CAMEL DONGA


Eucrite
Monomict, noncumulate
(Main Group–Nuevo Laredo trend)

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Found January 1984
30° 19' S., 126° 37' E.

This monomict breccia was found on the Nullarbor Plain of Western Australia by Mrs. J. C. Campbell after she spotted a 503 g specimen from a moving vehicle while travelling cross-country. Eleven additional stones were recovered in July 1985 during a subsequent search of the site, located 200 m west of Camel Donga. Later search parties recovered more stones within the 1 km² area bringing the total known weight to over 2.92 kg.

Camel Donga is a product of fractional crystallization within a magma source and is composed of a mixture of pyroxene and plagioclase in a 3:2 ratio. It contains an unusually high content of total Fe (18.6%), second only to that of NWA 4269 (23.18%). Camel Donga has a high metallic iron content of 2 wt% ranging in size from 5 to 20µm and finely dispersed in silicates. Because of the low siderophile content in this metallic iron, it is presumed that it formed by in situ reduction of an FeSiO component in association with pyroxene during thermal impact metamorphism. Data from Hf/W ratios indicate that this thermal metamorphism occurred ~10–15 m.y. after mantle differentiation, long after the extinction of the major radiogenic elements. This scenario constrains the cause of the heating event to a major impact on Vesta (Kleine et al., 2004). A similar impact event produced the pure Fe-metal in the eucrite NWA 6601 (Agee, 2011). The fine-grained gray matrix contains gabbroic and doleritic clasts. Camel Donga has an absolute crystallization age based on the Pu–Xe chronometer of 4.507 b.y., and it has a cosmic-ray exposure age of 36.6 (±1.4) m.y., including it within one of the five common breakup events occurring 6 (±2), 12 (±2), 21 (±4), 38 (±8), and 73 (±3) m.y. ago.

The pristine condition of these stones is evidence of a recent fall, and it is inferred from their shapes that a single fragmentation was followed by flight orientation of many of the individuals. The occurrence of regmaglypts, radial flow lines, and melt overflow is a common characteristic of many of the stones. The Camel Donga specimen pictured above is a 21.8 g individual with a cut face. The photo below shows the interior of this eucrite.


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