On the true antiquity of Eoarchean chemofossils – assessing the claim for Earth's oldest biogenic graphite in the Saglek Block of Labrador
A recent claim to have found traces of Earth's earliest life (>3.95 Ga) utilising isotopically light carbon in graphite-bearing metapelites from the Saglek Block of northern Labrador, Canada, is re-evaluated applying rigorous geological and geochronological criteria. The establishment of the...
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Elsevier BV
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Online Access: | https://hdl.handle.net/20.500.11937/74140 https://doi.org/10.1016/j.precamres.2019.01.001 |
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ftcurtin:oai:espace.curtin.edu.au:20.500.11937/74140 2023-06-11T04:12:18+02:00 On the true antiquity of Eoarchean chemofossils – assessing the claim for Earth's oldest biogenic graphite in the Saglek Block of Labrador Whitehouse, M. Dunkley, Daniel Kusiak, M. Wilde, Simon 2019 restricted https://hdl.handle.net/20.500.11937/74140 https://doi.org/10.1016/j.precamres.2019.01.001 unknown Elsevier BV http://hdl.handle.net/20.500.11937/74140 doi:10.1016/j.precamres.2019.01.001 Journal Article 2019 ftcurtin https://doi.org/20.500.11937/7414010.1016/j.precamres.2019.01.001 2023-05-30T19:55:56Z A recent claim to have found traces of Earth's earliest life (>3.95 Ga) utilising isotopically light carbon in graphite-bearing metapelites from the Saglek Block of northern Labrador, Canada, is re-evaluated applying rigorous geological and geochronological criteria. The establishment of these criteria in previous evaluations of early life claims from southern West Greenland and northern Canada is reviewed in order to provide a backdrop to discussion of the Saglek claim. In particular, we emphasise the importance of the scale of lithological continuity in determining the veracity of such claims, which are considerably easier to demonstrate from large, relatively less tectonised supracrustal remnants like the Isua Greenstone Belt than they are from smaller, isolated enclaves of the kind found on Akilia or the highly tectonised and imbricated unit that is found in the Saglek Block. Unambiguous field relationships between ca. 3.9 Ga tonalitic gneiss and the graphite-bearing metasediments have not been demonstrated in the literature that the Saglek claim relies upon, and earlier U-Pb-Hf isotopic studies on zircon from metasediments at one of the localities used in the claim indicate a Mesoarchean to Neoarchean time of deposition. We conclude that, irrespective of the validity of the carbon isotopic evidence, field relationships and geochronological evidence fail to demonstrate an age of >3.95 Ga for the potential traces of life. Article in Journal/Newspaper Greenland Curtin University: espace Canada Greenland Precambrian Research 323 70 81 |
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Curtin University: espace |
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ftcurtin |
language |
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description |
A recent claim to have found traces of Earth's earliest life (>3.95 Ga) utilising isotopically light carbon in graphite-bearing metapelites from the Saglek Block of northern Labrador, Canada, is re-evaluated applying rigorous geological and geochronological criteria. The establishment of these criteria in previous evaluations of early life claims from southern West Greenland and northern Canada is reviewed in order to provide a backdrop to discussion of the Saglek claim. In particular, we emphasise the importance of the scale of lithological continuity in determining the veracity of such claims, which are considerably easier to demonstrate from large, relatively less tectonised supracrustal remnants like the Isua Greenstone Belt than they are from smaller, isolated enclaves of the kind found on Akilia or the highly tectonised and imbricated unit that is found in the Saglek Block. Unambiguous field relationships between ca. 3.9 Ga tonalitic gneiss and the graphite-bearing metasediments have not been demonstrated in the literature that the Saglek claim relies upon, and earlier U-Pb-Hf isotopic studies on zircon from metasediments at one of the localities used in the claim indicate a Mesoarchean to Neoarchean time of deposition. We conclude that, irrespective of the validity of the carbon isotopic evidence, field relationships and geochronological evidence fail to demonstrate an age of >3.95 Ga for the potential traces of life. |
format |
Article in Journal/Newspaper |
author |
Whitehouse, M. Dunkley, Daniel Kusiak, M. Wilde, Simon |
spellingShingle |
Whitehouse, M. Dunkley, Daniel Kusiak, M. Wilde, Simon On the true antiquity of Eoarchean chemofossils – assessing the claim for Earth's oldest biogenic graphite in the Saglek Block of Labrador |
author_facet |
Whitehouse, M. Dunkley, Daniel Kusiak, M. Wilde, Simon |
author_sort |
Whitehouse, M. |
title |
On the true antiquity of Eoarchean chemofossils – assessing the claim for Earth's oldest biogenic graphite in the Saglek Block of Labrador |
title_short |
On the true antiquity of Eoarchean chemofossils – assessing the claim for Earth's oldest biogenic graphite in the Saglek Block of Labrador |
title_full |
On the true antiquity of Eoarchean chemofossils – assessing the claim for Earth's oldest biogenic graphite in the Saglek Block of Labrador |
title_fullStr |
On the true antiquity of Eoarchean chemofossils – assessing the claim for Earth's oldest biogenic graphite in the Saglek Block of Labrador |
title_full_unstemmed |
On the true antiquity of Eoarchean chemofossils – assessing the claim for Earth's oldest biogenic graphite in the Saglek Block of Labrador |
title_sort |
on the true antiquity of eoarchean chemofossils – assessing the claim for earth's oldest biogenic graphite in the saglek block of labrador |
publisher |
Elsevier BV |
publishDate |
2019 |
url |
https://hdl.handle.net/20.500.11937/74140 https://doi.org/10.1016/j.precamres.2019.01.001 |
geographic |
Canada Greenland |
geographic_facet |
Canada Greenland |
genre |
Greenland |
genre_facet |
Greenland |
op_relation |
http://hdl.handle.net/20.500.11937/74140 doi:10.1016/j.precamres.2019.01.001 |
op_doi |
https://doi.org/20.500.11937/7414010.1016/j.precamres.2019.01.001 |
container_title |
Precambrian Research |
container_volume |
323 |
container_start_page |
70 |
op_container_end_page |
81 |
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1768388063208144896 |