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S. De Oliveira and R. Imbernon (1998)

Weathering alteration and related REE concentration in the Catalao I carbonatite complex, central Brazil

Journal of South American Earth Sciences, 11(4):379-388.

REE geochemistry and mineralogy was investigated in a lateritic profile derived from the weathering alteration of the Catalao I complex. From bottom to top of the weathering profile the fresh rock (FR) changes gradually into an altered rock, an isalteritic saprolite (IS) and an alloteritic saprolite (AS). The FR is a phoscorite cut by abundant carbonatitic veins. In the IS apatite is the most abundant mineral, occurring together with goethite, quartz, and small amounts of a secondary Al-phosphate belonging to the plumbogummite-group minerals. AS is formed of goethite, plumbogummite-group minerals, and quartz. Within the FR, carbonatitic veins are richer in REE (REE2O3=0.32\%) than phoscorite (REE2O3=0.13\%). Both parent rocks are characterized by LREE enrichment, but LREE/HREE ratio is higher for carbonatite. REE concentration tends to intensify with weathering, being REE2O3= 0.6-0.8\% for IS and 1.3-1.9\% for AS. REE fractionation in the vertical direction is very weak, being the general pattern of REE distribution essentially inherited from the fresh rock. In addition to the REE-laterites, an extremely REE rich silicified facies within the IS (REE2O3 = 2.48-4.83\%) was also investigated. (C) 1998 Elsevier Science Ltd. All rights reserved.

profile, mobility, bauxite, rocks, soils, geochemistry, fractionation, rare-earth elements, trace-elements, redistribution
WOS:000078135400005
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