Geochronological Evidence of Pan-African Eclogites from the Central Menderes Massif, Turkey

The Menderes Massif in western Anatolia documents a complex geodynamic history from Precambrian to recent. Eclogitic relics found in metagabbros in the Precambrian basement were dated by the U/Pb method. The zircon age data from granulitic (coronitic) and eclogitic metagabbros is consistent with geological constraints as well as relative and radiometric ages of the host granulitic gneisses and augen gneisses. A Pan-African intrusion age (540 Ma) of the metagabbros and a shortly later eclogite facies event (530 Ma) are inferred. This scenario fits with the geodynamic evolution deduced form the acidic country rocks of the eclogitic metagabbros. Direct links between the Menderes Massif and Mozambique belt are obliterated by Alpine deformation. Nevertheless, the tectonic setting and age of the Menderes eclogites support a terminal collision of East and West Gondwana and the final suturing of the Mozambique Ocean during the Early Cambrian

Hydrous aluminosilicate metasomatism in an intra-oceanic subduction zone: Implications from the Kurancali (Turkey) ultramafic-mafic cumulates within the Alpine Neotethys Ocean

The Kurancali ultramafic-mafic cumulate body, an allochthonous ophiolitic sliver in central Anatolia, is characterized by the presence of abundant hydrous phases (phlogopite, pargasite) besides augitic diopside, plagioclase, and accessory amounts of rutile, sphene, apatite, zircon, and calcite. Based on modes of the essential minerals, the olivine-orthopyroxene-free cumulates are grouped as clinopyroxenite, hydrous clinopyroxenite, phlogopitite, hornblendite, layered gabbro, and diorite. Petrographical, mineralogical and geochemical features of the rocks infer crystallization from a hydrous magma having high-K calcalkaline affinity with slightly alkaline character, and point to metasomatised mantle as the magma source. Our evidence implies that the metasomatising component, which modified the composition of the mantle wedge source rock in an intraoceanic subduction zone, was a H2O, alkali and carbonate-rich aluminosilicate fluid and/or melt, probably derived from a subducted slab. We suggest that the metasomatic agents in the subarc mantle led to the generation of a hydrous magma, which produced the Kurancali cumulates in an island-arc basement in a supra-subduction-zone setting during the closure of the Izmir-Ankara-Erzincan branch of the Alpine Neotethys Ocean

Dating Subduction Events in East Anatolia, Turkey

Metamorphic studies in the cover sequences of the Bitlis complex allow the thermal evolution of the massif to be constrained using metamorphic index minerals. Regionally distributed metamorphic index minerals such as glaucophane, carpholite, relics of carpholite in chloritoid-bearing schists and pseudomorphs after aragonite in marbles record a LT-HP evolution:This demonstrates that the Bitlis complex was subducted and stacked to form a nappe complex during the closure of the Neo-Tethys. During late Cretaceous to Cenozoic evolution the Bitlis complex experienced peak metamorphism of 1.0-1.1 GPa at 350-400 degrees C. During the retrograde evolution temperatures remained below 460 degrees C. Ar-39/Ar-40 dating of white mica in different parageneses from the Bitlis complex reveals a 74-79 Ma (Campanian) date of peak metamorphism and rapid exhumation to an almost isothermal greenschist stage at 67-70 Ma (Maastrichtian). The HP Eocene flysch escaped the greenschist facies stage and were exhumed under very cold conditions. These single stage evolutions contrast with the multistage evolution reported further north from the Amassia-Stepanavan Suture in Armenia. Petrological investigations and isotopic dating show that the collision of Arabia with Eurasia resulted in an assemblage of different blocks derived from the northern as well as from the southern plate and a set of subduction zones producing HP rocks with diverse exhumation histories

Anatolidler’in Toridler’le Olan İlişkisi ve Geç Kretase – Eosen Tektono-metamorfik Evrimi

