NWA 12344 Eucrite Polymict - Items tagged as "Eucrite polymict"

Northwest Africa 12344 (NWA 12344)

(Northwest Africa)

Purchased: 2018 Jan

Classification: HED achondrite (Eucrite, polymict)

Petrography: (K. Metzler, IfP) Polymict breccia consisting of eucritic lithic clasts with ophitic textures and mineral fragments (pyroxene, plagioclase, silica polymorph) set in a fine-grained matrix of related debris. The matrix is clastic, bound by intergranular shock-melt, and intermingled with vesicular melt pockets (up to 5 mm). The latter show quench tetxtures, consisting of parallel aligned pyroxene and plagioclase skeletal crystals. Both pyroxenes with and without exsolution lamellae occur. Iron-rich olivine was found as isolated fragments and in the shape of veins in lithic clasts. Accessories are silica polymorph, ilmenite, Cr-spinel, troilite, and Ni-poor metal.

Geochemistry: Mineral compositions and geochemistry: Low-Ca pyroxene: Fs64.5±4.4Wo2.4±0.7 (Fs55.8-68.4Wo1.9-4.7); mean Fe/Mn (at.): 29.8; n=13. Ca-rich pyroxene: Fs30.8±1.0Wo42.5±0.6 (Fs28.4-32.2Wo41.6-43.4) n=12. Olivine: Fa75.0 (Fa74.6-75.7); mean Fe/Mn (at.): 44.1; n=3. Plagioclase An90.6±2.5Or0.3±0.3 (An86.9-94.0Or0.0-0.8); n=8.