CENTRAL AFRICAN REPUBLIC

The Central African Republic is a landlocked country within the interior of the African continent. Much of the country consists of flat or rolling plateau savannah, typically about 500 m above sea level. The Fertit Hills occur in the north-east, and there are also scattered hills in the south-western part of the country. To the north-west is the Yade Massif, a granite plateau which reaches an elevation of 1143 m.

The climate of the Central African Republic is generally tropical. The northern areas are subjected to the hot, dry, dust laden harmattan winds from southern Morocco. The northern regions have been subject to desertification and the north-east is desert. Other parts of the country are prone to flooding by rivers.

The economy of the Central African Republic is dominated by arable agriculture, including cultivation of cassava, groundnuts, maize, millet, plantain, sesame and sorghum. The country has potentially rich, but largely unexploited natural resources in the form of diamonds, gold, uranium and other minerals.

Diamonds constitute the most important export of the Central African Republic, frequently accounting for 40–55% of export revenue. However, an estimated 30–50% of the diamonds produced each year leave the country clandestinely [9.1].

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3.9.1. Geology

The central and southern parts of the country are mainly composed of undifferentiated basement rocks, reportedly a mixed assemblage of Archaean schists and paragneisses of sedimentary origin and intruded by granites of various ages (Fig. 3.12). Some identified Precambrian areas exist in the east of the country.

In the south-west and in some northern and central areas, there are undifferentiated continental Mesozoic sediments and in the north-west, undifferentiated continental Cenozoic sediments. There are a number of Tertiary granites in the north-western part of the country.

FIG. 3.12. Regional geological setting of Central African Republic showing the distribution of selected uranium deposits and occurrences. For the general uranium deposit and uranium occurrence legend see Fig. 2.1b. A general global geological legend is shown although not all geological units necessarily occur on this particular map.

The granitic summits of the Yade Massif decline eastwards into sandstone plateaux. In the east, gneisses and quartzites predominate, sometimes covered with sandstones, but with occasional isolated granitic knolls. The crest of the main watershed comprises metamorphic rocks and quartzites, which to the north are overlain by Tertiary sandstones of the Chad Basin and more recent alluvium.

For uranium, the main area of interest is the Bakouma region in the east-central part of the country, where the Bakouma uranium deposits were found. The Bakouma region is situated in a mobile Proterozoic zone between the cratonic basin of the Congo in the south and the cratonic area of the Nile in the north. A depositional basin located within this zone contains a Proterozoic platform sedimentary series, which ends in a dolomitic formation containing dykes, sills and doleritic flows, which is known as the Bakouma Formation. This region is marked by a system of fractures having a general orientation of N 65° E. Karst topography developed on the Bakouma dolomite, giving rise to palaeorelief characterized by depressions with steep walls up to 80 m in depth and 70–150 m in diameter, also aligned N 65° E.

During the Cretaceous, coarse detrital sediments with intercalations of red clay were deposited on the slopes of these depressions. A red ferruginous limestone, 50 m thick, was later deposited in some depressions. It is locally siliceous and phosphatic. In a great number of depressions, irregular accumulations of very fine argillaceous, siliceous and phosphatic sediments known as the M’Patou Series were later formed. Phosphate in the form of the microcrystalline carbonate fluorapatite can constitute as much as 50% of the rock. In other depressions, and in the intermediate shelves, the deposits which correspond to this M’Patou Series begin with an agglomerate of siliceous and ferruginous elements cemented by iron oxides and clay, followed by ferruginous sands with illite at the base and kaolinite uppermost [9.2, 9.3].

3.9.2. Uranium exploration

Historical exploration data are given in Table 3.6.

France’s Atomic Energy Commission (CEA) was the first organization to prospect for uranium in the Central African Republic. Initial reconnaissance work commenced in 1947 and exploration of the extensive zones of crystalline formations which border the west and occupy the centre of the country was conducted without success. In 1956, prospecting using improved techniques and benefiting from improved knowledge of uranium metallogeny was extended to the detrital siliceous series of the Middle Precambrian–Upper Precambrian (Nbafkl and Fouroumbala Series).

A major radiometric anomaly was discovered in the N’zako laterites, but importantly, a significant geological similarity was noted between the Fouroumbala Series and the Franceville in Gabon, where a uranium deposit had been discovered. Encouraged by this similarity, the CEA intensified its exploration in 1959 with a systematic programme of aerial prospecting, covering the entire eastern region of the country, an area of around 50 000 km². This work led, in 1961, to the discovery of the country’s first uranium deposit near the town of Bakouma.

