Carbonaceous
Name
*click on the Name for more information
Structure Class
Carbonaceous chondrites
Chemical Class
C3.00-ung
Country
Western Sahara
Year found
2018
Mass
779 g
[Museum Collection]
(1) 3.7g (2) 1.6g (3) 1.6g (4) 1.2g
History: Found close to Houza village by Elho Sbiti on June 10, 2018. Bought from Mohamed Elguirad in Guelmim in June and October 2018. More samples bought from Mohamed Elguirah, Habib-Naji Naji and Youssef Ait El Caid in January 2019. Some material bought by Nourddine Azelmat. Physical characteristics: Fragments and crusted stones, including a 158 g full stone. Cut surface reveals a dark porous interior with chondrules. Petrography: (J. Gattacceca, CEREGE) Chondrite with well-defined chondrules (average apparent diameter 480±300 μm, n=29) set in an abundant fine-grained iron-rich matrix (74 vol%, by point counting, n=371). Opaques are troilite, magnetite, rare metal (as inclusion in silicates and in the matrix). XRD over a ~1 cm2 area on a polished section (D. Borschnek, CEREGE) does not reveal the presence of hydrous phases (serpentine, tochilinite) typically observed in type 2 chondrites using the same experimental setup. In contrast to type 2 chondrites, IR transmission spectroscopy (L. Bonal, IPAG) on matrix grains only reveal a faint water and Si-O-band (attributable to phyllosilicates), reflecting a very low extent of aqueous alteration. Based on the structural order of the polyaromatic matter assessed by Raman spectroscopy (L. Bonal, IPAG), this meteorite appears to be less heated than the least heated type 3 ordinary chondrite, Semarkona. Geochemistry: Olivine Fa37.6±16.7, range Fa1.2-46.5 (n=16), Cr2O3 in ferroan olivine 0.39±0.12 wt% (n=11). Low-Ca pyroxene Fs3.1±3.0Wo0.8±0.3 (n=4). Defocussed (10 μm) microprobe totals in the matrix 90.9±1.2% (n=11). Oxygen isotopic composition (J. Gattacceca, C. Sonzogni, CEREGE) from analysis of one acid-washed 1.5 mg aliquot of a powdered 38 mg bulk sample is δ17O=0.42‰, δ18O=8.23‰ , Δ17O=-3.88‰ (linearized, slope 0.5247, analytical uncertainties 0.08‰, 0.12‰, 0.03‰ respectively). Classification: Carbonaceous chondrite (C3.00-ungrouped). This meteorite is distinct from CM2 chondrites for its larger chondrule size and only incipient aqueous alteration. Type 3.00 is based on the non-detection of phyllosilicates by XRD and microprobe total in the matrix higher than usually measured in type 2 chondrites (see e.g., Ebert et al. 2019, MAPS doi:10.1111/maps.13212), and Raman spectroscopy. Possibly paired with NWA 12957 and NWA 11750 despite having distinct oxygen isotopic composition. Specimens: Type specimen at CEREGE. Main mass with Jean Redelsperger and Nourddine Azelmat.
Name
*click on the Name for more information
Structure Class
Carbonaceous chondrites
Chemical Class
C2-ung
Country
Canada
Year found
2000
Mass
10 kg
[Museum Collection]
(1) 1.28g (2) 3g
A brilliant fireball followed by loud detonations was widely observed over the Yukon Territory and northern British Columbia. The fireball was also detected by satellites in Earth orbit. Dust clouds from terminal fragmentation events were widely observed. Jim Brook recovered several dozen meteorites totaling ~ 1 kg on the ice of Taku Arm, Tagish Lake, on January 25 and 26 (coordinates of first find given above). Between April 20 and May 8, ~ 500 additional specimens were located on the ice of Taku Arm and a small, unnamed lake 1.5 km to the east, but only ~ 200 were retrieved as many had melted down into the ice making their collection time consuming; recovery was prioritized based on meteorites' mass and degree of disaggregation. The total mass collected was between 5 and 10 kg. The strewnfield is at least 16 × 3 km, oriented approximately S30° E. Classification and mineralogy (M. Zolensky, JSC; M. Grady, NHM): possibly CI2 group; a matrix-dominated chondrite, with a few small chondrules, CAIs, and isolated grains; matrix mainly phyllosilicates, Fe-Ni sulfides and magnetite, with abundant Ca-Mg-Fe carbonates; olivine, Fa0–29, PMD = 2%, with a peak at Fa1; pyroxene, Fs1–7, PMD = 2%, with a peak at Fs2; bulk C content 5.4 wt%, with δ13C = +24.3‰; shock stage, S1. Oxygen isotopes (R. Clayton, UChi): δ18O = +18.0 to 19.0‰, δ17O = 8.3 to 9.2‰. Specimens: majority held by UCalg (contact A. Hildebrand) and UWO (contact P. Brown).