Characterization and identification of Au pathfinder minerals from an artisanal mine site using X-ray diffraction

Abstract

Gold-associated pathfinder minerals have been investigated by identifying host minerals of Au for samples collected from an artisanal mining site near a potential gold mine (Kubi Gold Project) in Dunkwa-On-Offin in the central region of Ghana. We find that for each composition of Au powder (impure) and the residual black hematite/magnetite sand that remains after gold panning, there is a unique set of associated diverse indicator minerals. These indicator minerals are identified as SiO2 (quartz), Fe3O4 (magnetite) and Fe2O3 (hematite), while contributions from pyrite, arsenopyrites, iridosmine, scheelite, tetradymite, garnet, gypsum and other sulfate materials are insignificant. This constitutes a confirmative identification of Au pathfinding minerals in this particular mineralogical area. The findings suggest that X-ray diffraction could also be applied in other mineralogical sites to aid in identifying indicator minerals of Au and the location of ore bodies at reduced environmental and exploration costs.

Elucidating Pathfinding Elements from the Kubi Gold Mine in Ghana

“…In contrast to previous observations by XRD [56] where the crystal structures were identified, we find that there are significant changes in the chemical bonds in the investigated materials. The XPS analysis confirms that there is covalent bonding between the Au atoms and ligands in particular for the coarse-grained, while the Au bulk and fine-grained powder indicate metallic bonding with other metals, as shown in the valence band spectra in Figure 8.…”

“…In our analysis, we have prepared the samples (fine and coarse-grained) from the untreated powder so that almost all sulfur-containing grains were discarded. This is due to the fact that the sulfide minerals are washed away The Fe in these alluvia Au samples is believed to be contributions from the presence of pyrite, pyrrhotite, chalcopyrite, and the "gangue mineral" magnetite [56]. According to Moslemia et al [93] and Corkhill et al [94], the oxidation of minerals such as Fe 3 O 4 and CuFeS 2 (pyrite group of minerals) under conditions such as pressure, temperature, pH, particles size, concentration, and electrochemical mechanisms results in the release of ferrous ions and other constituents [93,94].…”

“…This higher BE (708.4 eV) and the lower BE for marcasite FeS 2 is in close agreement with the peak at (706.9 eV) from the XPS spectra in Figure 7, which is consistent with reference data [70] for FeS 2 . It can be deduced that the deficient main Fe 2p 3/2 peak in the samples from the Kubi Gold project contains pure metal Fe and FeS 2 , since FeS 2 is one of the main indicator minerals in the mining area [56]. As telluric iron is extremely rare, we assume that the pure metallic Fe observed by our XPS measurements originates from iron oxides that are readily reduced in the argon monomer sputter cleaning process.…”

“…The binding energy (BE) scale was calibrated using the ISO-certified procedure, with the spectra referenced to the Fermi edge in order to circumvent discrepancies associated with employing the C 1s peak from adventitious carbon [55]. Prior to the XPS core and valence band measurements, the structural properties were investigated [56]. After XRD analysis [56], Au, quartz (SiO 2 ), magnetite (Fe 3 O 4 ), and hematite (Fe 2 O 3 ) were identified in these samples.…”

“…Prior to the XPS core and valence band measurements, the structural properties were investigated [56]. After XRD analysis [56], Au, quartz (SiO 2 ), magnetite (Fe 3 O 4 ), and hematite (Fe 2 O 3 ) were identified in these samples.…”