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Nitrogen Concentrations and Isotopic Compositions of Seafloor-Altered Terrestrial Basaltic Glass: Implications for Astrobiology
Observed enrichments of N (and the δ(15)N of this N) in volcanic glasses altered on Earth's modern and ancient seafloor are relevant in considerations of modern global N subduction fluxes and ancient life on Earth, and similarly altered glasses on Mars and other extraterrestrial bodies could se...
Autores principales: | , , , , , , |
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Formato: | Online Artículo Texto |
Lenguaje: | English |
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Mary Ann Liebert, Inc.
2018
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Materias: | |
Acceso en línea: | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5867513/ https://www.ncbi.nlm.nih.gov/pubmed/29106312 http://dx.doi.org/10.1089/ast.2017.1708 |
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author | Bebout, G.E. Banerjee, N.R. Izawa, M.R.M. Kobayashi, K. Lazzeri, K. Ranieri, L.A. Nakamura, E. |
author_facet | Bebout, G.E. Banerjee, N.R. Izawa, M.R.M. Kobayashi, K. Lazzeri, K. Ranieri, L.A. Nakamura, E. |
author_sort | Bebout, G.E. |
collection | PubMed |
description | Observed enrichments of N (and the δ(15)N of this N) in volcanic glasses altered on Earth's modern and ancient seafloor are relevant in considerations of modern global N subduction fluxes and ancient life on Earth, and similarly altered glasses on Mars and other extraterrestrial bodies could serve as valuable tracers of biogeochemical processes. Palagonitized glasses and whole-rock samples of volcanic rocks on the modern seafloor (ODP Site 1256D) contain 3–18 ppm N with δ(15)N(air) values of up to +4.5‰. Variably altered glasses from Mesozoic ophiolites (Troodos, Cyprus; Stonyford volcanics, USA) contain 2–53 ppm N with δ(15)N of −6.3 to +7‰. All of the more altered glasses have N concentrations higher than those of fresh volcanic glass (for MORB, <2 ppm N), reflecting significant N enrichment, and most of the altered glasses have δ(15)N considerably higher than that of their unaltered glass equivalents (for MORB, −5 ± 2‰). Circulation of hydrothermal fluids, in part induced by nearby spreading-center magmatism, could have leached NH(4)(+) from sediments then fixed this NH(4)(+) in altering volcanic glasses. Glasses from each site contain possible textural evidence for microbial activity in the form of microtubules, but any role of microbes in producing the N enrichments and elevated δ(15)N remains uncertain. Petrographic analysis, and imaging and chemical analyses by scanning electron microscopy and scanning transmission electron microscopy, indicate the presence of phyllosilicates (smectite, illite) in both the palagonitized cracks and the microtubules. These phyllosilicates (particularly illite), and possibly also zeolites, are the likely hosts for N in these glasses. Key Words: Nitrogen—Nitrogen isotope—Palagonite—Volcanic glass—Mars. Astrobiology 18, 330–342. |
format | Online Article Text |
id | pubmed-5867513 |
institution | National Center for Biotechnology Information |
language | English |
publishDate | 2018 |
publisher | Mary Ann Liebert, Inc. |
record_format | MEDLINE/PubMed |
spelling | pubmed-58675132018-03-27 Nitrogen Concentrations and Isotopic Compositions of Seafloor-Altered Terrestrial Basaltic Glass: Implications for Astrobiology Bebout, G.E. Banerjee, N.R. Izawa, M.R.M. Kobayashi, K. Lazzeri, K. Ranieri, L.A. Nakamura, E. Astrobiology Research Articles Observed enrichments of N (and the δ(15)N of this N) in volcanic glasses altered on Earth's modern and ancient seafloor are relevant in considerations of modern global N subduction fluxes and ancient life on Earth, and similarly altered glasses on Mars and other extraterrestrial bodies could serve as valuable tracers of biogeochemical processes. Palagonitized glasses and whole-rock samples of volcanic rocks on the modern seafloor (ODP Site 1256D) contain 3–18 ppm N with δ(15)N(air) values of up to +4.5‰. Variably altered glasses from Mesozoic ophiolites (Troodos, Cyprus; Stonyford volcanics, USA) contain 2–53 ppm N with δ(15)N of −6.3 to +7‰. All of the more altered glasses have N concentrations higher than those of fresh volcanic glass (for MORB, <2 ppm N), reflecting significant N enrichment, and most of the altered glasses have δ(15)N considerably higher than that of their unaltered glass equivalents (for MORB, −5 ± 2‰). Circulation of hydrothermal fluids, in part induced by nearby spreading-center magmatism, could have leached NH(4)(+) from sediments then fixed this NH(4)(+) in altering volcanic glasses. Glasses from each site contain possible textural evidence for microbial activity in the form of microtubules, but any role of microbes in producing the N enrichments and elevated δ(15)N remains uncertain. Petrographic analysis, and imaging and chemical analyses by scanning electron microscopy and scanning transmission electron microscopy, indicate the presence of phyllosilicates (smectite, illite) in both the palagonitized cracks and the microtubules. These phyllosilicates (particularly illite), and possibly also zeolites, are the likely hosts for N in these glasses. Key Words: Nitrogen—Nitrogen isotope—Palagonite—Volcanic glass—Mars. Astrobiology 18, 330–342. Mary Ann Liebert, Inc. 2018-03-01 2018-03-01 /pmc/articles/PMC5867513/ /pubmed/29106312 http://dx.doi.org/10.1089/ast.2017.1708 Text en © G.E. Bebout et al., 2017; Published by Mary Ann Liebert, Inc. This Open Access article is distributed under the terms of the Creative Commons Attribution Noncommercial License (http://creativecommons.org/licenses/by-nc/4.0/) which permits any noncommercial use, distribution, and reproduction in any medium, provided the original author(s) and the source are credited. |
spellingShingle | Research Articles Bebout, G.E. Banerjee, N.R. Izawa, M.R.M. Kobayashi, K. Lazzeri, K. Ranieri, L.A. Nakamura, E. Nitrogen Concentrations and Isotopic Compositions of Seafloor-Altered Terrestrial Basaltic Glass: Implications for Astrobiology |
title | Nitrogen Concentrations and Isotopic Compositions of Seafloor-Altered Terrestrial Basaltic Glass: Implications for Astrobiology |
title_full | Nitrogen Concentrations and Isotopic Compositions of Seafloor-Altered Terrestrial Basaltic Glass: Implications for Astrobiology |
title_fullStr | Nitrogen Concentrations and Isotopic Compositions of Seafloor-Altered Terrestrial Basaltic Glass: Implications for Astrobiology |
title_full_unstemmed | Nitrogen Concentrations and Isotopic Compositions of Seafloor-Altered Terrestrial Basaltic Glass: Implications for Astrobiology |
title_short | Nitrogen Concentrations and Isotopic Compositions of Seafloor-Altered Terrestrial Basaltic Glass: Implications for Astrobiology |
title_sort | nitrogen concentrations and isotopic compositions of seafloor-altered terrestrial basaltic glass: implications for astrobiology |
topic | Research Articles |
url | https://www.ncbi.nlm.nih.gov/pmc/articles/PMC5867513/ https://www.ncbi.nlm.nih.gov/pubmed/29106312 http://dx.doi.org/10.1089/ast.2017.1708 |
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