blocks at the bottom, and (3) a lower tectonic slice consisting of brittlely-deformed pelitic matrix at the top and tectonic breccia at the bottom. The mélange unit formed as a result of subduction-accretion processes and became attached to the base of the Pozantı-Karsantı ophiolite during final emplacement onto the Tauride Platform (Polat et al., 1996; Tekeli et al. 1983).
The metamorphic sole rocks of the Pozantı-Karsantı ophiolite crop out at different locations in a constant structural position between the harzburgitic mantle tectonites and the ophiolitic mélange (Fig. 17). The dynamothermal metamorphic sole displays a typical inverted metamorphic sequence grading from amphibolite facies directly beneath the highly sheared harzburgitic tectonite to greenschist facies close to the mélange contact (Çelik, 2007; Polat et al., 1996; Lytwyn and Casey, 1995; Thuizat et al., 1978). The metamorphic sole rocks are well-exposed in the northern part of the Pozantı-Karsantı ophiolite in Aladağ region (Fig. 17). The first outcrop is located approximately 8 km to the NNE of Ulupınar Village along the Zorkunlu valley (Fig. 17) where it has a structural thickness of around 450 m (Polat et al., 1996). The contact between the metamorphic sole and the ophiolite is defined by a 1.5–2 m thick zone of strongly-sheared tectonically intercalated serpentinized harzburgitic mantle tectonites and amphibolites (Figs. 18a, 18e). In this zone, the thicknesses of bands in the amphibolites and highly-sheared hazburgitic tectonites range from 4 to 15 cm. Foliation surfaces both in the amphibolites and the mantle tectonites are concordant (N-S/70-80E) (Fig. 18b). This contact is interpreted as indicating an intra-oceanic decoupling surface along which the volcanics on the top of the down-going slab were metamorphosed up to upper amphibolite facies and attached to the base of the hanging wall plate (Spray, 1984). The contact between the metamorphic sole and the serpentinized harzburgite is crosscut by a 7–8-m-thick mafic dyke which postdates intraoceanic metamorphism and high-temperature ductile deformation (Figs. 18a, 18d). Individual dykes are also observed to cut the metamorphic sole and the mantle tectonites at different structural levels. The metamorphic sole displaying granoblastic to nematoblastic textures, is represented by garnet amphibolite at the contact beneath the mantle tectonites and amphibolite to plagioclase-epidote-amphibole schist at a lower structural level. Metavolcanic, metachert, metapelite and quartzite rock associations are observed toward the contact with the ophiolitic mélange (Çelik, 2007; Polat et al., 1996). Mesostructures within the metamorphic sole suggest southward emplacement of the ophiolite (Figs. 18f, 18g). The second outcrop is located a few hundred meters to the north of Kapuzbaşı Village in the Aladağ region where alternations of amphibolite, quartz-plagioclase amphibolite, calcschist, micaschist and mica-amphibole schist are observed (Fig. 17). The metamorphic sole rocks display granoblastic, nematoblastic and lepidoblastic textures, are gently folded and contain marble lenses. The third outcrop is located 1 km to the south of Delialiuşağı Village (Fig. 17) where the metamorphic sole rocks are tectonically sandwiched between serpentinized mantle tectonites and ophiolitic mélange. The structural thickness of the metamorphic sole is approximately 120 m (Figs. 19a, 19d). These rocks are gently folded and contain a layer of highly deformed calcschist (Fig. 19c). The metamorphic sole rocks are represented by plagioclase-mica-amphibole schist, display nematoblastic to lepidoblastic textures and are intruded by isolated dykes (Fig. 19b). Apatite, rutile, sphene and zircon are common accessory minerals in the metamorphic sole rocks.
Figure 17. (a) Geological map and (b) column section of the Pozantı-Karsantı ophiolite (Bingöl, 1978).
Figure 18. (a) Cross section showing the field relations of mantle tectonite, metamorphic sole and a cross-cutting dyke in the Pozantı-Karsantı ophiolites at Ulupınar Village, field views of (b) foliated peridotite, (c) tectonic contact between mantle peridotite and the metamorphic sole, (d) dyke emplacement through the oceanic decoupling surface between the mantle peridotite and the metamorphic sole, (e) close up view of the tectonic intercalation of serpentinite and amphibolite along the oceanic decoupling surface, (f) and (g) mesostructures within the metamorphic sole showing top-to-south shearing.
