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| Northwest Africa 15341 | |||||||||||||||||||||||||||||||
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| Basic information | Name: Northwest Africa 15341 This is an OFFICIAL meteorite name. Abbreviation: NWA 15341 Observed fall: No Year found: 2022 Country: Mali Mass: 1210 g | ||||||||||||||||||||||||||||||
| Classification history: |
This is 1 of 4 approved meteorites classified as CO3-an. | ||||||||||||||||||||||||||||||
| Comments: | Approved 4 Apr 2024 | ||||||||||||||||||||||||||||||
Writeup | Writeup from MB 113: Northwest Africa 15341 (NWA 15341) Mali Purchased: 2022 Jan Classification: Carbonaceous chondrite (CO3-an) History: Found in Mali and purchased by Mbark Arjdal in January 2022 from a Malian dealer. Petrography: (A. Irving, UWS and J. Boesenberg, BrownU) Well-formed, relatively small chondrules (apparent diameter 230±170 µm, N = 26) containing glass or devitrified glass, plus some mineral fragments, AOA and very fine grained amoeboid CAI, are set in a fine grained matrix (~30 vol.%, red-brown in thin section) containing chromite, taenite, troilite and Cr-magnetite (associated with taenite and troilite). No kamacite was found. Geochemistry: Olivine (Fa23.1±20.4, range Fa0.7-56.1, N = 14; Cr2O3 in ferroan olivine 0.05-0.28 wt.%, mean 0.13 wt.%, sd 0.08 wt.%, N = 8), low-Ca pyroxene (Fs5.3±3.0Wo1.6±1.5, range Fs1.2-8.0Wo0.3-3.8, N = 4), diopside (Fs1.6±0.3Wo44.1±6.0, range Fs1.3-1.8Wo39.8-48.3, N = 2), Al-Ti-diopside in CAI (Fs1.7Wo50.2; Fs0.9Wo54.4; Al2O3 5.6-10.9 wt.%, TiO2 0.2-1.4 wt.%; N = 2), magnetite (Cr2O3 1.8-13.1 wt.%, N = 11). Classification: Carbonaceous chondrite (CO3, anomalous). Although magnetite is present in some low subtype CO3 chondrites. ( Rubin and Li, 2019), it is relatively Cr-poor (containing < 1 wt.% Cr2O3). The occurrence of relatively Cr-rich magnetite (containing up to 13 wt.% Cr2O3) as found in this specimen has not been previously reported in CO3 chondrites. Specimens: 27.0 g including one polished thin section at UWB; remainder with Mr. M. Arjdal. | ||||||||||||||||||||||||||||||
| Bibliography: |
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| Data from: MB113 Table 0 Line 0: |
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| Institutions and collections | UWS: University of Washington, Department of Earth and Space Sciences, 70 Johnson Hall, Seattle, WA 98195, United States (institutional address; updated 15 Jan 2012) UWB: University of Washington, Burke Museum of Natural History and Culture, Box 353010 Seattle, WA 98195, United States (institutional address; updated 9 Oct 2023) BrownU: Joseph Boesenberg Brown University Dept of Earth, Environmental and Planetary Sciences (DEEPS) 324 Brook Street Providence, RI 02912 , United States (institutional address; updated 4 Jan 2024) | ||||||||||||||||||||||||||||||
| Catalogs: | |||||||||||||||||||||||||||||||
| References: | Published in Meteoritical Bulletin, no. 113, in preparation (2024) | ||||||||||||||||||||||||||||||
| Photos: |
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CO3-an means:
"A carbonaceous chondrite of the CO group that is petrologic type 3, but which has anomalous properties."
The highlighted words are defined as follows:
carbonaceous chondrite: A major class of chondrites that mostly have Mg/Si ratios near the solar value and oxygen isotope compositions that plot below the terrestrial fractionation line.
CO group: The Ornans (CO) chemical group of carbonaceous chondrites, distinguished by small chondrules and refractory inclusions (<0.2 mm) occupying about half the volume of the rock, and generally showing a low degree of aqueous alteration.
type 3: Designates chondrites that are characterized by abundant chondrules, low degrees of aqueous alteration, and unequilibrated mineral assemblages. Many of the low-Ca pyroxene grains are monoclinic and exhibit polysynthetic twinning. The type 3 chondrites may be divided into subtypes ranging from 3.00 (least metamorphosed) to 3.9 (nearly metamorphosed to type 4 levels). If primary igneous glass occurs in the chondrules, it belongs to type 3.