Antarctic Meteorite Newsletter 31,1 - Petrographic Descriptions
| Sample No.: | LAR 06869 |
| Location: | Larkman Nunatak |
| Field No.: | 19740 |
| Dimensions (cm): | 3.0 x 2.5 x 1.5 |
| Weight (g): | 18.258 |
| Meteorite Type: | CK6 Chondrite |
| Pairing: | LAR 06869, LAR 06872, LAR 06873 |
Macroscopic Description: Kathleen McBride
The exteriors of these meteorites range from rough brown/black fusion crust to smooth black exterior. The interiors have dark gray to black matrix with evaporites, some are rusty and very hard and have small light colored inclusions.
Thin Section (,2) Description: Tim McCoy, Linda Welzenbach and Cari Corrigan
The sections exhibit a mixture of fine-grained mixture of olivine, calcic pyroxene and plagioclase with individual grains reaching a few hundred microns, but most grains of apparently finer grain size, perhaps owing to shock. Shock veins cross cut the sections forming a network. Vesicular, melted fusion crust was only present on one of the sections examined. Oxides and sulfide are relatively common to abundant. Olivine is Fa34, pyroxene is an Al-bearing (2-4 wt.% Al2O3) augite of Fs12Wo50, and a small number of plagioclase analyses suggest considerable heterogeneity An43-88Or0-8. Iron oxide is abundant and appears to be magnetite with significant Fe3+ present (based on low totals), as well as 5 wt.% Cr2O3 and 2 wt.% Al2O3. Sulfide is an Fe,Ni sulfide, likely pentlandite. The meteorites are strongly shocked and metamorphosed chondrites, probably CK6.
Oxygen Isotopic Analysis: D. Rumble, Geophysical Laboratory, Carnegie Institution of Washington
Magnetic fractions (magnetite) were analyzed (after ultrasonication in dilute HCl), which is important because an analysis of silicates will almost certainly give heavier small delta values.
Oxygen isotopic analyses of two small (2-5 mg) pieces of LAR 06872 yielded the following results:
δ17O = -5.98, δ18O = -2.46, Δ17O = -4.692
[where Δ17O = δ17O – 0.526 x δ18O]
Thin Section Images
| Plane-Polarized Light LAR 06869 |
Reflective Light LAR 06869 |
Cross-Polarized Light LAR 06869 |
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Lab Images
| North View LAR 06869 |
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