OFIOLITI

Plagiogranites within the supra-subduction zone (SSZ) type Saikaraman Ophiolite (SO), Central Anatolia, are very fine to coarse grained leucocratic rocks with a range of occurrences as simple narrow fracture infilling to wide complex zones of net-veining or agmatites with numerous, partly assimilated enclaves of gabbro and dolerite. Petrographically, they are characterized by the textures ranging from hypidiomorphic granular to granophyric intergrowths of quartz and plagioclase. Geochemically, major and trace elements data revealed that the plagiogranites belong to the typically low-potassium series of ophiolitic complexes and show similar geochemical characteristics with the Ocean-Ridge Granites. They are characterized by 10-20 times enriched flat chondrite REE patterns with a negative Eu anomalies relative to mafic component in the SO. This confirms the cogenetic nature of the plagiogranites and indicates progressive fractionation in the Sarikaraman mafic magma. Field observations coupled with major-element and trace element chemistry support to a model by which the plagiogranites of SO could be formed as a fractional crystallization of Sarikaraman basaltic magma in SSZ setting, like the other eastern Mediterranean ophiolitic plagiogranites such as Troodos, Pindos, and Oman

GEOLOGICAL JOURNAL

Isolated outcrops of ophiolitic rocks, termed the Central Anatolian Ophiolites, are found as allochthonous bodies in the Central Anatolian Crystalline Complex, that represent the metamorphosed passive northern edge of the Tauride-Anatolide Platform, central Turkey. In terms of pseudostratigraphic relationships of the magmatic units and their chemical designation, the Central Anatolian Ophiolites exhibit a supra-subduction zone (fore-arc) setting within the Vardar-Izmir-Ankara-Erzincan segment of the Neotethys. The epi-ophiolitic sedimentary cover of the Central Anatolian Ophiolites is generally characterized by epiclastic volcanogenic deep-sea sediments and debris flows intercalated with pelagic units. The richest and most significant planktonic foraminiferal association recorded from the lowest pelagic members infer a formation age of early-middle 'Turonian to early Santonian. K/Ar ages of post-collisional granitoids (81-65 Ma) intruding the basement rocks as well as the Central Anatolian Ophiolites suggest a post-early Santonian to pre-middle Campanian emplacement age. The marked high volume of epiclastic volcanogenic sediments intercalated with the pelagics of the Central Anatolian Ophiolite is suggestive of rifting in a marginal sea adjacent to a volcanic are. Penecontemporaneous tectonism is reflected in repetitions in the stratigraphy and in debris flows, which result from major slides and mass-gravity reworking of pre-existing units and of are-derived volcanics and sediments. Correlating the rock units and formation/obduction ages of the Central Anatolian Ophiolites with further supra-subduction zone type ophiolites in the eastern (Turkey) and western (Greece) parts of the Vardar-Izmir-Ankara-Erzincan segment of Neotethys we conclude that the intraoceanic subduction in the east is definitely younger and the closure history of this segment is more complex than previously suggested. Copyright (C) 2000 John Wiley & Sons, Ltd

Geochemistry and petrogenesis of intrusive and extrusive ophiolitic plagiogranites, Central Anatolian Crystalline Complex, Turkey

Plagiogranites associated with the Sarikaraman ophiolite of the Central Anatolian Crystalline Complex, Turkey, closely resemble other plagiogranites from supra-subduction zone-type ophiolites of Neotethys, The ophiolite is remarkable in displaying a higher proportion of the plagiogranite suite (ca. 10% by volume) than is usually associated with such bodies. The Sarikaraman plagiogranites are represented by intrusive sheets and netvein trondhjemites largely developed at the top of the upper gabbros and as multiphase dykes within the sheeted dyke complex. The plagiogranite dykes are considered to feed extrusive silicified rhyolites associated with the basaltic lavas in the volcanic section of the ophiolite. Field relations suggest that the trondhjemites were probably generated from the roof section of a dynamic and evolving gabbroic magma chamber. Both the deep-seated trondhjemites and the volcanic rhyolites constitute the Sarikaraman plagiogranite suite. Geochemically there is complete overlap between the intrusive trondhjemites and extrusive rhyolites, which are characterised by (MORB-normalized) low HFS element contents with small negative Nb-Ta anomalies and variably enhanced LIL element abundances. Unlike other plagiogranites, however, the Sarikaraman suite is not characterized by consistently low K2O contents; a feature that reflects the variable mobilization of the Ln elements under lower greenschist facies conditions. The REE are uniformly enriched relative to the basic components of the complex, but have similar normalized patterns exhibiting mild light REE depletion. In terms of their origin, the initial or most primitive plagiogranite melts could have been generated by either fractional crystallization (70-85% of clinopyroxene-feldspar +/- amphibole) or partial melting (5-15% batch melting) of a gabbroic 'source material', although only the first process can produce most of the range of the plagiogranite compositions. As a group the plagiogranites exhibit some degree of internal variation which can be generated by further fractionation largely dominated by feldspar with minor apatite and amphibole. (C) 1998 Elsevier Science B.V

