Chassigny

OTHER MARTIAN NOBLE GAS RESERVOIRS Martian interior (Chassigny) 

With less than two dozen meteorites, it is remarkable that we seem to have both the atmosphere and the interior well represented. In fact, we may have several reservoirs other than the atmosphere represented, although some might be closely related to the 

Unlike the case for Earth, where the noble gases in the interior (such as MORB and 

OIB samples (Graham 2002, this volume)) are more radiogenic than the atmosphere, the 

Martian interior, as represented by Chassigny, is much less radiogenic. Hence Chassigny must sample an undegassed interior reservoir. 

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Misawa, K., Shih, C.-Y., Reese, Y., Bogard, D. D. andNyquist, L. E. (2006) Rb-Sr, Sm-Nd and Ar-Ar isotopic systematics of Martian dunite Chassigny. Earth and Planetary Science Letters, 246, 90-101. 

Source Lodders (1998) Shergotty and QUE94201 are basaltic shergottites, ALH 77005 is a lherzolitic shergottite, ALH 84001 is an orthopyroxenite, Nakhla is a nakhlite, and Chassigny is a chassignite. Analytical uncertainties are Is deviations for multiple analyses. 

Lodders, K. (1998) A survey of shergottite, nakhlite and chassigny meteorites whole-rock compositions. Meteoritics and Planetary Science, 33, A183-A190. 

Sheroottites. The shergottite meteorites are a rare class of meteorites which consist essentially of pyroxene and maskelynite. Their composition, petrography, age and gases trapped within the fabric of the meteorite have led to a widespread idea that these meteorites, and the related nakhlites and Chassigny meteorites, were ejected from Mars,... 

Twenty-six meteorites are believed to be martian rocks. This group was formerly referred to by the acronym SNC (for Shergottites, Nakhlites, and Chassigny). However, this designation is no longer comprehensive, and the simple... 

Figure 29 Weight percentages of FeO and MnO in solar-system basalts and martian meteorites. Filled circles are SNC basalts, open circles are other martian meteorites, and filled squares are Mars surface materials. Martian meteorites have essentially the same FeO/MnO ratio as do Mars surface materials and eucrite basalts. Only Chassigny has a comparable FeO/MnO ratio to terrestrial basalts (source Treiman et al., 2000).

Chassigny is the only known martian dunite. It is an olivine-chromite cumulate consisting of 90% olivine (Fa. 32), 5% pyroxene, 2% feldspar (An 2o) that has been transformed into maskelynite, and 3% accessory minerals including chromite (Figure 30(d)). Melt inclusions in olivine contain hydrous amphibole. 

Floran R. J., Prinz M., Hlava P. F., Keil K., Nehru C. E., and Hinthorne J. R. (1978a) The Chassigny meteorite a cumulate dunite with hydrous amphibole-bearing melt inclusions. Geochim. Cosmochim. Acta 42, 1213-1229. 

Smith J. V., Steele 1. M., and Leitch C. A. (1983) Mineral chemistry of the shergottites, nakhfites, Chassigny, Brachina, pallasites, and ureilites. Proc. I4th Lunar Planet. Sci. Conf. J. Geophys. Res. 88 (suppL), B229-B236. 

Mathew K. J. and Marti K. (2001) Early evolution of Martian volatiles nitrogen and noble gas components in ALH84001 and Chassigny. J. Geophys. Res. 106, 1401-1422. 

Ott U., Lohr H.-P., and Begemann F. (1987) Noble gases in ALH 84025 like Brachina, unlike Chassigny. Meteoritics 22, A16-A11. 

Terribilini D., Eugster O., Burger M., Jakob A., and Krahenbiihl U. (1998) Noble gases and chemical composition of Shergotty mineral fractions, Chassigny and Yamato 793605 the trapped argon-40/argon-36 ratio and ejection times of Martian meteorites. Meteorit. Planet. Set 33, 677 -684. 

Element Shergotty QUE94201 ALH77005 ALH84001 Nakhla Chassigny... 

Greenwood J. P., Riciputi L. R., McSween H. Y., and Taylor L. A. (2000) Modihed sulfur isotopic compositions of sulhdes in the nakhlites and Chassigny. Geochim. Cosmochim. Acta 64, 1121-1131. 

Jones J. H. (1989) Isotopic relationships among the Shergottites, the Nakhlites and Chassigny. Proc. Lunar Planet. Sci. Conf. 19, 465-474. 

Mathew K. J., Kim J. S., and Marti K. (1998) Martian atmospheric and indigenous components of xenon and nitrogen in the Shergotty, Nakhla, and Chassigny group meteorites. Meteorit. Planet. Sci. 33, 655-664. 

The noble gas isotopic composition of the martian interior is only available for xenon. Data for the martian meteorite Chassigny found xenon with little scope for radiogenic additions (Ott, 1988 Mathew and Marti, 2001), indicating that this reservoir had a high Xe/Pu ratio, at least during the lifetime of Data from other... 

Ott U. (1988) Noble gases in SNC meteorites Shergotty, Nakhla, Chassigny. Geochim. Cosmochim. Acta 52, 1937-1948. 

The martian mantle has high xenon concentrations and distinct abundance patterns. Martian meteorites contain components other than those derived directly from the atmosphere (see detailed discussion by Swindle, 2002). In particular, noble gases in the dunite meteorite Chassigny appear to represent a distinct interior reservoir. The " Kr/i Xe ratio of 1.2 (Ott, 1988) is lower than both the martian atmosphere (20) and solar (16.9) values, but is similar to that of Cl chondrites. If this is truly a source feature, it indicates that heavy noble gases trapped within the planet suffered substantially different elemental fractionation than the atmosphere. The interior " Kr/ Ar ratio of 0.06 is much higher than the solar value of 2.8 X 10 ", but it is close to the atmospheric value of 0.02 and so does not display the same contrast as the Kr/Xe ratio. Unfortunately, it is not possible to determine if the measured elemental abundance ratios were modified by planetary processing or transport and incorporation into the samples. 

The presence of salts in SNC (Shergotty-Nakhla-Chassigny) Martian meteror-ites [23-26] and the acknowledgement of the presence of sulphates in the Martian... 

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