BatıAnadolu’da İzmir-Ankara-Erzincan sütur zonunun güney kesimi büyük oranda ‘Anatolidve ‘Toridler’den yapılıdır. Erken-Orta Triyas’ta Neotetis Okyanusu’nun güneykolunun açılmasıyla Gondwana’nın kuzey kenarından ayrılmış bir kıtasal bloğu(Anatolid-Torid Bloğu; ATB) ifade eden bu üniteler yapısal dokanaklarlabirbirilerinden ayrılan çok sayıda tektonik zondan yapılıdır. Söz konusu blokgünümüzde; 1-Kuzeyde yer alan ve bloğunkuzey kenarının Geç Kretase – Erken Tersiyer’de Sakarya Zonu altına yitimi ileilişkilendirilen ‘Anatolidler’ ve 2-Güneydeyer alan ve bloğun yitime katılmamış kesimini tanımlayan ‘Toridler’ olmaküzere iki ana üniteye ayrılmaktadır. Geç Kretase öncesi ortak evrim nedeniyle,doğal olarak Anatolid ve Toridler benzer stratigrafik özellikler sunmaktadır.Baskınolarak karbonatlardan yapılı tortullardan oluşan Toridler ilksel fasiyesözellikleri değerlendirildiğinde kuzeyden güneye doğru Bozkır, Bolkardağ,Aladağ, Geyikdağı, Antalya ve Alanya birlikleri olmak üzere altı üniteyeayrılmaktadır. Erken Triyas öncesinde Gondwana’nın kuzey pasif kıta kenarına konumlandırılanbu üniteler benzer Paleozoyik istiflere sahiptir. Günümüzde ise bu ünitelerbirbirinden tektonik dokanaklarla ayrılan birlikler olarak tanımlanmaktadır.Anatolidlerkuzeyden güneye doğru Tavşanlı Zonu (TZ), Afyon Zonu (AZ) ve Menderes Masifi’nden(MM) yapılıdır. En kuzeyde yer alan Tavşanlı Zonu ATB’ nin kuzey yönlü deringömülmesi sonucu Kampaniyen’de mavişist – eklojit fasiyesi koşullarında (20-25kbar / 430-550 oC)yüksek basınç / düşük sıcaklık başkalaşımına uğramıştır. Orta tektonik üniteyioluşturan Afyon Zonu platformun Maastrihtiyen’de iç ekaylanmaya uğraması sonucubenzer şekilde yüksek basınç / düşük sıcaklık mavişist fasiyesi koşullarında (9-12kbar / 380-420 oC)metamorfizmaya uğramıştır. En güneydeki tektonik üniteyi tanımlayan MenderesMasifi güneye doğru taşınmakta olan Afyon Zonu ve üzerleyen Likya napları /ofiyolit dilimleri altına gömülerek Eosen’de orta – yüksek basınç koşullarında(6-13 kbar / 450-600 oC)başkalaşım geçirmiştir.Korunmuş ilksel fasiyesözellikleri ve fosil bulguları Anatolidler’i oluşturan metamorfitlerinToridler’e ait Bolkardağı ve Aladağ birliklerinden türediğini göstermektedir. Stratigrafik,petrolojik ve jeokronolojik veriler Anatolidler’i oluşturan tektonik zonlarda; 1-Neotetis Okyanusu’nun kapanma sürecindeplatformun kuzey kenarında sedimantasyonun güneye doğru gençleşerek devamettiğini (TZ: Senomaniyen; AZ: Kampaniyen, MM: Paleosen), 2-Yitimle ilişkili Alpinmetamorfizmalarının kuzeyden güneye doğru gençleşme gösterdiğini (TZ: 82-80 my; AZ: ~70 my, MM: 45-35 my) ve 3-Yitime giren ünitelerin gömülmederinliğinin güneye doğru azaldığını (TZ: ~70-80 km; AZ: ~35-40 km; MM: ~25-30 km) ortaya koymaktadır. Bu düzenli bölgesel jeolojikdeğişimler; 1-Geç Kretase-Eosenaralığında Neotetis ve İç-Toros okyanuslarının kapanma sürecinde ATB’ nin kuzeykenarının Sakarya Zonu (Lavrasya) ve Kırşehir Bloğu altına kuzey yönlü yitimi, 2-İzleyen evredeki kıtasal çarpışma ve 3-Son evrede Anatolidler’in güneye, yitimegirmeyen Toridler üzerine yerleşmesi süreçleri ile ilişkilendirilebilir.</p

The wide distribution of HP-LT rocks in the Lycian Belt (Western Turkey): implications for accretionary wedge geometry

