Iowaite in serpentinite muds at Sites 778, 779, 780 and 784: a possible cause for the low chlorinity of pore waters

Abstract

The silt fraction of the muds consists predominantly of chrysotile, brucite, and ample amorphous constituents. Chlorite and smectite are less abundant components. Of special interest is the occurrence of iowaite, a brucite-like, Cl-bearing mineral with a layered structure. Iowaite was not found in the samples from the summit site of one of the seamounts drilled; however, it is scattered throughout the strata, composing the flanks of both seamounts investigated. No systematic change of the iowaite abundance with depth was observed. The distribution of iowaite is confined to the surface of the flanks of the seamount, formed by oxidation of some of the ferrous iron in brucite contained in the serpentine muds as it contacted abyssal seawater during protrusion onto the seafloor. -from Authors