Grove Mountains 090407 (GRV 090407)        72°46’42.1"S, 75°19’10.9

Antarctica

Find: 23 Jan 2010

Classification: Ordinary chondrite (L4, melt breccia)

Physical characteristics: The specimen is dark black with a surface partially covered by remnant fusion crust.

Petrography: In thin-section, GRV 090407 shows a porphyritic structure. Phenocrysts (~30 vol%) are euhedral to subhedral olivine with an average diameter of 100~200 μm, and remnant chondrules are present. Olivine shows shock effects such as planar deformation fractures and undulatory extinction. In transmitted light, the matrix (~70 vol%) is opaque, and is mainly composed of glass with traces of granular silicates and metal. The granular silicates in the matrix are <50 μm in size, and include mainly low-calcium pyroxene, olivine and feldspar. The other opaque minerals in the matrix are represented by kamacite, taenite, troilite and chromite. With the exception of oxidized metallic veins developed along fractures, the metal is dispersed in circular droplets (previously molten) between 5 and 30 μm. The GRV 090407 is a breccia with melted matrix.

Geochemistry: The minerals have uniform chemical compositions, with an olivine (phenocrysts and granular matrix) composition of Fa_23.52±0.19, pyroxene of Fs_23.52±0.19Wo_1.49±0.11. The compositional characteristics of olivine and low calcium pyroxene are consistent with the L group.