Figure 19. (a) Cross section showing the field relations of mantle tectonites, metamorphic sole and ophiolitic mélange in the Pozantı-Karsantı ophiolite at Delialiuşağı Village, field views of (b) dyke emplacement in the metamorphic sole, (c) a deformed calcschist-marble layer within the metamorphic sole, and (d) the tectonic contact between the metamorphic sole and the ophiolitic mélange.
The Pozantı-Karsantı ophiolite is characterized by from bottom to top, mantle tectonites, ultramafic to mafic cumulates, and isotropic gabbro with plagiogranite intrusions (Bingöl, 1978). Mantle tectonites constitute approximately 60% of the whole ophiolite, are exclusively represented by harzburgite and display plastic deformation indicated by alternating bans of orthopyroxenite and dunite (Fig. 18b). The harzburgitic tectonites generally exhibit porphyroclastic textures and are variably serpentinized toward the top. The mantle tectonites are very fresh close to the contact with the metamorphic sole, include chromitite pods surrounded by dunitic envelopes at different structural levels and are intruded by gabbro and diabase dykes. The ultramafic cumulates generally rest on the mantle tectonites with a tectonic contact. A discordant contact relationship was also reported by Bingöl and Juteau (1977) in the Kızılyüksek region (Fig. 17). The ultramafic cumulates start with a ~2-km-thick dunite layer at the bottom in which there are well-known stratiform chromite deposits (Bingöl, 1978). Above this, a transition zone is characterized by alternating olivine- and pyroxene-rich rocks, namely dunite, wehrlite, olivine clinopyroxenite, clinopyroxenite and olivine websterite (Parlak et al., 2002). Gabbroic cumulates composed almost exclusively of gabbronorites constitute 40% of the whole cumulate section and are around 1 300 m thick (Bingöl, 1978). They exhibit accumulate-mesocumulate textures and show magmatic accumulation features such as igneous lamination, crystal size grading and rhythmic layering. Olivine-rich gabbroic cumulates are also documented in the western part of the Pozantı-Karsantı ophiolite (Çataklı, 1983). Some parts of the gabbros are isotropic in character and exhibit doleritic to subophitic texture (Parlak et al., 2000). A number of isolated microgabbro and diabase dykes cut the mantle tectonites and metamorphic sole at different structural levels ans also the contact between the metamorphic sole and the harzburgitic mantle tectonites (Figs. 17, 18, 19). They do not cut the underlying mélange and Tauride Platform rocks, indicating that some dyke emplacement postdated the formation of the ophiolite and the metamorphic sole but pre-dated its final obduction onto the Tauride Platform (Çelik, 2007; Parlak, 2000; Lytwyn and Casey, 1995; Thuizat et al., 1981; Çakır et al., 1978).
Geochemical studies on the mantle section of the Pozantı-Karsantı ophiolite suggest the existence of both weakly depleted mantle peridotites produced by low degrees of partial melting in a mid-ocean ridge environment and re-melted and highly-depleted mantle peridotites formed in a supra-subduction zone setting (Saka et al., 2014). The whole rock and mineral chemistry of the cumulate rocks suggests that the primary magma generating the Pozanti-Karsanti ophiolite was compositionally similar to those observed in modern island arc tholeiitic sequences (Parlak et al., 2000). The mineral chemistry of the basal ultramafic cumulates (dunite, wehrlite, websterite) shows evidence of high-pressure crystallization, typical for the base of an island arc system whereas the mineral chemistry of the cumulate gabbronorites indicates lower-pressure crystallization by the presence of amphibole (Parlak et al., 2002). Isolated post-metamorphic diabase dykes which intrude the metamorphic sole, the mantle tectonites and the crustal sequence, are subalkaline in character and compositionally similar to island arc tholeiitic basalts and basaltic andesites. They display large-ion-lithophile (LIL) element enrichment and are depleted in high-field-strength (HFS) elements (Nb, Ti, Y) relative to N-MORB. The presence of positive Th and LIL anomalies and a negative Nb anomaly relative to the other incompatible elements, are thought to indicate a subduction-related setting during their emplacement (Parlak, 2000). Çelik (2007) documented late-stage pyroxenite dykes intruding the metamorphic sole beneath the Pozantı-Karsantı ophiolite that were interpreted to be a result of offaxis magmatism fed by melts that originated within an asthenospheric window caused by slab break-off. Lytwyn and Casey (1995) postulated that the post-metamorphic dykes in the ophiolite as well as the metamorphic sole were emplaced due to a ridge subduction event during intraoceanic transport of the Pozantı-Karsantı ophiolite. Thuizat et al. (1978) reported a K-Ar age of 71±3 Ma on a plagioclase separate from the post-metamorphic dykes. A similar young LA-MC-ICP-MS U-Pb zircon age of 69.1±2.1 Ma has recently been obtained from crustal rocks (gabbro cumulate) of the Pozantı-Karsantı ophiolite (Parlak et al., 2013) and is interpreted as reflecting island arc tholeiitic (IAT) melt generation in an SSZ setting along the Inner Tauride Ocean prior to emplacement of the ophiolites onto the Tauride-Anatolide Platform (Parlak et al., 2013).
