Authigenic iron sulphides in recent sediments of the Venice Lagoon (Northern Italy)

Abstract

The data indicate early formation of microcrystalline pyrite, in both the framboids and the grains which are disseminated in the organic matter; it is frequently surrounded by massive pyrite growths and/or mixed Fe sulphides. Authigenic Fe sulphide formation in recent sediments (10-30 years old) in the Venice Lagoon is due to the anoxic conditions which seasonally affect the surface sediments and lead to interactions between reactive iron in solution and H2S. Iron may also be solubilized in a reducing environment from ferric hydroxides adsorbed on clays, from organo-metallic complexes, or directly by reduction of clastic grains of Fe oxides and hydroxides; H2S is produced in the same environment by bacterial reduction of sulfates in the pore-water. -from Authors