Geological Map of Chad
Micaschists and quartzites
Lower Tibesti Series
dolerites and rhyolites)
Upper Tibesti Series
rocks and rhyolites)
Lower Grit Series
Silurian Middle Grit Series
Lower Devonian Upper Grit Series
Upper Devonian grits
Carboniferous Marine Series
(grits, sandstones and limestones)
Lame Series (conglomerates,
Nubie Series (grits,
conglomerates and siltstones)
Eocene Marine Series
sandstones and siltstones)
(iron stones, grits
laterites and siltstones)
dunes and laterite
Back Data 0 250 km
Africa Mining 2000
Extracts from Mining Journal Chad Supplement September 1995
Economic Geology and Recent Exploration programme. Geochemical exploration surveys of
Although numerous mineral occurrences have the Mayo Kebbi greenstone belts, identified three
been reported since the early 1950s, it was not distinct gold regions, Lere, Mourbame and Pala,
until the recent UNDP/DRGM geological and where quartz veins and silicified zones show
mining research programmes that they were visible gold and have returned grades up to 33 g/t.
evaluated in any detail. The research
programmes, which considerably updated Chad's The Lere gold occurrences are located west of
mineral inventory, also identified new mineral the town of Lere. The gold is hosted in
deposits and have provided an excellent Precambrian amphibolites and greenschists, and in
indication of Chad's mineral potential. local granitoid intrusions such as the Mayo Kebbi
batholith and the alkaline granite of Zabili. The
It is important to note that Chad is still very rocks are crosscut by mafic to ultramafic
under-explored compared to other African instrusions and by microgranite dykes. One
countries. There has been no systematic strong geochemical anomaly was delineated at
reconnaissance using modern exploration Teubara in the Zabili greenschists.
techniques, no airborne geophysical data for
example are available for 95% of the country. Gold in the Mourbame area is also contained
The only area covered by an aeromagnetic and within a greenschist assemblage, comprising meta-
radiometric survey is the Mayo Kebbi area. volcanic and meta-sedimentary formations. The
gold, which can be visible, is found in quartz veins
The Tibesti massif is thought to be one of Chad's in shears, along with pyrite, arsenopyrite,
most attractive areas for mineral development. It chalcopyrite and malachite, which are
is known to host significant occurrences of concentrated in the meta-sedimentary
tungsten, tin, niobium and tantalum. Preliminary formations. To date only trench samples have
exploration has also indicated that further studies been taken. These have returned grades of 1.2-
should be made on the Tibestian volano- 33 g/t gold.
sedimentary formations for gold, silver, base
metals, as well as precious and semi-precious There are four main areas of gold mineralisation
gemstones associated with the granitic stocks. in the Pala region; Gamboke, Goueigoudoum,
Massonebare and Mbibou. These are all located
Gold in volcano-sedimentary formations, with abundant
Gold exploration over the past few years has igneous intrusions such as serpentine, diorite and
focused on the Precambrian formations of microgranites. Mineralisation occurs in quartz
Ouadday, Lake Fitri in Guera and Mayo Kebbi. veins, often as stockworks cutting the host rocks.
The gold is sometimes visible and is often
The excellent gold potential in Mayo Kebbi has associated with galena, pyrite, chalcopyrite,
been known since the 1940s, when the only arsenopyrite, covellite and malachite. Most of the
recorded gold production came from two areas have been investigated by trenching, but
primary gold deposits owned by Compagnie only the Massonebare and Gouelgoudoum
Minière de l'Oubangui Oriental: one, situated deposits have been drilled, revealing grades of
near Gamboke, operated between 1939-41 and 3.5-4.6 g/t Au over 1-1.3 m and 1.3-3.3 g/t over
produced 180 kg Au. The other was a small 0.3-3.25 m respectively.
operation near Lere, which produced 4.9 kg in
1941. However, it was not until the end of the One particularly rich alluvial deposit discovered in
1980s that any notable exploration was the Mayo Kebbi region was Mayo N'Dala, located
conducted in the area under the DRGM/UNDP north of Pala. The ore grades 4 g/m3 of gold
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with over 3 t of gold metal resource. Small-scale Base Metals
production of the deposit began in 1992 and a To date, discoveries of base metals in Chad have
further four small-scale mining permits were been uneconomic. Copper sulphides, silver-
issued to local groups to work this resource. In bearing galena and traces of zinc were found in
1994, a 400 g gold nugget was found in the Mayo breccias in the Ofouni granitic stock in Tibesti.
