Northwest Africa 8744 (NWA 8744)

(Northwest Africa)

Purchased: 2014 Sep

Classification: HED achondrite (Diogenite)

History: In September 2014 two large stones were purchased by Aziz Habibi in Agadir, Morocco, and two smaller stones were purchased by Gary Fujihara from a dealer in Zagora, Morocco.

Physical characteristics: The four pieces (11001 g, 1356 g, 185 g, 25.2 g) all share the same distinctive appearance. Domains composed of gray pyroxene plus variable amounts of milky plagioclase occur within a predominant lithology composed of highly vesicular, very fine grained material.

Petrography: (A. Irving and S. Kuehner, UWS) Melt-matrix breccia consisting of clasts (~30 vol.%) of orthopyroxenitic diogenite, feldspathic diogenite and noritic diogenite (with 10-40 vol.% plagioclase) plus related crystalline debris within a predominant, very fine grained, vesicular matrix. All orthopyroxene is turbid and pale clove brown in thin section and is notably ferroan; calcic plagioclase (anorthite) is polycrystalline. Some orthopyroxene contains irregular "patches" of clinopyroxene. Accessory phases are chromite, olivine and minor troilite blebs in orthopyroxene.

Geochemistry: Orthopyroxene in clasts (Fs_35.4-37.0Wo_6.5-4.3, FeO/MnO = 29-31, N = 5), clinopyroxene in clast (Fs_16.1Wo_40.8, FeO/MnO = 27), "patchy" pigeonitic pyroxene (Fs_26.4-38.0Wo_6.4-10.8, FeO/MnO = 29-30, N = 3), pigeonite in vesicular matrix (Fs_42.5Wo_13.4, FeO/MnO = 27), olivine (Fa_48.9, FeO/MnO = 44, N = 1), plagioclase (An_93.5-95.6Or_0.2-0.1, N = 3).

Classification: Diogenite (feldspathic, shock melted). The amount of plagioclase in some of the remnant diogenitic clasts is higher than in typical diogenites, and low-Ca pyroxene is unusually ferroan. There is evidence for intense shock modification in this material (involving extensive melting and vesiculation).

Specimens: 21.3 g including two polished thin sections and one polished slice at UWB; main masses of the large stones are with Mr. A. Habibi; Mr. G. Fujihara owns the 185 g and 25.2 g stones.