Quantifying noble gas contamination during terrestrial alteration in Martian meteorites from Antarctica

S. P. Schwenzer, R. C. Greenwood, S. P. Kelley, U. Ott, A. G. Tindle, R. Haubold, S. Herrmann, J. M. Gibson, M. Anand, S. Hammond, I. A. Franchi

Research output: Contribution to journalArticle

5 Citations (Scopus)

Abstract

We investigated exterior and interior subsamples from the Martian shergottite meteorites Allan Hills (ALH) A77005 and Roberts Massif (RBT) 04261 for secondary minerals, oxygen isotopes, Ar-Ar, and noble gas signatures. Electron microprobe investigations revealed that RBT 04261 does not contain any visible alteration even in its most exterior fractures, whereas fracture fillings in ALHA77005 penetrate into the meteorite up to 300 μm, beyond which the fractures are devoid of secondary minerals. Light noble gases seem to be almost unaffected by terrestrially induced alteration in both meteorites. Thus, a shock metamorphic overprint of 30-35 GPa can be deduced from the helium measurements in RBT 04261. Oxygen isotopes also seem unaffected by terrestrially weathering and variations can easily be reconciled with the differences in modal mineralogy of the exterior and interior subsamples. The measurements on irradiated samples (Ar-Ar) showed a clear Martian atmospheric contribution in ALHA77005, but this is less apparent in our sample of RBT 04261. Exterior and interior subsamples show slight differences in apparent ages, but the overall results are very similar between the two. In contrast, krypton and xenon are severely affected by terrestrial contamination, demonstrating the ubiquitous presence of elementally fractionated air in RBT 04261. Although seemingly contradictory, our results indicate that RBT 04261 was more affected by contamination than ALHA77005. We conclude that irrespective of on which planet the alteration occurred, exposure of Martian rocks to atmosphere (or brine) introduces noble gases with signatures elementally fractionated relative to the respective atmospheric composition into the rock, and relationships of that process with oxygen isotopes or mineralogical observations are not straightforward.

Original languageEnglish
Pages (from-to)929-954
Number of pages26
JournalMeteoritics and Planetary Science
Volume48
Issue number6
DOIs
Publication statusPublished - Jun 2013

Fingerprint

SNC meteorites
Martian meteorite
noble gas
oxygen isotopes
Antarctic regions
oxygen isotope
rare gases
contamination
secondary mineral
meteorites
meteorite
minerals
signatures
Allan Hills meteorite
shergottite
rocks
krypton
atmospheric composition
xenon
weathering

ASJC Scopus subject areas

  • Geophysics
  • Space and Planetary Science

Cite this

Schwenzer, S. P., Greenwood, R. C., Kelley, S. P., Ott, U., Tindle, A. G., Haubold, R., ... Franchi, I. A. (2013). Quantifying noble gas contamination during terrestrial alteration in Martian meteorites from Antarctica. Meteoritics and Planetary Science, 48(6), 929-954. https://doi.org/10.1111/maps.12110

Quantifying noble gas contamination during terrestrial alteration in Martian meteorites from Antarctica. / Schwenzer, S. P.; Greenwood, R. C.; Kelley, S. P.; Ott, U.; Tindle, A. G.; Haubold, R.; Herrmann, S.; Gibson, J. M.; Anand, M.; Hammond, S.; Franchi, I. A.

In: Meteoritics and Planetary Science, Vol. 48, No. 6, 06.2013, p. 929-954.

Research output: Contribution to journalArticle

Schwenzer, SP, Greenwood, RC, Kelley, SP, Ott, U, Tindle, AG, Haubold, R, Herrmann, S, Gibson, JM, Anand, M, Hammond, S & Franchi, IA 2013, 'Quantifying noble gas contamination during terrestrial alteration in Martian meteorites from Antarctica', Meteoritics and Planetary Science, vol. 48, no. 6, pp. 929-954. https://doi.org/10.1111/maps.12110
Schwenzer, S. P. ; Greenwood, R. C. ; Kelley, S. P. ; Ott, U. ; Tindle, A. G. ; Haubold, R. ; Herrmann, S. ; Gibson, J. M. ; Anand, M. ; Hammond, S. ; Franchi, I. A. / Quantifying noble gas contamination during terrestrial alteration in Martian meteorites from Antarctica. In: Meteoritics and Planetary Science. 2013 ; Vol. 48, No. 6. pp. 929-954.
@article{1bc7ebd3e44548d685c3563c622e5f5f,
title = "Quantifying noble gas contamination during terrestrial alteration in Martian meteorites from Antarctica",
abstract = "We investigated exterior and interior subsamples from the Martian shergottite meteorites Allan Hills (ALH) A77005 and Roberts Massif (RBT) 04261 for secondary minerals, oxygen isotopes, Ar-Ar, and noble gas signatures. Electron microprobe investigations revealed that RBT 04261 does not contain any visible alteration even in its most exterior fractures, whereas fracture fillings in ALHA77005 penetrate into the meteorite up to 300 μm, beyond which the fractures are devoid of secondary minerals. Light noble gases seem to be almost unaffected by terrestrially induced alteration in both meteorites. Thus, a shock metamorphic overprint of 30-35 GPa can be deduced from the helium measurements in RBT 04261. Oxygen isotopes also seem unaffected by terrestrially weathering and variations can easily be reconciled with the differences in modal mineralogy of the exterior and interior subsamples. The measurements on irradiated samples (Ar-Ar) showed a clear Martian atmospheric contribution in ALHA77005, but this is less apparent in our sample of RBT 04261. Exterior and interior subsamples show slight differences in apparent ages, but the overall results are very similar between the two. In contrast, krypton and xenon are severely affected by terrestrial contamination, demonstrating the ubiquitous presence of elementally fractionated air in RBT 04261. Although seemingly contradictory, our results indicate that RBT 04261 was more affected by contamination than ALHA77005. We conclude that irrespective of on which planet the alteration occurred, exposure of Martian rocks to atmosphere (or brine) introduces noble gases with signatures elementally fractionated relative to the respective atmospheric composition into the rock, and relationships of that process with oxygen isotopes or mineralogical observations are not straightforward.",
author = "Schwenzer, {S. P.} and Greenwood, {R. C.} and Kelley, {S. P.} and U. Ott and Tindle, {A. G.} and R. Haubold and S. Herrmann and Gibson, {J. M.} and M. Anand and S. Hammond and Franchi, {I. A.}",
year = "2013",
month = "6",
doi = "10.1111/maps.12110",
language = "English",
volume = "48",
pages = "929--954",
journal = "Meteoritics and Planetary Science",
issn = "1086-9379",
publisher = "The University of Arkansas Press",
number = "6",

