Characterisation of alluvial gold exploration data to improve gold recovery in Ghana
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ORIGINAL PAPER
Characterisation of alluvial gold exploration data to improve gold recovery in Ghana Gordon Foli 1
&
Kofi Agyemang 1 & Blestmond Afrifa Brako 1 & Simon Kafui Yao Gawu 1 & Prosper Mackenzie Nude 2
Received: 14 January 2020 / Accepted: 2 October 2020 # Saudi Society for Geosciences 2020
Abstract This study uses exploration data to optimise overburden thickness, cut-off grade and stripping ratio at some alluvial gold mines in the Kibi mining district to improve gold recovery in Ghana. The specific objective is to determine sampling location, overburden thickness, gravel thickness, gravel grade and gold contents. Secondary data are from 48 mining blocks at Kwabeng mine and primary data from 20 mining blocks at Kibi goldfields. Data are analysed using basic statistics and binary plots. Gold content varies at constant total gravel section grade, as overburden thickness and gold grade vary at 0.2 m from 0 to 2.0 m and at 0.05 g/m3 from 0.10 to 0.65 g/m3, respectively. Average values of gravel thickness and gravel grade from both sites are 2.1 m and 0.57 g/m3, respectively. Percentage change in gold content only becomes positive after optimum overburden thickness and a cut-off grade of 0.90 m and 0.285 g/m3, respectively, while the stripping ratio is 0.43:1. The spatial plot of gravel grades using the Surfer Software for the Kwabeng deposit presents a unique resource block model. The optimised values can be used to review the resource block model and combining with established improved operational procedures from previous works. Keywords Cut-off grade . Stripping ratio . Gold recovery . Block grade
Abbreviations TSG Total section grade GSG Gravel section grade OS Overburden section DGS Diluted gravel sections GS Gravel section DF Dilution factor TS Total section g/m3 Grams per meter cube M Metre Oz Ounce (1 oz = 28.35 g) R2 Coefficient of determination < Less than > Greater than Responsible Editor: Murat Karakus * Gordon Foli [email protected] 1
Geological Engineering Department, Kwame Nkrumah University of Science and Technology, PMB, University Post Office, Kumasi, Ghana
2
Department of Earth Science, University of Ghana, P. O Box LG 58, Legon, Accra, Ghana
Subscripts Initial quantity o Variable quantity I
Introduction Gold production in Ghana is generally from primary lodes, paleo-placers and alluvial deposit sources (Kesse 1985; Griffis et al. 2002). The primary lodes occur in deep-seated shear zones within the Paleoproterozoic Birimian supergroup (Chudasama et al. 2016; Smith et al. 2016). The paleo-placers occur in association with Paleoproterozoic sedimentary Tarkwaian group in synclinal troughs overlying Birimian metavolcanic rocks (Chudasama et al. 2016; Smith et al. 2016). The alluvial deposits occur in floodplains and lowlying areas and are classified into major geographic zones (Griffis et al. 2002; Rae et al. 2009). A typical example of the major geographic zones of the alluvial gold deposits is the Kibi alluvial gold mining district, which is associated with the Kibi-Winneba me
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