N'Dala River. The UNDP/DRGM programme also discovered
copper sulphides and galena in the gold-bearing
The Ouadday region is also known to host gold, veins of Massonebare and in Poyeme. Malachite is
which was first discovered in Goz Beida in 1963. reported in various locations south of Teubara
In 1988 the UNDP/DRGM project undertook and in hornblendes east of Mourbame.
further exploration work in the form of
geological mapping and regional geochemical When taking into account the copper
surveys on the Ouadday massif. The project mineralisation in neighbouring Niger, where
identified some 40 gold anomalies around Goz mineralisation is reported in extensions of
Beida, Ade Ardelik, Echbara, Karoub and Koukou geological formations found in Chad, it is thought
Angarana. Further detailed analyses of these that economic base metal deposits in Chad are
anomalies identified auriferous quartz veins and undiscovered, rather than non-existent.
stockworks within volcano-sedimentary schist
assemblages. The most promising gold Other Metals
occurrences noted were: There is an excellent potential for the discovery
of a wide range of other metals in Chad including
• - Am Ouchar - gold is found in a shallow tin and tungsten, iron ore, bauxite and various
dipping shear zone, thought to be a thrust. minor metals.
Channel and trench samples indicated 33 g/t
of gold. Typical intersections are 4.73 g/t Tin and tungsten mineralisation has been
over 16 m, 5.7 g/t over 12 m and 6.8 g/t over recorded in association with post-tectonic granite
20 m. The mineralisation can be traced at stocks in the Yedri massif in Tibesti. The greisen
surface for over 100 m along strike. mineralisation contains large cassiterite
• - Goz Beida - several anomalies were accumulations that are often capped with a dome
discovered, the most promising is associated of quartz veins and stockworks, which also host
with a granite/quartzite contact and is wolframite, cassiterite and copper. Gigantic
traceable at surface over a distance of 500 m. wolfram crystals weighing several hundred
Exploration trenches gave grades of 1.5 g/t kilograms have been found in the Yedri massif.
over 4 m and 3 g/t over 2 m. Alluvial gold has During the 1930s, 22 t of wolframite was
also been found at Goz Beida, the primary collected from the surface of the massif. Similar
source has not yet been identified. mineralisation has been reported at other Tibesti
• Echbara - five anomalies were identified, massifs.
including one that extends over 1,600 m. The
down-dip continuity of these anomalies has Some iron deposits have been worked on a small-
not yet been verified. scale in the past. Iron can be found in the
• Ade Ardelik - five gold anomalies were Precambrian ferruginous quartzites of Hadjer
defined, one of which was traced over 1,100 Hadid (near Gourgoundji) and Ouadday; in
m and graded 4.3 g/t gold. haematite schists of the Koukou Angarama region
in Ouadday; in oolitic iron formations near Tile
Following the discovery of gold nuggets in Nougar (in the far south of Guera); and in laterite
alluvium in the Aozou area and Tibesti, and the crusts in various areas. No reserve estimations
favourable geological terrain, it is considered that have been made for these deposits.
there is a good potential of finding primary gold
deposits in this area. The Koro bauxite deposit, located south of
Guidari in southern Chad, comprises several
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small plateaus topped by ferruginous crusts that been unsuccessful. It is thought that some alluvial
trapped an oolitic bauxite layer up to 10 m thick. diamonds on the C.A.R. border could derive
The layer grades 57.3% Al2O3 and reserves have from the neighbouring country. However, where
been estimated at around 7 Mt. Other bauxite the hydrographic network is poorly developed
crusts were formed above the basalts and and is located too far from the border, for
sandstones of Massalit, above the northern end of example at Guera and Ouadday, the primary
the Ouadday batholith and above terrestrial sources, it is believed, must be within Chad.
sediments in the Ennedi region.
Oil And Gas
The post-tectonic granitic stocks of Tibesti also Exploration for oil and gas began in the 1960s in
host niobium, tantalum and beryllium. Columbo- the Chad Basin, with the first oil discovery being
tantalite and beryl are commonly associated with made in 1974 by Conoco. Fifteen years later the
cassiterite, although in Chad they occur mainly in Sedigui deposit, in the Kanem Basin, was
pegmatites in the Yedri massif and the Orda discovered by a consortium controlled by Esso,
Oudengui massif (southeast of Yedri). Large with Shell and Elf as partners.
pegmatite veins have been recorded, such as at
Yedri, where seven 4 km long veins were found The Sedigui deposit has estimated reserves in the
with columbo-tantalite content grading 47.5% Ta order of 150 Mbbl and is currently being
and 19.5% Nb. Columbo-tantalite has also been developed by the Société d'Etudé et d'Exploition
found in alluvial deposits in Tibesti (grading 145 de la Raffinerie du Chad (SEERAT). Sedigui is
g/m3) and in Ouadday (200-840 g/m3). expected to be on stream by 2005. The
government holds a 51% interest in SEERAT,
Various titanium deposits have been reported, along with Esso 18.4%, Shell 18.4% and Elf 12.3%.
including an alluvial ilmenite deposit, grading 50 Crude oil will be exported through a new 1,200
kg/m3, at Guera massif and an alluvial rutile km pipeline which crosses Cameroon to the
deposit downstream from Bousso. Manganese newly constructed terminal at the Atlantic port of
mineralisation has recently been discovered in the Kribi.
