A mass transfer model of bauxite formation

Journal Article · Sun Dec 01 04:00:00 EST 1996 · Geochimica et Cosmochimica Acta

DOI:https://doi.org/10.1016/S0016-7037(96)00319-5· OSTI ID:569826

Soler, J M; Lasaga, A C ^[1]

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1. Yale Univ., New Haven, CT (United States)

The formation of bauxite due to weathering of a granitic protolith has been simulated by means of a one-dimensional flow and reaction model based on the mass transfer principle. The model couples mineral dissolution and precipitation reactions, speciation in solution, and advective solute transport in a porous medium. A very important aspect of the modeling study is the use of mineral reaction rates determined experimentally in the laboratory. The important effects of solution saturation state and pH have been incorporated into the kinetic rate laws governing the heterogeneous reactions. The values of these parameters have been obtained from the scientific literature to guarantee that realistic reaction rates are used in the simulations. Albite and quartz are the minerals that make up the parent rock in the model. Gibbsite, kaolinite, and a Na-mica (as a surrogate for smectite) are the secondary minerals that have been taken into account. Long-term simulations (>1 Ma) have been run, and the formation of a bauxitic profile, with an upper gibbsite-rich and a lower kaolinite-rich zone, is predicted. In early stages of the process (up to a few hundreds of thousands of years), both gibbsite and kaolinite precipitate directly from solution as a consequence of albite dissolution. In later stages, the bulk of gibbsite precipitation derives from the incongruent dissolution of kaolinite, while kaolinite precipitation is still caused by the dissolution of albite. This is also reflected by the formation of two reaction fronts in the profile. These results are compared with weathering sequences from the Los Pijiguaos bauxite deposit, Venezuela. The overlap between the gibbsite and kaolinite zones and the replacement of kaolinite by gibbsite are consistent with model calculations. 59 refs., 22 figs., 1 tab.

• DOE Contract Number: FG02-90ER14153
• OSTI ID: 569826
• Journal Information: Geochimica et Cosmochimica Acta, Journal Name: Geochimica et Cosmochimica Acta Journal Issue: 24 Vol. 60; ISSN GCACAK; ISSN 0016-7037
• Country of Publication: United States
• Language: English

Related Subjects

54 ENVIRONMENTAL SCIENCES
58 GEOSCIENCES
BAUXITE
FLUID FLOW
MASS TRANSFER
MATHEMATICAL MODELS
ORIGIN
POROUS MATERIALS
ROCK-FLUID INTERACTIONS