Economic Potential of Gold in Batouri (Eastern Cameroon)

The aim of this work is the valorization of the economic potential of gold in the Batouri region. The study is undertaken on five sites of which two alluvials (Djengo and Mongonam localities) made up of flat and river gold, two eluvials (Kambele and Bote) containing gold of veins in quarries, and one semi mechanized exploitation (METALICON) working on the two previous types. Laboratory works consist of traditional melting, determination of the various grades of gold through densimetry and spectrometry analysis and refining using the Miller Chloration method. The main results from these analyses are: i) recovery concentration is low, (about 0.5 g/t) for the traditional mining and higher with the semi mechanization (1.5-2 g/t). Densimetry and spectrometry analyses show that gold of semi mechanized sites has an average grade of about 24 carats, 22 carats and 20 for alluvial and eluvial gold respectively. ii) For 26 kg of gold refined, a weight of 16.681 kg is obtained at a cost of 4 051 946 (four million fifty one thousand and nine hundred forty six) CFA F. Spectrometry analyses reveal the presence of silver and copper impurities, elements that can still be valorized through the presence of a gold refining unit. Hence, the absence of a gold refining unit in our country leads to poor transformation of its ores and loss of devices.


Introduction
The diversity of the geological formations (plutonic, volcanic, metamorphic and sedimentary) in Cameroon give it a rich subsoil full of important and interesting minerals which, if well exploited within founding projects, will inescapably lead to an emerging country by 2035 (Strategy Document for Growth and Employment ECSD, 2009). In this respects, we distinguish base metals, precious stones and precious metals notably gold.

Field Descriptions and Geological Setting
The Batouri area is located in the Eastern region of Cameroon (04° 21' to 04° 29' North and 14° 17' and 14° 29' East), within a humid tropical climatic zone. The geomorphology of the study area is a savanna plain with low altitudes (400-800 m). It covers an area of approximately 408 km 2 . It comprises the localities of Djengo, Mongonam, Kambele, Bote and Metalicon ( fig. 1), where samples were collected. The study area is located within the so-called « Eastern golden district » which is the most mineralized area in Cameroon. The metallogenic importance of the area is related to the geology of the whole region. It belong to the polycyclic granitic basement of Adamaoua (Toteu et al., 2004;Van Schmus et al., 2008), an intrusive syntectonic complex of N130 orientation. On the petrographic point of view, it comprises alkali granite, calc-alkali granite and charnockites; with minor quartz-syenite, syenite, quartz-diorite and gabbros. In these rocks, they are veins and lenticular bodies of quartz containing primary gold. The secondary gold (eluvial and alluvial) of Batouri is probably their alteration product and erosion.

Material and Methods
The data collection phase was done through field campaign and laboratory works. The field campaign comprised the choice of study sites, the identification of various sites and the presentation of list of questions to stakeholders. Samples used were collected after the washing step. Laboratory work involved traditional melting of gold and the determination of different grades of gold by densimetry using by the principle of Pushed of Archimedes and X-ray fluorescence spectrometry using SKY Ray instrument, EDX pocket III model.
The concentration criterion is given by equation (1): (1) Where Ϭ L represents the density of the heavy solid phase, the density of the light solid phase, and Ϭ p the density of the liquid used. Water is usually the liquid in which the particles are washed.
In the laboratory, artisanal gold melting and determination of different grades of gold by densimetry and X-ray-fluorescence spectrometry were done on 22 samples.
The different losses were calculated using the following formulas: (2)  loss rate denoted T a :  loss on fusion denoted P f : = 2 3 (4)  loss rate denoted T f :  absolute loss denoted P T :  loss rate denoted T G : The determination of the gold titre by densimetry is illustrated by the following formulas: * * = (7.1) m Au = Au . . Where V e corresponds to the volume of water displaced, and also equal to the volume of gold bullion. Au =density of pure gold e = density of water X-ray fluorescence spectrometry permitted the determination of the gold titre using the equation below: Where %Au = Percent gold Concerning refining, the technique involves chlorination of raw gold by the Miller process where pure gold is obtained at 99, 5% before undergoing a second treatment, that of the Wohlwill's electrolysis where pure gold is obtained at 99.99 %.

Results
The use of these various methods enabled us to obtain the results presented in the following lines.

