Mineralogical, Geochemical and Textural Characterization of Akobo Gold Deposit for Ore Beneficiation, South Western Ethiopia
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Date
2023-10
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Addis Ababa University
Abstract
Gold, a precious metal since ancient times, was one of the first metals used by humans due to its availability in placer deposits. However, efficient gold ore processing faces challenges in achieving optimal gold recovery. Inadequate mineral and geochemical characterizations of the ore contribute to inefficient processing. The objective of the project was to assess the mineralogy and geochemical properties of the Akobo gold deposit in order to identify effective treatment methods for optimal gold recovery. Various methods such as optical microscopy, XRD, ICP-AES/MS and SEM are used to evaluate the mineralogy, geochemistry and texture of the gold deposit. The Akobo gold deposit is hosted in metavolcanics and metasedimentary rock, with common alterations including talc alteration, carbonatization, and silicification. Gold mineralogy identified in the area includes krennerite, montbrayite, buckhornite, austobite, calaverite,
nagyagite and gold phosphorus thallium selenide. Gangue minerals associated with gold include magnetite, arsenopyrite, pyrite, chalcopyrite, quartz, actinolite, chlorite, siderite, cubanite, covellite, stibnite, and bertherite. Geochemical analysis showed that gold concentration ranged from 0.001 ppm to 9.76 ppm, silica ranged from 26.2% to 58%, iron oxide concentration ranged from 3.79% to 19.3% and the maximum concentration of titanium oxide is 2.47%. The gold
particles in the deposit are encapsulated in gangue minerals and range in size from submicroscopic to microscopic (as it ranges from 20μm to 2mm). Most grain size ranges from 50μm to 100μm (about 41%). The Akobo gold deposit is classified as a refractory ore due to its mineral composition, consisting mainly of telluride along with some sulfide and selenide minerals. The processing of this refractory gold requires pretreatment methods such as roasting,
bio-oxidation, and pressure oxidation to minimize losses. Comprehensive metallurgical testing is
necessary to select a suitable and efficient gold processing method.
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Keywords
Gold Ore Mineralogy, Roasting, Pre-Treatment, Amalgamation, Flotation, Telluride, Refractory Ore, Free Milling