Abstract
The present study, which focuses on the behavior of gold and its accompanying chemical elements developed on an alteration profile, is carried out in a humid equatorial zone at Mintom in South Cameroon (Central Africa). The methodology used to achieve the results obtained focused on the description of the morphology of the outcrop, the petrography of the rock studied, the study of heavy minerals accompanying gold in the weathering materials on smear slides, mineralogical analysis of weathering materials by X-ray diffraction (XRD), scanning electron microscopy (SEM) analysis of gold and geochemical analyzes by ICP - AES and ICP - MS of weathering materials. The main results obtained from this methodology inform us that on the petrographic level the main rock studied is the gold-bearing quartz vein located in Zom, consisting mainly of quartz and opaque minerals. Morphologically, the weathering materials developed on this granite basement present an advanced ABC-type profile characterized by a significant thickness (4 to 6 m). The morphological and chemical characters of the gold particles have evolved from the mineralized zone to the surface. This development was marked by an increase in blunt, rounded grains. Morphoscopy and scanning electron microscopy of the gold particles have shown hollow, blunt to sub-blunt grains, non-evolved free particles, and evolved free particles, respectively. In most samples of weathered material gold is found in association with chemical elements such as Ag, Cr, Co, Cu, Ni, V and figure 10 show identical behavior between these chemical elements and gold, but particularly between silver and gold, which would testify to an identical origin. Au concentrations are very high in most samples of weathering material. Also, these samples of altered materials with a high proportion of gold (0.01 to 2.28 ppm) also present high concentrations of silver (Ag) which justifies that the occurrence or the gold deposit is associated with silver and can be exploited as a geochemical parameter to prospect for gold in the study area.
Highlights
4.1 Description of the Weathering Profile Studied (PE) The studied gold profile has geographic coordinates of N020 30" 14" and E130 19" 59" with a thickness of approximately 3.45 meters above the quartz vein bedrock (Figure 3). This profile resulting from the alteration of the underlying bedrock presents three main groups including: the saprolite, the glebular group and the clay-sandy group. The morphology of this profile is similar to that described in the weathering layers of the African equatorial zone (Bocquier et al, 1984; Tardy, 1993)
This layer is surmounted by a red (5YR 6/4) or reddish brown (10YR 2/2) centimetric gravelly layer enriched with quartz and accessory minerals embedded in a matrix of sandy clay consisting of kaolinite, goethite, hematite and more or less smectite; (2) the nodular unit (40-80 cm) consists of millimetric to decimetric ferruginous nodules of hematite and goethite
The weathering materials developed on the gold-bearing quartz vein at the level of the upper slope of the interfluve have been observed in different bioclimatic zones (Edou Minko, 1989; Freyssinet et al, 1989a; Colin and Vieillard, 1991; Edou Minko et al, 1992; Colin, 1992; Bowell et al, 1993; Colin et al, 1993; Mann, 1984; Smith and Keele, 1984; Freyssinet et al, 1989b; Sanfo et al, 1992; Freyssinet, 1993; Ouangrawa et al, 1996; Akwinga, 2010)
Summary
The vertical distribution of gold and its mobility in surface and sub-surface environments associated with weathering processes have been well studied by many authors in recent decades (Baker, 1978; Mann, 1984; Webster et Mann, 1984; Andrade et al, 1991; Benedetti and Boulègue, 1991; Bowell et al, 1993a, 1993b; Colin et al, 1993; Leybourne et al, 2000; Aleksandrov, 2007; Myagkaya et al, 2016a, 2016b). The behavior of gold, its mobility and its distribution in this landscape have been sufficiently studied (Edou-Minko, 1989; Freyssinet et al, 1989b; Colin & Vieillard, 1991; Edou-Minko et al, 1992; Colin, 1992; Colin et al, 1993; Mbenoun et al, 2013). The objective of this study relates to the behavior of gold and its accompanying chemical elements in a weathering profile on a quartz vein at Mintom (Cameroon, Central Africa)
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