Microbial and diagenetic origins for BIFs mineralogy
Final Report Abstract
The Precambrian chemical sediments, Banded iron formations (BIFs), are the primary repositories of information on the surface environment and biosphere at the time of deposition. Archean BIFs are likely to be formed by anoxygenic photosynthetic bacteria oxidizing Fe(II) ("photoferrotrophs") prior to atmospheric O2, but the low amounts of organic carbon associated with BIFs argued against a strong microbial influence. In this project we showed that BIF mineral assemblages, i.e. magnetite and siderite, are consistent with a photoferrotrophic origin and subsequent diagenesis (moderate heat and pressure) of cells and Fe(III) (oxyhydr)oxides. The mechanisms have been evaluated under Precambrian ocean conditions and compared to the mineral assemblages of BIFs. Trace element analysis (TE; e.g. Mo, Co, Cu, Zn, Ni) aided in evaluating a microbial origin. We used microspectroscopic and spectromicroscopic analyses to quantify trace elements incorporated in photoferrotrophic organic matter vs. minerals after diagenesis. The trace element signature of BIF minerals, partitioning coefficients into sulfide and Fe(III) (hydr)oxide minerals have been determined and used to determine the trace element concentrations of the Precambrian ocean, and to infer which microbial metabolisms were supported.
Publications
- (2014) Cobalt and marine redox evolution. Earth & Planetary Science Letters, 390:253-263
Swanner, E.D., Planavsky, N.J., Lalonde, S.V., Robbins, L.J., Bekker, A., Rouxel, O.J., Saito, M.A., Kappler, A., Mojzsis, S.J., Konhauser, K.O.
(See online at https://doi.org/10.1016/j.epsl.2014.01.001) - (2015) Limited Zn and Ni mobility during simulated Iron Formation diageneis. Chemical Geology 402:30-39
Robbins, L.J., Swanner, E.D., Lalonde, S.V., Eickhoff, M., Paranich, M.L., Reinhard, C.T., Peacock, C.L., Kappler, A., Konhauser, K.O.
(See online at https://doi.org/10.1016/j.chemgeo.2015.02.037) - (2015) Using modern ferruginous habitats to interpret Precambrian banded iron formation deposition. International Journal of Astrobiology FirstView, 1-13
Koeksoy, E., Halama, M., Konhauser, K.O., Kappler, A.
(See online at https://doi.org/10.1017/S1473550415000373) - (2016) Evaluation of siderite and magnetite formation in BIFs by pressure-temperature experiments of Fe(III) minerals and microbial biomass. Earth and Planetary Science Letters, Volume 450, 15 September 2016, Pages 243-253
Halama, M., Swanner, E.D., Konhauser, K.O., Kappler, A.
(See online at https://doi.org/10.1016/j.epsl.2016.06.032)
