--> Abstract: Organic Production by Iron Microbial Mats – Implications for Volcaniclastic Successions and Hydrocarbons on Mars; #90063 (2007)

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Organic Production by Iron Microbial Mats – Implications for Volcaniclastic Successions and Hydrocarbons on Mars

 

Schieber, Juergen1 (1) Indiana University, Bloomington, IN

 

Study of microbial mats associated with a ferrous iron producing freshwater spring reveals a highly productive mat community. The mat is largely constructed from iron encrusted sheaths of Leptothrix spp., with variable contributions of Gallionella spp. stalks, and has an open framework texture. At a spring flow of between 5-10 m3/day the mat produces 5 mm daily growth over 15 m2. The TOC content of dried mat can exceed 5 wt. %.

 

The heterotrophic sheathed bacterium Leptothrix produces most of the organic matter, smaller contributions come from the autolithotrophic Gallionella. Several hundred grams of organic matter are produced per day. Assuming fixation of 100 gC/day yields a primary productivity of 2430g/m2yr, exceeding typical marine rates by a factor of 25. Iron bacteria thrive over a wide range of salinities and temperatures. Where abundant iron bearing fluids enter a basin, such as from shallow marine freshwater springs, cold seeps, and deep sea hot springs, iron bacteria could be a significant contributor of organic matter to the accumulating sediments. Iron encrustation of the sheaths probably enhances preservation potential.

 

Iron microbes still thrive near submarine hot springs today. In early Earth history, with iron-rich volcanigenic successions and high crustal heatflow, they may have contributed significantly to the organic matter buried in Archean sedimentary successions. Mars is a planet with a mafic, iron-rich crust. Early in its history free water existed at the surface. Microorganisms could have exploited iron oxidation as an energy source and simultaneously produced significant amounts of preservable organic matter.

 

AAPG Search and Discover Article #90063©2007 AAPG Annual Convention, Long Beach, California