The whole-rock and mineral chemistry of amphibolites from the metamorphic sole rocks suggest their derivation from different precursors, namely alkaline basalt and N-MORB basalt (Lytwyn and Casey, 1995), ocean island basalt (OIB), mid-ocean ridge basalt (MORB) and island arc basalt (IAT) (Çelik, 2007) or OIB-like alkali basalt to N- to E-MORB (Polat et al., 1996). The alkaline, OIB-like basalts were mainly metamorphosed in the amphibolite facies and the N- to E-MORB lavas and their pelagic intercalations were metamorphosed under greenschist facies conditions (Polat et al., 1996; Lytwyn and Casey, 1995). Polat et al. (1996) suggested on the basis of geochemical work that intra-oceanic subduction may have taken place in the vicinity of an off-axis plume or a plume-centered spreading ridge within the Inner Tauride Ocean where the lithosphere would have been young and hot, providing the thermal source for metamorphism. Pressure-temperature conditions (P/T) under which the metamorphic sole rocks formed were 570–580 ℃ and 5–6 kbar (Çelik, 2007). 40Ar/39Ar age dating on separates of hornblende (90.4±0.9 to 91.7±0.6 Ma) and muscovite (92.4±1.3 Ma) from the metamorphic sole rocks of the Pozantı-Karsantı ophiolite yielded Late Cretaceous ages (Çelik et al., 2006; Dilek et al., 1999). Earlier, Thuizat et al. (1981) had also reported similar Late Cretaceous (Cenomanian–Turonian) K-Ar ages on hornblende (95±4 Ma) and biotite (92±3 Ma) separates.
The Pınarbaşı (Kayseri) ophiolite, emplaced onto the Tauride Platform in the Late Cretaceous, covers an area of approximately 500 km2 in the southeastern part of the central Anatolian crystalline complex (CACC) (Göncüoğlu et al., 1996–1997). The eastern Tauride autochthon (Geyikdağ unit of Özgül, 1976), ranging in age from Cambrian to Eocene, is tectonically overlain by allochthonous thrust sheets that are represented by a platform-type carbonate-dominated lower thrust sheet and an ophiolite-related upper thrust sheet (Tekeli et al., 1983; Blumenthal, 1947). The allochthonous lower thrust sheet in the region is composed of, in ascending order, the Gülbahar and Domuzdağ nappes (Figs. 20, 21). The Gülbahar nappe, ranging in age from Middle Triassic to Late Cretaceous, consists mainly of mafic volcanics, calciturbidites, radiolarite and chert-bearing micritic limestone and cherty limestone (Şenel, 1997a, b). The Domuzdağ nappe (Poisson, 1977), consisting of Mesozoic platform type carbonates, rests tectonically on the Gülbahar nappe (Figs. 20, 21). The overlying allochthonous upper thrust sheet is represented, from bottom to top, by an ophiolitic mélange, a metamorphic sole and an ophiolite sequence (Figs. 20, 21). The Upper Campanian–Maastrichtian, unmetamorphosed ophiolitic mélange comprises blocks of ophiolite-derived, igneous (serpentinized harzburgitic to dunites, gabbro, diabase and volcanics), metamorphic (amphibolite) and sedimentary rocks (volcanogenic sandstone, radiolarite and shale) enclosed in a serpentinitic to pelitic matrix (Erkan et al., 1978). The ophiolitic mélange crops out in the southern part of the