Noble gas contents of shergottites and implications for the Martian origin of SNC meteorites

Bogard, D. D.; Nyquist, L. E.; Johnson, P.

doi:10.1016/0016-7037(84)90028-0

Cited by 159 publications

(120 citation statements)

References 40 publications

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“…Hitherto secondary break-up has been considered unlikely (e.g., Bogard et al, 1984;Warren, 1994), but Popova et al (2007), conclude that in space some bolides consist of highly fractured ''swarms" traveling as a single mass, as shown by progressive fragmentation as they enter a planetary atmosphere, as evidenced by clusters of closely associated craters. For ''small clusters" of craters with diameters of tens of meters spread over a region of a few hundred meters, Popova et al (2007) infer that the parent meteoroid masses were fractured during prior asteroid collisions.…”

Section: Northwest Africa 1460 In Martian Contextmentioning

confidence: 99%

Concordant Rb–Sr, Sm–Nd, and Ar–Ar ages for Northwest Africa 1460: A 346Ma old basaltic shergottite related to “lherzolitic” shergottites

Nyquist¹,

Bogard²,

Shih³

et al. 2009

Geochimica et Cosmochimica Acta

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Multiple lines of evidence show that the Rb-Sr, Sm-Nd, and Ar-Ar isotopic systems individually give robust crystallization ages for basaltic (or diabasic) shergottite Northwest Africa (NWA) 1460. In contrast to other shergottites, NWA 1460 exhibits minimal evidence of excess 40 Ar, thus allowing an unambiguous determination of its Ar-Ar age. The concordant RbSr, Sm-Nd, and Ar-Ar results for NWA 1460 define its crystallization age to be 346 ± 17 Ma (2r). In combination with petrographic and trace element data for this specimen and paired meteorite NWA 480, these results strongly refute the suggestion by others that the shergottites are $4.1 Ga old. Current crystallization and cosmic-ray exposure (CRE) age data permit identification of a maximum of nine ejection events for Martian meteorites (numbering more than 50 unpaired specimens as of 2008) and plausibly as few as five such events. Although recent high resolution imaging of the Martian surface has identified limited areas of sparsely cratered terrains, the meteorite data suggest that either these areas are representative of larger areas from which the meteorites might come, or that the cratering chronology needs recalibration. Time-averaged 87 Rb/ 86 Sr = 0.16 for the mantle source of the parent magma of NWA 1460/480 over the $4.56 Ga age of the planet is consistent with previously estimated values for bulk silicate Mars in the range 0.13-0.16, and similar to values of $0.18 for the ''lherzolitic" shergottites. Initial e Nd for NWA 1460/480 at 350 ± 16 Ma ago was +10.6 ± 0.5, which implies a time-averaged 147 Sm/ 144 Nd of 0.217 in the Martian mantle prior to mafic melt extraction, similar to values of 0.211-0.216 for the ''lherzolitic" shergottites. These time-averaged values do not imply a simple two-stage mantle/melt evolution, but must result from multiple episodes of melt extractions from the source regions. Much higher ''late-stage" e Nd values for the depleted shergottites imply similar processes carried to a greater degree. Thus, NWA 1460/480, the ''lherzolitic" shergottites and perhaps EET 79001 give the best (albeit imperfect) estimate of the Sr-and Nd-isotopic characteristics of bulk silicate Mars. Published by Elsevier Ltd.

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Section: Northwest Africa 1460 In Martian Contextmentioning

confidence: 99%

Concordant Rb–Sr, Sm–Nd, and Ar–Ar ages for Northwest Africa 1460: A 346Ma old basaltic shergottite related to “lherzolitic” shergottites

Nyquist¹,

Bogard²,

Shih³

et al. 2009

Geochimica et Cosmochimica Acta

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“…Many investigators have attempted to discern how many events were required to eject the SNC meteorites (Wood and Ashwal 1981;Nyquist 1983;Bogard et al 1984;Vidal 1984;McSween 1985;Jones 1986;Vickery and Melosh 1987;Mouginis-Mark et al 1992). Revisions of the meteorites' crystallization ages and ejection ages, as well as further insight into their chemistries, now appear to indicate that multiple ejection events are required between ~20 and 0.7 Ma (e.g., Treiman 1995;Eugster et al 1997;Nyquist et al 1998;.…”

