Ore-forming Fluid Evolution in the Shourab Gold Prospect, Isfahan: Insights from Quartz Chemistry and Fluid Inclusions

This study investigates the ore-forming fluid evolution in the Shourab gold prospect, Central Iran, through integrated quartz chemistry and fluid inclusion analysis. The Shourab gold prospect occurs within the early Eocene diorite to granodiorite, intruding the Cretaceous carbonate and volcanic rocks. The prospect displays alteration zone of sodic-calcic, biotite-magnetite, carbonatization, and silicification associated with gold mineralization. Early-stage quartz from biotite-magnetite alteration zone contains elevated Ti (BDL-410 ppm), formed from high-temperature (Th of fluid inclusions= 343–495 °C, mode= 390 °C) and saline (11–29 wt% NaCl eq., avr. 17 wt% NaCl eq.). Late-stage quartz in silicified zones shows significant Al (704–2307 ppm) and alkali enrichment (BDL–349 ppm Na and 96–247 ppm K), associated with cooler (198–338 °C, mode= 324 °C), less saline fluids (7–11 wt% NaCl eq., avr. 8 wt% NaCl eq.). Gold mineralization is associated with late-stage fluids, where cooling of hydrothermal fluids promoted metal deposition. Veins formed by low-temperature, less saline fluids with high Al and alkali elements in quartz serve as a potential for Au mineralization and can guide future exploration in the region.