Basalt-Seawater-Microbe Interactions During Oxidative Alteration of the Upper Ocean Crust

Wolfgang Bach, Marine Chemistry & Geochemistry
Katrina Edwards, Marine Chemistry & Geochemistry

DOEI Project Funded: 2002

Proposed Research

Fluid flow and water-rock interaction have important implications for changes in the chemical and physical properties of the seafloor and for exchange of heat and matter between the Earth?s interior and the oceans. The chemical reactions and mineralogical transformations in the upper crust take place very slowly and chemical equilibrium is usually not attained. Microorganisms have developed strategies to catalyze geochemical reactions and use the chemical energy released for cellular growth.

We have recently found evidence that iron-oxidizing microorganisms can grow on basalt glass while using bicarbonate as the only carbon source. We hypothesize that this microbial iron oxidation is an important process in ocean crust alteration and has a large control on chemical exchange between circulating seawater and upper crust. The rates of other chemical reactions may also be microbially controlled. We will conduct laboratory culturing experiments to examine the geochemical effects of microbially mediated recrystallization of basalt glass. We will use nano-analytical tools to identify textures and chemistries of organic matter and inorganic secondary products. We will use natural samples to study micro-textures and nano-scale chemical and mineralogical variations in incipiently weathered basalt. This approach will allow us to provide links between fluid flow, chemical exchange, and microbial activity within the uppermost ocean crust.