Geochemistry, factor analysis and clay mineral distribution of the sediments and relationship with the associated ferromanganese nodules from the SW Carlsberg ridge

Abstract

Calcareous clay and ooze from the southwestern Carlberg Ridge show wide range of concentrations in Si (4.62-23.88%), Al (1.63-7.98%), Ti (0.43-1.70%) and CaCO sub(3) (8.50-79.75%) and reveal association of the elements with carbonate, and hydrothermal ferromanganese oxide phases. R-mode factor analysis produced 5 major factors-biological, detrital, hydrothermal and authigenic origin for the concerned sediments and further represents a transition from hydrothermal to authigenic origin. Geochemical data indicate the Cu and Ni have resulted from biogenic processes, whereas Fe, Zn and Co are from hydrothermal source. The Mn/Fe ratios (0.08-0.36 for sediments; 0.90-1.48 for nodules) and relationship of Mn with Cu, Ni and Zn for nodules and sediments suggest diagenetic supply of Mn sup(+2) through pore waters during early diagenesis. Distribution of clay minerals show that illite and smectite are more abundant than kaolinite and chlorite, whereas palygorskite and montmorillonite occur as poorly crystalline phases. Illite and chlorite are derived from Indus source due to dispersion in the southern latitudes whereas smectite and kaoklinite are authigenic and point towards the alteration of submarine volcanic rocks