Sample Petrographic Description
Sample Number | MIL 090785 |
Newsletter | 34,1 |
Location | Miller Range |
Field Number | 20684 |
Dimensions (cm) | 4.0 x 3.5 x 3.5 |
Weight (g) | 90.34 |
Original Classification | CO3 Chondrite |
Mineral Composition (%Fa & %Fs) | |
Fayalite (mol%): 1-44;Ferrosilite (mol%): 1 | |
Weathering | |
C | |
Fracturing | |
A/B | |
Macroscopic Description - Roger Harrington, Kathleen McBride, Cecilia Satterwhite | |
These carbonaceous chondrites have varying amounts (20-100%) of brown/black fusion crust with oxidation haloes and rusty areas. Some exterior surfaces are pitted. The interiors of these meteorites range in color from brown to dark gray to black. Most have a fine-grained matrix with light colored inclusions. | |
Thin Section Description (,2) - Cari Corrigan, Linda Welzenbach | |
These sections are so similar that a single description suffices. The sections consist of abundant (up to 1 mm) chondrules, chondrule fragments and mineral grains in a dark matrix. Metal and sulfide occur within and rimming the chondrules. Glass within chondrules appears to be very clear/fresh. CAIs are abundant in many sections (mostly Type A), and range in size up to 1 mm, many containing blue hibonite grains. At least one compound CAI was found. AOAs up to 1 mm exist, as well. Olivine ranges in composition from Fa0-80. Pyroxene analyses range from Fs0-44 (most from Fs0-13). These meteorites are somewhat terrestrially altered. They are CO3 chondrites (likely type 3.0-3.2) and are probably members of the MIL 07099 pairing group. | |
Notes | |
MIL 090785 has a distinctly lower CRE age than other MIL CO3s; together with its lower magnetic susceptibility (3.85) it is an unique sample that has been removed from the large MIL pairing group. Data supporting these pairing updates for MIL CO3 chondrites were presented in Righter et al. (2021, 2022, 2023). |
Antarctic Meteorite Images for Sample MIL 090785 | ||||
Thin Section Photo(s) : | ||||
References for Sample MIL090785 | |
Prestgard, T., Bonal, L., Eschrig, J., Gattacceca, J., Sonzogni, C., and Beck, P., 2021, Miller Range 07687 and its place within the CM-CO clan. Meteoritics & Planetary Science, 56, 1758–1783, doi: 10.1111/maps.13736. | |
Alexander, C. O. D., Greenwood, R. C., Bowden, R., Gibson, J. M., Howard, K. T., & Franchi, I. A. , 2018, A multi-technique search for the most primitive CO chondrites. Geochimica et Cosmochimica Acta, 221, 406-420, https://doi.org/10.1016/j.gca.2017.04.021. | |
Sears, D. W., 2016, The CO chondrites: Major Recent Antarctic finds, Their Thermal and Radiation History, and Describing the Metamorphic History of Members of the Class. Geochimica et Cosmochimica Acta, 188, 106–124. | |
RELAB, , Reflectance Experiment Lab , catalogue of samples. |