TABLE 3.6. URANIUM EXPLORATION DATA [9.4]

Year Aerial radiometric surveys

Three deposits were discovered. Geologically, the host is a uranium bearing phosphatic formation of Eocene age. The notable feature is the exceptionally high uranium content for a formation of this type.

However, the phosphatic nature of the ore made it difficult to develop a suitable processing method. In 1963, the CEA and the Compagnie Française des Minéraux d’Uranium (CFMU) formed a syndicate to continue exploration and to study the feasibility of mining the deposit. A jointly owned mining company, the Bakouma Uranium Mining Company (URBA), was set up in 1969 between the State and the CEA and CFMU partnership. However, the result of the feasibility study on the mining of the deposit was unfavourable and activities by URBA ceased in 1971.

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After the oil crisis in the winter of 1973–1974, numerous foreign companies showed interest in the Bakouma deposit, and Aluminium Suisse S.A. of Zurich resumed studies on the mining of the deposit. In February 1975, a new mining company was set up between Aluminium Suisse and the three original partners of URBA. This new company adopted the name of the Central African Uranium Company (URCA).

Prospecting conducted by the Atomic Energy Commission, URBA and URCA used the following methods:

(a) Geological investigation and cartography;

(b) Airborne radiometric surveys;

(c) Ground radiometric surveys;

(d) Ground verification of selected anomalous zones;

(e) Drilling of boreholes at different spacing intervals;

(f) Geochemical analysis of soil, water and alluvial sediments.

However, subsequent technical, metallurgical and economic studies indicated that the deposits were not economically viable at the then prevailing price of uranium and in 1978 the project was terminated.

In May 2006, UraMin Inc. was granted one mining permit and two research permits for exploration of uranium mineralization in the Bakouma region. Reverse circulation percussion drilling commenced at the Patricia deposit in August 2006 to confirm the presence of uranium mineralization and to increase the known resource. Initial drilling of 66 holes on a 100 m × 50 m grid spacing delineated the extent of the Patricia deposit. Data from these holes were used as the basis for the resource estimate. Reverse circulation infill drilling on a 50 m × 50 m grid spacing commenced and a diamond drilling campaign to acquire additional geological and geotechnical information was also planned. Further reverse circulation and diamond drilling was planned at the other deposits that comprise the Bakouma project.

On 30 July 2007, the owner of Bakouma and other African uranium deposits, UraMin Inc. was acquired by AREVA for US $2.5 billion. This transaction gave AREVA a 90% interest in the project, which included ten discrete deposits, with a 10% carried interest retained by the State.

Start-up of the Bakouma pilot project was planned for 2010. At full capacity, the mine would have a production of 2000 tons U per year. Then, the AREVA group suspended the uranium mining project at the end of 2011 for one to two years. In June 2012, gunmen attacked the Bakouma uranium mine project site and since, all activities were suspended.

3.9.2.1 Geology of the Bakouma deposit

The Bakouma Basin is filled with recent unconsolidated sediments bordered by sandy and quartzitic hills of Precambrian age. The geological section of the Bakouma Basin, as determined from numerous exploratory boreholes, indicates an underlying Precambrian karstic dolomite intruded by dolerites. This depression has served as an erosional corridor which was filled in the Jurassic by the diamondiferous sands of Mouka-Ouadda, which in turn were uncovered and redeposited during the Eocene as the M’Patou Series. The Bakouma Basin was finally covered by laterites and the alluvial deposits of the M’Patou River.

Numerous faults cut through all of the formations.

The uranium mineralization of the Bakouma Basin is associated with phosphate lenses intercalated with the silts and siliceous horizons of the M’Patou Series. It is these lenses that have the highest concentrations of uranium mineralization and these are grouped into several small to large deposits: Palmyre, Pama, Pamela, Pâquerette, Patou and Patricia, which make up the Bakouma deposit. Patricia, the best explored deposit contains 11 512 t U at a grade of 0.138%.

3.9.3. Uranium resources

3.9.3.1. Identified resources

The Bakouma uranium deposit, which in 1986 was estimated to contain about 16 000 tU in ore with an average grade of 0.26% U at an average depth of 35–40 m, is described in Table 3.7.

TABLE 3.7. IDENTIFIED BAKOUMA BASIN (IN SITU) RESOURCES (tU) [9.5]

Deposit RAR^a <US $80/kgU RAR <US130/kgU

Palmyre

a RAR: reasonably assured resources.

