MacKay Glacier 12002 (MCY 12002)        77° 14.4667’ S, 158° 2.2167’ E

Antarctica, Antarctica

Find: 2013 Jan 03

Classification: Carbonaceous chondrite (CM2)

History: A dark stony fragment (7 cm across) was recovered from the MacKay Glacier ice field, Antarctica, during the 2012-2013 Italian Programma Nazionale delle Ricerche in Antartide (PNRA) meteorite search campaign

Physical characteristics: Dark stony fragment (7 cm across) with partially preserved fusion crust. The total mass of the sample is 42.6 g.

Petrography: The investigated section (about 2 cm²) is composed of 20 vol.% chondrules, 15 vol.% PCP and <1 vol.% CAIs, embedded in a fine-grained matrix (65 vol.%). Calcium carbonate (1.5 vol.%), sulfides (0.8 vol.%) and FeNi blebs (0.14 vol.%) and are also present within the matrix. Chondrule mean diameter is 480±270 µm and chondrules are mainly IA and IB POP types, with scarce CC, BO and IIA chondrule types. Mesostases in porphyritic chondrules are altered to hydrous mineral phases, but neighboring phenocrysts are unaffected. There is no evidence of brecciation, but few chondrules appear fragmented. There is no evidence of limonite surrounding Fe-Ni metal, but just a mild staining noticeable under transmitted light, which confers to this meteorite a weathering grade W0.

Geochemistry: Chemical analyses where conducted using the EPMA at NHMV), Austria using 15 kV of acceleration voltage and beam current of 20 nA. In both cases, ZAF correction was applied and natural and synthetic minerals were used as reference material. Olivine is mainly Fo₁₀₀, although some type IIA chondrules contain olivine with composition Fo_11. Both low-Ca and high-Ca pyroxenes are Fe-poor: En_97.6±0.9Fs_1.3±0.7Wo_1.1±0.8; En_68.2±11.8Fs_1.4±0.8Wo_33.5±11.6. Sulphides are stoichiometric troilite and pentlandite. PCPs have a Fe/SiO₂ ratio of 1.52.

Classification: Carbonaceous chondrite (CM2). Low shock and weathering grade.