}

TY - JOUR

T1 - Quantifying noble gas contamination during terrestrial alteration in Martian meteorites from Antarctica

AU - Schwenzer, S. P.

AU - Greenwood, R. C.

AU - Kelley, S. P.

AU - Ott, U.

AU - Tindle, A. G.

AU - Haubold, R.

AU - Herrmann, S.

AU - Gibson, J. M.

AU - Anand, M.

AU - Hammond, S.

AU - Franchi, I. A.

PY - 2013/6

Y1 - 2013/6

N2 - We investigated exterior and interior subsamples from the Martian shergottite meteorites Allan Hills (ALH) A77005 and Roberts Massif (RBT) 04261 for secondary minerals, oxygen isotopes, Ar-Ar, and noble gas signatures. Electron microprobe investigations revealed that RBT 04261 does not contain any visible alteration even in its most exterior fractures, whereas fracture fillings in ALHA77005 penetrate into the meteorite up to 300 μm, beyond which the fractures are devoid of secondary minerals. Light noble gases seem to be almost unaffected by terrestrially induced alteration in both meteorites. Thus, a shock metamorphic overprint of 30-35 GPa can be deduced from the helium measurements in RBT 04261. Oxygen isotopes also seem unaffected by terrestrially weathering and variations can easily be reconciled with the differences in modal mineralogy of the exterior and interior subsamples. The measurements on irradiated samples (Ar-Ar) showed a clear Martian atmospheric contribution in ALHA77005, but this is less apparent in our sample of RBT 04261. Exterior and interior subsamples show slight differences in apparent ages, but the overall results are very similar between the two. In contrast, krypton and xenon are severely affected by terrestrial contamination, demonstrating the ubiquitous presence of elementally fractionated air in RBT 04261. Although seemingly contradictory, our results indicate that RBT 04261 was more affected by contamination than ALHA77005. We conclude that irrespective of on which planet the alteration occurred, exposure of Martian rocks to atmosphere (or brine) introduces noble gases with signatures elementally fractionated relative to the respective atmospheric composition into the rock, and relationships of that process with oxygen isotopes or mineralogical observations are not straightforward.

AB - We investigated exterior and interior subsamples from the Martian shergottite meteorites Allan Hills (ALH) A77005 and Roberts Massif (RBT) 04261 for secondary minerals, oxygen isotopes, Ar-Ar, and noble gas signatures. Electron microprobe investigations revealed that RBT 04261 does not contain any visible alteration even in its most exterior fractures, whereas fracture fillings in ALHA77005 penetrate into the meteorite up to 300 μm, beyond which the fractures are devoid of secondary minerals. Light noble gases seem to be almost unaffected by terrestrially induced alteration in both meteorites. Thus, a shock metamorphic overprint of 30-35 GPa can be deduced from the helium measurements in RBT 04261. Oxygen isotopes also seem unaffected by terrestrially weathering and variations can easily be reconciled with the differences in modal mineralogy of the exterior and interior subsamples. The measurements on irradiated samples (Ar-Ar) showed a clear Martian atmospheric contribution in ALHA77005, but this is less apparent in our sample of RBT 04261. Exterior and interior subsamples show slight differences in apparent ages, but the overall results are very similar between the two. In contrast, krypton and xenon are severely affected by terrestrial contamination, demonstrating the ubiquitous presence of elementally fractionated air in RBT 04261. Although seemingly contradictory, our results indicate that RBT 04261 was more affected by contamination than ALHA77005. We conclude that irrespective of on which planet the alteration occurred, exposure of Martian rocks to atmosphere (or brine) introduces noble gases with signatures elementally fractionated relative to the respective atmospheric composition into the rock, and relationships of that process with oxygen isotopes or mineralogical observations are not straightforward.

UR - http://www.scopus.com/inward/record.url?scp=84879271170&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=84879271170&partnerID=8YFLogxK

U2 - 10.1111/maps.12110

DO - 10.1111/maps.12110

M3 - Article

AN - SCOPUS:84879271170

VL - 48

SP - 929

EP - 954

JO - Meteoritics and Planetary Science

JF - Meteoritics and Planetary Science

SN - 1086-9379

IS - 6

ER -