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.


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The Karakoç Magmatic Association (KMA) within the Central Anatolian Crystalline Complex (CACC) consists of ultramafic cumulates, layered gabbros and diorite. The KMA intruded the carbonate dominated upper part of the CACC as a network and includes host rock xenoliths. The KMA is characterized by abundance of Ca-rich phases (green diopside (Mg#=57-93), pargasite (Mg#=41-86), plagioclase (An=91-95), scapolite (Me=42-92), calcite) and Ca-free minerals (phlogopite (Mg#=71-76), alkali-feldspar). The accessories...
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The Idis Dagi Igneous Complex is one of a number of late-stage plutonic bodies within the Central Anatolian Crystalline Complex. It intrudes Paleozoic-Mesozoic metamorphic basement rocks and Late Cretaceous granitoids. The complex comprises mainly quartz syenites and alkali-feldspar quartz syenites known as the Idis Dagi Syenitoids.
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The Southeast Anatolian Orogenic Belt (SAOB) is characterized by a tectonic assemblage consisting of dismembered ophiolites, subduction-related as-semblages, and continental fragments. Whether the subduction-related volcanic assemblages formed in a Southern Neotethys oceanic arc-basin system (the Yüksekova Complex) or in a back-arc basin (the Maden Complex) originated after the closure of Southern Neotethys is still debated. To shed light on this matter, we focus on the Maden area, known as the type localit...
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The remnants of the Neotethyan Izmir-Ankara Ocean, the main branch of Neotethys in the eastern Mediterranean are represented by the Dagkuplu Melange Complex in Central Sakarya, NW Turkey. It comprises several blocks or tectonic slices of pillow lavas, some of which include mudstones and radiolarian cherts as intra-pillow-fillings or interlayers. In the Igdecik area, a huge basaltic block has been studied in detail Geochemical data reveal three distinct basalt types separated by sheared contacts The first of...
Citation Formats
F. Toksoy Köksal and M. C. Göncüoğlu, “Hydrous aluminosilicate metasomatism in an intra-oceanic subduction zone: Implications from the Kurancali (Turkey) ultramafic-mafic cumulates within the Alpine Neotethys Ocean,” MINERALOGY AND PETROLOGY, pp. 273–290, 2009, Accessed: 00, 2020. [Online]. Available: https://hdl.handle.net/11511/31149.