[meteorite-list] NWA 2400

[Jeff Kuyken]

Hi,

Did anyone else notice in the new Met. Bull. that it looks like a pairing
for NWA 011 has been found?

Cheers,

Jeff



Northwest Africa 2400
Morocco or Algeria
Purchased 2003 April
Achondrite (ungrouped)
A 137 g light tan to rusty brown, fully crusted stone was purchased
in Rissani, Morocco in April 2003. Description and classification
(T. Bunch and J. Wittke, NAU; A. Irving and S.
Kuehner, UWS): composed mainly of approximately mm-sized,
randomly oriented pigeonite (Fs64-64.8Wo5.6-6.4) with very fine,
parallel exsolution lamellae of augite (Fs38-49.1Wo36.7-23), and
interstitial, recrystallized plagioclase (<0.10mm in size,
~An86Or0.5) with prominent triple junctions, and rare, unrecrystallized,
tabular plagioclase relicts (<1mm, zoned from An80 to
An89). FeO/MnO ratios for all pyroxenes range from 59.5 to 68.7
(avg. 64.7). Only small amounts of pyroxene are present in the
recrystallized zones. Accessory minerals occurring predominantly
in the recrystallized plagioclase zones include a silica
polymorph, chromite [Cr/(Cr + Al) = 83, Fe/(Fe + Mg) = 67],
ilmenite (53.5 wt.% TiO2, 43.6 wt.% FeO; with small baddeleyite
inclusions), merrillite (some with minor amounts of Na2O, MgO,
and FeO), Zn-bearing troilite, pentlandite, Cr-ulvöspinel and
altered Fe metal (associated with minor troilite, barite and calcite).
Shock damage is not apparent and, with the exception of
the oxidation of minor metal, weathering effects are very low.
Oxygen isotopes (D. Rumble, CIW): replicate analyses by laser
fluorination gave d17O = -0.15 ± 0.1‰, d18O = +3.27 ± 0.2‰,
?17O = -1.57 ± 0.03‰. In its texture, mineral mode, mineral
compositions and oxygen isotope composition NWA 2400 is
nearly identical to the anomalous achondrite NWA 011 (Yamaguchi
et al., 2002; Promprated et al., 2003), which strongly indicates
that these two stones are paired. Specimens: type specimen
20.2 g and three polished thin sections, NAU; main mass,
anonymous purchaser.