Characterization of Alluvial Gold Bearing Sediments of Betare Oya District-East Cameroon, Implication for Gold Exploration and Recovery

Abstract

Field studies (location Au pits, sampling of different layers of sedimentary sequences filling the pits, panning of sediments), litho-stratigraphic investigations, grain size analysis and outlining of depositional conditions revealed a characteristic fining upward sequence in all the sections of 08 Au-pits within the Betare Oya basin. A typical profile is 2.5 to 4.5 m thick and is composed of a 30 to 50 cm organic topsoil layer, underlain by a 1.5 m thick reddish brownish gold free saprolite, which is underlain by 1.5 m sandy section. From litho-stratigraphic investigations and grain size analysis results a quartz dominated gravelly 1.4 m thick layer consisting in boulders (275 mm), cobbles (2-<20 mm) and subrounded pebbles (28 -38 mm) mixed with sand grains (0.9 -1.5 mm) and silt (0.01 -0.02 mm). Pyrite, chalcopyrite and arsenopyrite are minor minerals and could be referred as to Au pathfinders (As, Fe, Cu). This layer overlays paleo-Proterozoic basement rocks (Nyong series) and is overlain by a poorly sorted sandy layer containing rounded whitish quartz grains and plagioclase fractions (Ca, Na), minor silts (0.02 -0.2 mm), gravel and feldspar (K) leached from granitic plutons along shear zones in the area. The saprolite horizon overlaying the sandy layer derives from weathering and leaching of basement rocks under warm-humid climatic conditions. From gold grain count, the gravelly layer is the main productive horizon. Au is lithologically controlled and could be an important exploration factor in the study area. The calculated aspect ratios for pebbles from the gravelly and sandy layers disclosed two polynomial trends: 1) y = −0.0148x 2 + 1.2187x + 2.0344, R² = 0.6929 (sandy layer); 2) y = 0.0617x 2 + 1.0849x + 0.8097, R² = 0.8694 (gravelly layer); and y > R 2 is satisfied in both cases. This implies that Au recovery from these layers could be effective through gravity separation using sieves mounted on classifiers of 7 cm (sandy layer) and 10 cm (gravelly layer) diameter.

Multi-scale analysis and modelling of aeromagnetic data over the Bétaré-Oya area in eastern Cameroon, for structural evidence investigations

“…13) and propose the litho-stratigraphic model updated below (Table 4). Crustal formations in our model are in accordance with those obtained by Benkhelil et al (2002) from seismic data from south Cameroon, and the summary above is in accordance with the geological study of Mboudou et al (2017).…”

“…The tilt angle (Miller and Singh 1994;Verduzco et al, 2004;Salem et al, 2007) is defined by Eq. (1) below for a potential field anomaly T :…”

“…The tilt-angle operator can be used for mapping geological structures because it permits their contacts and their shapes to be located and delimited (Miller and Singh, 1994). By coupling it to the extension upward, it becomes more interesting because one obtains the lateral extension of body but also of depth and therefore its three-dimensional shape.…”

“…The geological synthesis of Cameroon allows us to have a lithostratigraphic sketch of the Lom Formation. Recently, the near-surface work of Mboudou et al (2017) at Bétaré-Oya proposed the lithological model with topsoil, saprolites, sandy layer, conglomeritic sand, and schist formations.…”

Regional geochemical baseline concentration of potentially toxic trace metals in the mineralized Lom Basin, East Cameroon: a tool for contamination assessment

“…In addition to the hypogene and supergene hematite sources, other possible sources of Fe in the studied sediments are the sulphide minerals pyrite and arsenopyrite associated with the primary gold bearing quartz veins [ 48 ]. Besides Cu, As and Pb, Fe is considered as another pathfinder for gold in the area [ 46 ]. Hence, deep chemical weathering in this tropical basin results in the enrichment of Fe and Mn in the sediments.…”