Mars Meteorite Update
THE METEORITICAL BULLETIN 84-1
June 2, 2000
Jeffrey N. Grossman, Editor (jgrossman@usgs.gov)
Below, you will find announcements of new Mars meteorites
that will be published in Meteoritical Bulletin, No. 84, 2000 August. These are:
Sayh al Uhaymir 005 and 008 Martian basalts found in Oman.
Dar al Gani 670 and 735 Martian basalts found in Libya.
Dhofar 019 Martian basalt found in Oman.
Los Angeles Martian basalts found in California.
The entire text of the new Meteoritical Bulletin (abstract below) may be viewed at
http://www.uark.edu/campus-resources/metsoc/metbull/mb84v2.pdf
Information in this document is subject to minor revision until
July 13, 2000.
Sayh al Uhaymir 005 20*59.76’N, 57*19.55’E
Sayh al Uhaymir 008 20*58.83’N, 57*19.14’E
Oman
Found 1999 November 26
Martian basalt (shergottite)
At two locations, 1864 m apart, 5 grey-greenish stones were found which are macroscopically identical. Sayh al Uhaymir (SaU) 005 comprises one fragment of 547 g and two individuals of 561g and 236g, which are partially covered by fusion crust and show regmaglyptes. SaU 008 comprises one large individual of 7805 g and a smaller fragmented individual of 774 g. On the latter, the fresh black fusion crust is almost completely preserved. The total mass of SaU 005/008 is 9923 g. Mineralogy and classification (J. Zipfel, MPI): porphyritic texture with large olivine phenocrysts (Fo64-71) in a fine-grained groundmass of pigeonite (En61-70Wo6-13) and maskelynite (An51-65Or0.3-0.9); minor phases are augite, phosphates and opaques; strongly shocked: mosaicism and planar deformation of olivines, twinning and fracturing of
clinopyroxene, and up to mm-sized shock melted areas with quench textures are common; brown-orange ringlike structures formed by extremely fine-grained intergrowths of unidentified phases are abundant in impact melt areas and pyroxenes;. the meteorite is extremely fresh, with only a few of the larger cracks partially filled with calcite. Bulk chemical analyses (B. Spettel, G. Dreibus, MPI; H. Palme, Kˆln), noble gas analyses (M. Paetsch, L Schultz, MPI), and Sm-Nd systematics (E. Jagoutz, MPI): texture, bulk chemistry, noble gases and Sm-Nd systematics indicate a very close relationship to Dar al Gani 476/489/670/735; however, based on the distinct mineral chemistry and the place of find, simple pairing with those meteorites can be excluded. Specimens: type specimen, 60 g, MPI; main mass with anonymous finder.
Dar al Gani 670 exact location unknown
Libya
Found 1999
Martian basalt (shergottite)
A dark-brown stone, broken into three adjoining pieces, with a total mass of 1619 g, was found in the Dar al Gani region. Mineralogy and classification (L. Folco, MNA-SI): cm-sized patches of fusion crust are present on the external surfaces; porphyritic texture consisting of mm-sized phenocrysts of brown olivine (Fo58-80) set in a fine grained basaltic groundmass of tabular pyroxene and interstitial feldspathic glass (An52-72Or0-1); pyroxene is primarily pigeonite (En56-66Wo9-13) with subordinate enstatite (En73-82Wo2-3) and augite (En48-50Wo31-36); other minerals are chromite, titanian chromite, ilmenite, merrillite and pyrrhotite; shock features include strong mosaicism and planar deformation in olivine, undulose extinction and twinning in pyroxene, and abundant impact melt pockets and veinlets; pervasive veins filled in by calcite are due to terrestrial weathering. Oxygen isotopes (A. Sexton and I. A. Franchi, OU): d17O = +2.83 â, d18O = +4.95 â, D17O = +0.26 â. The petrography and level of
terrestrial weathering are essentially identical to those of DaG 476 and DaG 489, and the three are very likely paired. Specimens: main mass with anonymous finder; 11.9 g and one polished thin section at MNA-SI.
