Uranium-Lead (U-Pb) geochronology and geochemistry of metamorphic sole rocks and mafic dikes from Meydan mélange, Helete, City of Adıyaman, Türkiye


Nurlu N.

9th Geochemistry Symposium with International Participation, Aydın, Turkey, 17 - 21 October 2022, vol.1, pp.1

  • Publication Type: Conference Paper / Summary Text
  • Volume: 1
  • City: Aydın
  • Country: Turkey
  • Page Numbers: pp.1
  • Çukurova University Affiliated: Yes

Abstract

Metamorphic sole rocks at the base of the mantle tectonites of the Meydan ophiolite are directly overlain by sheared serpentinites and cut by un-metamorphosed mafic dikes. Metamorphic sole rocks 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). These rocks are identified as island arc tholeiites because of their major- and trace-element whole-rock chemistry and mineral composition. The mafic dikes intruding into the metamorphic sole rocks and mantle tectonites show tholeiitic affinity (Nb/Y = 0.03–0.13) and are geochemically similar to island-arc basalts. The multi-element, rare earth element trends and related diagrams suggest that the mafic dikes are generated in a supra-subduction setting. Geothermobarometric examinations based on chemical compositions of magnesio-hornblende in the amphibolites suggest that the pressure the pressure was approximately 2.4 kbar (at depths of roughly 9 km) and the temperature during metamorphism was approximately 630 ̊C. To help understand 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 metamorphic sole rocks give ages between 81.4 ± 0.69 Ma and 85.4 ± 0.93 Ma (Santonian–Campanian). It is herein proposed that the geochemical, geochronological, petrological, and field evidence show that the Meydan ophiolite and mafic dikes occurred in a supra-subduction environment and that the metamorphic sole rocks were formed as a result of intra-oceanic thrusting during supra-subduction events in the basin throughout the closing of the South-eastern Anatolian Orogenic Belt (SAOB) in the Late Cretaceous.