This study aims to differentiate between Cu-Mo and Cu-Au porphyry deposits within Iran through fractal modeling, utilizing the Mo/Au geochemical index as a primary determinant. Employing the Concentration-Number (C-N) fractal model, the Mo and Au values within Iranian copper porphyry deposits were comprehensively classified. The findings from the fractal modeling reveal distinct criteria for separating these deposits. Cu-Mo porphyry deposits are identified by Mo concentrations ≥141 ppm, while Cu-Au porphyry deposits are characterized by Au concentrations ≥398 ppb. The pivotal threshold for the Mo/Au ratio stands at 1585, facilitating the division between these distinct types of porphyry deposits. Within the Urumieh-Dokhtar magmatic arc, numerous Cu-Mo porphyry deposits, exemplified by globally recognized sites like Sarcheshmeh and Sungun, are prevalent. Conversely, Cu-Au porphyry deposits are found in the NW and SW regions of the Urumieh-Dokhtar magmatic arc and eastern Iran, typified by occurrences like Dalli. The study's findings reveal a correlation between geological characteristics and the ages of porphyry deposits, indicating that those formed during the Miocene period and later are predominantly of the Cu-Mo (Copper-Molybdenum) porphyry type.
The objective of this paper is to detect various gold and copper mineralization stages according to surface lithogeochemical data utilizing zonality index and spectrum-area (S-A) multifractal modeling along with geological data in the Au-(Cu) intrusion-related Gouzal-Bolagh deposit, northwestern Iran. Gold mineralization at Gouzal-Bolagh consists of quartz-sulfide veins within the Paleocene batholithic granitoid complex, which has intruded into the Mesozoic and older metamorphic rocks and shales. Considering the mineralization type, a zonality index was determined as (Au + Cu)/(As + Sb). Au, Cu, and zonality index values were categorized by the S-A multifractal model and the log–log plots. Moreover, multifractal modeling of the zonality index in correlation with geological (specifically mineralographical) data shows that there are three stages for mineralization including Pre-, main and post-mineralization (supergene enrichment). The main stage of mineralization formed from two sub-stages:A (Quartz vein and veinlet sulfidation), B (Quartz sulfide brecciation). In addition, various stages of mineralization contain zonality index values of < 31.8, 31.8–507.3, 507.3–758.3, 758.3–1628.7 and >1628.7 for background, pre-mineralization, sub-stages A, B and supergene, respectively. The background is a granitic batholith containing silicic mineralized veins with a NE-SW trend. Results obtained by this study demonstrate that there are major occurrences of gold and copper mineralization in the sulfidation and brecciation sub-stages, respectively.
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