The occurrences of gold deposit in Cameroon with focus on the Batouri gold district

CHAPTER ONE

INTRODUCTION

1.1 BACKGROUND

Gold is widespread in low concentrations in all igneous rocks. Its abundance in Earth’s crust is estimated at about 0.005 part per million. It occurs mostly in the native state, remaining chemically uncombined except with tellurium, selenium, and bismuth. The element’s only naturally occurring isotope is gold-197. Gold often occurs in association with copper and lead deposits, and, though the quantity present is often extremely small, it is readily recovered as a by-product in the refining of those base metals. Large masses of gold-bearing rock rich enough to be called ores are unusual. Two types of deposits containing significant amounts of gold are known: hydrothermal veins, where it is associated with quartz and pyrite (fool’s gold); and placer deposits, both consolidated and unconsolidated, that are derived from the weathering of gold-bearing rocks.

Veins enriched in gold form when the gold was carried up from great depths with other minerals, in an aqueous solution, and later precipitated. The gold in rocks usually occurs as invisible disseminated grains, more rarely as flakes large enough to be seen, and even more rarely as masses or veinlets. Crystals about 2.5 cm (1 inch) or more across have been found in California. Masses, some on the order of 90 kg (200 pounds), have been reported from Australia.

Alluvial deposits of gold found in or along streams were the principal sources of the metal for ancient Egypt and Mesopotamia.

The Geology Cameroon has favoured the emplacement of several mineral deposits such as gold (Au), cobalt and nickel, diamond, rutile, iron ore and bauxite. Au mineralization is usually spatially and temporally related to granitoids Gold mineralization in Cameroon ranges from Archean to Proterozoic during or postdating granitic intrusion. Therefore, several questions arise concerning the chronology and the role of geological events, the source of metal and the mechanisms which have led to the ore deposition. In the north part of the country, gold mineralization is associated with the Neoproterozoic Poli Series and coincident with the NE-SW trending Tcholliré shear zone. In the south, gold mineralisation is associated with Archean to Palaeoproterozoic greenstone belts, BIF, and ultramafic rocks which have been deformed by NNE-SSW and E–W (Djoum-Akonolinga), as well as N–S-trending (Ntem), shear zones and faults. The Neoproterozoic Lom Series in Eastern Cameroon has been focus terrains for artisanal gold mining for several decades. Artisanal gold mining activities in Batouri, Bétaré Oya and Colomine Districts around the 50s, recorded a production peak of 717 k. Au mining in these Au districts till the 70s remained basically artisanal and constituted the main source of livelihood for the indigenous community. This gradually changed due to the increase in gold price around the 1970s. The constant increase in this commodity price led to a cooperation between the United Nations Development Programme (UNDP) and Cameroon Ministry of Mines, Water and Energy, on a project aimed at evaluating the mineral potential of gold in this part of Cameroon, from 1981 to 1986. Batouri, Bétaré Oya and Colomine gold districts were areas of great interest, due to high gold contents. Mineralized veins strike NNE-SSW and NE-SW along the Bétaré Oya Shear Zone, NE-SW and E-W along the Colomine Shear Zone, and NNE-SSW and NE-SW along the Batouri Shear Zone. Some veins cut the Neoproterozoic metavolcanicmetasedimentary rocks, undated older metamorphic rocks, and the Pan-African plutonic rocks, but other auriferous veins occur along the contact between rock layers (Freyssinet et al., 1989; Suh et al., 2006;Fon et al., 2012;Vishiti et al.;Azeuda Ndonfack et al., 2021;). Milési et al. (2006) estimated gold resources as ~20 t in the Bétaré Oya district, ~12 t Au in the Woumbou-Colomine-Ketté district, and ~15 t Au in the Batouri district.

In the Batouri gold mining district, primary gold mineralization is related to hydrothermally altered Pan African granitoids (Asaah et al., 2014;Tata et al., 2018) cut across by small-scale high grade auriferous discordant quartz veins/veinlets in structurally favourable sites (Suh et al., 2006;Asaah et al., 2014;Vishiti et al., 2019). The veins are enclosed by hydrothermally altered zones traceable in the wallrock (Suh and Lehmann, 2003;Suh et al., 2006;Suh, 2008;Asaah et al., 2014) and the soils (Vishiti et al., 2015). According to Suh et al. (2006), the quartz veins are defined by NE-SW-trending shear zones which form part of the Central Cameroon Shear Zone system. …

The mineralized quartz veins show a characteristic stockwork texture with gold contents that vary from 0.04-53.5 g/t (Suh et al., 2006; Asaah, 2010;Vishiti et al., 2019;Tchouankam et al., 2020). The wallrock Au contents reach a high of 2.6 g/t Au (Suh et al., 2006) and concentrations ranging from 0.048 to 0.191 g/t are recorded in the soils (Vishiti et al., 2015). Mineralogically the veins are composed of quartz ± gold ± carbonates ± haematite ± sulphides ± chlorite ± albite ± epidote and few selvages of wallrock bearing sericite .

In the Batouri area, primary gold occurs in association with NE-SW-trending ductile to brittle shear zones that cut across Pan-African granitoids (Asaah et al., 2015) and the hypogene gold occurs as disseminations in quartz veins and in the wallrocks (Suh et al., 2006;Asaah, 2010). Gold is also recovered from the weathered overburden (Suh and Lehmann, 2003;Vishiti et al., 2015). The Bétaré Oya gold district forms part of the Lom pull-apart basin.

1.2 AIM

This paper is aim at describing the occurrences of gold deposit in Cameroon with focus on the Batouri gold district

1.3 OBJECTIVES

• -To determine the different gold deposit types in Cameroon.

• To determine the minerisation style of gold at Batouri.

• To determine the host rock for gold in the Batouri.

1.4 LOCATION STUDY AREA

The study area is located in the south eastern part of  Cameroon.Batouri is located in southeastern Cameroon . It belongs to the geopolitical East Region of Cameroon(formerly East Province) and serves as the administrative headquarters of the Kadei Division. The area consists of gently rolling hills that are occasionally interrupted by elevated residual basement cores (elevations range between 550 and 700 m). The hills are generally ero-sional landforms, commonly terminating in entren chedriver valleys. Due to the thick weathering cover, rock outcrops are sparsely distributed. Sampling was, there-fore, not systematic but followed the distribution of the outcrops and.Geologically, the Batouri area is part of the AYD. It is underlain by variably deformed, deeply weathered granitic rocks that are locally cut by systems of gold-bearing quartz veins. The rock types exposed in the area include K-feld-spar granite, syeno-monzogranite, granodiorite, and tonalite. Biotite-gneiss enclaves are ubiquitous in mostrock outcrops in the area. These enclaves are believed to represent fragments of the underlying Palaeoproterozoic–Archaean basement rocks or Neoproterozoic high-grademetasedimentary rocks (e.g. Toteu et al. 1994,2004,2006a;VanSchmuset al. 2008). Aplitic granite, pegmatitedikes, and quartz veins cut the granitic rocks. Structures in the Batouri area include variably dipping regional-, meso-, and micro-scale fault-vein sets, trendingNNE–SSW, NE–SW, ENE–WSW, and WNW–ESE. Evidence of crystal-plasticity and shearing is expressed as bent twin lamellae in plagioclase, sub-parallel fractures in plagioclase, sigmoidal fabric in quartz ribbons,and pressure shadows (Asaah 2010). The patterns of inter-secting faults/veins define three major generations of fault/shear zones and veins, namely pre-, syn-, and post-gold mineralization. The NNW to WNW-trending faults are considered pre-mineralization and are associated with International Geology Review 3D

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