Evaluating the biosignature potential of nitrogen concentrations in graphite and associated K-silicates
The oldest remnants of life on Earth from various localities in the Isua supracrustal belt in Greenland date back to >3.7 billion years ago (Ga). They are in the form of graphite, whose biogenicity is controversial. Previous studies used the presence and isotopic composition of nitrogen in graphi...
Published in: | Chemical Geology |
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2023
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Online Access: | https://research-portal.st-andrews.ac.uk/en/researchoutput/evaluating-the-biosignature-potential-of-nitrogen-concentrations-in-graphite-and-associated-ksilicates(0c7642ae-9d2b-48d0-b8ac-7e966375a958).html https://doi.org/10.1016/j.chemgeo.2022.121274 https://research-repository.st-andrews.ac.uk/bitstream/10023/26697/1/Stueken_2023_CG_Evaluating_biosignature_CC.pdf |
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ftunstandrewcris:oai:research-portal.st-andrews.ac.uk:publications/0c7642ae-9d2b-48d0-b8ac-7e966375a958 2024-06-23T07:52:27+00:00 Evaluating the biosignature potential of nitrogen concentrations in graphite and associated K-silicates Stueeken, Eva Elisabeth Szilas, Kristoffer van Hinsberg, Vincent J. 2023-02-05 application/pdf https://research-portal.st-andrews.ac.uk/en/researchoutput/evaluating-the-biosignature-potential-of-nitrogen-concentrations-in-graphite-and-associated-ksilicates(0c7642ae-9d2b-48d0-b8ac-7e966375a958).html https://doi.org/10.1016/j.chemgeo.2022.121274 https://research-repository.st-andrews.ac.uk/bitstream/10023/26697/1/Stueken_2023_CG_Evaluating_biosignature_CC.pdf eng eng https://research-portal.st-andrews.ac.uk/en/researchoutput/evaluating-the-biosignature-potential-of-nitrogen-concentrations-in-graphite-and-associated-ksilicates(0c7642ae-9d2b-48d0-b8ac-7e966375a958).html info:eu-repo/semantics/openAccess Stueeken , E E , Szilas , K & van Hinsberg , V J 2023 , ' Evaluating the biosignature potential of nitrogen concentrations in graphite and associated K-silicates ' , Chemical Geology , vol. 617 , 121274 . https://doi.org/10.1016/j.chemgeo.2022.121274 Eoarchean Nitrogen abundances Graphite Biosignatures article 2023 ftunstandrewcris https://doi.org/10.1016/j.chemgeo.2022.121274 2024-06-13T01:23:47Z The oldest remnants of life on Earth from various localities in the Isua supracrustal belt in Greenland date back to >3.7 billion years ago (Ga). They are in the form of graphite, whose biogenicity is controversial. Previous studies used the presence and isotopic composition of nitrogen in graphite from along the Isua belt to argue both for and against biogenicity. To determine if the nitrogen chemistry of graphite can indeed serve as a biosignature, we investigated a hydrothermal graphite deposit from south-east Greenland (1.87–1.82 Ga). We found indications that molar C/N ratios of hydrothermal graphite may be similar to those of biogenic graphite from the Archean rock record, meaning that the nitrogen content of graphite is itself perhaps not diagnostic of ancient life, requiring caution in future studies. However, the hydrothermal graphite deposit also revealed unusually low N concentrations in associated silicates, despite a wide range of K concentrations up to 5 wt%. Using a thermodynamic model of nitrogen speciation in the presence of graphite, paired with previously published partition coefficients for ammonium in K-silicates, we show that abiotic process can explain these low N-concentrations of around 1 μg/g in potassic silicates. Higher concentrations of >10 μg/g, such as those found in graphitic metapelites from the Isua supcracrustal belt, would, however, require an unusually N-rich fluid. Such a N-rich fluid is most easily derived from the breakdown of biomass within sediments prior to graphitization. We therefore conclude that potassic silicates associated with graphite can serve as an indirect biosignature. Our approach supports previous inferences of life on Earth back to at least 3.7 Ga. Article in Journal/Newspaper East Greenland Greenland University of St Andrews: Research Portal Greenland Chemical Geology 617 121274 |
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Open Polar |
collection |
University of St Andrews: Research Portal |
op_collection_id |
ftunstandrewcris |
language |
