Johnson Manu

A comparative study of bulk leach extractable gold (BLEG) and fire assay methods on the Wassa deposit at Golden Star Limited, Wassa mine

Golden Star Resources Limited conducts Bulk Leach Extractable Gold (BLEG) and Fire Assay methods on samples from its exploration program. Additionally, for mining control and as part of the sampling and analytical protocol, residues of samples whose assay values are greater than 10 g/t are subjected to fire assay to determine the quantity of gold. However, there is gold retained in the tails or residue after leaching and to verify the suitability and efficiency of the analytical method, drill samples (RC and DD) with control samples were analysed using BLEG method based on the accelerated cyanide leach extraction and Fire Assay method on the tails. Percentages of the prepared samples were subjected to BLEG orientation study to investigate the leachability and efficiency of the BLEG method on the ore samples. Fire Assay analysis was also carried out on the selected tailing samples to find out the assay reproducibility of the samples. The analytical analyses carried out on the samples revealed that the ore samples were leachable with gold recovery levels ranging between 96% and 100% when there is total pulverization of samples to make BLEG method possible and that this procedure is also cheaper than the conventional Fire Assay.

Hydrologic fluxes in the Volta River watershed : A paleo-terrestrial environment in West Africa

The hydrologic cycle plays an important role in carbon cycling, due to the coupling of vapour release and CO2 uptake during photosynthesis. This coupling, expressed as water use efficiency of transpiration ratio, can provide an inexpensive alternative for estimating the Net Primary Productivity (NPP) of terrestrial ecosystem. Stable isotopes of hydrogen and oxygen and long-term hydrologic and meteorological data together with stoichiometric relations of water and carbon are used to constrain water and carbon balances for the Volta River watershed. Soils annually respire 0.199 Pg C, and the balance of these fluxes or Net Ecosystem Productivity (NEP) is +0.029 Pg C Yr -1 , implying an annual flux of CO2 to the atmosphere. Annually, the Volta river watershed receives about 380 km 3 of rainfall. Approximately 50% of this volume of water is returned to the atmosphere through plant transpiration. Associated with annual transpiration flux is a carbon flux of 0.170 ◊ 10 15 g C yr -1 or 428 g C m -2 yr -1 from the terrestrial ecosystem. Modeled estimates of heterotrophic soil respiration exceed slightly the NPP estimate, implying that carbon flux to and from the Volta river watershed is close to being in balance or the watershed is a small annual source of carbon dioxide to the atmosphere. In addition to terrestrial carbon flux, the balance of photosynthesis and respiration in Volta Lake is also examined. The lake was found to release carbon dioxide to the atmosphere, although the magnitude of the flux is smaller than that of the terrestrial ecosystem.

Conventional potassium - Argon age of the Shai Hills, Southeastern Ghana

Abstract KAr ages of samples from the Dahomeyan orogen have been determined. Hornblendes of three plagioclase-garnet-hornblende-gneiss samples from the Shai Hills area, southeastern Ghana give KAr ages of 649 ± 4, 549 ± 8, 562 ± 6 M.a. respectively while hornblendes from two plagioclase-garnet-hornblende-gneisses from about one kilometer east of these samples give ages of 547 ± 2 M.a. and 667 ± 9 M.a.. The average age of 595 ± 29 M.a. is in agreement with recently reported measurements on hornblende of a single rock sample from the Shai Hills. This result supports the belief that the Shai Hills were highly affected by the Pan-African orogeny of the late Precambrian to Cambrian (500 – 700 M.a.) and the Hills did not preserve any record of the Birimian during the Pan-African orogeny. The possible explanation of the 120 M.a. range in ages is briefly discussed.