Belinga, Batoala, Boka Boka, Minkebe, Mebaga, Ngama, Mela, Tchbanga Mouteli, Mbalam, Avima, Zanaga
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The iron deposits at Belinga (Mecambo), Batoala, Boka Boka, Minkebe, Mebaga and N'gama are located in the north-eastern corner of Gabon, while Mela and Tchbanga Mouteli are in the west and south of the country respectively. The Mbalam deposit is in Cameroon immediately across the border from Belinga, and Avima and Zanaga are nearby in the Congo (Brazzaville).
These deposits lie on the northwestern section of the Congo (Zaire) craton where a broad upwarp of the du Chaillu granite-greenstone terrane stretch across Gabon, extending into the Congo to the south and into Cameroon to the north where it grades into the Ntem charnockite terrane.
The Gabon Orogenic Belt, within which these deposits lie, is a major Eburnian tectono-thermal event. The oldest rocks in the belt in Gabon and Congo are the 3.13 to 2.6 Ga, medium to high metamorphic grade, du Chaillu granite-gneiss and greenstone terrane. These old rocks are unconformably overlain by the thick Paleoproterozoic (2.3 to 2.0 Ga) sandstones, conglomerates and shales of the Francevillian Supergroup, which is in turn overthrust on its western side by the Ogooue Metamorphics that are also considered to be of Paleoproterozoic age. All of these rocks are concealed on the margins of the upwarp by Neoproterozoic and Mesozoic cover.
The du Chaillu granite-greenstone terrane is largely composed of two granitoid generations, all of which are overprinted by a north-south foliation. Both have been dates at around 2.7 Ga. The older granitoid is a grey granodioritic to quartz-dioritic biotite or biotite-amphibole gneiss. These are cut by veins of the younger granitoid, pink, mostly potassic migmatites.
Within the granitoids there are septa of older schists and greenstones which have not been completely granitised. Examples of the larger of these septa cover areas of the order of 20 x 5 and 30 x 25 km and contain steeply dipping banded iron formation (BIF), amphibolites, pyroxeno-amphibolites, biotite gneisses, amphibolite bearing quartzites, pyroxenites and in one case a small dunite mass.
To the north, in Cameroon, the du Chaillu granite-greenstone terrane grades into the high grade granulite facies charnockite terrane which was formed at about 2.9 Ga. It results from the intense metamorphism of highly evolved precursor rocks including dolerite dykes. These charnockitic products then suffered cataclasis, retrograde metamorphism as well as granitisation during the 2.7 Ga event that accompanied the introduction of granitoids into the du Chaillu terrane.
The probably Mesoarchaean iron formations of the du Chaillu schist-greenstone terrane host the iron mineralisaiton in the Belinga and other iron deposits.
At Belinga, which is in the Makokou district, there are a series of north-south ridges formed by the outcrop of the iron formation, with spurs branching off in different directions over an area of 35 x 10 km. The ridges rise to heights of about 500 m above the surrounding countryside and have steep slopes, except where relict canga deposits are preserved. The canga covered slopes, generaly on dip slopes, usually end at a cliff of up to 20 m height, although the canga is usually only about 1 m thick over hydrated slabs of ore. On the opposite side of the ridges, cliffs of up to 35 m are found, exposing hard ore, hydrated slabs and in situ iron formation. The principal ore mineral is hematite with accessory goethite and magnetite.
At Batoala, which is 50 km to the east of Belinga, the main ore mineral is hematite with accessory goethite and magnetite.
At Boka-Boka, which is east of Batoala, the ore has a similar mineralogy.
At Minkebe, which is close to Belinga, the ore has a similar mineralogy.
Mebaga, which is in the Mitzic district, believed to be close to the deposits previously listed, also has a similar mineralogy.
N'gama, which, like Mebaga is in the Mitzic district and has the same characterisitcs.
At Mela, which is in the Kango district in the western part of Gabon, the mineralogy comprises hematite with accessory magnetite.
At Tchbanga Mouteli, which is near the town of Tchibanga in the south-western part of Gabon, the ore is predominantly of hematite.
At Mbalam, which is in Cameroon, 150 km NNW of Belinga, the ore is predominantly of martite and hematite in at least two deposits, the larger of which has a strike length of around 2 km and average width of approximately 400 m (see the seperate Mbalam record).
At Avima, which is just over the border from the Makokou district, in Congo, the ore is predominantly of hematite and goethite with a grade estimated at about 65% Fe.
At Zanaga is also just over the border, in Congo, and is hosted by the Zanaga Greenstone Belt of the Chaillu crystalline massif and comprises near surface enriched BIF above a hematite-magnetite banded iron formation with around 43% Fe and 20% SiO2.
Published reserve and resource figures include:
Belinga - 566 Mt @ 62% Fe, 3.5% SiO2, 0.11% P (Marelle, 1970); 1 Gt @ 60% Fe (Republic of Gabon, Ministry of Mines).
Batoala - 117 Mt @ 66% Fe, 2.9% SiO2 (Marelle, 1970).
Boka-Boka - 194 Mt @ 62% Fe, 3.5% SiO2, 0.11% P (Marelle, 1970).
Batoala/Boka-Boka District - 850 Mt @ >60% Fe, (Kumba Resources).
Minkebe - 60 Mt @ 64% Fe, 3.0% SiO2, 0.11% P (Marelle, 1970).
Mebaga - 15 Mt @ 60% Fe, 4.0% SiO2 (Marelle, 1970).
N'gama - 50 Mt @ 47% Fe, 22% SiO2 (Marelle, 1970).
Mela - 100 Mt @ 46% Fe, 30% SiO2 (Marelle, 1970).
Tchbanga Mouteli - 114 Mt @ 43% Fe, 27% SiO2, 0.18% P (Marelle, 1970).
Mbalam - 132 Mt @ 60% Fe, (Rundqvist, et al., 2006); 215 Mt @ 60% Fe + 2.38 Gt @ 38% Fe (Sundance Resources, 2009).
Mbalam - 219 Mt @ >60% Fe, Resource, within 800 Mt of mineralisation (Sundance Resources, 2007, after UNDF report).
Lobi Lobi - 300 Mt @ 40 to 45% Fe, (Bureau de Reserches Geologiques et Minieres).
Avima - 100 Mt @ 60% Fe, (Rundqvist, et al., 2006).
Zanaga - 300 Mt @ 50% Fe, (Rundqvist, et al., 2006); 562 Mt @ 65% Fe (Arab Steel 2006 Symposium paper).
This record is a combination of information from a range of published sources, including Petters (1991), Regional Geology of Africa; Rundqvist, et al., (2006), Largest Mineral Deposits of the World; Marelle (1970), Iron Ore Deposits of Africa in Survey of World Iron Ore Resources; and others.
The most recent source geological information used to prepare this summary was dated: 2006.
This description is a summary from published sources, the chief of which are listed below.
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