THE VERTICAL CHANGE IN CLAY MINERAL-COMPOSITION AND CHEMICAL CHARACTERISTICS OF SMECTITE IN SEDIMENT CORES FROM THE SOUTHERN PART OF THE CENTRAL PACIFIC BASIN

Clay mineral composition and chemical characteristics of smectite in five piston core samples collected from different sedimentary provinces in the Central Pacific Basin were studied using XRD and ATEM. The results show that submarine authigenic smectite occurs as the most abundant constituent in four clay mineral assemblages throughout the Neogene, whereas it was diluted by continental clastic clay minerals, such as illite, chlorite and kaolinite, which were transported to the ocean in Quaternary time. The submarine authigenic smectite is characterized as di-octahedral iron-rich beidellite, its morphology comprising the fleecy or lath forms which are considered to have been formed by submarine volcanism or hydrothermal reactions.