Les étapes de la dolomitisation des diatomites marines immergées sur la marge du Pérou

Dolomitic Late Miocene to Pleistocene diatomites have been collected during the Nautile cruise along the Pacific convergent margin off Peru. Petrographic studies (Cathodoluminescence, SEM, electron microprobe) reveal several stages of dolomitization of an initial siliceous mud. Several micritic and sparitic fabric phases of the sediment are controlled by the initial composition, by the early hydroplastic deformation of the soft sediment; at least three fracturation stages have been observed. These phases are controlled by the differential compaction of the thick soft mudstones, siltstones and diatomitic oozes, along the slope. Compaction processes favoured the circulation of interstitial fluids and the dolomitization process throughout the burial period.