Chemical alteration and preservation of sedimentary/organic nitrogen isotope signatures in a 2.7 Ga seafloor volcanic sequence

L. D. Anderson, Gray Edward Bebout, Matthew Richar Izawa, N. J. Bridge, N. R. Banerjee

Research output: Contribution to journalArticle

1 Citation (Scopus)

Abstract

Massive to lobate volcanic flows and brecciated hyaloclastite units in the Abitibi greenstone belt allow investigation of Late Archæan seafloor alteration and associated incorporation into these rocks of nitrogen (N) biogeochemical signatures. In this suite (the Blake River Group), hyaloclastite units containing putative microbial ichnofossils are particularly enriched in large-ion lithophile elements (K, Rb, Ba, Cs), B, and Li, consistent with their having experienced the greatest fluid–rock interaction during subseafloor hydrothermal alteration. Similarly, silicate-δ18O and δ15N values for samples from the hyaloclastites show the greatest shifts from plausible magmatic values. The chemical and isotopic patterns in these tholeiitic igneous rocks greatly resemble those in modern altered seafloor basalts, consistent with the preservation of an Archæan seafloor alteration signature. The N enrichments and shifts in δ15N appear to reflect stabilization of illite and interaction with fluids carrying sedimentary/organic signatures. Enrichments of N (and the δ15N of this N) in altered glass volcanic rocks on Earth's modern and ancient seafloor point to the potential utility of N for tracing past and present biogeochemical processes in similar rocks at/near the Mars surface.

Original languageEnglish
Pages (from-to)1-16
Number of pages16
JournalInternational Journal of Astrobiology
DOIs
Publication statusAccepted/In press - Nov 20 2017

Fingerprint

nitrogen isotopes
chemical alteration
nitrogen isotope
organic nitrogen
volcanology
isotopes
seafloor
rocks
signatures
igneous rocks
hyaloclastite
volcanic rocks
basalt
illite
nitrogen
silicates
Mars surface
glass
shift
ions

Keywords

  • Archæan biogeochemistry
  • Basalt
  • Greenstone belt
  • Nitrogen isotopes
  • Palagonite

ASJC Scopus subject areas

  • Ecology, Evolution, Behavior and Systematics
  • Physics and Astronomy (miscellaneous)
  • Space and Planetary Science
  • Earth and Planetary Sciences (miscellaneous)

Cite this

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abstract = "Massive to lobate volcanic flows and brecciated hyaloclastite units in the Abitibi greenstone belt allow investigation of Late Arch{\ae}an seafloor alteration and associated incorporation into these rocks of nitrogen (N) biogeochemical signatures. In this suite (the Blake River Group), hyaloclastite units containing putative microbial ichnofossils are particularly enriched in large-ion lithophile elements (K, Rb, Ba, Cs), B, and Li, consistent with their having experienced the greatest fluid–rock interaction during subseafloor hydrothermal alteration. Similarly, silicate-δ18O and δ15N values for samples from the hyaloclastites show the greatest shifts from plausible magmatic values. The chemical and isotopic patterns in these tholeiitic igneous rocks greatly resemble those in modern altered seafloor basalts, consistent with the preservation of an Arch{\ae}an seafloor alteration signature. The N enrichments and shifts in δ15N appear to reflect stabilization of illite and interaction with fluids carrying sedimentary/organic signatures. Enrichments of N (and the δ15N of this N) in altered glass volcanic rocks on Earth's modern and ancient seafloor point to the potential utility of N for tracing past and present biogeochemical processes in similar rocks at/near the Mars surface.",
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AU - Anderson, L. D.

AU - Edward Bebout, Gray

AU - Richar Izawa, Matthew

AU - Bridge, N. J.

AU - Banerjee, N. R.

PY - 2017/11/20

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