Yarle Lakes 004        30°30’S, 131°28’E

South Australia, Australia

Found: 11 May 2009

Classification: Carbonaceous chondrite (CK4)

History: D. Bradley found a single piece lying on the Nullarbor Plain.

Physical characteristics: The meteorite weighs 4.6 g and measures 2.2 cm x 1.6 cm x 0.7 cm. The surface is dark maroon to black and has no obvious fusion crust. The freshly cut surface reveals a dark rusted brown interior with several paler chondrules scattered throughout.

Petrography: (Kim Lai N. Bell, Monash) Large PO chondrules within a dark stained, fine-grained matrix and are difficult to discern due to the staining. Chondrules have a size range of 0.3-1 mm, with an average diameter of 0.6 mm. Mineralogy differs from an ordinary chondrite in that it contains no obvious metals or sulfides. Mineralogy dominated by olivine, plagioclase, pyroxenes and magnetite. Olivine and pyroxene grains have straight to undulose extinctions and occur within chondrules or as fragments in the matrix. Plagioclase tends to occur as small grains (≤50 μm) within both the matrix and chondrules. The silicates are stained a rusty brown, with up to 75% staining affecting them. Magnetite (4%) grains are irregular shaped, <0.1 mm in size and can be found rimming chondrules and within the matrix.

Geochemistry: EMPA (wt%) Olivine: SiO₂ = 36.85, TiO₂ = 0.02, Al₂O₃ = 0.02, FeO = 28.87, MnO = 0.26, MgO = 34.49, CaO = 0.02, Na₂O = 0.01, K₂O = 0.00, (Fa_31.95±0.13, n = 6). Plagioclase: SiO₂ = 55.73, TiO₂ = 0.01, Al₂O₃ = 26.27, FeO = 0.52, MnO = 0.01, MgO = 0.22, CaO = 9.71, Na₂O = 5.83, K₂O = 0.65 (An_47.26±18.59, n = 5). Pentlandite: Fe = 27.96, Ni = 30.66, Cr = 1.26, Mg = 0.71. Magnetite: Fe = 61.25, Cr = 3.27, Al = 1.33, Ti = 0.74, Mg = 0.34, Ni = 0.19.

Classification: Carbonaceous chondrite (CK4, S2, W1-4).

Specimens: Sample and one thin section held by A. Tomkins at Monash.