| Summary: | Mineraiogical analyses (bulk sediment and <2μum clay fraction) were carried out on the sediment deposits from the abyssal plains of Madeira (NE Atlantic) and Nares (NW Atlantic) these deposits were sampled during the ESOPE océanographie cruise organised by IFREMER. In spite of the depth of the basin (5376 m), deposits in the Madeira plain are highly carbonated (40-60%) nannofossil ooze and calcareous mud whereas in the Nares plain (57 95 m deep) sediments are mainly composed by silty clayey muds and silty muds with a unique carbonate episode. Clay phases are in both cases made up of a mixture of illite, smectite, chlorite and kaolinite. Non clay minerals associated with the clay fraction are recorded in the East (very fine-grained quartz) and in the West (amphiboles, feldspars and some quartz). After comparison of the results obtained with those from studies from adjacent marine and continentai environments, it is suggested that settling was particularly marked by gravity flows originated from the continental slopes (mainly for the Madeira Basin) and by advective transport processes over long distances (for the Nares Basin). A small part of deposits might be the result of wind-borne transport. Latouche Claude, Maillet Noèle, Auffret Gérard. Mineralogical study of two sites in the abyssal plains of Madeira and Nares (North Atlantic Ocean) ESOPE cruise. In: Proceedings of the 9th international Clay Conference, Strasbourg, 1989. Vol IV : Clays in sediments. Diagenesis and hydrothermalism. Strasbourg : Institut de Géologie – Université Louis-Pasteur, 1990. pp. 73-81. (Sciences Géologiques. Mémoire, 88)
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