Country in focus
Almost the entire Ivory Coast is underlain by extremely
ancient metamorphic and igneous crystalline basement rock
between 2.1 and more than 3.5 billion years old, comprising
part of the stable continental crust of the West African
Craton. The rock types found are dominated by granulite
and migmatitegneiss, with some granitoids and banded iron
formations in remnant supracrustal belts. These rocks were
affected by at least two orogenic mountain building events.
The coast is marked by a strip of prominent recent sediments,
extending offshore. Coastal sedimentary basins formed as
a result of the rifting apart of the supercontinent Pangaea,
during the opening of the Atlantic Ocean.
The oldest mining is related to gold and alluvial diamonds.
Native gold is hosted in steeply dipping quartz veins near
the boundaries of volcanic belts and sedimentary basins, in
disseminated and massive sulfide deposits or as alluvial gold
in river gravels. Gold is also found as paleoplacer alluvial
gold and is included in conglomerates and sericite–quartz
schist with grades up to 3g/t.
Diamonds have been found in alluvial deposits, south of
Korhoga at Tortiya and at Seguela. Kanangone, Seguela,
and Tortiya have kimberlite intrusions, but none have
been found to contain diamonds to date. Iron is another
important mineral for Côte d'Ivoire. The Monogaga
deposit near Sassandra is a Minette Oolitic type iron
deposit formed in the Miocene and Pliocene and has a 40%
iron concentration. Mount Gao, Segaye, Tia, Tortro, and
Klahoyo all have Lake Superior type magnetite deposits.
In recent years, there has been an increase in interest in the
high-grade manganese deposits. The manganese occurs as
carbonates, silicates, and oxides and reaches concentrations
of up to 47% in lenticular bodies, in the north-western
regions of the country. The underlying phyllite and gondite
became enriched in manganese near the Blafa-Gueto hills
and Mokta, forming the residual caps.
end of the civil war, there has been a slow and steady rise in the
number of companies working in the country and I believe there
to be considerable untapped potential in the country for well-
funded junior explorers, particularly in the gold space,” says Strong.
Sought after mining jurisdiction
According to David Morgan, managing director at consultants
Knight Piésold, Côte d'Ivoire has become a proven region of high
geological prospectivity for gold projects. “Junior and mid-tier gold
companies have been actively exploring and have enjoyed good
success in the country over the past 10 years,” says Morgan.
Morgan says several factors have contributed to the elevation of
Côte d'Ivoire as a mining hub. “Relatively easy access to historical
geological databases and mapping have made the timing from
initial exploration to successful development relatively quick. The
capital Abidjan is a regional transport hub and provides good
logistics for project support and development. In addition, the
overall infrastructure in Côte D’Ivoire is pretty good compared
with other West African countries, Morgan tells African Mining.
He adds that the local population is well educated and keen to
further develop their skills.
According to Morgan, political stability is still a concern. “Despite
these interruptions, however, the overall political climate continues
to improve. Government is generally supportive of the mining
and gold sector, but further government support is required with
respect to the tax and royalty regimes,” Morgan concludes. b
Geology and minerals of Côte d'Ivoire
Barrick’s Tongon gold mine consists of two opencast
operations and it produced 288 680oz of gold in 2017.
The tropical weathering products and resulting clays are also
of importance as it contains laterite deposits. Biankoumo has
nickel-rich laterite soils on top amphibolite gneisses, close
to the border with Guinea. These nickel deposits contain
an appreciable amount of cobalt. West Africa is also known
for its bauxite deposits and Côte d'Ivoire hosts significant
deposits, although not as large as neighbouring Guinea.
The country is endowed with a large number of other
mineral deposits that have not been developed in most
cases. These range from nickel–copper deposits associated
with platinum group minerals to beach heavy mineral sand
deposits of titanium, tantalite, and glass sand. There is also
modest offshore oil and gas reserves.
Source: Nicolaas Steenkamp, independent geological consultant.
www.africanmining.co.za
MAY - JUNE 2019 AFRICAN MINING
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