Antarctic Meteorite Petrographic Description

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Sample Petrographic Description

Sample Number

PCA 82500

Newsletter

6,2

Location

Pecora Escarpment

Field Number

2723

Dimensions (cm)

7.0 x 5.0 x 2.8

Weight (g)

90.92

Original Classification

LL6 Chondrite

Updated Classification

CK3 Chondrite

Mineral Composition (%Fa & %Fs)

Fayalite (mol%): 31

Weathering

Fracturing

Macroscopic Description - Carol Schwarz

This specimen is very unusual looking. It is extremely fragmented with numerous cavities, some extending through the thickness of the sample. The cavities were filled with ice and snow when the sample was removed from the freezer. Several patches of fusion crust are present. The exterior surfaces are a dark gray color with the fresher areas exhibiting a light gray to yellowish color. Inclusions (chondrules?) have been exposed on the exterior surface. The interior contains much white evaporite deposit along with areas of yellowish weathering residue. A dark gray fine-grained matrix is visible in less weathered areas as are minute metal flecks and a few yellowish dots of oxidation.

Thin Section Description (,2) - Brian Mason

The section snows a single porphyritic olivine chondrule, diameter 3.6 mm, in an aggregate of turbid anhedral olivine grains averaging 0.1 mm. Small amounts of troilite and nickel-iron are present, the nickel-iron being largely weathered to brown limonite. Microprobe analyses gave olivine composition Fa₃₁; no pyroxene was found, but occasional grains of plagioclase ranging in composition from An₂₀ to An₄₀ were analyzed. The meteorite is classified as an LL6 chondrite.

Reclassification Notes (AMN 41,1)

Reclassification of PCA 82500 currently a CK5, but should be a CK3. The observations supporting the low petrologic grade include (1) lack of ilmenite exsolution from magnetite, a property typically seen in type 3 CKs and (2) olivine zoning observed in BSE within the largest chondrule in the type section. Taken together, these suggest classification as a type 3.

Antarctic Meteorite Images for Sample PCA 82500

Field Photo(s) :

ANSMET PCA 82500 - Field Number: 2723, NASA Photo Number: jsc2009e041595

ANSMET PCA 82500 - Field Number: 2723, NASA Photo Number: jsc2009e041596

ANSMET PCA 82500 - Field Number: 2723, NASA Photo Number: jsc2009e041597

ANSMET PCA 82500 - Field Number: 2723, NASA Photo Number: jsc2009e041598

ANSMET PCA 82500 - Field Number: 2723, NASA Photo Number: jsc2009e041599

Field photo image(s) courtesy of the ANSMET (ANtarctic Search for METeorites) Program, Case Western Reserve University and the University of Utah

Antarctic Meteorite Images for Sample PCA 82500

Lab Photo(s) :

Antarctic Meteorite Images for Sample PCA 82500

Thin Section Photo(s) :

Thin Section Photo of Sample PCA 82500 in Cross-Polarized Light

Thin Section Photo of Sample PCA 82500 in Plane-Polarized Light

Thin Section Photograph of Sample PCA 82500 in Reflected Light

References for Sample PCA82500

Tanbakouei, S., Trigo-Rodriguez, J.M., Llorca, J., Moyano-Cambero, C.E., Williams, I.P., and Rivkin, A.S., 2021, The reflectance spectra of CV–CK carbonaceous chondrites from the near-infrared to the visible. , Monthly Notices of the Royal Astronomical Society, 507 , 651–662 , https://doi.org/10.1093/mnras/stab2146 .

Simkus, D. N., Aponte, J. C., Elsila, J. E., Parker, E. T., Glavin, D. P., & Dworkin, J. P., 2019, Methodologies for Analyzing Soluble Organic Compounds in Extraterrestrial Samples: Amino Acids, Amines, Monocarboxylic Acids, Aldehydes, and Ketones. , Life, 9 , 47 .

Chaumard, N., Devouard, B., 2016, Chondrules in CK carbonaceous chondrites and thermal history of the CV–CK parent body. , Meteoritics & Planetary Science, 51 , 547–573 .

Burton, A. S., Mclain, H., Glavin, D. P., Elsila, J. E., Davidson, J., Miller, K. E., Andronikov, A. V., Lauretta, D., Dworkin, J. P., 2015, Amino acid analyses of R and CK chondrites. , Meteoritics & Planetary Science, 50 , 470-482 .

