DESCRIPTIVE MODEL OF KARST TYPE BAUXITE DEPOSITS

MODEL 38c

By Sam H. Patterson

APPROXIMATE SYNONYM Aluminum ore (Bardossy, 1982).

DESCRIPTION Weathered residual and transported materials.

GENERAL REFERENCE Bardossy (1982).

GEOLOGICAL ENVIRONMENT

Rock Types Residual and transported material on carbonate rocks. Transported material may be felsic volcanic ash from a distant source or any aluminous sediments washed into the basin of deposition.

Textures Pisolitic, nodular, massive, earthy.

Age Range Paleozoic to Cenozoic.

Depositional Environment Surficial weathering mainly in wet tropical area.

Tectonic Setting(s) Stable land areas allowing time for weathering and protected from erosion.

Associated Deposit Types Limestone, dolomite, and shale; some are associated with minor coal and are low in Fe due to organic complexing and removal of Fe during formation.

DEPOSIT DESCRIPTION

Mineralogy Mainly gibbsite in Quaternary deposits in tropical areas. Gibbsite and boehmite mixed in older Cenozoic deposits, boehmite in Mesozoic deposits and in Paleozoic deposits; gangue minerals hematite, goethite, anatase, kaolin minerals, minor quartz.

Texture/Structure Pisolitic, massive, nodular.

Alteration Formation of bauxite is itself a form of alteration of aluminous sediments.

Ore Controls Deposits tend to be concentrated in depressions on karst survaces.

Weathering Intense weathering required to form bauxite. Bauxite continues to form in the present weathering environment in most deposits.

Geochemical Signature Al, Ga.

Example European and Jamacan examples are reviewed in Bardossy (1982).