Northwest Africa 11444 (NWA 11444)

Mauritania

Find: 2017

Classification: Lunar, melt breccia

History: Sample was collected at an unknown locality, with hearsay evidence suggesting that this was somewhere in Mauritania. The sample material was purchased by Graham Ensor from Ali El Wali. A large number of fragments collected in the same area. Some fragments were found on the surface, which have a dark, pitted surface colouration due to desert weathering. Other pieces were recovered from within the soil layer and are lighter in color with patches of reddish soil and relatively unpitted.

Physical characteristics: The sample comprises approximately 200 pieces, with a total mass of 1323 g. Some of these pieces have a dark appearance, possibly the result of wind abrasion. Fragments with a lighter-colored outer surface are also present and these often have variable amounts of adhering sand. It is presumed that these were at least partially buried at the time of recovery. In hand specimen, all the pieces display prominent angular to sub-rounded, feldspar-rich, clasts, up to 1.5 cm in diameter, enclosed in a dark matrix, laden with smaller, angular fragments.

Petrography (R. Greenwood, OU): The sample is a complex breccia, containing a wide variety of fragments and variable amounts of flow-banded glass. Fragments are generally angular and include coarse-grained to aphanitic gabbros and basalts and a wide range of single-crystal types. There are many examples of clasts consisting of brown, devitrified basaltic glass with acicular plagioclase microlites. Angular, crystal fragments can be up to 0.5 mm in diameter and consist predominantly of plagioclase, pyroxene (often displaying well-developed exsolution lamellae), and olivine. Both high and low Ca pyroxenes are present in the gabbroic clasts, with both often showing prominent exsolution lamellae. The specimen contains a few percent of anhedral Fe,Ni metal grains (kamacite), up to 150 μm in diameter. The glass is often highly vesicular, flow-banded and contains a diverse range of crystals and lithic fragments.

Geochemistry: Mineral compositions and geochemistry: Pyroxenes show wide compositional variation, with both high and low Ca varieties present. Average composition: Fs_35.1±11.4Wo_16.1±14.2 (N=15, range Fs₃₀Wo₄ to Fs₁₈Wo₄₂). Olivine, average composition: Fa_37.1±16.9 (N = 21, range Fa_7-67). Well-developed exsolution lamallae are commonly present. Plagioclase shows limited compositional variation: An_96.5±0.5 (N=11). Fe, Ni Metal grains (up to 150 microns in diameter) are kamacite (7 to 8 wt.% Ni) (N = 6). All mineral compositions determined by EDS analysis. Oxygen isotopes: δ¹⁷O 3.28 per mil; δ¹⁸O 6.28 per mil; Δ¹⁷O 0.01 per mil (using standard formula: Δ¹⁷O = δ¹⁷O - 0.52 δ¹⁸O) (Analysis is consistent with the oxygen isotopic composition of other lunar meteorites).

Classification: Lunar, melt breccia. Moderate weathering

Specimens: Main mass with Graham Ensor