Petrographical and geochemical investigations of the Eğrikar (Torul, Gümüşhane) Fe-Cu Skarn deposit

Egrikar Fe-Cu skarn deposit is located about 100 km nortwest of Gümüşhane (NW Turkey). Sedimantary and volcanic rocks in Eğrikar (Torul-Gümüşhane) and its surrounding are of late Cretaceous age and they consist of dacite containing limestone at the base and hornblende-andesite above it. These rocks are cut by late Cretaceous Eğrikar Granitoid composed of monzogranite, granodiorite and diorite. Dacitic rocks have porphyry texture andare comprised of mainly quartz, plagioclase, biotite and opaque minerals. On the otherhand, limestones are sporadically turned into marble and crystallized. Horblnde-andesites have micro-granular porphyric and glomeroporphyric textures and contain plagioclase, hornblende, biotite and quartz. Eğrikar Granitoid comprises three different lithologies (monzogranite, granodiorite and diorite) and show myrmekitic, scripture and sieve textures. These rocks essentially comprises of plagioclase, quartz, hornblende, orthoclase and mucovite. The contact metamorphism occurred due to intrusion of granitoidic rocks (especially monzogranite) into the limestone and volcanics in the southwesten of Eğrikar Plateau, and skarn zone developed. The formation of endoskarns and exo skarns zones from monzogranit toward limestone are determined. In the skarn zone pyroxene, garnet, epidote, quartz, clacite and actinolite-tremolite form the skarn minerals. In the skarn zone hedenbergite is found as pyroxene type and grossular-andradite and andradite are found as garnet type, respectively. The ore mineral paragenesis of Eğrikar skarn deposits consist of magnetite, pyrite, hamtite, chalcopyrite, gold and native copper. The patterned framework, boxwork, acicular, fibrous and banded textures are seen with magnetite and hematite. Goethite, limonite, digenit, malachite, azurite, bornite and lepidocrocite are determine as secondary ore minerals The volcanics of Eğrikar Fe-Cu skarn deposits are of calc-alkalen character. On the other hand granitoids have calc-alkalen composition with medium K. The trace element characteristics of Eğrikar Granitoidic rocks in general show similarity to arc granites and Fe-skarn related to granitoids in Eğrikar Fe-Cu skarn field are determined to be occurred in post subduction. Fluid inclusions are classified as primary, pseudo-secondary and secondary through the fluid inclusion studies made on quartz minerals from exoskarn zone of Eğrikar Fe-Cu skarn deposit. The measurements made on quartz samples determined that temperatures are between 160-380 °C and salinity between % 3.4-7.6 for the exoskarn zone, supporting an epithermal and skarn origin. In Eğrikar Fe-Cu skarn deposits, pyroxene and garnet main forming the silicate minerals and apperance of abundant magnetite, hematite and very little pyrite along with fluid inclusion data obtained indicate that this deposit formed under oxidizing conditions by shallow intrusion.