The Koidu Kimberlite Complex, Sierra Leone: Geological Setting, Petrology and Mineral Chemistry

Tompkins, Linda A.; Haggerty, Stephen E.

doi:10.1016/b978-0-444-42273-6.50015-8

Cited by 15 publications

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“…For example, the composition of garnet (a chromium-rich, calcium-poor variety) and spinel (a chromium-and magnesium-rich variety) from the Neoproterozoic Weasua kimberlites suggest that these pipes may be prospective for diamonds (Skinner et al, 2004). Similarly, the chemistry of large ilmenite crystals recovered from kimberlites at Camp Alpha in Liberia (Haggerty, 2015) and from Koidu in Sierra Leone (Tompkins and Haggerty, 1984) suggests that these kimberlites are highly prospective for diamonds. The presence of micro-diamonds in a kimberlite is another strong indicator of the macro-diamond potential of a kimberlite.…”

Section: Kimberlite Indicator Mineralsmentioning

confidence: 99%

A review of the mineral potential of Liberia

Gunn

Dorbor

Mankelow

et al. 2018

Ore Geology Reviews

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The Republic of Liberia in West Africa is underlain mostly by Precambrian rocks of Archaean (Liberian) age in the west and of Proterozoic (Eburnean) age in the east. By analogy with similar terranes elsewhere in the world, and in West Africa in particular, the geology of Liberia is favourable for the occurrence of deposits of a wide range of metals and industrial minerals, including gold, iron ore, diamonds, base metals, bauxite, manganese, fluorspar, kyanite and phosphate.Known gold deposits, mostly orogenic in style, occur widely and are commonly associated with north-easttrending regional shear zones. Gold mining commenced at the New Liberty deposit in western Liberia in 2015, while significant gold resources have also been identified at several other sites in both Archaean and Proterozoic terranes. Liberia has large resources of itabirite-type iron ores, most of which are located in the Liberian terrane, and was the largest producer in Africa prior to the onset of civil war in 1989. Production of iron ore is currently restricted to a single mine, Yekepa, in the Nimba Range. Other important deposits, some of them previously mined, include Bong, the Western Cluster, Putu and Goe Fantro. There is a long history of alluvial diamond production in western and central Liberia, together with more than 160 known occurrences of kimberlite. Most of the known kimberlites occur in three clusters of small pipes and abundant dykes, located at Kumgbor, Mano Godua and Weasua, close to the border with Sierra Leone. Many of these are considered to be part of a single province that includes Jurassic age diamondiferous kimberlites in Sierra Leone and Guinea.Deposits and occurrences of a wide range of other metals and industrial minerals are also known. Several of these have been worked on a small scale in the past, mainly by artisanal miners, but most are poorly known in detail with sub-surface information available at only a few localities. By comparison with most other countries in West Africa, the geology of Liberia is poorly known and there has been very little systematic exploration carried out for most commodities other than gold, iron ore and diamonds since the 1960s and 1970s. Further detailed field and laboratory investigations using modern techniques are required to properly evaluate the potential for the occurrence of economic deposits of many minerals and metals in a variety of geological settings. Digital geological, geochemical, geophysical and mineral occurrence datasets, including new national airborne geophysical survey data, provide a sound basis for the identification of new exploration targets, but in almost every part of the country there is a need for new and more detailed geological surveys to underpin mineral exploration.

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Section: Kimberlite Indicator Mineralsmentioning

confidence: 99%

A review of the mineral potential of Liberia

Gunn

Dorbor

Mankelow

et al. 2018

Ore Geology Reviews

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“…Phlogopites similar to the brownish and colorless microphenocrysts have been noted in chlorite-phlogopite intergrowths from Koidu, Sierra Leone by Tompkins and Haggerty (1984); however, compositionally the core and rims are reversed.…”

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confidence: 61%

“…There is a similarity between the occurrences of kimberlite in Guinea and those in Sierra Leone (Granthan and Allen, 1960;Tompkins and Haggerty, 1984) and Liberia (Haggerty, 1982). In the three regions dikes seem to predominate over pipes, which are all relatively small.…”

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confidence: 89%

The kimberlites of Guinea, West Africa

International Kimberlite Conference Extended Abstracts: 1986

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The most extensive field of kimberlites in West Africa occurs in south-central Guinea, but in spite of their discovery in 1952 by Soguinex and later considerable work by Russian geologists in the 1960's (Vladimirov et al., 1971) little information is available in the scientific literature. About 20 small kimberlite pipes and numerous dikes have been emplaced into Archaean basement rocks consisting mostly of granitic gneisses and quartzitic schists, possibly of Dahomeyan or Birrimian age. Extensive dolerite magmatism occurred about 180 Ma ago and this predates the kimberlitic events. The kimberlite dikes are often oriented almost E-W, but other trends such as 055° and 115° are present.Dikes vary in width from thin stringers or veins (cms), to proper dikes 3 m thick. Dikes may occur "en echelon" or in groups of 3 or more, and extend for 2-3 km. The pipes are relatively small, resembling more the "blows" of South Africa. The largest pipe, Antochka, is roughly 5.2 ha in size.In some instances numerous veins and stringers are localized and form kimberlite stockworks. Clusters of pipes occur, for example at Banankoro, and often it appears that pipes have originated at the inter¬ section of dikes. The absolute age of the kimberlitic magmatism is unknown, but is younger than the 180 Ma age of the dolerites which are often cross-cut by the kimberlite dikes. The kimberlites have undergone erosion since emplacement and probably represent root zone facies.

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“…The indicator mineral suite of the Man Craton kimberlites is well represented by the common indicator minerals: ilmenite, chromite, garnet (peridotitic and eclogitic) and clinopyroxene. Indicator mineral chemistry from the Koidu complex, predominantly from mantle xenoliths, has previously been studied by Haggerty, 1984 andFung andHaggerty, 1995 which indicate a shield geotherm of 40mW/m 2 and sampling from within the diamond stability field. Haggerty et al, 1979 reviewed indicator mineral compositions from western Liberia kimberlites where the full suite of typical kimberlitic indicators was recovered but with clinopyroxene and garnet being predominantly eclogitic.…”

Section: Indicator Mineralsmentioning

confidence: 99%

Kimberlites of the Man craton

International Kimberlite Conference Extended Abstracts: 2003

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The Koidu Kimberlite Complex, Sierra Leone: Geological Setting, Petrology and Mineral Chemistry

Cited by 15 publications

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A review of the mineral potential of Liberia

A review of the mineral potential of Liberia

The kimberlites of Guinea, West Africa

Kimberlites of the Man craton

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