Pore Fluids of Recent Marine Sediments: I., Oxidizing Sediments of 20° N, Continental Rise to Mid-atlantic Ridge

Abstract

ABSTRACT Pore fluids were extracted on shipboard from 12 deep-sea sediment cores taken during all east to west traverse from Africa to the Mid-Atlantic Ridge between latitudes 18N and 20°N. They were analyzed for Cl, SO4 Mg, Ca, K, Sr, SiO2, B, Li, and Mn. Excepting Cl, SO4, and Ca, which are very close to sea water composition, other components examined are slightly but systematically different from normal sea water. Constancy of Cl in samples of varying clay: CaCO3, ratios negate semipermeable membrane behavior of compacting clays, at least for the top 10 meters of sediment. K and B enrichments mirrored by Mg depletions suggest authigenic chlorite formation at the expense of illite K-feldspar and perhaps montmorillonite. The rather constant SiO SUB>2 level and its enrichment over that of bottom water appear indicative of control by clay-silica equilibria. Minor variations of all elements along depths of cores become magnified and more erratic in the Ridge area, due to heterogeneity of mineralogy or perhaps local hydrothermal effects.