Chaumard, N., Devouard, B., Bouvier, A., Wadhwa, M., 2014, Metamorphosed calcium-aluminum-rich inclusions in CK carbonaceous chondrites. , Meteoritics & Planetary Science, 49 , 419-452 .

Rubin, A. E., Huber, H., 2005, A weathering index for CK and R chondrites. , Meteoritics & Planetary Science, 40 , 1123-1130 , http://dx.doi.org/10.1111/j.1945-5100.2005.tb00178.x .

Oura, Y., Takahashi, C., Ebihara, M., 2004, Boron and chlorine abundances in Antarctic chondrites: A PGA study. , Antarctic meteorite research, 17 , 172-184 , http://ci.nii.ac.jp/naid/110001052380/en/ .

Schultz, L., Franke, L., 2004, Helium, neon, and argon in meteorites: A data collection. , Meteoritics & Planetary Science, 39 , 1889-1890 , http://dx.doi.org/10.1111/j.1945-5100.2004.tb00083.x .

Scherer, P., Schultz, L., 2000, Noble gas record, collisional history, and pairing of CV, CO, CK, and other carbonaceous chondrites. , Meteoritics & Planetary Science, 35 , 145-153 .

Clayton, R. N., Mayeda, T. K., 1999, Oxygen isotope studies of carbonaceous chondrites. , Geochimica et Cosmochimica Acta, 63 Issues 13-14 , Jul-99 , 2089-2104 , ISSN 0016-7037 , http://dx.doi.org/10.1016/S0016-7037(99)00090-3 .

Rubin, A. E., 1993, Magnetite-sulfide chondrules and nodules in CK carbonaceous chondrites: Implications for the timing of CK oxidation. , Meteoritics, 28 , 130-135 .

Xiaoyue, X., Lipschutz, M. E., 1992, Labile trace elements in carbonaceous chondrites: A survey. , Journal of Geophysical Research: Planets, 97 , 10199-10211 , http://dx.doi.org/10.1029/92JE00895 .

Scott, E. R. D., Keil, K., Stöffler, D., 1992, Shock metamorphism of carbonaceous chondrites. , Geochimica et Cosmochimica Acta, 56 Issue 12 , Dec-92 , 4281-4293 , ISSN 0016-7037 , http://dx.doi.org/10.1016/0016-7037(92)90268-N .

Rubin, A. E., 1992, A shock-metamorphic model for silicate darkening and compositionally variable plagioclase in CK and ordinary chondrites. , Geochimica et Cosmochimica Acta, 56 Issue 4 , Apr-92 , 1705-1714 , ISSN 0016-7037 , http://dx.doi.org/10.1016/0016-7037(92)90236-C .

Kallemeyn, G. W., Rubin, A. E., Wasson, J. T., 1991, The compositional classification of chondrites: V. The Karoonda (CK) group of carbonaceous chondrites. , Geochimica et Cosmochimica Acta, 55 Issue 3 , Mar-91 , 881-892 , ISSN 0016-7037 , http://dx.doi.org/10.1016/0016-7037(91)90348-9 .

Marvin, U. B., MacPherson, G. J., 1989, Field and Laboratory Investigations of Meteorites from Victoria Land and the Thiel Mountains Region, Antarctica 1982-1983 and 1983-1984. , Smithsonian Contributions to the Earth Sciences Number, 28 , 146 .

Nishiizumi, K., Elmore, D., Kubik, P. W., 1989, Update on terrestrial ages of Antarctic meteorites. , Earth and Planetary Science Letters, 93(3) , 299-313 .

Schultz, L., Kruse, H., 1989, Helium, neon, and argon in meteorites—A data compilation. , Meteoritics, 24 , 155-172 .

Kallemeyn, G. W., 1987, Compositional comparisons of metamorphosed carbonaceous chondrites. , Memoirs of National Institute of Polar Research., Special issue 46 , 151-161 , http://ci.nii.ac.jp/naid/110000010249/en/ .

Scott, E. R. D., Taylor, J., 1985, Petrology of types 4-6 carbonaceous chondrites. , Journal of Geophysical Research: Solid Earth, 90 , C699-C709 , http://dx.doi.org/10.1029/JB090iS02p0C699 .

RELAB, , Reflectance Experiment Lab , catalogue of samples, .

Antarctic Meteorite Petrographic Description

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