The geology of the Ağvanis metamorphic rocks and neighbouring formations

The area studied is located in Northeast Anatolia between the Pontide and Tauride orogenic belts. The metamorphic rocks called Ağvanis Group are bounded to the north and south by faults of the North Anatolian Fault Zone; in the east and west they are unconformably overlain by sedimentary rocks of Eocene and younger age. The Ağvanis Group consists mainly of metabasic rocks with lesser amounts of marble, phyllite, metadacite and metaacidic plutonic rocks. The major metaacidic pluton is the Gökseki metatrondhjemite which forms a large sheet. Metamorphic and surrounding rocks are cut by hundreds of dacite sills, stocks and a quartz-diorite pluton related to Paleocene acid magmatism. The western part of the Ağvanis Group forms a WNW-ESE trending large anticlinorium whereas in the east N-S trending antiform and synforms, probably as part of older structural elements, are preserved. Metamorphic rocks of the Ağvanis Group have undergone regional metamorphism in greenschist facies; a contact metamorphism superimposed on the regional metamorphism has developed around the quartz-diorite pluton. In terms of lithology, stratigraphy and type of metamorphism rocks of the Ağvanis Group resemble those of the Tokat Massif and probably constitute, like the Tokat Massif, the basement to the Pontide Mesozoic sequence. Hacıören Formation of Liassic age consisting of volcano-clastic sediments occurs to the north of the Ağvanis metamorphic rocks; whereas to the northeast of the Ağvanis metamorphic rocks there is the newly described Taşdemir Formation consisting of olistostromes of Paleocene age. Taşdemir Formation is tectonically overlain by the Boynuktepe Group which forms a nappe of Jurassic-Cretaceous limestones. Eocene sandstones lie unconformably on the Ağvanis metamorphic rocks and on the Taşdemir Formation. The youngest rocks in the area are terrigenous deposits probable of Oligomiocene age and poorly consolidated sandstone conglomerate, clay, marn and basalts of Neogene age