In SW Turkey, Fe-Mg-carpholite has recently been recognized in the basal metasediments of the Lycian Nappes, which overthrust the Menderes Massif on its southern flank. This high-pressure-low-temperature (HP-LT) metamorphic index mineral was widely found in the Bodrum peninsula region. Our new metamorphic and structural data on similar carpholite-bearing rocks found farther north in several klippen of the Lycian Nappes located on top of the Menderes Massif show that HP-LT rocks in SW Turkey occur over a distance of >200 km in both north-south and east-west directions, thus indicating a wide HP-LT metamorphic belt. The deformation pattern from the Bodrum peninsula to Civril, all along the contact between the Lycian Nappes and the Menderes Massif, reveals the role played by major top-to-the-NE shear zones contemporaneous with exhumation of the Lycian HP-LT rocks. This deformation shows an oblique direction of opposite shear sense relative to the earlier southward translation of the Lycian Nappes over the Menderes Massif, for which top-to-the-south displacements are preserved in the upper units of the Lycian Nappes on the Bodrum peninsula, as well as at the base of the Lycian nappe klippen located farther north. The widespread distribution of well-preserved Fe-Mg-carpholite-bearing rocks in the Lycian Nappes has implications for the geometry of the accretionary wedge responsible for HP-LT metamorphism in SW Turkey

Neotethyan closure history of western Anatolia: a geodynamic discussion

This paper addresses the lithosphere-scale subduction-collision history of the eastern termination of the Aegean retreating subduction system, i.e. western Anatolia. Although there is some general consensus on the protracted subduction evolution of the Aegean since the early Cenozoic at least, correlation with western Anatolia has been widely debated for more than several decades. In western Anatolia, three main tectonic configurations have been envisaged in the past years to reconstruct slab dynamics during the closure of the Neotethyan oceanic realm since the Late Cretaceous. Some authors have suggested an Aegean-type scenario, with the continuous subduction of a single lithospheric slab, punctuated by episodic slab roll-back and trench retreat, whereas others assumed a discontinuous subduction history marked by intermittent slab break-off during either the Campanian (ca. 75 Ma) or the Early Eocene (ca. 55-50 Ma). The third view implies three partly contemporaneous subduction zones. Our review of these models points to key debated aspects that can be re-evaluated in the light of multidisciplinary constraints from the literature. Our discussion leads us to address the timing of subduction initiation, the existence of hypothetical ocean basins, the number of intervening subduction zones between the Taurides and the Pontides, the palaeogeographic origin of tectonic units and the possibility for slab break-off during either the Campanian or the Early Eocene. Thence, we put forward a favoured tectonic scenario featuring two successive phases of subduction of a single lithospheric slab and episodic accretion of two continental domains separated by a continental trough, representing the eastern end of the Cycladic Ocean of the Aegean. The lack of univocal evidence for slab break-off in western Anatolia and southward-younging HP/LT metamorphism in continental tectonic units (from similar to 85, 70 to 50 Ma) in the Late Cretaceous-Palaeogene period suggests continuous subduction since similar to 110 Ma, marked by roll-back episodes in the Palaeocene and the Oligo-Miocene, and slab tearing below western Anatolia during the Miocene

Middle triassic magmatism in the Afyon Zone of the Anatolides/Eastern Mediterranean: Implications for the extension of the Northern margin of Gondwana and opening of the Inner-Tauride Ocean

The northward subduction of the Paleo-Tethys beneath the southern margin of Laurasia during the Triassic caused the development of an extensional tectonic regime on the northern Gondwana by pull-forces. The Middle Triassic volcanic activity on the passive continental margin of Gondwana can be attributed to this rifting stage. The Afyon Zone represents the deeply buried northern margin of the Anatolide-Tauride Block (ATB), which was rifted from Gondwana in the Triassic by the opening of the southern Neo-Tethys. It is characterized by the existence of widespread Middle Triassic volcanic activity, which unconformably cover deeply eroded pre-Triassic basement. Early Middle Triassic rhyolites and andesites (245.2 ± 2.0 Ma) represent the first stage of the magmatic activity and exhibit a subduction signature, attributed to the former short-lived southward subduction of the Paleo-Tethys beneath northern Gondwana during the Carboniferous. The second stage of magmatic activity is dominated by trachyandesitic volcanic rocks (243.1 ± 1.9–239.2 ± 1.2 Ma) and rhyolites (243.0 ± 2.9–238.2 ± 1.2 Ma), which were generated in a rift setting. The final stage of magmatic activity at the northern margin of the ATB is characterized by extensional anorogenic alkaline rhyolitic volcanism (237.2 ± 2.3–229.4 ± 2.7 Ma), following the earlier stages described. During Middle to Late Triassic, this rifting on the northern Gondwana led to the synchronous opening of the Inner Tauride Ocean in the north and the southern branch of the Neo-Tethys in the south. The generation of these two oceans and the separation of the ATB and Kırşehir blocks from the northern margin of Gondwana should have resulted in the failure of the northern branch of the Neo-Tethys to open as a new oceanic basin