Papineau, D;
DeGregorio, B;
Sagar, J;
Thorogate, R;
wang, J;
Nittler, L;
Kilcoyne, D;
... Thornton, G; + view all
(2019)
Fossil biomass preserved as graphitic carbon in a late Paleoproterozoic banded iron formation metamorphosed at more than 550oC.
Journal of the Geological Society of London
, 176
(4)
pp. 651-668.
10.1144/jgs2018-097.
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Abstract
Metamorphism is thought to destroy microfossils, partly through devolatilization and graphitization of biogenic organic matter. However, the extent to which there is a loss of molecular, elemental, and isotope signatures from biomass during high-temperature metamorphism is not clearly established. We report on graphitic structures inside and coating apatite grains from the ca. 1,850 million years old Michigamme silicate banded iron formation from Michigan, metamorphosed above 550 oC. Traces of N, S, O, H, Ca, and Fe are preserved in this graphitic carbon and X-ray spectra show traces of aliphatic groups. Graphitic carbon has an expanded lattice around 3.6Å, forms microscopic radiating rosettes, and has homogeneous 13C values around -22‰, identical to bulk analyses. Graphitic carbon inside apatite is associated with nanometre-size ammoniated phyllosilicate. Precursors of these metamorphic minerals and graphitic carbon originated from ferruginous clay-rich sediments with biomass. We conclude that graphite coatings and inclusions in apatite grains indicate fluid remobilization during amphibolite facies metamorphism of precursor biomass. This new evidence fills-in observational gaps of metamorphosed biomass into graphite and supports the existence of biosignatures in the highly metamorphosed iron formation from the Eoarchean Akilia Association, which dates from the beginning of the sedimentary rock record.
| Type: | Article |
|---|---|
| Title: | Fossil biomass preserved as graphitic carbon in a late Paleoproterozoic banded iron formation metamorphosed at more than 550oC |
| Open access status: | An open access version is available from UCL Discovery |
| DOI: | 10.1144/jgs2018-097 |
| Publisher version: | http://dx.doi.org/10.1144/jgs2018-097 |
| Language: | English |
| Additional information: | This version is the author accepted manuscript. For information on re-use, please refer to the publisher’s terms and conditions. |
| Keywords: | graphite, metasedimentary, carbon isotopes, biosignature, correlated microscopy. |
| UCL classification: | UCL UCL > Provost and Vice Provost Offices > UCL BEAMS UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Chemistry UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > Dept of Earth Sciences UCL > Provost and Vice Provost Offices > UCL BEAMS > Faculty of Maths and Physical Sciences > London Centre for Nanotechnology |
| URI: | https://discovery-pp.ucl.ac.uk/id/eprint/10070027 |
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