Dar al Gani 735 27*10’N, 16* 10′ E
Libya
Found 1996/97 winter
Martian basalt (shergottite)
A 588 g complete stone covered with desert varnish was collected in the Dar al Gani region. Classification and mineralogy (F. Wlotzka, MPI; M. Kurz, Neukirchen, Germany): a porphyritic basalt with
mm-sized olivines (normally zoned from Fa28 to Fa37) in a finer
grained matrix of pigeonite (Fs25-28) and feldspathic glass (An65); a direct comparison with a thin section of DaG 476 shows that both stones are very similar and are probably paired; however, DaG 735 does not contain terrestrial carbonate veins, and appears less
weathered than DaG 476. Specimens: type specimen, 6 g, MPI; main mass with anonymous finder.
Dhofar 019 18*18.97’N 54*08.87’E
Oman
Found 2000 January 24
Martian basalt (shergottite)
A brownish gray stone weighing 1056 g was found in the desert.
Mineralogy and classification (M. Nazarov and M. Ivanova, Vernad; L. A. Taylor, UTenn): fusion crust absent; meteorite is a doleritic rock consisting of subhedral grains (0.2-0.5 mm) of pigeonite
(Wo9-15 En40-70, Fe/Mn = 20-40 at.), augite (Wo30-40 En40-55), olivine (Fo25-60, Fe/Mn = 50-60 at.), and feldspar (An36-68) converted to maskelynite; olivine has higher Fe/Mg than that of coexisting pyroxenes, as it is in nakhlites; mineral modes (approx. vol%) are pyroxene = 65, maskelynite = 25, and olivine = 10, with accessory silica,
K-rich feldspar, whitlockite, chlorapatite, chromite, ilmenite,
titanomagnetite, magnetite, and pyrrhotite; secondary phases are calcite, gypsum, smectite, celestite, and Fe hydroxides; shock
features include fracturing and mosaicism, maskelynite, and rare impact melt pockets; extensive terrestrial weathering present mainly as carbonate veins crosscutting the meteorite, however there are smectite-calcite-gypsum ìorangettesî replacing maskelynite, which are similar to those in Allan Hills 84001 and could be of Martian origin; bulk chemistry close to Shergotty, with light rare earth elements strongly depleted. Specimens: type specimens, 113 g, 4 g, and 2 g, and two thin sections, Vernad; main mass with anonymous finder.
Los Angeles (original find location unknown)
Los Angeles County, California, USA
Recognized 1999 October 30
Martian basalt (shergottite)
Two stones, weighing 452.6 g and 245.4 g respectively, were
found by Bob Verish in his back yard while he was cleaning out
a box of rocks that was part of his rock collection. The
specimens may have been collected ~20 years ago in the Mojave
Desert. Classification and mineralogy (A. Rubin, P. Warren and
J. Greenwood, UCLA): a basalt with a texture closely resembling
that of the QUE 94201; plagioclase laths, 43.6 vol%, An41Or4 to
An58Or1, have been shocked to maskelynite; Ca-pyroxene, 37.7
vol%, ranges from Fs45Wo13 to Fs45Wo37 to Fs72Wo24; other
mineral modes, 4.9 vol% silica, 4.2 vol% fayalite, 2.4 vol%
K-rich felsic glass, 3.5 vol% titanomagnetite, 2.7 vol% Ca
phosphate (including whitlockite and chlorapatite), 0.7 vol%
pyrrhotite, and 0.2 vol% ilmenite; contains a higher proportion
of plagioclase than Shergotty or Zagami, and has pyroxene that
is moderately more ferroan than that in QUE 94201. Specimens:
main masses with finder; 30 g, UCLA. Note, one may encounter
references to the two masses as Los Angeles 001 and 002, or
stone no. 1 and no. 2, respectively; these are unofficial
designations.
