Eucrite, polymict, anomalous
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no coordinates recorded Four pieces of a polymict eucrite having a combined weight of 1,193 g were purchased by M. Jost from a Moroccan dealer. A type sample was sent to the University of Washington in Seattle (A. Irving and S. Kuehner) for analysis and classification, and NWA 10674 was determined to be an anomalous polymict eucrite breccia. Northwest Africa 10674 is a complex breccia composed predominantly of eucritic clasts (orthopyroxene with exsolved pigeonite and calcic plagioclase) having variable textures, mixed with disaggregated eucrite-related clastic material. Minor phases in the eucrite breccia include silica polymorph, chromite, ilmenite, troilite and fayalite, as well as sparse diogentic clasts (~2 vol%). The meteorite is unusual in that it contains abundant metal-bearing vitric breccia clasts (20 vol%) composed of magnesian silicates (orthopyroxene and olivine) interspersed with grains of FeNi-metal (kamacite) within glass. Interestingly, Warren et al. (2017) identified several cm-scale, metal-rich (12–17 vol%), ovoid silicate nodules in the polymict eucrite Camel Donga. These nodules are enriched in Ni and trace siderophile elements and lack other evidence for in situ reduction. They concluded that the metal nodules reflect the addition of an impactor component to the material that was precursory to Camel Donga. They speculate that this was a complex two-stage process involving metasomatic alteration by a reducing fluid that originated as a metal- and volatile-rich carbonaceous-chondritic (e.g., CM-type) contaminant. See the Camel Donga page for a photo and further details about this alteration process. The specimen of NWA 10674 shown above is a 7.08 g partial slice acquired from the Space Jewels Switzerland Collection of Marc Jost. Click on the top photos below to see magnified images. Another representative slice of NWA 10647 is also shown below, courtesy of Marc Jost.
click on photos for a magnified view It is noteworthy that the anomalous howardite NWA 3197 exhibits a striking similarity to NWA 10674 in both its exterior and interior appearance; compare the photo of NWA 10674 individuals and slices below to photos of NWA 3197 on the webpage of J. Utas here. Among the differences that do exist between these two meteorites is the fact that no recrystallized H chondrite clasts have been observed in the NWA 10674 samples analyzed.
Photo courtesy of Marc Jost