Guyana-Surinam Bauxite - Onverdacht, Lelybad, Kaaimangrasi, Klaverbad, Moengo, Bakhuis, Nassau
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The Guyana-Surinam bauxite belt is marked by a crescent shaped zone containing numerous bauxite deposits within the Atlantic Ocean coastal plains of these two countries. This zone is near 800 km long and 20 to 40 km wide and is outboard of the Guyana Shield. The bulk of the deposits form a 170 km long, NNW-SSE trending chain in northeastern Guyana from near the capital Georgetown, extending into northwestern Surinam. After a gap with less frequent occurrences, a second group of deposits form another ~160 km long, east-west oriented string in northeastern Surinam, extending eastward from immediately to the south of the capital Paramaribo to the French Guiana border.
The southern boundary of this belt is defined by the line beyond which the laterite deposits are too ferruginous and too siliceous to be economic, or where un-lateritised basement rock is exposed at the surface. The northern boundary largely corresponds to the point where the overburden is too thick, even
if bauxite is present at depth (Moses and Michell, 1963).
In addition to this line of deposits on the coastal plains, a number of others are also developed south and west of the craton margin on remnant plateaux surfaces representing Tertiary and older peneplains.
From ~1945 to ~1955, Guyana (then British Guiana) and Surinam produced around 50% of the world's bauxite. Although the tonnage produced continued to rise to a peak of ~10.5 Mtpa in 1970, compared to the ~7 Mtpa in 1955, the share of world output declined markedly as both demand and supply from other sources increased substantially.
For details of the history of discovery and mining and the overall geology and mineralisation of the belt, as well as descriptions of the individual deposits and deposit clusters in Guyana, see the separate "Guyana-Surinam Bauxite - Linden-Mackenzie, Ituni, Aroaima, Kwakwani, Tarakulli, Canje, Bonasika, Blue Mountains, Pakaraima" record.
Districts and Deposits
The key deposits within Surinam include, from west to east:
• Bakhuis - 140 km ESE of Kwakwani (Guyana), and 200 km SW of Paramaribo
(#Location: 4° 42' 34"N, 56° 47' 52"W).
• Lelybad 3 - 20 km S of Paramaribo, in Surinam (#Location: 5° 39' 34"N, 55° 12' 7"W).
• Lelydorp - 20 km S of Paramaribo, in Surinam (#Location: 5° 38' 25"N, 55° 11' 8"W).
• Onverdacht - 20 km SSE of Paramaribo, in Surinam (#Location: 5° 38' 1"N, 55° 8' 22"W).
• Klaverbad - 20 km SE of Paramaribo, in Surinam (#Location: 5° 40' 1"N, 55° 1' 40"W).
• Kaaimangrasi - 40 km SE of Paramaribo, in Surinam (#Location: 5° 37' 38"N, 54° 52' 57"W).
• Moengo - 100 km ESE of Paramaribo, in Surinam (#Location: 5° 32' 52"N, 54° 18' 53"W).
• Nassau Plateau - 120 km SE of Paramaribo, in Surinam (#Location: 4° 50' 0"N, 54° 35' 33"W).
Bakhuis is the westernmost deposit cluster in Surinam, lying between the string of deposit clusters in Guyana and the greater density of worked deposits in NE of Surinam. The deposits occur on a SW-NE aligned plateau that is ~90 x 20 km, but has been strongly dissected by erosion, into a few large and many small remnants.
The bauxite at Bakhuis comprises 63% gibbsite, 5% kaolinite, 1% quartz, 8% hematite, 18% goethite and 2% anatase (Bauxite Institute of Suriname, 2009).
The total bauxite resource at Bakhuis in western Surinam has been estimated at 198 Mt with an average thickness of 4.6 m, containing an average of 48.6% Al2O3, with a low temperature process recovery of 42.8% Al2O3, whilst the reactive silica content is 2.5% SiO2. The higher grade bauxite accounts for a little over half of the total tonnage (see reserves below) and has an average thickness of 3.9 m, containing 52.7% Al2O3 (50% by low temperature processing), 2.0% SiO2, 14.8% Fe2O3.
On the basis of 3000 drill holes in the Adampada-Kabalebo region of the district in 1971-73, Reynolds-Surinam estimated a proved + probable + possible reserve of 40 Mt, 18 Mt of which was 6 to 8 m thick with an overburden of 1 to 1.5 m, and averaged 46 to 47% Al2O3, with 1 to 1.5% SiO2.
The total resource of the district, contains a High Grade reserves - 104 Mt @ 52.7% Al2O3, 2.0% SiO2, 14.8% Fe2O3 that averages 3.9 m in thickness. The balance is a Low Grade tonnage of 94 Mt @ 44.0% Al2O3, 3.9% SiO2.
More recent estimates by the Bauxite Institute of Suriname (2009) quoted a JORC compliant resources as follows:
Measured resource - 79.9 Mt @ 44% Al2O3, 3.5% SiO2, 23.6% Fe2O3, 1.6% TiO2, 26.1% LOI, 0.5% TOC, and averages 4.3 m in thickness with 1 m of overburden.
