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Onverdacht, Lelydorp, Moenggo, Coermotibo

Suriname

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The Onverdacht, Lelydorp, Moenggo and Coermotibo bauxite deposits are located in Suriname on the northern margin of the Guyana (Guiana) Shield and were deposited during Eocene-Oilgocene time.

The Lelydorp open pit mine is located in the coastal plain of Suriname, approximately 25 km south of Paramaribo and 17 kilometres west of the Paranam Refinery. The Coermotibo surface strip mine is located 150 kilometres east of the Paranam refinery. The two mines comprise the Paranam operation of the Suriname Aluminium Company, L.L.C (Suralco).

Other deposits in Suriname include Para, Kankantrie, Kaaimangrasie and Klaverblad.

Total Suriname bauxite reserves in 1994 were estimated at 575 Mt.

The Onverdacht, Lelydorp and Moenggo deposits lie on the northern margin of the Precambrian Guiana Shield where it is overlain by sediments of the coastal plain deposited from the cyclic denudation of the shield. The Guiana Shield is predominantly composed of flysch- and molasse-like sediments that are 2 Ga and older and have been metamorphised during the 2 to 1.8 Ga Trans-Amazonian orogenic event into low to high-grade schists, gneisses and chranockitic granulites. These are overlain and intruded by 1.8 Ga ultramafic, gabbroic and felsic magmatic rocks and covered by the 1.6 Ga Roraima Sandstones and cut by NW striking dolerite dykes and sills. These were all influenced by the 1.2 Ga Nickerie Orogenic event to form blastomylonitic gneisses that formed the NE striking horsts and grabens in Guyana and Suriname.

The overlying coastal plain sediments are irregular in distribution, represented by up to 4500 m of unconsolidated Eocene, Miocene, Oligocene and Pleistocene to Holocene sequences preserved as 20 to 40 m high inselbergs.

The largest of these bauxite deposits, Onverdacht, contains more than 200 Mt of economic bauxite resources which are high in alumina (45 to 62 Al2O3) and low in both silica (1 to 10% SiO2) and iron (0.5 to 25% Fe2O3), predominantly composed of gibbsite with lesser hematite, little quartz, kaolinite, boehmite and accompanying heavy minerals. The bauxite is turn overlain by 0 to 40 m of unconsolidated sediments.

The bauxitic horizon occurs as a bauxitic capping on Paleocene to early Eocene unconsolidated parent rocks which are composed of alternating layers of medium- to coarse-grained sands, locally with some kaolin and pure, tough kaolinitic clays. The cappings form flat, inverted saucer shaped tops and steep sided, escarpment flanked mesas. Dendritic drainage systems are incised into the mesas to a depth of around 4 m. Where covered, these sediments are overlain by Miocene and younger successions of alternating unconsolidated sandy and clayey layers which thicken to the north west.

The lateritic profile may be summarised as follows:

* Alternating pure quartz sands of varying grain size with clays, peaty clays, kaolinitic sands and clays, of Miocene age, varying from 0 m in the south to 40 m or more in the north;
* Hard, reddish to bluish to brown iron rich capping (originally an iron-rich bauxite or bauxitic iron laterite), preseved as inverted pyramidal remnants (pseudo-breccia) in an orange-pink top layers with re-silicification (kaolinite and metahyalloysite) and iron leaching phenomena - 2 to 4 m thick;
* Main horizon of high grade concretionary pink to tan, low iron bauxite, often with clayey gibbsite matrix between the 0 to 10 cm concretions and iron and silica contents of <3% - 2 to 5 m thick;
* Lower horizon of nodular, cellular and boxwork textured light tan bauxite with 0.5 to 4 cm vugs, usually filled with kaolinitic or pure gibbsitic clay - 1 to 30 m thick;
* Relict sedimentary beds of fine- to medium-grained gibbsite crystals with colour and grain size banding, as well as kaolinitic streaks lower in the interval - 0.05 to 1 m thick;
* Up to 15 m of Paleocene to Eocene, pure, mostly white to violet kaolinitic clay with heavy mineral and muscovite rich bands.

For detail see the reference(s) listed below.

The most recent source geological information used to prepare this summary was dated: 2002.    
This description is a summary from published sources, the chief of which are listed below.
© Copyright Porter GeoConsultancy Pty Ltd.   Unauthorised copying, reproduction, storage or dissemination prohibited.


  References & Additional Information
   Selected References:
Aleva, G.J.J.,  1981 - Essential differences between the bauxite deposits along the southern and northern edges of the Guiana Shield, South America: in    Econ. Geol.,   v.76, pp. 1142-1152.


Porter GeoConsultancy Pty Ltd (PorterGeo) provides access to this database at no charge.   It is largely based on scientific papers and reports in the public domain, and was current when the sources consulted were published.   While PorterGeo endeavour to ensure the information was accurate at the time of compilation and subsequent updating, PorterGeo takes no responsibility what-so-ever for inaccurate or out of date data, information or interpretations.

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