Geochemistry, petrogenesis and massive sulphide mineralizations of the Artvin district of the pontid belt, NE Turkey

Geochemistry, Petrogenesis and Massive Sulphide Mineralizations of the Artvin District of the Pontid Belt, NE Turkey. SUMMARY Artvin district which is located in between Pontid and Lasser Caucassus has been investigated for magma tic petrology and related polymetallic massive sulphide depositions. The base of the succession which comprieses the basic lavas and their metamorphics, are of Jurasssic age. These are named as "Lower Basic Series" by previous authors. The "Lower basic series" are cut by the Artvin granitoid. This granitoid is overlain by ore-bearing dacites and tuffs. All these are cut by purple-colored dacites. this successions is conformably overlain by the volcano-sedimantary series. In some places the units of Upper Cretaceous ages show graduation into the Paleocene formations. Flych -like formations of Middle Eocene age unconformibly overlie the older formations. The younger Q-diorites and hornblende dacites of Post Eocene age are the youngest formations of the area studied. Artvin area indicates an island arc enviroment. Resulted granitization and associated dacites caused the intensive magma tic hydrothermal activities. Related to this dacitic volcanism many massive or vein type sulphide mineralizations deposited. These generally are of Cu-Zn-Pb composition. Some Mn mineralization whith limited size are also seen. The most impotant massive sulphides are the Kuvarshan, İr sahan, Sinkot, Seyitler, Kafkasor, Eski Gümüşhane and Ormanlı mineralizations. These deposits are related to the hydrothermal fluids which were dischargeced from conduits around the volcanic centers and are contemporaneous with the depositions of dacitic pyroclastics. Starting temperature of the deposition of the ore minerals is around 400-350°C. Presence of colloform pyrites also indicate the pyrite gel depositions at lower temperatures. Contemporary and younger reddish biomicrites overlie the ore formations. Depositions continued at the end of Eocene time. After Eocene, the area were faulted and folded because of the regional compresional stresses. vii