Discussion
The results from densimetric and X-ray fluorescent spectrometric methods are slightly different. This could probably be due to the fact that the densimetric method is quite complex and sometimes poses difficulties in reading the balance. The X-ray fluorescence spectrometer has the advantage that it gives not only the chemical composition of the analyzed metal highlighting the associated elements of the gold, but also, the results are more reliable.
The values of titres for alluvial gold were higher than those of the eluvial gold. Furthermore, the lower the carat, the higher the loss rate. This is due to the fact that the eluvial gold grains often contain small boulders difficult to separate, and the presence of poorly washed ferromagnesian particles constitute impurities which in the course of melting are dissolved in nitric acid, thus increasing their loss rate.
Washing techniques used in Batouri (pan and sluice) lead to considerable loss rates of over 50%.

Calculation of the concentration criterion C in the Batouri site
We have ϬL = 15 -19.3; Take ϬL = 16; Ϭl = 2.65 (about 3 for some gangue minerals) Ϭp = 1 Finally C = 7.5 This concentration criterion was compared to Tagart's criterion table (Weiss, 1985, table 6). Table 6. Various values of the concentration criterion C or Tagart's criterion (Weiss, 1985) Criterion Applicability C > 2,5 Easy separation 1,75< C< 1,50 Possible separation for the particles of dimension > to 0,2 mm 1,50< C < 1,25 Possible separation for the particles of dimension > to 1,65 mm C< 1,25 Almost impossible separation The criterion C is significantly higher than 2.5. The Batouri gold is that of easy separation (Weiss, 1985). At first the concentration methods used on different sites (sluice and panning) which are physical processes based on gravity, will give satisfactory results.
During our investigations, we found that the gold washing methods result in large losses (more than 50 %) while the actual recovery rate would be around 70%.
Most of the artisanal sluices used in Batouri contain neither riffles nor strips. These traps can undoubtedly improve metal recovery yield. These processes based on proven physical laws are used on an industrial scale, an equally important aspect of the slope of the sluice. In industrial practice, the slope is on average 5 °. In the sites visited, this angle is between 13 and 15°. According to International Labour Organization (ILO, 2009), for maximum gold recovery, the construction of a washing ramp provides: a manifold equipped with a grating at the bottom and a flow channel of 30 to 50 cm width and about one to two metres long. This channel must be fitted with a wedged under carpet webs. The sluice must be disposed at an inclined angle plane between 4 ° and 6 ° to claim a recovery rate of about 80%. Also, aluminum bowls or non-grooved calabash serving pan is the last stage of recovery of concentrates from Long Tom. But for a good recovery, Keita (2001) proposed to use dark grooved frames in sahelian region. He believes that the grooves can retain the gold nuggets and the colour for easy identification at night.
Hence, to reduce the strain at work and increase efficiency, this paper recommends to use the gold wash table designed and tested by the Precasem team described on figure 2:

At refining
To reduce refining costs and increase opportunities for local processing of gold, it would be better to establish a gold refining unit.
The establishment of a refining unit will enable CAPAM to put at the disposal of the Ministry of Finance 24-carat gold instead of 22 carat fused gold as is the case now. The unit will also offer products and services for clock industries, jewellery, nationally and internationally. Its activities may eventually be extended to the production of medals for decorative purposes, stamps and other alloy products with other metals (silver, copper, bronze, etc.). The production cost would be reduced due to the shortening of the production time and the increase of the quantity (table 7). Also, it will enhance the elements associated with gold. In addition, the DMCA stipulates that 15% of the production of mineral substances extracted in Cameroon must be processed locally. Refining is part of the transformation process and helps to greatly increase the value of the gold produced in Cameroon. Modifications of decree and laws on mining activities could increase the local processing rate of gold and even take it to 100 %, regarding refining. This will increase the utilization capacity rate of the refining unit and increase profit while ensuring better traceability of the gold produced in Cameroon. The present work had as main objective the enhancement of the economic potential of gold. For this, the study was conducted in five sites, two alluvial, two eluvial, and a semi-mechanized, combined with laboratory work consisting of artisanal gold melting and determination of different titres. It follows: at the extraction, a low recovery rate for craft sites 0.5 g / t in contrast to the semi mechanization 1.5-2 g / t. In the laboratory, the different loss rates were evaluated. Also, different titres of gold calculated by densimetric measurement and X-ray fluorescent spectrometric analysis show that semi mechanized sites have an average capacity approaching 24 carats, that of alluvial gold around 22carats and the eluvial gold around 20. At refining, for 26 kg of gold which were refined, a weight of 16.681 kg was obtained at a cost of 4,051,946 (four million fifty one thousand nine hundred and forty-six) FCFA. However, due to the lack of a gold refining unit, the state has a shortfall in processing these ores. Also, the organization of artisans in CIG (Common Initiative Group) a b esr.ccsenet.org Vol. 9, No. 2;2020 28 and their enlightening on modern recovery techniques will increase their production rate.