Northwest Africa 5519 (NWA 5519)

Morocco

Purchased: 2001

Classification: Ordinary chondrite (LL3)

History: The meteorite was purchased in Tucson, Arizona, in 2001 by D. Gregory from A. Aaronson. Origin is Erfoud, Morocco.

Physical characteristics: Rounded, fusion crust-covered individual with moderate desert polish.

Petrography: Cut faces reveal variously coloured chondrules set in a dark brown matrix, with sparse metal. Most larger chondrules show flattening of up to 1.3:1 aspect ratio, defining a foliation fabric in the bulk rock. In polished thin section, chondrules are well defined with sulphide-rich dark rims in a dark matrix. Chondrules have average diameters of 634±238 μm (n=23) and are dominantly of types PO, BO, POP. Olivine and pyroxene grains show mosaic extinction and extensive development of planar fracturing. In BSE images and EDS elemental maps, olivine and pyroxene grains show significant normal zoing to Fe rich rims, and chondrule mesostasis is typically feldspathic glass. Metal occurs as isolated subhedral grains. Sulfides are typically fine grained and are a major component of chondrule rims. Minor Fe oxides locally fill cracks.

Geochemistry: EPMA: olivine Fa_16.5 (range Fa_0.7-28.4, N=63); Ca-poor pyroxene Fs_17.0Wo_2.6 (range Fs_1.1-35.2Wo_0.1-14.9, N=34). An _18.26 g sample gives a magnetic susceptibility of log χ (× 10^-9 m³/kg) = 4.47.

Classification: Ordinary chondrite: LL3 (S4) W1. Estimated subtype 3.2. Large chondrule size, low metal content and low magnetic susceptibility are consistent with a relatively fresh LL chondrite. Strongly zoned olivine and pyroxene grains with large EPMA compositional variation indicate that the meteorite is unequilibrated. Pervasive chondrule glassy mesostasis and fine sulfide rims on chondrules suggest type 3.2. Mineral deformation and chondrule flattening is consistent with shock S4.

Specimens: Type specimen with polished thin section at UWO. Main mass Gregory.