Origin of the Early-Middle Devonian magmatism in the Sakarya Zone, NW Turkey: Geochronology, geochemistry and isotope systematics

Abstract

A unique example of isotopically-dated Devonian metagranitoid (the camlik metagranite; Okay et al., 1996) crops out in the Biga Peninsula, NW Turkey, although its contact relationships with the country rocks and geodynamic setting have remained to be enigmatic so far. Our field work, however, has shown that a number of metagranitoid bodies similar to the camlik metagranite intruded the country rocks and developed contact metamorphic zones, consisting of andalusite and calcsilicate hornfelses, garnet-epidote and diopsite-wollastonite skarns. The country rocks of these metagranitoids are made up of regionally metamorphosed metaclastic successions with subordinate metacarbonate-metachert-metabasites (the Kalabak formation), intercalated with tectonic slices of meta-serpentinites. The metagranitoids and the Kalabak formation are collectively termed here the Havran Unit which forms a NE-SW trending, 20 km wide and 80 km long belt in the Biga Peninsula. The Havran Unit is unconformably overlain by the Late Triassic shallow marine sediments and is in tectonic contact with the Permo-Triassic Karakaya Complex, interpreted as the Palaeotethyan subduction-accretion complex.