Formation and emplacement ages of the SSZ-type Neotethyan ophiolites in Central Anatolia, Turkey: palaeotectonic implications

Isolated outcrops of ophiolitic rocks, termed the Central Anatolian Ophiolites, are found as allochthonous bodies in the Central Anatolian Crystalline Complex, that represent the metamorphosed passive northern edge of the Tauride-Anatolide Platform, central Turkey. In terms of pseudostratigraphic relationships of the magmatic units and their chemical designation, the Central Anatolian Ophiolites exhibit a supra-subduction zone (fore-arc) setting within the Vardar-Izmir-Ankara-Erzincan segment of the Neotethys. The epi-ophiolitic sedimentary cover of the Central Anatolian Ophiolites is generally characterized by epiclastic volcanogenic deep-sea sediments and debris flows intercalated with pelagic units. The richest and most significant planktonic foraminiferal association recorded from the lowest pelagic members infer a formation age of early-middle 'Turonian to early Santonian. K/Ar ages of post-collisional granitoids (81-65 Ma) intruding the basement rocks as well as the Central Anatolian Ophiolites suggest a post-early Santonian to pre-middle Campanian emplacement age. The marked high volume of epiclastic volcanogenic sediments intercalated with the pelagics of the Central Anatolian Ophiolite is suggestive of rifting in a marginal sea adjacent to a volcanic are. Penecontemporaneous tectonism is reflected in repetitions in the stratigraphy and in debris flows, which result from major slides and mass-gravity reworking of pre-existing units and of are-derived volcanics and sediments

Petrology and geotectonic significance of plagiogranite from the Sarikaraman Ophiolite (Central Anatolia, Turkey)

Plagiogranites within the supra-subduction zone (SSZ) type Saikaraman Ophiolite (SO), Central Anatolia, are very fine to coarse grained leucocratic rocks with a range of occurrences as simple narrow fracture infilling to wide complex zones of net-veining or agmatites with numerous, partly assimilated enclaves of gabbro and dolerite. Petrographically, they are characterized by the textures ranging from hypidiomorphic granular to granophyric intergrowths of quartz and plagioclase. Geochemically, major and trace elements data revealed that the plagiogranites belong to the typically low-potassium series of ophiolitic complexes and show similar geochemical characteristics with the Ocean-Ridge Granites. They are characterized by 10-20 times enriched flat chondrite REE patterns with a negative Eu anomalies relative to mafic component in the SO. This confirms the cogenetic nature of the plagiogranites and indicates progressive fractionation in the Sarikaraman mafic magma

Chromitite deposits of Turkey in Tethyan ophiolites

Some parts of the Tethyan ophiolites of Alpine-Himalayan suture belt are located within Turkey. The Tethyan belt splits into two branches in Turkey. The northern branch follows the İzmir-Ankara-Erzincan Zone, while the southern branch extends along the Anatolide-Tauride and Bitlis-Zagros suture zone. The subsections of the latter reach Iran in the east and Oman ophiolites in the south east. These ophiolites are also the only environments in which chromitite deposits occur. Consequently, the ophiolites in Turkey are significantly rich in terms of Alpine type chromitite occurrences and they are the oldest metallic mine products. There has been chromitite ore production in Turkey since the nineteenth century. With their refractory quality, chromitite produced in Turkey has always had a good standing in the market. Chromitite, which was exported as lump ore until mid-twentieth century, started to be used in the domestic market as the country’s industry developed, but still, even today an important part of the production is exported. In addition, since the chromitite developments near to the surface are almost completely exhausted, the chromitite ore production in the country has evolved to concentrated ore obtained from low grade deposits, through beneficiation. Although there are many active beneficiation plants in various parts of the country, there is still a significant amount of concentrate ore production; especially in the deposits of Adana-Aladağ region. In this chapter, the mentioned chromitite occurrences are discussed in a specific order from west to east, taking into account the ophiolite sequences to which they belong. The North Anatolian Ophiolites are introduced in the first three sections whereas the other three sections present the chromitite deposits of the South Anatolian Ophiolites. Nevertheless, considering the historical records and future production potentials, Turkey’s most important chromitite production regions could be listed in order of priority as Guleman (Elazığ), Kopdağ region (Erzincan), Muğla-Fethiye region, Aladağ-Pınarbaşı (Adana-Kayseri), Orhaneli-Harmancık (Bursa)-Eskişehir region and Hatay. It is clear that these should all be taken into consideration for further prospecting targeting. © Springer Nature Switzerland AG 2019