Indicated resource - 147 Mt @ 44.1% Al2O3, 5% SiO2, 22.8% Fe2O3, 1.5% TiO2, 25.5% LOI, 0.6% TOC, and averages 3.8 m in thickness with 0.8 m of overburden.
Inferred resource - 98 Mt @ 41.1% Al2O3, 3.3% SiO2, 27% Fe2O3, 1.8% TiO2, 25.5% LOI, 0.6% TOC, and averages 3.2 m in thickness with 1.1 m of overburden.
TOTAL resource - 324.7 Mt @ 43.2% Al2O3, 4.1% SiO2, 24.3% Fe2O3, 1.8% TiO2, 25.5% LOI, 0.6% TOC, and averages 3.7 m in thickness with 1 m of overburden.
No mining had taken place to 2016.
This string of deposits is distributed over an east-west interval of ~50 km, immediately to the south of Paramaribo.
Onverdacht, the largest deposit in the Paramaribo district contained >60 Mt capable of producing to the specifications of <5% SiO2, 14.8% Fe2O3 and <3% moisture at a recoverable grade of ~50% Al2O3 (Dixon, 1979).
This deposit was a single, shallow north dipping lens of bauxite, >5 km long, averaging 2 km in width and 6 m in thickness. Several other lenses are known in the area. The main lens is separated from an undulose, deeply weathered Precambrian bedrock by the unconformable Late Cretaceous to early Eocene Onverdacht Formation, which commences with a basal 20 to 30 m of poorly sorted, coarse to medium sand containing some residual feldspar. These sands are, in turn, overlain by the kaolinitic clay that forms the immediate footwall to the bauxite lens. The bauxite is overlain by the Oligocene to Miocene Coesewijne (or White Sand) Formation, which comprises a lower 0 to 6 m thick unit that thickens at the expense of the bauxite, and is composed of kaolinitic clays, sandy at the base, overlain by an upper 0 to 3 m thick unit of kaolinitic sands that pinches an swells along strike. These are overlain, in turn, by the Quaternary Coropina Formation, which is composed of ~10 m of laminated mottled clays with fine sand lenses and zones rich in organic material, that pass upwards into sandy clay. These are capped by 0 to 6 m of the Recent Demerara Formation, comprising a lower unit of dark organic rich swamp clays and a thin layer of modern swamp.
The bulk of the bauxite is relatively soft. It contains up to 60% Al2O3, has a concretionary texture and is almost entirely composed of gibbsite with minor impurities, including limonite minerals with1 to 3% Fe2O3, and 1 to 2% SiO2 occurring as colloform silica or kaolinite. The bauxite has an LOI of between 14 and 30%. The soft ores have an SG of 1.3, whilst the harder, more compact varieties increase to 1.6 and 1.9.
The top of the bauxite lens is occupied by a lensoid band up to 1 m thick with a very uneven texture and composition, containing irregular ferricrete like patches of iron oxide, enclosed within massive gibbsite-rich material that is cut by numerous kaolinite veinlets. This band contains 8 to 28% Fe2O3 and 15 to 30% SiO2.
Towards the base of the bauxite lens, the texture changes from nodular to predominantly laminated bauxites, enclosing pockets of massive bauxite, as well as a cellular, cavity ridden variety, formed by septa of bauxitic material. The basal contact with the underlying kaolinitic clay, although sharp, is very irregular, with blocks up to 1 m across found above the base of the bauxite. This irregular contact zone tends to be silica rich, and when it exceeds 15% SiO2 was not mined. The laminated bauxite contains thin associated lenses of kaolinite and small, but significant heavy minerals.
Two main areas of bauxite have been exploited in the Moengo area, the main Moengo mine, near the town of the same name to the west, in the West Range, and Coermotibo, 10 to 15 km to the NE in the East Range. Mining commenced at Moengo in 1916, and was exhausted by 1991. Production commenced at Coermotibo in the same year (BHP Billiton, 2006).
The original Moengo deposit covered an area of 5 x 1 km and yielded ~10 Mt of bauxite and are 3 to 7 m thick, mostly occurring as a capping on the hills with only thin superficial cover. Most bauxite accumulations at Moengo rest directly on transported kaolin that overlies weathered schist and other basement metamorphic rocks, although in some locations the kaolin is separated from crystalline basement by coarse sands. The bauxite lenses at Moengo are composed of the following bauxite varieties (Patterson et al., 1986):
• Dense, pink to yellow-white bauxite, which varies from being fine grained to aggregates of up to 4 mm crystals of gibbsite, with clay infilled vugs.
• Laminated bauxite, comprising alternating layers of gibbsite and kaolinite, or dense and porous gibbsite.
• Porous bauxite, characterised by vugs of variable size, some of which retain the form of leached quartz grains.
