Genesis of the Gedabek Au-Ag-Cu deposit (Azerbaijan) in the Lesser Caucasus: Insights from geochemistry, fluid inclusion and sulfur isotope

Abstract

The Gedabek Au-Ag-Cu deposit located in the western part of Azerbaijan is hosted by quartz porphyry which is situated at contact between Middle Jurassic andesitic tuff and Late Jurassic-Early Cretaceous Gedabek intrusive rocks consisting of granodiorite, diorite and gabbro. Geochemical investigations for the Gedabek intrusive rocks indicate that these are calc-alkaline, and probably developed pre-collisional regime. The Gedabek Au-Ag-Cu deposit, mainly observed in the advanced argillic alteration, is composed of native gold, electrum, hessite, petzite, chalcopyrite, sphalerite, galena, molybdenite, pyrite, arsenopyrite, fahlore, enargite, bornite, hematite, barite, jarosite, adularia, covellite, chalcocite, malachite and azurite. The Gedabek Au-Ag-Cu deposit predominantly comprises Au, Ag, Cu, Zn, Pb, Fe, As, and S for the ore-bearing samples. Homogenization temperatures and salinities of fluid inclusions (FIs) trapped in quartz and sphalerite range from 134 to 371 degrees C and 227 to 410 degrees C; 3.4 to 15.2 wt% NaCl equivalent and 4.0-12.0 wt% NaCl equivalent, respectively. The delta S-34(H2)S values (2.0-5.9 parts per thousand) of sulfides (chalcopyrite, pyrite and sphalerite) from the Gedabek Au-Ag-Cu deposit indicate a magmatic origin for the ore-forming fluids. The geological, mineralogical, geochemical, isotopic, and micro-thermometric data for the Gedabek Au-Ag-Cu deposit suggest a high sulfidation epithermal deposit associated with porphyry system.