Pınarbaşı (Kayseri) ophiolite. The metamorphic sole is tectonically sandwiched between the overlying harzburgitic tectonites and underlying ophiolitic mélange between Büyükgürleğen and Karahacılı (Fig. 20). It exhibits well-developed foliation patterns and has a thickness of around 250 m. The metamorphic sole displays inverted metamorphic zonation, grading from amphibolite facies directly beneath the highly sheared harzburgitic tectonite to greenschist facies near the mélange contact. The metamorphic sole rocks display granoblastic to nematoblastic textures and are represented by amphibolite, plagioclase amphibolite, plagioclase-amphibole schist, epidote-plagioclase-amphibole schist and calcschist (Vergili and Parlak, 2005). The Pınarbaşı ophiolite is exposed in the northern part of the study area (Fig. 20) and comprises the lower parts of an oceanic lithosphere system such as mantle tectonites and ultramafic and mafic cumulates (Vergili and Parlak, 2005). Contacts between units are tectonic. The mantle tectonites are represented by harzburgites and dunites with chromitite pods. The cumulate rocks consist of wehrlite, clinopyroxenite, troctolite, olivine gabbro and gabbro. Numerous isolated dykes of microgabbro, diabase and pyroxenite cut the mantle tectonites at all structural levels (Figs. 20, 21) but dyke emplacement is not observedin the metamorphic sole of the Pınarbaşı ophiolite. The Pınarbaşı ophiolite is covered by Paleocene conglomerate, pebbly sandstone, sandstone and limestone, deposited in an environment transitional between alluvial fan and lagoon (Erkan et al., 1978).
Figure 20. Geological map of the Pınarbaşı ophiolite (Vergili and Parlak, 2005).
Figure 21. Column section of the Pınarbaşı ophiolite and tectonostratigraphic units in the eastern Tauride belt (Vergili and Parlak, 2005).
Vergili and Parlak (2005) found that isolated microgabbro-diabase dykes cutting the mantle tectonites are tholeiitic in character and their trace element contents suggest that they formed in a subduction-related environment. The amphibolites from the metamorphic sole beneath the Pınarbaşı ophiolite exhibit two distinct geochemical features. The first group is alkaline and more akin to within-plate alkali basalts, whereas the second group is tholeiitic in nature and displays geochemical characteristics of island arc tholeiitic basalts (Vergili and Parlak, 2005).
The only available geochronological age determination for the Pınarbaşı ophiolite was zircon U-Pb dating of an isolated diabase dyke cutting the harzburgitic mantle tectonites. Zircon separates from that dyke yielded a very young crystallization age of 65.4±3.2 Ma (Parlak et al., 2013).
The Divriği ophiolite is located at the eastern end of the Tauride belt between Divriği and Çetinkaya (Sivas) in east-central Anatolia (Fig. 22). The area is characterized by, from bottom to top, autochthonous Tauride Platform carbonates, ophiolitic mélange, metamorphic sole, ophiolitic rocks, volcanic-sedimentary unit, granitoid rocks and cover sediments (Yılmaz and Yılmaz, 2004; Yılmaz et al., 2001) (Fig. 23).
