Characterization of Ore and Gangue Mineralogy at the Ashashire Gold Deposit, Benishangul-Gumuz Region, Western Ethiopia

Abstract

This research presents a comprehensive mineralogical characterization of the Ashashire gold deposit in western Ethiopia to inform processing strategies. We analyzed six representative core samples using fire assay with atomic absorption spectroscopy (AAS), inductively coupled plasma (ICP), and quantitative evaluation of minerals by scanning electron microscopy (QEMSCAN). The gold content varied from 1.47 g/t to 5.27 g/t, with a mean value of 2.54 g/t. The results indicate that gold primarily occurs as native gold and gold-telluride, closely associated with tellurium, and is predominantly occurs as free particles or in association with gangue minerals such as quartz and pyrite. Pyrite (2.1-6.73 wt%) is the dominant sulfide mineral, with only trace chalcopyrite detected. The gangue assemblage is dominated by quartz (10.3-42.3 wt%), ankerite-dolomite (9.1-27.6 wt.%), muscovite (8.0-22.6 wt%), chlorite (0.2-17.4 wt%), and albite (5.6-33.7 wt%). Gold grain size distribution reveals 19.2% coarse particles (>60 µm), 27.6% in the 20-40 µm range, and 3.8% very fine particles (<2 µm). The presence of tellurium and gold-tellurides indicates a refractory gold component requiring specialized processing. We recommend an integrated flowsheet that combines gravity separation, flotation, pressure oxidation, and cyanidation (CIL/CIP) to optimize gold recovery. These findings provide a foundation for developing efficient and sustainable processing strategies tailored to the deposit's unique characteristics.