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| Northwest Africa 11889 | |||||||||||||||||||||||||||||
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| Basic information | Name: Northwest Africa 11889 This is an OFFICIAL meteorite name. Abbreviation: NWA 11889 Observed fall: No Year found: 2017 Country: (Northwest Africa) Mass:  75 g | ||||||||||||||||||||||||||||
| Classification history: |
This is the only approved meteorite classified as CO3.1-an. Search for other: Carbonaceous chondrites, Carbonaceous chondrites (type 3), CM-CO clan chondrites, and CO chondrites | ||||||||||||||||||||||||||||
| Comments: |
Approved 3 Aug 2018 Revised 28 Mar 2020: reclassified | ||||||||||||||||||||||||||||
| Writeup |
Writeup from MB 107:
Northwest Africa 11889 (NWA 11889) (Northwest Africa) Purchased: 2018 Classification: Carbonaceous chondrite (CM2) Physical characteristics: Dark stone. Cut surface reveals homogeneous dark interior. Petrography: (J. Gattacceca, CEREGE) Chondrules, some with fine grained dust rim, with average size 180±70 μm (N=20) set in a abundant fine grained iron rich matrix (61 vol% by point counting). Opaques are magnetite and troilite. No metal was observed. Low microprobe analyses totals in the matrix indicate the presence of phyllosilicates. Geochemistry: Olivine Fa1.0-46.6, Cr2O3 0.25±0.14 wt% (n=10). Defocalized (10 µm) electron microprobe analyses in the matrix yield totals of 75 wt%. Classification: CM2 Specimens: 23.5 g and a polished section at CEREGE. Main mass with R. Lenssen. Writeup from MB 109: Northwest Africa 11889 (NWA 11889), revised text and classification Classification: CO3.1-anom Physical characteristics: Dark stone. Cut surface reveals homogeneous brownish interior with small chondrules. Petrography: (J. Gattacceca, CEREGE) Chondrules, some with fine-grained dust rims, with average size 180±70 μm (N=20,) set in a abundant, fine grained, iron-rich matrix (61 vol% by point counting). Opaques are magnetite and troilite. Magnetite is found as large spherical grains within chondrules. No metal was observed, except as rare µm-sized grains enclosed in silicates. 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. Geochemistry: Olivine Fa11.1±15.8, Fa PMD 115%, range Fa0.6-53.3 (n=35), Cr2O3 in ferroan olivine 0.332±0.179 wt% (n=27). Low Ca pyroxene Fs4.3±2.2Wo2.1±1.1 (n=4), Ca pyroxene Fs1.2Wo36.1 (n=1). Matrix microprobe over areas of 20 × 20 µm2: total 80.1%, FeO 33.7 wt% (n=3). Oxygen isotopic composition (J. Gattacceca, C. Sonzogni, CEREGE) from analysis of one acid-washed 1.5 mg aliquot of a powdered 144 mg bulk sample is δ17O=-5.33‰, δ18O=-1.20‰ , Δ17O=-4.71‰ (linearized, slope 0.5247, analytical uncertainties 0.08‰, 0.12‰, 0.03‰ respectively). Classification: Carbonaceous chondrite (CO3.1-anomalous). The anomalous designation is from the high abundance of matrix, absence of metal and presence of magnetite as the main opaque phase. Subtype from the Cr2O3 content of ferroan olivine (similar to Colony CO3.1). Specimens: 23.5 g and a polished section at CEREGE. Main mass with R. Lenssen. | ||||||||||||||||||||||||||||
| Data from: MB107 Table 0 Line 0: |
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| Plots: | O isotopes: | ||||||||||||||||||||||||||||
| Institutions and collections |
CEREGE: CEREGE
BP 80
Avenue Philibert, Technopole de l'Arbois
13545 Aix-en-Provence Cedex 4
France, France (institutional address; updated 10 Jun 2023) |
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| Catalogs: |
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| References: | Published in Meteoritical Bulletin, no. 107, MAPS 55, 460-462 Published in Meteoritical Bulletin, no. 109, in preparation (2020)
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| Geography: |
Statistics: This is 1 of 9429 approved meteorites from (Northwest Africa) (plus 1876 unapproved names) | ||||||||||||||||||||||||||||