K-Ar ages of granitoids unravel the stages of Neo-Tethyan convergence in the eastern Pontides and central Anatolia, Turkey

Abstract

K-Ar dating of mineral separates extracted from various granitoid rock units of the eastern Pontides and central Anatolia, Turkey, has provided some new insights unravelling various stages of the Neo-Tethyan convergence system, which evolved with northward subduction between the Eurasian plate (EP) to the north and the Tauride-Anatolide platform (TAP) to the south along the degrees zmir-Ankara-Erzincan suture (IAES) zone. Arc-related granitoid rocks are only encountered in the eastern Pontides and yield K-Ar cooling ages of both Early Cretaceous (138.5 +/- 2.2 Ma) (early arc), and Late Cretaceous, ranging from 75.7 +/- 0.0 to 66.5 +/- 1.5 Ma (mature arc), respectively. The multi-sourced granitoids of the eastern Pontides, with a predominant mantle component and K-Ar ages between 40 and 50 Ma, are considered to be a part of post-collisional slab break-off magmatism accompanied by tectonic denudation of pre-Late Cretaceous granitoid rocks following juxtaposition of the EP and the TAP around 55-50 Ma in the eastern Pontides. The K-Ar cooling ages of collision-related S-, I- and A-type granitoids in central Anatolia reflect good synchronism between 80 and 65 Ma, suggesting a coeval genesis in a unique geodynamic setting but with derivation from various sources-namely, purely crustal, purely mantle and/or of mixed origin. This sort of simultaneous generation model for these S-I-A-type intrusives seems to be consistent with a post-collisional lithospheric detachment related geodynamic setting. I-type granodioritic to tonalitic intrusives with K-Ar cooling ages ranging from 40 to 48 Ma in east-central Anatolia are interpreted to have been derived from a post-collisional, within-plate, extension-related geodynamic setting following the amalgamation of the EP and the TAP in east-central Anatolia.