Epithermal Pb-Zn-Cu (Ag-Au) Mineralization at İnler Yaylası Deposit (Şebinkarahisar, Giresun)

Abstract

İnler Yaylası Pb-Zn-Cu (Ag+Au) deposits are located approximately 23 km northwest of Şebinkarahisar (Giresun). Mineralization is developed as veins and disseminated types along of the NE-SW trending fractures in the Late Cretaceous volcanic rocks. Propylitic, sericitization and silicification are developed in the wall rock. Three main stages of mineralization have been defined as pre-ore, main sulfide and supergene. In the first stage, hematite, chlorite and epidote developed. Sericitization and silicification are associated with the sulfide phase. Quartz is in the form of mosaic-textured and filling open-space vein with a crustiform and comb-textured. The textural features show that the main sulfide phase develops in two sub-phases. First sub-phase composed of sphalerite, galena, pyrite and less abundant chalcopyrite, Ag-sulfosalts and Pb-sulfosalts. The second sub-phase consist of pyrite, chalcopyrite, sphalerite, galena, and less abundant Ag-sulfosalts and gold. Supergene stages characterized by bornite, covellite, malachite, azurite, smithsonite, limonite, calcite, and chalcedony.

In the İnler Yaylası, base and precious metal element contents are between 631 and >150.000 ppm for Zn, 637 and 48.875 ppm for Pb, 132 and >150.000 ppm for Cu, 3 and 2564 ppm for As, 20 and 344 ppm for Ag, 0.1 and 1.6 ppm for Au, 0.5 and 413 ppm for Sb. The Ag:Au ratio range from 40:1 to 1721:1. Strong positive and negative correlation confidents between Pb‒Zn (R²=0.70), Au‒Cu (R²=0.83) and Pb‒Cu (R²=0.91), Zn‒Cu (R²=0.60) manifest that Pb‒Zn and Cu‒Au mineralization in the region is related to the different sub-phase. The strong correlation confidents between Ag‒Sb are (R²=0.78) associated with Ag-rich sulfosalt. Mineral assemblage and geochemical properties indicate that İnler Yaylası deposit typically characterize an intermediate-sulfidation epithermal type deposit.