NORTHWEST AFRICA 6047


C3-ungrouped (CK-like)
(CK3 in MetBull #102)

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click on photo for a magnified view

Found 2009
no coordinates recorded

A single 264 g meteorite was found in Northwest Africa and subsequently purchased by M. Jost of Space Jewels Switzerland. A sample was sent for analysis and classification to the Museum für Naturkunde in Berlin, Germany (A. Greshake), and based on mineralogical analyses NWA 6047 was determined to be a rare unequilibrated CK3 chondrite.

This meteorite has a dark-brown, fine-grained matrix with large, well-defined chondrules, and its silicates preserve a wide compositional range, features which are indicative of a low degree of thermal metamorphism consistent with a classification of type 3. This carbonaceous chondrite exhibits an unusually high matrix to chondrule ratio with an almost complete lack of FeNi-metal. Minor phases include Ni-rich sulfides, Cr-bearing magnetite, and rare CAIs. It is unshocked to very weakly shocked (S2) and has experienced significant terrestrial weathering (W3).

Comparatively, the CK group has a high oxidation state which has resulted in a very low content of FeNi-metal and a correspondingly high content of magnetite and sulfides. The dispersion of these sub-µm- to µm-sized magnetite and sulfide (pentlandite) grains within vesicles of like size has caused pronounced silicate darkening in all metamorphic grades. In addition, CK chondrites generally have high matrix to chondrule ratios, with the matrix composing ~50–70 vol%. Chaumard and Devouard (2016) reported a large range in chondrule abundances among CK chondrites in their study, which they attributed to re-equilibration during metamorphism.

Previous studies (e.g., Sanborn et al., 2014) have established that a coupled Δ17O vs. ε54Cr diagram is one of the best diagnostic tools for determining genetic relationships between meteorites. New Cr- and O-isotopic analyses were conducted by Yin et al. (2017) for two new equilibrated CK chondrites (NWA 7461 and NWA 7704) as well as for unequilibrated NWA 6047 and CV3 Allende. When combined with previous analyses, it was determined that CK chondrites have an average ε54Cr value of +0.66 (±0.06), while the CV chondrites have an average value of +0.88 (±0.06). The significantly higher ε54Cr (+1.23 [±0.09]) and Δ17O values determined for NWA 6047 indicate that it likely represents a unique parent body separate from that of CK, CV, and CO chondrites (see diagram below).

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Diagrams credit: Yin et al., 48th LPSC, #1771 (2017)

The photo of NWA 6047 shown above is a 6.92 g slice measuring 5 cm across with a small portion of a CAI visible. The photo below shows a nice slice of NWA 6047 in the collection of Stephan Kambach.

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Photo courtesy of Stephan Kambach