The Tauride Platform in the area consists of the Munzur limestone that exhibits continuous carbonate deposition from the Upper Triassic to the Upper Cretaceous. This unit comprises neritic limestones representing shallow to stable shelf conditions at the bottom and pelagic limestones at the top (Özgül and Turşucu, 1984). The Tauride Platform is tectonically overlain by the Yeşilyayla ophiolitic mélange (Fig. 22) that contains limestone blocks and metamorphic rock fragments set in a serpentinized matrix. The limestone blocks typically range from tens of meters to several hundred meters in size. The metamorphic rock fragments are represented by gneiss, amphibolite, metavolcanics, metaquartzite, calcschist and micaschist. The metamorphic sole has a constistant structural position between the mantle tectonites and the Yeşiltaşyayla mélange to the west of Ekinbaşı (Fig. 22). A pronounced regional foliation, mineral lineations and intrafolial folds were produced during intraoceanic deformation. The rocks exhibit granoblastic to nematoblastic textures and are represented by amphibolite, plagioclase amphibolite, plagioclase-amphibole schist, plagioclase-epidote-amphibole schist and marble (Fig. 24c) (Parlak et al., 2006). The metamorphic sole is cut by isolated unmetamorphosed diabase dykes (Fig. 24a). The Divriği ophiolite tectonically overlies the metamorphic sole and it displays a complete oceanic lithospheric section except for volcanics, namely serpentinized mantle tectonites, cumulates, isotropic gabbros and sheeted dykes (Fig. 23). Contacts from the cumulate to the isotropic gabbros and from the isotropic gabbros to the sheeted dykes are transitional. On the other hand, contacts between the other units are tectonic (Figs. 22, 23). The mantle tectonite is dominated by serpentinized harburgite containing dunitic lenses with chromite pods and subordinate lherzolite. The harzburgites are intruded by pyroxenite and gabbroic to diabasic dykes at different structural levels (Fig. 24b). The ultramafic to mafic cumulate rocks comprise dunite, wehrlite, olivine websterite, olivine gabbro and gabbro. The isotropic gabbros are represented by gabbro and diorite. The sheeted dykes are representeed by isolated dykes in the upper part of the isotropic gabbros and become dominant in the lower part of the sheeted complex. They range from 20 to 50 cm in width, and consist of diabase and microdiorite (Parlak et al., 2006). The ophiolitic rocks are unconformably overlain by a Campanian–Maastrichtian volcanic-sedimentary assemblage that in turn was intruded by basic dykes (Yılmaz et al., 2001). Granitoid rocks in the Divriği region cut all the former units and have calcalkaline to alkaline compositions (Boztuğ et al., 2007; Kuşçu et al., 2010). They yielded zircon U-Pb crystallization ages of 70.4±1.5 to 67.7±1.4 Ma (Campanian–Maastrichtian) (Parlak et al., 2013).
Figure 24. (a) Cross section showing the field relations of the mantle tectonite, metamorphic sole and the isolated dykes from the Divriği (Sivas) ophiolite. Field views of (b) mantle tectonites, isolated dykes and the metamorphic sole along the Çaltı River. (c) Close up view of foliated amphibolite.
The gabbroic cumulate rocks of the Divriği ophiolite are characterized by high Ca-plagioclase (An97–83), magnesian olivine (Fo87–76) and clinopyroxene (Mg#82–78), suggesting that they formed in an arc setting (Parlak et al., 2005). Trace element contents of the sheeted dykes and the isotropic gabbros also exhibit subduction-related compositions (Parlak et al., 2005). The isolated dykes cutting the metamorphic sole and the mantle tectonites exhibit are alkaline in character and are geochemically similar to within-plate alkaline basalts (Parlak et al., 2006). The alkaline dykes are attributed to late-stage magmatism fed by melts that originated within an asthenospheric window caused by slab break-off, shortly before the emplacement of the Divriği ophiolite onto the Tauride Platform (Parlak et al., 2006). The metamorphic-sole rocks beneath the Divriği ophiolite can be divided into two groups with distinct geochemical features as tholeiitic and alkaline. The protolith of the tholeiitic amphibolites was derived from island-arc tholeiitic basalts, whereas the protolith of the second group was more akin to within-plate alkali basalts.
Zircon separates from a cumulate gabbro of the Divriği ophiolite were dated by U-Pb LA-MC-ICP-MS technique and yielded an 88.8±2.5 Ma crystallization age (Parlak et al., 2013). Hornblende separates from the metamorphic sole rocks beneath the Divriği ophiolite were analysed by 40Ar/39Ar and they yielded robust plateau ages, ranging from 89.65±0.97 to 87.49±0.48 Ma (Parlak et al., 2013). An isolated post-metamorphic dyke cutting the metamorphic sole yielded an 40Ar/39Ar cooling age of 75.94±0.30 Ma (Parlak et al., 2013).