Details
| Original language | English |
|---|---|
| Pages (from-to) | 181-186 |
| Number of pages | 6 |
| Journal | GEOLOGY |
| Volume | 52 |
| Issue number | 3 |
| Early online date | 3 Jan 2024 |
| Publication status | Published - 1 Mar 2024 |
Abstract
The biological nitrogen (N) cycle on early Earth is enigmatic because of limited data from Archean (meta-)sediments and the potential alteration of primary biotic signatures. Here we further investigate unusual 15N enrichments reported in 2.7 Ga meta-sediments from the Abitibi greenstone belt, Canada, purportedly related to a 15N-enriched Archean atmosphere. Given that sediments from this region are contemporaneous with large-scale volcanogenic massive sulfide deposits, we utilize Cu and Zn contents to trace the effects of hydrothermal circulation on N isotope fractionation. We show that high δ15Nbulk values as high as +23%o are associated with Cu-Zn mineralization, whereas unmineralized organic-rich shales exhibit much lower δ15Nbulk and δ15Nkerogen values. Moreover, we find a large offset between δ15Nbulk and δ15Nkerogen of as much as 17%o and relate this to the addition of organic-bound N during the late-stage emplacement of organic-rich veins. We conclude that the previously reported high δ15N values are most parsimoniously explained by biotic and abiotic mechanisms rather than a 15N-enriched atmosphere. Crucially, both mechanisms require the presence of NH4+ in hydrothermal fluids, supporting the hypothesis that hydrothermal discharge was an important nutrient source for Neoarchean marine life.
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In: GEOLOGY, Vol. 52, No. 3, 01.03.2024, p. 181-186.
Research output: Contribution to journal › Article › Research › peer review
}
TY - JOUR
T1 - Mechanisms of nitrogen isotope fractionation at an ancient black smoker in the 2.7 Ga Abitibi greenstone belt, Canada
AU - Martin, A. N.
AU - Stüeken, E. E.
AU - Michaud, J. A.S.
AU - Münker, C.
AU - Weyer, S.
AU - van Hees, E. H.P.
AU - Gehringer, M. M.
N1 - Funding Information: Funding for Martin, Münker, Weyer, and Gehringer was provided by the German Research Foundation (DFG) priority program “SPP-1833 Building a Habitable Earth,” and for Michaud by the DFG priority program “SPP-2238 Dynamics of Ore Metals Enrichment” (HO1337/49-1). Stüeken acknowledges support from a UK Natural Environment Research Council (NERC) Frontiers grant (NE/V010824/1) and a Leverhulme Trust grant (RPG-2022-313).
PY - 2024/3/1
Y1 - 2024/3/1
N2 - The biological nitrogen (N) cycle on early Earth is enigmatic because of limited data from Archean (meta-)sediments and the potential alteration of primary biotic signatures. Here we further investigate unusual 15N enrichments reported in 2.7 Ga meta-sediments from the Abitibi greenstone belt, Canada, purportedly related to a 15N-enriched Archean atmosphere. Given that sediments from this region are contemporaneous with large-scale volcanogenic massive sulfide deposits, we utilize Cu and Zn contents to trace the effects of hydrothermal circulation on N isotope fractionation. We show that high δ15Nbulk values as high as +23%o are associated with Cu-Zn mineralization, whereas unmineralized organic-rich shales exhibit much lower δ15Nbulk and δ15Nkerogen values. Moreover, we find a large offset between δ15Nbulk and δ15Nkerogen of as much as 17%o and relate this to the addition of organic-bound N during the late-stage emplacement of organic-rich veins. We conclude that the previously reported high δ15N values are most parsimoniously explained by biotic and abiotic mechanisms rather than a 15N-enriched atmosphere. Crucially, both mechanisms require the presence of NH4+ in hydrothermal fluids, supporting the hypothesis that hydrothermal discharge was an important nutrient source for Neoarchean marine life.
AB - The biological nitrogen (N) cycle on early Earth is enigmatic because of limited data from Archean (meta-)sediments and the potential alteration of primary biotic signatures. Here we further investigate unusual 15N enrichments reported in 2.7 Ga meta-sediments from the Abitibi greenstone belt, Canada, purportedly related to a 15N-enriched Archean atmosphere. Given that sediments from this region are contemporaneous with large-scale volcanogenic massive sulfide deposits, we utilize Cu and Zn contents to trace the effects of hydrothermal circulation on N isotope fractionation. We show that high δ15Nbulk values as high as +23%o are associated with Cu-Zn mineralization, whereas unmineralized organic-rich shales exhibit much lower δ15Nbulk and δ15Nkerogen values. Moreover, we find a large offset between δ15Nbulk and δ15Nkerogen of as much as 17%o and relate this to the addition of organic-bound N during the late-stage emplacement of organic-rich veins. We conclude that the previously reported high δ15N values are most parsimoniously explained by biotic and abiotic mechanisms rather than a 15N-enriched atmosphere. Crucially, both mechanisms require the presence of NH4+ in hydrothermal fluids, supporting the hypothesis that hydrothermal discharge was an important nutrient source for Neoarchean marine life.
UR - http://www.scopus.com/inward/record.url?scp=85187214912&partnerID=8YFLogxK
U2 - 10.1130/G51689.1
DO - 10.1130/G51689.1
M3 - Article
AN - SCOPUS:85187214912
VL - 52
SP - 181
EP - 186
JO - GEOLOGY
JF - GEOLOGY
SN - 0091-7613
IS - 3
ER -