Precipitation of iron minerals by a natural microbial consortium

A microbial biofilm consortium enriched from Shield surface water is able t o mediate geochemical cycling of iron within a biofilm. Iron can be leached from Fe(II) containing minerals such as magnetite, biotite and ilmenite to generate a colloidal Fe(III) suspension. The Fe(III) can then be reduced b ack to Fe(II) by iron-reducing bacteria that utilize it as an electron acce ptor. On precipitation, different iron compounds are formed depending on th e ratio of iron to carbon in the media and upon the local environment. Moss bauer and X-ray diffraction spectroscopy show these compounds to include fe rrous hydroxide, vivianite, ferrihydrite and hematite. These minerals may t hen become incorporated into stratifer iron deposits such as Banded Iron Fo rmations. Copyright (C) 1999 Elsevier Science Ltd.