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vol.25 issue2GEOCHEMICAL CHARACTERIZATION OF ROCKS IN A CRETACEOUS SEQUENCE IN LAGO DE MARACAIBO BASINGEOCHEMISTRY OF CRUDE OILS FROM THE ORINOCO OIL BELT, VENEZUELA author indexsubject indexarticles search
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Revista de la Facultad de Ingeniería Universidad Central de Venezuela

Print version ISSN 0798-4065

Abstract

LO MONACO, Salvador  and  LOPEZ, Carlos. STUDY OF LATERITIC WEATHERING PROFILES NEAR UPATA, BOLIVAR STATE. Rev. Fac. Ing. UCV [online]. 2010, vol.25, n.2, pp.29-39. ISSN 0798-4065.

Lateritic profiles from the tops of Algarrobo, Copeyal, El Chorro, Mesa de la Carata and El Toro hills, located near Upata in Bolivar State, were studied. The aim of this study is to establish the complexity of the lateritic profiles which form the upper part of the mentioned hills, in order to clarify the processes that gave rise to them. Idealized profiles were established using field relations. Textural elements were studied on macro (hand specimens and binocular magnifying glass) and micro (EPMA) scale. The recognized and proposed profiles on these hills do not correspond to the classical lateritic profile evolution, but represent sequences of lateritic materials of a different nature deposited after the erosion of preexisting lateritic and bauxitic substrates. On Copeyal Hill, in a 50 m thick profile, the limits of sedimentary sequences deposited on the slope of an old valley can be seen. Two erosional surfaces (S1 and S2) were identified. Above the S1 surface, the contact of the strata has an apparent ‘sawteeth’ shape, which could correspond to ‘flame type’ structures, a paleoseismicity indicator. The EPMA analysis allowed us to infer the spatial distribution of elements in minerals. Results confirm the complex nature of the samples, showing evidence of diagenetic processes supporting the sedimentary origin of these profiles. Based on the texture, mineralogy and chemical composition of the bauxite and laterite samples from these hills, a petrographic fabric suggest that polygenetic origin and diagenetic nature becomes evident

Keywords : Weathering profile; Bauxite; Laterite; EPMA; Polygenetic surfaces; Upata.

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