Sulfur isotopic compositions of individual sulfides in Martiian meteorites ALH840001 and Nakhla: Implications for crust-regolith exchanges on Mars

James P. Greenwood, S. Mojzsis, Christopher D. Coath

Research output: Contribution to journalArticle

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Abstract

Atmospheric chemical reactions on Mars have been invoked to explain non-mass-dependent Δ33S anomalies (Δ33S = δ33S-0.516δ34S) reported from bulk analyses of Martian meteorites. To explore this signature in detail, a new ion microprobe multi-collector technique was developed to obtain precise in situ 32S, 33S and 34S measurements of individual sulfide grains from Martian meteorites ALH84001 (>4.0 Ga) and Nakhla (1.3 Ga). This technique permits high-precision simultaneous measurement of multiple isotopes to uniquely evaluate Δ33S at the grain scale (33S anomalies in two seperate ALH84001 pyrite grains (Δ33S = -0.74 ± 0.39‰ and -0.51 ± 0.38‰, 2σ); none were detectable in Nakhla pyrrhotite (total range in Δ33S = -0.4 ± 0.5‰ to-0.07τ0.5‰, 2σ). Our results might reflect a difference in how these meteorites exchanged sulfur with the Martian regolith and/or difference in their sources (atmospheric versus meteoritic) of anomalous sulfur. Nebular heterogeneities in sulfur isotope composition are indicated by Δ33S anomalies preserved in, for example, the ureilites. The Δ33S anomalies in ALH84001 pyrite could suggest that early (pre-4 Ga) additions of a meteoritic component carried isotopically anomalies sulfur to the Martian regolith, and was stored there as seen in the detection of Δ33S anomalies from bulk measurements of Nakhla. Therefore, meteoritic contributions should also be considered in addition to atmospheric effects when explaining the large non-mass-dependent anomalies seen in Martian meteorites. These studies provide insight into how hydrothermal systems have facilitated exchange between volatile reservoirs on Mars, a planet that lacks efficient crustal recycling mechanisms and preserves ancient (and anomalous) Δ33S signatures.

Original languageEnglish
Pages (from-to)23-35
Number of pages13
JournalEarth and Planetary Science Letters
Volume184
Issue number1
DOIs
Publication statusPublished - 2000

Fingerprint

Meteorites
regolith
Sulfides
meteorites
Sulfur
meteorite
mars
sulfides
Mars
crusts
Ion exchange
isotopic composition
sulfur
sulfide
anomalies
crust
anomaly
SNC meteorites
Martian meteorite
Chemical analysis

Keywords

  • ALH84001
  • Ion probe
  • Isotope ratios
  • Mars
  • Nakhla meteorite
  • Regolith
  • Sulfur

ASJC Scopus subject areas

  • Geochemistry and Petrology
  • Geophysics

Cite this

Sulfur isotopic compositions of individual sulfides in Martiian meteorites ALH840001 and Nakhla : Implications for crust-regolith exchanges on Mars. / Greenwood, James P.; Mojzsis, S.; Coath, Christopher D.

In: Earth and Planetary Science Letters, Vol. 184, No. 1, 2000, p. 23-35.

Research output: Contribution to journalArticle

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abstract = "Atmospheric chemical reactions on Mars have been invoked to explain non-mass-dependent Δ33S anomalies (Δ33S = δ33S-0.516δ34S) reported from bulk analyses of Martian meteorites. To explore this signature in detail, a new ion microprobe multi-collector technique was developed to obtain precise in situ 32S, 33S and 34S measurements of individual sulfide grains from Martian meteorites ALH84001 (>4.0 Ga) and Nakhla (1.3 Ga). This technique permits high-precision simultaneous measurement of multiple isotopes to uniquely evaluate Δ33S at the grain scale (33S anomalies in two seperate ALH84001 pyrite grains (Δ33S = -0.74 ± 0.39‰ and -0.51 ± 0.38‰, 2σ); none were detectable in Nakhla pyrrhotite (total range in Δ33S = -0.4 ± 0.5‰ to-0.07τ0.5‰, 2σ). Our results might reflect a difference in how these meteorites exchanged sulfur with the Martian regolith and/or difference in their sources (atmospheric versus meteoritic) of anomalous sulfur. Nebular heterogeneities in sulfur isotope composition are indicated by Δ33S anomalies preserved in, for example, the ureilites. The Δ33S anomalies in ALH84001 pyrite could suggest that early (pre-4 Ga) additions of a meteoritic component carried isotopically anomalies sulfur to the Martian regolith, and was stored there as seen in the detection of Δ33S anomalies from bulk measurements of Nakhla. Therefore, meteoritic contributions should also be considered in addition to atmospheric effects when explaining the large non-mass-dependent anomalies seen in Martian meteorites. These studies provide insight into how hydrothermal systems have facilitated exchange between volatile reservoirs on Mars, a planet that lacks efficient crustal recycling mechanisms and preserves ancient (and anomalous) Δ33S signatures.",
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AB - Atmospheric chemical reactions on Mars have been invoked to explain non-mass-dependent Δ33S anomalies (Δ33S = δ33S-0.516δ34S) reported from bulk analyses of Martian meteorites. To explore this signature in detail, a new ion microprobe multi-collector technique was developed to obtain precise in situ 32S, 33S and 34S measurements of individual sulfide grains from Martian meteorites ALH84001 (>4.0 Ga) and Nakhla (1.3 Ga). This technique permits high-precision simultaneous measurement of multiple isotopes to uniquely evaluate Δ33S at the grain scale (33S anomalies in two seperate ALH84001 pyrite grains (Δ33S = -0.74 ± 0.39‰ and -0.51 ± 0.38‰, 2σ); none were detectable in Nakhla pyrrhotite (total range in Δ33S = -0.4 ± 0.5‰ to-0.07τ0.5‰, 2σ). Our results might reflect a difference in how these meteorites exchanged sulfur with the Martian regolith and/or difference in their sources (atmospheric versus meteoritic) of anomalous sulfur. Nebular heterogeneities in sulfur isotope composition are indicated by Δ33S anomalies preserved in, for example, the ureilites. The Δ33S anomalies in ALH84001 pyrite could suggest that early (pre-4 Ga) additions of a meteoritic component carried isotopically anomalies sulfur to the Martian regolith, and was stored there as seen in the detection of Δ33S anomalies from bulk measurements of Nakhla. Therefore, meteoritic contributions should also be considered in addition to atmospheric effects when explaining the large non-mass-dependent anomalies seen in Martian meteorites. These studies provide insight into how hydrothermal systems have facilitated exchange between volatile reservoirs on Mars, a planet that lacks efficient crustal recycling mechanisms and preserves ancient (and anomalous) Δ33S signatures.

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