Geochronology And Geochemistry Of Blueschist Facies Assemblages In A Neotethyan Ophiolitic Melange From The Eastern Part Of The Central Taurides


KOP A., PARLAK O. , ALAN İ., KARAOĞLAN F. , NEUBAUER F.

7th Internatıonal Symposıum On Eastern Medıterranean Geology, Adana, Turkey, 18 - 22 October 2010, pp.12

  • Publication Type: Conference Paper / Summary Text
  • City: Adana
  • Country: Turkey
  • Page Numbers: pp.12

Abstract

In the eastern part of central Taurides, five tectonic units that display distinct features in terms of stratigraphy, metamorphism and structures have been recognized in Ereğli (Konya), Ulukışla (Niğde), Karsantı (Adana) and Namrun (İçel) regions. These tectonic units, from bottom to top, are called Geyik Dağı, Bolkar Dağı, Namrun, Aladağ and Bozkır and in terms overlain by Tertiary sedimentary units of the Ereğli-Ulukışla, the Ayrancı-Adana and the Karsantı basins. An ophiolitic melange, belonging to the Bozkır unit, rests tectonically on the top of the metamorphic Bolkar Dağı unit and represented by serpentinite, serpentinized harzburgite, isolated diabase dikes, volcanics, amphibolite and metacarbonate blocks. The amphibolite that represents a metamorphic sole displays well developed foliation patterns and is intercallated with metacarbonate rocks. The 40Ar-39Ar isotopic age determinations performed on amphibole separates yielded ages from 92.29±0.38 Ma to 94.96±0.50 Ma. The metamorphic sole rocks exhibit two distinct geochemical features. The first group is alkaline (Nb/Y=1.43-2.05), whereas the second group is tholeiitic (Nb/Y=0.04-0.58) in nature. The REE patterns, multi-element and tectonomagmatic discrimination diagrams suggest that the protholith of the first group is similar to within-plate alkali basalts, whereas the second group is more akin to MORB-island arc tholeiitic basalts. The isolated diabase dikes are tholeiitic in character (Nb/Y=0.03-0.13). The REE patterns, multi-element and tectonomagmatic discrimination diagrams suggest that the isolated dikes formed in a subduction-related environment. Petrographic studies of the amphibolitic sole and the isolated diabase dike rocks indicate that these rocks display blueschist facies overprinting, represented by glaucophane mineral. All the field and geochemical data show that the ophiolitic rocks formed along the Inner Tauride ocean, bounded by the Kırşehir block in the north and the Taurides in the South. A metamorphic sole developed at the inception of north-dipping intraoceanic subduction during the Late Cretaceous. Subduction-accretion units and the leading edge of the northern margin of the Tauride Carbonate Platform were underthrust, deeply buried and metamorphosed under HP-LT conditions. The metamorphosed rift/passive margin units and the distal edge of the Tauride Carbonate Platform were uplifted and emplaced together with the over-riding ophiolites in Late Cretaceous-early Tertiary. Upper Paleocene to Middle Eocene successions rest unconformably on the top of the above-mentioned units. The LA-ICP-MS zircon U-Pb measurements suggest that the Horozdağ granitoid intruded into all these units at 48-49 Ma.