Geological setting and geochemical signatures of the mafic rocks from the Intra-Pontide suture zone: implications for the geodynamic reconstruction of the Mesozoic Neotethys.

A number of suture zones exist in Turkey, which is believed to represent the closure of Paleo and NeoTethyan oceanic basins. Regarding the development of the latter oceanic entity, namely Neotethys, the geodynamic evolution of the Intra-Pontide branch, the northernmost one of a number of oceanic basins remains enigmatic. The Intra-Pontide Suture Zone (IPSZ) in Northwest Turkey includes several tectonic units most of which are characterized by the occurrence of mafic rocks with distinct geochemical signatures. In this paper, the mafic rocks collected from four of these units (the Domuz Dağ Unit, the Saka Unit, the Daday Unit and the Arkot Dağ Mèlange) have been studied in detail along two selected transects. The Domuz Dağ Unit is characterized by amphibolites, micaschists and marbles, which have been overprinted by low-grade metamorphism.The Saka Unit is in turn represented by an assemblage of slices of amphibolites, marbles and micaschists metamorphosed under upper amphibolite facies metamorphic conditions in the Late Jurassic time. In these units, the amphibolites and their retrograded counterparts display E-MORB-, OIB- BABB- and IAT-type signatures. The Daday Unit is characterized by metasedimentary and metamafic rocks metamorphosed under blueschist to sub-greenschist facies conditions. The metamafic rocks comprise actinolite-bearing schists and Na-amphibole-bearing varieties possibly derived from basaltic and gabbroic protoliths. They have a wide range of chemical compositions, displaying N-MORB-, E-MORB-, OIB- BABB- and IAT-type signatures. The Arkot Dağ Mèlange consists of a Late Santonian assemblage of slide-blocks mainly represented by basaltic lithologies showing affinities ranging from N-MORB- and IAT- to BABB-type magmas. The geochemical signature of the studied mafic rocks indicates that the tectonic units documented along the two studied transects of the Intra-Pontide Suture Zone have been derived from a supra-subduction zone. This hypothesis corroborates the available data collected from the Aylı Dağ Ophiolite Unit cropping out in the westernmost studied transect. This finding can provide new insights for the reconstruction of the geodynamic history of the Intra-Pontide domain.