• Cellular bauxite, with very thin walls that are predominantly composed of crystalline gibbsite.
• Bauxitic clay, containing concretions up to 1.5 cm in diameter of dense fine grained bauxite resembling kaolinite.
The Bauxite Institute of Suriname (2009) quotes remaining reserves at Coermotibo as 18 to 37 Mt of bauxite.
Nassau, Lely and Bloomsberg Mountains
These deposits are located well inland of the coastal plain, and were developed in situ on crystalline basement, with only minor superficial cover.
The bauxite deposits of the Nassau Mountains are ~120 km SE of Paramaribo, and within 10 to 20 km west of the border with French Guiana.
The bauxite ore is located on four connected plateaux, ranging in elevation from 500 to 564 m above sea level (asl) and within a few metres below the surface of the plateau. The surrounding countryside, within 2 km of the plateau rim, is at an altitude of <100 masl. The 'L' shaped plateau has an east-west base that is ~13 km long by 3 km wide, and an irregular north-south arm of similar length that tapers northward broadening to form a partially separated northern extremity plateau several km in diameter. Some 4 larger bauxite developments are found within these plateaux, known a Plateau A, B and C from east to west on the southern limb, and Plateau D in the northern extremity, with a number of smaller accumulations in between. Of the 8230 ha area of the plateau, ~1000 ha is bauxitic.
The Nassau plateau is a remnant of an early Tertiary (65 to 57 Ma) denudation surface or peneplain (King et al., 1964), and is underlain by Palaeoproterozoic (>2000 Ma) rocks of the Trans-Amazonian Marowijne Group greenstone belt (Bosma et al., 1977). The Nassau Mountains are made up of ocean-floor meta basalts and island-arc meta-andesites, as well as meta-cherts of the Paramaka Formation.
Alluvial and eluvial gold is also mined on the same plateau, mainly by artisanal miners.
It is estimated that the Nassau deposit contains about 40 million dry tonnes of bauxite ore, most of which is located in shallow lateritic deposits, with an average overburden thickness of 1.5 m and 1.7 m of bauxite ore.
A typical profile comprises, crystalline basement which occurs at a depth of ~34 m, overlain by ~30.5 m of kaolin clay, 0.5 m of silica-bauxite, 1.7 m of bauxite, 1.1 m of ferruginous duricrust and ~0.2 m of topsoil.
Doeve (1957) estimated the reserves of bauxite in the Nassua Mountains at 14 Mt @ 53.5 to 55.5% Al2O3, 3 to 5% SiO2, 8.5 to 10.5% Fe2O3, 4 to 6% TiO2, 27-29% LOI. Additional low grade reserves were 6 Mt @ 47.5 to 49.5% Al2O3, 17.5 to 19.5% Fe2O3. The Bauxite Institute of Suriname (2009) quotes a resource of 32 to 60 Mt for the Nassau Plateau.
The similar bauxitic Lely Plateau is located ~65 km south of the Nassau Plateau, and according to the Bauxite Institute of Suriname (2009) has a resource of 15 to 27 Mt of bauxite.
The similarly bauxitic Bloomsberg Mountains plateau is located ~60 km west of Nassau Plateau, ~130 km south of Paramaribo, on the northwestern shores of the Brokopondo Reservoir, and according to the Bauxite Institute of Suriname (2009) has a resource of 8.7 to 14.8 Mt of bauxite.
Total reserves and resources
The reserve/resource estimates in Surinam is variable, as quoted by USGS Professional Paper 1076-B (1986) were as follows:
• Data supplied to the International Bauxite Association by the Surinam Government (1976),
Measured reserves - 270.8 Mt and Total reserves - 490 Mt, excluding the 198 Mt at the Bakhuis deposits (see above),
• U.S. Bureau of Mines estimate (Baumgardner and McCawley, 1983) of total reserves - 575 Mt + total resources - 800 Mt,
• Historic production from 1975 to 1983 - 30 Mt.
• Historic production from the eastern deposits to 1960 - 45 Mt.
• Bauxite Institute Suriname (2009):
resources in existing mines - 11 Mt
resources in un-mined concessions - 90 to 158 Mt
resources at Bakhuis - > 325 Mt.
Much of this summary is drawn from Patterson, S.H., Kurtz H.F., Olson, J.C. and Neeley, DC.L., 1986 - World Bauxite Resources; U.S. Geological Survey Professiona Paper 1076-8."
The most recent source geological information used to prepare this summary was dated: 2009.
Record last updated: 11/2/2016
This description is a summary from published sources, the chief of which are listed below.
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| References in PGC Publishing Books:||
Herrington R, Smith M, Maslennikov V, Belogub E, Armstrong R, 2002 - A short review of Palaeozoic hydrothermal magnetite iron-oxide deposits of the south and central Urals and their geological setting, in Porter T M, (Ed.), Hydrothermal Iron Oxide Copper-Gold & Related Deposits: A Global Perspective, v2 pp 343-353|
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