English |
topic |
Eoarchean Nitrogen abundances Graphite Biosignatures |
spellingShingle |
Eoarchean Nitrogen abundances Graphite Biosignatures Stueeken, Eva Elisabeth Szilas, Kristoffer van Hinsberg, Vincent J. Evaluating the biosignature potential of nitrogen concentrations in graphite and associated K-silicates |
topic_facet |
Eoarchean Nitrogen abundances Graphite Biosignatures |
description |
The oldest remnants of life on Earth from various localities in the Isua supracrustal belt in Greenland date back to >3.7 billion years ago (Ga). They are in the form of graphite, whose biogenicity is controversial. Previous studies used the presence and isotopic composition of nitrogen in graphite from along the Isua belt to argue both for and against biogenicity. To determine if the nitrogen chemistry of graphite can indeed serve as a biosignature, we investigated a hydrothermal graphite deposit from south-east Greenland (1.87–1.82 Ga). We found indications that molar C/N ratios of hydrothermal graphite may be similar to those of biogenic graphite from the Archean rock record, meaning that the nitrogen content of graphite is itself perhaps not diagnostic of ancient life, requiring caution in future studies. However, the hydrothermal graphite deposit also revealed unusually low N concentrations in associated silicates, despite a wide range of K concentrations up to 5 wt%. Using a thermodynamic model of nitrogen speciation in the presence of graphite, paired with previously published partition coefficients for ammonium in K-silicates, we show that abiotic process can explain these low N-concentrations of around 1 μg/g in potassic silicates. Higher concentrations of >10 μg/g, such as those found in graphitic metapelites from the Isua supcracrustal belt, would, however, require an unusually N-rich fluid. Such a N-rich fluid is most easily derived from the breakdown of biomass within sediments prior to graphitization. We therefore conclude that potassic silicates associated with graphite can serve as an indirect biosignature. Our approach supports previous inferences of life on Earth back to at least 3.7 Ga. |
format |
Article in Journal/Newspaper |
author |
Stueeken, Eva Elisabeth Szilas, Kristoffer van Hinsberg, Vincent J. |
author_facet |
Stueeken, Eva Elisabeth Szilas, Kristoffer van Hinsberg, Vincent J. |
author_sort |
Stueeken, Eva Elisabeth |
title |
Evaluating the biosignature potential of nitrogen concentrations in graphite and associated K-silicates |
title_short |
Evaluating the biosignature potential of nitrogen concentrations in graphite and associated K-silicates |
title_full |
Evaluating the biosignature potential of nitrogen concentrations in graphite and associated K-silicates |
title_fullStr |
Evaluating the biosignature potential of nitrogen concentrations in graphite and associated K-silicates |
title_full_unstemmed |
Evaluating the biosignature potential of nitrogen concentrations in graphite and associated K-silicates |
title_sort |
evaluating the biosignature potential of nitrogen concentrations in graphite and associated k-silicates |
publishDate |
2023 |
url |
https://research-portal.st-andrews.ac.uk/en/researchoutput/evaluating-the-biosignature-potential-of-nitrogen-concentrations-in-graphite-and-associated-ksilicates(0c7642ae-9d2b-48d0-b8ac-7e966375a958).html https://doi.org/10.1016/j.chemgeo.2022.121274 https://research-repository.st-andrews.ac.uk/bitstream/10023/26697/1/Stueken_2023_CG_Evaluating_biosignature_CC.pdf |
geographic |
Greenland |
geographic_facet |
Greenland |
genre |
East Greenland Greenland |
genre_facet |
East Greenland Greenland |
op_source |
Stueeken , E E , Szilas , K & van Hinsberg , V J 2023 , ' Evaluating the biosignature potential of nitrogen concentrations in graphite and associated K-silicates ' , Chemical Geology , vol. 617 , 121274 . https://doi.org/10.1016/j.chemgeo.2022.121274 |
op_relation |
https://research-portal.st-andrews.ac.uk/en/researchoutput/evaluating-the-biosignature-potential-of-nitrogen-concentrations-in-graphite-and-associated-ksilicates(0c7642ae-9d2b-48d0-b8ac-7e966375a958).html |
op_rights |
info:eu-repo/semantics/openAccess |
op_doi |
https://doi.org/10.1016/j.chemgeo.2022.121274 |
container_title |
Chemical Geology |
container_volume |
617 |
container_start_page |
121274 |
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