Inferred resources of 36 475 tU at 0.3% were reported by AREVA at the end of 2016.

The UDEPO database lists the most significant deposits for the Central African Republic as Fosse-Pamela, Patricia, Pama, Pato, Petits Amas.

3.9.3.2. Undiscovered resources

No undiscovered resources have been estimated. In 1983, IUREP estimated a range of 10 000–50 000 tU of speculative resources [9.6].

3.9.3.3. Unconventional resources

There is no report for unconventional resources. While the Bakouma uranium deposit is associated with phosphates, it is classified as a conventional deposit because of the relatively high (0.15-0.30% U) uranium grade [9.6].

3.9.4. Potential for new discoveries

In the central and southern part of the country, undifferentiated basement rocks, comprising mainly a mixed assemblage of Archaean schists and gneisses of sedimentary origin, have been intruded by granites of various ages. Rocks of Precambrian age are also present in the east. There exists the possibility of finding unconformity-related deposits within these Precambrian areas, especially within the Lower, and possibly Middle, Proterozoic rocks.

In the south-west, and in some northern and central areas, undifferentiated continental Mesozoic sediments occur. There are undifferentiated continental Cenozoic sediments in the north-west, in particular the Tertiary sandstones of the Chad Basin. These continental sediments may be prospective for uranium.

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Deposits similar to the known Bakouma deposits found in depressions in dolomite could be a possible prospecting target and this deposit type holds the greatest potential for additional discoveries [9.3].

3.9.5. Future projects

On 1 August 2008, AREVA signed an agreement with the Government of the Central African Republic to mine the Bakouma deposit. The Bakouma project was scheduled to start production in the fourth quarter of 2010, using open pit mining and with an envisaged average annual production rate of 2000 tU.

The project was indefinitely stopped in 2012 after being attacked by rebels.

3.9.6. Comments

No uranium had been produced in the Central African Republic. The Central African Republic has no nuclear power generation.

References to Section 3.9

[9.1] CENTRAL INTELLIGENCE AGENCY, The World Factbook: Central African Republic (2008), https://www.cia.gov/library/publications/the-world-factbook/index.html

[9.2] SCHLÜTER, T., Geological Atlas of Africa, 2nd edn, Springer, Berlin and Heidelberg (2008) 68–69.

[9.3] JOINT STEERING GROUP ON URANIUM RESOURCES, World Uranium: Geology and Resource Potential, Miller Freeman Publications, Inc., San Francisco (1980) 524 pp.

[9.4] OECD NUCLEAR ENERGY AGENCY, INTERNATIONAL ATOMIC ENERGY AGENCY, Uranium Resources, Production and Demand, OECD, Paris (1979).

[9.5] OECD NUCLEAR ENERGY AGENCY, INTERNATIONAL ATOMIC ENERGY AGENCY, Uranium Resources, Production and Demand, OECD, Paris (1986).

[9.6] INTERNATIONAL ATOMIC ENERGY AGENCY, Speculative Resources of Uranium, A Review of IUREP Estimates 1982–83, IAEA, Vienna (1983).

3.10. CHAD

Chad is situated in north central Africa, lying between 8° and 24° N and between 14° and 24° E. The dominant topographic feature is a wide basin bounded to the north, east and south by mountain ranges.

Lake Chad, after which the country is named, is all that remains of a lake that occupied an estimated 330 000 km² of the Chad Basin as recently as 7000 years ago. At an elevation of 3414 m, Emi Koussi, a dormant volcano in the Tibesti Mountains, is the highest point.

The annual tropical weather system known as the intertropical front traverses Chad from south to north, bringing the wet season, which lasts from May to October in the south and from June to September in the Sahel. Variations in local rainfall divide the country into three major geographical zones. The Sahara occupies the northern third of the country, where the annual rainfall is less than 50 mm. In the Sahel, a steppe of scrub gradually gives way to savannah in the south. Annual rainfall in this belt is over 900 mm.

Over 80% of Chad’s population relies on subsistence farming and raising livestock for their livelihood.

The crops grown and the locations of herds are determined by the local climate. The most fertile arable land lies in the southernmost 10% of the country. This area is a major producer of millet and sorghum.

The Sahel is ideal pasture for cattle, donkeys, goats, horses and sheep. Prior to development of the oil industry, cotton production was the dominant industry and the major employer of labour, accounting for approximately 80% of export revenue. Oil production began in 2003 with the completion of a pipeline that links the southern oilfields to terminals on the Atlantic coast of Cameroon.

