Prognosis of gold mineralization phases by multifractal modeling in the Zehabad epithermal deposit, NW Iran

Concentration–Number (C–N) fractal method has been used for determining and separating mineralization phases based on surface lithogeochemical Au, Ag, Cu, Pb, Zn, As, and Sb data in the Zehabad epithermal deposit, NW Iran. Five mineralization phases are demonstrated by multifractal modeling for the mentioned elements correlating with geological studies. The extreme phase of Au mineralization is higher than 7.9 ppm, which is correlated with hematite deposition in silicic veins and veinlets, whereas Ag (˃79.43 ppm), Cu (˃15.85%), Pb (˃63.1%), Zn (˃11.2%) extreme phases are associated with the main stage sulfidation phases. The results show that Au, Cu, Pb, Zn, and Ag have two different mineralization trends based on the multifractal nature in this area. These trends are presented based on oxidic and sulfidic mineralization. According to mineralogical studies, the main stages of mineralization include 1) formation of chalcopyrite ± sphalerite in silicic veins in sulfidic trend; 2) deposition of native gold and specular hematite in silicic veins in response to boiling, in oxidic trend; 3) next phase of fluid penetration and replacing chalcopyrite by galena, sphalerite and tetrahedrite-tennantite in the sulfide veins, in sulfidic trend. Neighboring copper and silver are due to the formation of a tetrahedrite-tennantite solid solution. The obtained results show a positive correlation between mineralization phases and the faults present at the deposit. Moreover, mineralization phases of these elements demonstrate a good correlation with silicification and silicic veins and veinlets.