International Geological Journal - Official Journal of the Carpathian-Balkan Geological Association

U–Pb zircon geochronology and geochemistry of the metamorphic sole rocks of the Meydan mélange, South-East Turkey: Implications for ophiolite emplacement and protolith

Published:

Pages: 183 - 205

DOI: https://doi.org/10.31577/GeolCarp.71.2.6

Authors: NUSRET NURLU

Abstract: Metamorphic sole rocks at the base of the mantle tectonites of the Meydan ophiolite in South-East Anatolia, Turkey, are directly overlain by sheared serpentinites and cut by unmetamorphosed mafic dikes. They are found in areas close to the forefront of the Tauride thrust and are described as biotite amphibole schist (Bt + Hbl + Act + Plg + Rt ± Zrn), prehnite–pumpellyite–amphibole schist (Prh + Pmp + Act + Plg ± Rt ± Ttn), amphibole schist (Fe2+– Act + Qtz + Plg ± Anl ± Zrn), and amphibolite (Mg–Hbl + Plg ± Zrn ± Rt). They are identified as island arc tholeiites (IATs) based on their major- and trace-element whole-rock chemistry and mineral composition. The mafic dikes intruding into the metamorphic sole rocks and mantle tectonites exhibit tholeiitic affinity (Nb/Y = 0.03–0.13) and are geochemically similar to island-arc basalts. The multiple elements, rare earth element (REE) trends, and related diagrams suggest that the mafic dikes were generated in a supra-subduction zone (SSZ) setting. Geothermobarometric examination based on the chemical compositions of the magnesio-hornblende in the amphibolites indicated that the pressure and temperature during the metamorphism were ~ 2.4 kbar (at depths of roughly 9 km) and ~ 630 °C, respectively. To elucidate the relationship and timing between the formation of the Meydan ophiolite and that of the metamorphic sole rocks, this paper presents new zircon U–Pb geochronological data from two samples of sole rocks, the ages of which are indicated to lie in the range of 81.4 ± 0.69 Ma to 85.4 ± 0.93 Ma (Santonian–Campanian). The precise U–Pb geochronology and the detailed petrographical and geochemical features of the metamorphic sole rocks and the protolith are evaluated to identify the tectonic environments of supra-subduction realms characterizing the South-Eastern Anatolian Orogenic Belt (SAOB). The metamorphic sole rocks were formed as a result of intra-oceanic thrusting during supra-subduction events in the basin throughout the closure of the SAOB in the Late Cretaceous.

Keywords: Metamorphic sole, Meydan mélange, South-East Anatolia, U–Pb geochronology, zircon

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Volume 71 no. 2 / April 2020

Volume 71 no. 2