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A composite sphere assemblage model for porous oolitic rocks:Application to thermal conductivity

Journal of Rock Mechanics and geotechnical Engineering 2017年第1期9卷 54-61页

作者： F. Chen A. Giraud D. Grgic K. Kalo geo ressources laboratory Université de Lorraine (ENSG) CNRS CREGU Vandoeuvre-lès-Nancy F-54518 France

The present work is devoted to the determination of linear effective thermal conductivity of porous rocks characterized by an assemblage of grains(oolites) coated by a matrix. Two distinct classes of pores, *** or intra oolitic pores(oolite porosity) and mesopores or inter oolitic pores(inter oolite porosity), are taken into account. The overall porosity is supposed to be connected and decomposed into oolite porosity and matrix porosity. Within the framework of Hashin composite sphere assemblage(CSA)models, a two-step homogenization method is developed. At the first homogenization step, pores are assembled into two layers by using self-consistent scheme(SCS). At the second step, the two porous layers constituting the oolites and the matrix are assembled by using generalized self-consistent scheme(GSCS) and referred to as three-phase model. Numerical results are presented for data representative of a porous oolitic limestone. It is shown that the influence of porosity on the overall thermal conductivity of such materials may be significant.

关键词： Effective thermal conductivity Three-phase model Oolitic limestone Composite sphere assemblage(CSA) model

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Petrographic and geochemical Characterization of Mayedo and Kinzoki Ranges (Sumbi Bauxite Region, Kongo Central/DR Congo)

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Journal of geoscience and Environment Protection 2023年第7期11卷 98-117页

作者： Derick Ungu Ramazani Ivon Ndala Tshiwisa Charles Mpiana Kenababo Albert Ongendangenda Tienge Valentin Kanda Nkula Esperit Mwanakangu Hope Nathan Bamba Nkwansambu Don Luemba Vimbi Dominique Wetshondo Osomba geo-Hydro-Energy Research Group Geosciences Department Faculty of Sciences and Technologies University of Kinshasa Kinshasa Democratic Republic of Congo geosciences Department Faculty of Sciences and Technologies University of Kinshasa Kinshasa Democratic Republic of Congo Gestion des ressources Minérales et Pétrolières Université de Kinshasa Kinshasa Democratic Republic of Congo Laboratoire de Géologie des Argiles Mention Géosciences Faculté des Sciences et Technologies Université de Kinshasa Kinshasa République Démocratique du Congo Centre de Recherches Géologiques et Minières (CRGM) Kinshasa Democratic Republic of Congo

The bauxitic region of Sumbi and its surroundings in Central Kongo (DR Congo) is located in an area corresponding to “bands” of basic rocks made up of microdolerites, basalts and andesites. The problem of this study is linked to the similarity of the phenomena that generated the depositional process of these ferruginous and aluminous formations. The aim of this article is to carry out a chemical and petrographic study of samples of bauxitic materials from the Mayedo and Kinzoki regions, with a view to their possible recovery. To this end, the chemical and petrographic analysis of the weathering formations outcropping in the study area was carried out using X-ray fluorescence and thin section methods. The latter revealed that two lithologies were detected in the healthy rocks: basalts with a mineralogical assemblage of plagioclase crystals, pyroxene microcrystals and oxide opaques;and dolerites represented by plagioclase crystals, pyroxenes and a few quartz crystals. X-ray fluorescence revealed high levels of Al2O3 (32.69%) in the Mayedo zone (MHb1). This visibly gibbsite-rich level corresponds to the zone of friable, homogeneous bauxite with a massive, blood-red texture, with an estimated gibbsite percentage of 55.50. The percentage of Fe2O3 is high in these zones at 42.77%, hence the dark red colour, reflecting a strong zone of ferruginasation. This horizon contains a high concentration of hematite and goethite minerals. Highly variable SiO2 contents ranging from 13.48% to 40.82%. These variations are essentially due to the dissolution of silica by leaching and resilification.

关键词： Bauxite Ferruginasation X-Ray Fluorescence Thin Film Mayedo Kinzoki Valorisation

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