Néoformations et altérations dans trois faciès volcanosédimentaires du Pacifique Sud

A sedimentological, biostratigraphical, mineralogical, geochemical (major and trace elements including rare earths) and isotopic (Rb/Sr) study was made of core samples drilled between the Touamotou Archipelago and the Marquises Islands. This structurally complex region of the South Pacific is characterised by volcanism and deep ocean water circulation. The samples consisted of two 20 cm cores of surface sediment, and a flattened nodule with indurated centre, taken close to the cores. One core sample (T KR 07) is entirely composed of brown, soft sediment. The top part of the second core (T KS 19) is also brown mud but the bottom is indurated. The brown sediment is essentially composed of phillipsite, palagonite. micronodules and nontronite. The indurated part contains volcanic glass, smectite and phillipsite. The nodule core has the same composition as the indurated sediment. The radiolarian fauna establishes a Middle Eocene age for the indurated horizon and the nodule core, while the brown surface mud contains Eocene to Plio-Quaternary faunas. [NOT CONTROLLED OCR]