Goz Beida area and comprises a 0.2-0.3 m thick
manganese hydroxide layer, with a strike length Extensive exploration has also been conducted in
of 50 m. the Doba and Doseo Basins in southern Chad
where reserves were first discovered in 1989 by
Diamonds Conoco. The Esso, Shell and Elf consortium
The main areas of alluvial diamond production in identified oil deposits in the Lower and Upper
Chad are in Abeche, Biltine, Am Zoer and Adre Cretaceous detrital sediments of the Doba Basin
in Ouadday, and at Melfi-Bitkine in Guera. Local and its eastern extension, the Doseo Basin.
prospectors have also discovered alluvial Preliminary geophysics and drilling tests have
diamonds in many regions, including Melfi, central indicated reserves amounting to 500 Mt of oil and
Ouadday and the Lim River in Baibokoum. The 510,000 million m3 of natural gas. Further
latter region, which is located in the far evaluation is under way in order to define the
southwest of Chad, has similar geology to that of deposits characteristics.
the small-scale diamond mining areas across the
border in the Central African Republic and The Erdis Basin was explored for hydrocarbons
Cameroon. This supports the belief that further by the Petropar/SNPA consortium during 1961-
finds will be made. 65, but the results have never been released. As
the Libyan extension of the Erdis Basin has
In 1993 the UNDP/DRGM project conducted an producing oil wells, the potential for discovering
exploration programme over 2,500 km2 in the far new oil deposits within the Chad sector is
south of Chad looking for diamonds and their deemed very likely.
indicator minerals, such as ilmenite, pyrope and
chrome diopside. To date the programme has
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Evaporites uranium, in Cambro-Ordovician conglomerates
Chad has large reserves of a number of and sandstones, has also been reported at
evaporites, the two most common and extensive Bouboa, Ouadi Bakou near Fada and Tibesti.
being trona and salt. Evaporites are renewable
with continued evaporation. It has been Industrial And Construction Minerals
estimated that for every cubic metre of water The UNDP/DRGM project identified a number of
evaporated around 250,000 t of salt is produced. promising marble deposits in Mayo Kebbi, Guera
and Ouadday. High-quality marble was
There are two main regions where large discovered at Zoubou in Guera, with a range of
quantities of trona can be found. The area colours from pure white to grey. At Zafai, Rey
around Borkou, Ennedi and Tibesti hosts trona and Modo near Goz Beida, large reserves of
both in salt ponds, such as at Ounianga Kabir, marble have been found totalling 3.5 million m3.
Ounianga Seghir and Ouadi Doum, and on the These deposits are regarded as economically
surface of the sand where direct precipitation has viable both in terms of quantity and quality. A
occurred. This can be seen to the south of Faya number of granites and igneous rocks occur in
and in the Tibesti calderas. The second region, Chad that are suitable for ornamental stones,
to the northeast of Lake Chad, hosts trona in such as the granites southeast of Lake Trene; the
dune valleys on the lakeshore. These trona Sodjembaye syenite north of Pala; and several
deposits are around 25 km wide and extend from granite intrusions in the Guera massif.
the Niger border to Doum-Doum.
Although sand and gravel deposits are
Trona mining has always been on a small-scale widespread, the main production comes from
and is centred on the Liwa-Kaya region. quarries near N'Djaména. The main aggregate
Production is estimated at 12,000 t/y, of which quarry is Dandi, south of Lake Chad. Clay is also
70% is traded with neighbouring countries, mainly mined on a small-scale for the local manufacture
Nigeria. Current renewable trona reserves are of bricks.
estimated at 650,000 t/y.
Large reserves of limestone are found in Mayo
Numerous salt lakes can be found in Chad. The Kebbi, Guera, Ouadday, Ennedi, Tibesti and
largest concentration of these salinas is in the Tenere. Preliminary studies on a deposit near
Borkou and Ennedi region, stretching from Faya Baore in Mayo Kebbi have indicated its suitability
to the north of Fada and covering 60,000 km2. to supply a local Portland cement plant, with
There are 15 large salinas that are well known for production from the deposit totalling 50,000 t/y.
their salt content. These cover an area of about High-grade limestone is occasionally extracted for
20 km2 and comprise 1-4 km long basins with the production of lime at Tagobo Faulbe in Mayo
widths of up to 2 km and grades of 22-91% NaCl. Kebbi, which has estimated reserves of 90,000 t.
The Demi, Oueta, N'Teiguei, Bedo and Orori
salinas have extremely high NaCl grades. Other significant minerals known to exist in Chad
Several gypsum occurrences have been reported
in late Cenozoic formations in the Bahrel-Ghazal • large quantities of graphite, found mainly in
area, north of N'Djaména. However, little layers of Precambrian graphitic schists in
information is known on the exact extent of Guera, Ouadday and Baib-okoum;
these deposits. • significant kaolinite deposits at Abou-Dela,
southeast of Mongo, with an estimated
Uranium 525,000 t of reserves;
Radioactive mineralisation, essentially uranium, • good quality diatomite resources totalling
has been identified in both Tibesti and Mayo 3,000 Mt that extend over 115,000 km2
Kebbi, where they occur in veins associated with between Lake Chad and Fada.
alkaline granite and syenite stocks. Sedimentary
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