The clay mineralogy of particulate material from some surface seawaters of the eastern Atlantic Ocean

The concentrations of the clay minerals montmorillonite and illite have been determined in 28 samples of particulate material from surface (0–～5 m) waters along the eastern margins of the Atlantic Ocean, and the concentrations of chlorite and kaolinite have been determined in nineteen of the samples.The average concentration of the four clays in the particulate material decreases in the following order: illite (～42%) > kaolinite (～25%) > chlorite (～19%) > montmorillonite (～14%). There are specific trends in the latitudinal distributions of illite and kaolinite in the particulate material; illite decreases and kaolinite increases towards low latitudes. These trends are also found in eolian dusts and deep-sea sediments from the same region, and these clays are considered to have a detrital origin.The concentrations of montmorillonite in the particulate material and deep-sea sediments are similar in the North Atlantic. However, in the South Atlantic the sediments contain about twice as much montmorillonite as does the particulate material. It is suggested that whereas the montmorillonite in North Atlantic deep-sea sediments is largely detrital, that in South Atlantic sediments is both detrital and authigenic.