3.10.1. Geology

Precambrian rocks (Tibesti Massif) are present in the north-western part of the country, in the eastern central part of Chad and in the southernmost part of the country, thus defining the north-eastern and

southern limits of the Chad Basin (Fig. 3.13). Lower Palaeozoic sandstones, correlative to the Tassili Series of Algeria, overlie Precambrian strata in the Tibesti area in the north and also in the northern part of the eastern central area. Uranium has been discovered in the Hoggar area of Algeria, at the base of the Tassili Series, in channels cut into the underlying Precambrian.

In the Kufra Basin, the Lower Palaeozoic is overlain by the continental Nubian sandstone. Continental Cretaceous clastics overlying Precambrian strata are present in the south-western part of the country and extend northwards into the Chad Basin. The whole of the Chad Basin was covered originally by clastic sediments. Uranium occurrences in the Continental Intercalaire are known in Niger (Arlit area).

Cainomanian and Turonian marine sedimentation followed the Cretaceous continental sequence.

Palaeocene continental sandstones are known in the southern part of the country. During the Pleistocene, thick, extensive lacustrine deposits were laid down (Chad Formation). Dune sands immediately overlie the Chad Formation throughout the basin.

FIG. 3.13. Regional geological setting of Chad showing the distribution of selected uranium deposits and occurrences. For the general uranium deposit and uranium occurrence legend see Fig. 2.1b. A general global geological legend is shown although not all geological units necessarily occur on this particular map.

Uranium has been discovered in the Mayo-Kebbi area (near Lere) of south-western Chad. Uraninite and various uranium oxide minerals occur in veins cutting a granite intrusion of Tertiary age [10.2, 10.3].

3.10.2. Uranium exploration

In 1946, France’s Atomic Energy Commission (CEA) sent several missions to various countries in Africa, including Chad. In Chad, the area surveyed was in the north-western part of the country. The work undertaken comprised a preliminary reconnaissance, but the results were negative.

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In 1972–1980, the United Nations Development Programme (UNDP) assisted the Government of Chad in an exploration project for metallic and non-metallic mineral resources in the Mayo-Kebbi area of south-western Chad. An area of about 10 000 km² was covered by airborne radiometric and magnetic surveys.

Several anomalies were found in granitic and sedimentary terrain. As a result of this survey, vein uranium mineralization was found in the Lere alkaline granite [10.4]. The anomalies in the sediments were not very favourable.

In 1978, the second phase of the UNDP supported project also discovered uranium mineralization in the Mayo-Kebbi area in the south-western part of the country, near the border with Cameroon. Here, the uranium minerals (coffinite and pitchblende) occur as disseminations and veinlets in syenitic rocks.

Following a wide spaced airborne radiometric survey, uranium mineralization was discovered at Mandagzang and confirmed by diamond drilling. Exploration drilling had to be discontinued in 1980 as the result of political considerations.

In early 2008, London based Brinkley Exploration SA was granted three exploration licences to explore for uranium, gold and base metals in the Mayo-Kebbi area. The Mayo-Kebbi region covers an area of approximately 8000 km², comprising an exposed basement complex with syntectonic alkaline intrusions and Cretaceous platform cover. Brinkley Exploration conducted a detailed airborne survey which delineated a number of radiometric anomalies. The company ended all uranium exploration activities in Chad in 2008.

Signet Mining Services Ltd has six concessions covering 841 km², including the Lere project, located in south-western Chad near the towns of Lere and Pala. Signet is evaluating the Lere uranium deposit which is hosted in subvertical shear zones and secondary foliation in albitized and silicified granite in a mixed terrain of Precambrian units. Signet classifies the deposit as the intra-granitic variety and has defined a preliminarily in situ inventory estimate of over 2690 tU. A Lere project resource compliant with the South African Code for Reporting of Exploration Results, Mineral Resources and Mineral Reserves was expected by early to mid-2010, based on the drilling of 13 695 m of percussion holes and additional trench samples. Signet reported a high grade drill intercept from the Lere project, including 8 m at 1350 ppm U [10.310.8].

UDEPO classify the deposit as metasomatite, Na-metasomatite, granite-derived.

3.10.3. Uranium resources

In 1983, IUREP reported a range of 10–50 000 tU of speculative resources in sandstones, veins and disseminated magmatic geological environments [10.8].