Clay Mineral Diagenesis in Parts of the Western Indian Ocean

Drill core samples of DSDP sites 241 and 250 in the Somali and Mozambique Basins respectively have been examined to understand the nature and extent of burial diagenesis in the deep-sea pelitic sediments of the western Indian Ocean based on X-ray diffractometry and partial chemical analysis. The clay mineral suite is almost identical in both the basins with montmorillonite being the dominant mineral. Illite and kaolinite are present in minor amounts white chlorite is present only in traces. The sediments are in early diagenetic stage. The apparent breakdown of kaolinite and illite and the adsorption of K by the clay minerals has resulted in montmorilloniteillite mixed layers being the only phase present at depth. The mineral trends observed suggest that diagenesis is indeed initiated at much shallower depths as proposed by Matter.