Sample Petrographic Description
Sample Number | LAR 12240 |
Newsletter | 36,2 |
Location | Larkman Nunatak |
Field Number | 23250 |
Dimensions (cm) | 5.0 x 3.0 x 3.0 |
Weight (g) | 57.60 |
Original Classification | Shergottite |
Pairing | LAR 12095; LAR 12240; |
Mineral Composition (%Fa & %Fs) | |
Fayalite (mol%): 28-42;Ferrosilite (mol%): 25-31 | |
Weathering | |
A/B | |
Fracturing | |
A | |
Macroscopic Description - Cecilia Satterwhite | |
The exteriors are a rough, fractured texture with brown/black fusion crust and some evaporites. Areas without fusion crust show tan matrix with some olivine grains. The interiors are greyish tan with abundant green mineral grains and some darker grains visible. Minor oxidation is present. | |
Thin Section Description (,2) - Cari Corrigan, Linda Welzenbach | |
These meteorites are similar enough that one description will suffice. Each section is composed of a coarse-grained assemblage of pyroxene, olivine and maskelynite. Olivine occurs as phenocrysts with grain sizes up to 3 mm. Olivines have a brown staining probably due to shock. Pyroxene and maskelynite in the matrix are finer grained, typically reaching 0.5 mm. Sulfides and oxides are present, as is one shock melt vein in each section. Olivine is Fa28-42; pyroxenes exhibit a range of compositions from pigeonite to subcalcic augite (Fs25-31Wo8-18; Fe/Mn27-32); feldspar is intermediate in composition (An54-64Or0-1). These meteorites are olivine-phyric shergottites. |
Antarctic Meteorite Images for Sample LAR 12240 | ||||
Lab Photo(s) : | ||||
Antarctic Meteorite Images for Sample LAR 12240 | ||||
Thin Section Photo(s) : | ||||
References for Sample LAR12240 | |
Nicklas, R.W., Day, J.M.D., Vaci, Z., Udry, A., Liu, Y., and Tait, K.T., 2021, Uniform oxygen fugacity of shergottite mantle sources and an oxidized martian lithosphere. Earth and Planetary Science Letters, 564, 116876, https://doi.org/10.1016/j.epsl.2021.116876. | |
Clay, P.L., Strekopytov, S., and Ballentine, C.J., Joy, K.H., O'Driscoll, B., Busemann, H., Ruzié-Hamilton, L., Burgess, R., Fellowes, J., Joachim-Mrosko, B., Pernet-Fisher, J., 2020, Heavy halogen geochemistry of martian shergottite meteorites and implications for the halogen composition of the depleted shergottite mantle source. American Mineralogist, 105, 289–306. | |
Dunham, E. T., Balta, J. B., Wadhwa, M., Sharp, T. G., & McSween Jr, H. Y., 2019, Petrology and geochemistry of olivine?phyric shergottites LAR 12095 and LAR 12240: Implications for their petrogenetic history on Mars. Meteoritics & Planetary Science, 54, 811-835. | |
Tait, K. T., & Day, J. M., 2018, Chondritic late accretion to Mars and the nature of shergottite reservoirs. Earth and Planetary Science Letters, 494, 99-108. |