Section: Constraints On and Past Searches For Snc Source Regions On Marsmentioning

confidence: 99%

Searching for the source regions of martian meteorites using MGS TES: Integrating martian meteorites into the global distribution of igneous materials on Mars

Hamilton

Christensen

McSween

et al. 2003

Meteorit & Planetary Scien

164

165

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Abstract-The objective of this study was to identify and map possible source regions for all 5 known martian meteorite lithologies (basalt, lherzolite, clinopyroxenite, orthopyroxenite, and dunite) using data from the Mars Global Surveyor Thermal Emission Spectrometer (MGS TES). We deconvolved the TES data set using laboratory spectra of 6 martian meteorites (Los Angeles, Zagami, ALH A77005, Nakhla, ALH 84001, and Chassigny) as end members, along with atmospheric and surface spectra previously derived from TES data. Global maps (16 pixels/degree) of the distribution of each meteorite end member show that meteorite-like compositions are not present at or above TES detectability limits over most of the planet's dust-free regions. However, we have confidently identified local-scale (100s-1000s km 2 ) concentrations of olivine-and orthopyroxene-bearing materials similar to ALH A77005, Chassigny, and ALH 84001 in Nili Fossae, in and near Ganges Chasma, in the Argyre and Hellas basin rims, and in Eos Chasma. Nakhla-like materials are identified near the detection limit throughout the eastern Valles Marineris region and portions of Syrtis Major. Basaltic shergottites were not detected in any spatially coherent areas at the scale of this study. Martian meteorite-like lithologies represent only a minor portion of the dust-free surface and, thus, are not representative of the bulk composition of the ancient crust. Meteorite-like spectral signatures identified above TES detectability limits in more spatially restricted areas (

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“…It is interesting to note that the measurement of Lithology C of the shergottite Elephant Moraine (EET) A79001 (Bogard and Johnson 1983;Becker and Pepin 1984;Bogard et al 1984) and later calculated as SPB (Swindle et al 1986) is at one extreme of the proposed shergottite mixing array, while whole rock (dominated by pyroxene) analyses have uniformly low 129 Xe/ 132 Xe and Kr/Xe ratios close to that of Chassigny. However, given that whole rock Shergotty data is not a mixture of an atmospheric shock glass component and an interior component, it is not clear in Fig.…”

Section: Spb Earthmentioning

confidence: 99%

“…It remains unclear whether the elevated 129 Xe/ 132 Xe ratio observed in this component is evidence of an admixture (Ott 1988). Data is from literature (Owen et al 1977;Ozima and Podosek 1983;Becker and Pepin 1984;Bogard et al 1984;Swindle et al 1986;Ott 1988;Ott et al 1988;Wiens 1988;Swindle et al 1989;Ott and Lohr 1992;Drake et al 1994;Miura et al 1995;Swindle et al 1995;Murty and Mohapatra 1997;Bogard and Garrison 1998;Garrison and Bogard 2000;Mohapatra and Ott 2000;Swindle et al 2000;Terribilini 2000;Bart et al 2001 However, the preservation of a fission anomaly from 244 Pu in the young meteorites suggests degassing that ceased early in martian history. This allowed xenon components with elevated 136 Xe/ 132 Xe ratios to form as 244 Pu decayed and subsequently conserve these components.…”

Section: Spb Earthmentioning

confidence: 99%

Martian xenon components in Shergotty mineral separates: Locations, sources, and trapping mechanisms

Ocker

Gilmour

2004

Meteorit & Planetary Scien

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Noble gas contents of shergottites and implications for the Martian origin of SNC meteorites

Cited by 159 publications

References 40 publications

Concordant Rb–Sr, Sm–Nd, and Ar–Ar ages for Northwest Africa 1460: A 346Ma old basaltic shergottite related to “lherzolitic” shergottites

Concordant Rb–Sr, Sm–Nd, and Ar–Ar ages for Northwest Africa 1460: A 346Ma old basaltic shergottite related to “lherzolitic” shergottites

Searching for the source regions of martian meteorites using MGS TES: Integrating martian meteorites into the global distribution of igneous materials on Mars

Martian xenon components in Shergotty mineral separates: Locations, sources, and trapping mechanisms

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