Press Release

The Meteoritical Bulletin E-mail Announcement 87-1, January 28, 2003

By SpaceRef Editor
January 28, 2003
Filed under , ,

    Northwest Africa 998
      Algeria or Morocco
    • Purchased 2001 September
    • Martian meteorite (nakhlit

    e)

    A. and G. Hupe (Hupe) purchased from dealers at the Tucson Gem and
    Mineral Show in 2002 February the main mass from a 456 g stone that
    had been acquired at an unspecified site in western Algeria or
    eastern Morocco in 2001 September. Dimensions before cutting: 72 mm
    by 65 mm by 48 mm. Classification and mineralogy (A. Irving and S.
    Kuehner, UWS): a friable, dark green rock with minor orange-brown
    alteration products that probably are of pre-terrestrial origin. It
    is composed mainly of subhedral, olive-green, complexly zoned
    subcalcic augite (Fs22Wo39) with subordinate yellow olivine (Fa64),
    orthopyroxene (Fs49Wo4), interstitial plagioclase (Ab61Or4 containing
    0.1 wt% SrO, and exhibiting normal birefringence), titanomagnetite,
    chlorapatite and pyrrhotite. The overall texture is that of a
    hypabyssal, adcumulate igneous rock, and the apparent crystallization
    sequence is olivine, orthopyroxene, titanomagnetite, augite, apatite,
    plagioclase. There is a weak preferred orientation of prismatic
    pyroxene crystals, many of which have very distinctive zoning, with
    cores of augite surrounded by irregular, inverted pigeonite rims (now
    consisting of orthopyroxene with fine augite lamellae). Trains of
    tiny melt inclusions are present along healed fractures within
    pyroxene; microprobe study confirms that most of these are K-Na-Al-
    bearing silicate glass, but some are intergrowths of glass and Fe-
    bearing carbonate, which may represent quenched immiscible silicate-
    carbonate liquids. Symplectitic intergrowths of titanomagnetite and
    low-Ca pyroxene are present at grain boundaries between large,
    discrete olivine and titanomagnetite grains, but are not present
    around chromian titanomagnetite inclusions within olivine. These
    observations suggest that a pre-terrestrial oxidation process
    produced the symplectites, and involved high temperature, deuteric
    fluid infiltration along grain boundaries; such fluids also may have
    produced the irregular pigeonitic rims on augite crystals. Secondary
    (probably pre-terrestrial) ankeritic carbonate, K-feldspar (some Fe-
    bearing), serpentine (?), calcite and a Ca sulfate are present on
    grain boundaries and within cracks in augite. Oxygen isotopes (D.
    Rumble, CIW): replicate analyses of acid-washed augite by laser
    fluorination gave d18O = +3.9 +/- 0.2, d17O = +2.4 +/- 0.1, D17O =
    +0.30 +/- 0.02 permil. Specimens: type specimens, 20 g, UWS, 20 g,
    FMNH, and two polished thin sections, UWS; main mass, Hupe.

    Northwest Africa 1195

    • Morocco
    • Purchased 2002 March/April
    • Martian meteorite (basaltic shergottite)

    A. and G. Hupe1 (Hupe) purchased a 50 g fragment of a broken stone
    with a distinctive, thin weathering rind collected by nomads near
    Safsaf, Morocco in 2002 March, and subsequently purchased the
    remainder of the same elongated stone (total weight 315 g).
    Dimensions of the reassembled stone are 133 mm x 43 mm x 37 mm.
    Classification and mineralogy (A. Irving and S. Kuehner, UWS):
    olivine megacrysts (up to 4 mm) are set in a groundmass of low-Ca
    pyroxene and maskelynite (Ab37Or0.5 to Ab41Or0.7) with minor Ti-
    chromite, pyrrhotite, ilmenite and Mg-bearing merrillite. The
    euhedral to subhedral shapes of most of the olivine grains suggest
    that they are phenocrysts rather than xenocrysts. Olivine exhibits
    strong compositional zoning (cores Fa19, FeO/MnO = 54; rims Fa40,
    FeO/MnO = 62), and contains abundant inclusions of chromite,
    clinopyroxene, orthopyroxene and pyrrhotite. The groundmass low-Ca
    pyroxenes are zoned from cores of pigeonite (Wo7Fs26, FeO/MnO = 37.1)
    or, less commonly, orthopyroxene (Wo4Fs23, FeO/MnO = 37.0) to rims of
    more Fe-rich pigeonite (Wo12Fs33, FeO/MnO = 36.6). Occurring very
    rarely on groundmass pyroxene grains are patchy overgrowths of an Fe-
    rich mineral (possibly related to chamosite or chlorite, with 35 wt%
    FeO, 5 wt% Al2O3, 1.5 wt% MgO and a low oxide sum of 85 wt%,
    suggesting the presence of water or hydroxyl). Calcite occurs
    sparsely along grain boundaries and as thin veinlets. Texture and
    mineral compositions are similar to those in olivine-phyric basaltic
    shergottite DaG 476/670, but olivine is much more magnesian than in
    other olivine-phyric basaltic shergottites Sau al Uhaymir 005/008 and
    Northwest Africa 1068/1110. Specimens: type specimen, 20 g, and two
    polished thin sections, UWS; main mass, Hupe.

SpaceRef staff editor.