Northwest Africa 12220 (NWA 12220)

(Northwest Africa)

Purchased: 2007 June

Classification: Rumuruti chondrite (R3-4)

History: Purchased from a Moroccan dealer at the meteorite show in Ensisheim, France.

Petrography: (K. Metzler, IfP) Chondritic breccia, consisting of light chondritic clasts, embedded in a matrix of isolated chondrules and chondritic debris. Many chondrules and chondrule fragments are unequilibrated and stem from lithologies of type 3. Light clasts are metamorphosed and belong to the petrologic type 4.

Geochemistry: Mineral compositions and geochemistry: Clasts of petrologic type 4: mean olivine composition Fa_39.3±0.6 (Fa_37.6-40.0); n=12; mean pyroxene composition Fs_13.1±2.3Wo_43.2±2.3 (Fs_9.8-16.6Wo_39.8-46.2); n=14. Fragments of petrologic type 3: range of observed olivine compositions Fa_2.5-20.8; n=16; range of observed low-Ca pyroxene compositions: Fs_1.7-18.4Wo_0.4-5.0; n=17. Mineral compositions and geochemistry: Clasts of petrologic type 4: mean olivine composition Fa_39.3±0.6 (37.6-40.0); n=12; mean pyroxene composition Fs_13.1±2.3Wo_43.2±2.3 (Fs_9.8-16.6Wo_39.8-46.2); n=14. Fragments of petrologic type 3: mean olivine composition Fa_13.5±5.5 (Fa_2.5-20.8); n=16; mean pyroxene composition Fs_7.1±6.8Wo_2.2±1.7 (Fs_1.7-18.4Wo_0.4-5.0); n=17.

Classification: R chondrite based on mineral chemistry. Genomict breccia, consisting of chondrules and chondrule fragments from type 3 lithologies (unequilibrated olivine and pyroxene) and type 4 clasts (equilibrated olivine and unequilibrated pyroxene).