DAR AL GANI 262


Lunar Feldspathic Breccia
(regolith breccia)
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Found March 23, 1997
27° 11.02' N., 16° 18.02' E.

A 513 g stone was found in the Sahara by one of the pioneers of hot desert meteorite hunting, Rainhard Welz. This polymict anorthositic highlands breccia is the first lunar meteorite recovered from the Northern hemisphere. It consists mostly of light-colored clasts, mainly anorthositic lithologies high in Al and Ca, and feldspathic crystalline impact-melt breccias, along with glass fragments and rare melt spherules, embedded in a fine-grained, very coherent matrix. It has a shock stage of S3 (15–20 GPa), and contains abundant impact melt veins throughout. FeNi-metal particles are found associated with the veins and matrix, with ilmenite, troilite, and Ti-,Cr-spinel occurring as accessory phases. It has a high concentration of solar-wind-implanted gases indicative of a long residence at shallow depth within the lunar regolith.

Because of the very low abundance of mafic components and the specific bulk composition, the source rock was likely a pristine highland terrane lacking igneous rocks, impact melts, mare components, KREEP, and other mafic signatures of large impact craters. A probable source is the Feldspathic Highlands Terrane, which encompasses 65% of the lunar surface, including most of the farside. Argon dating studies of DaG 262 give a wide range of ages, from as old as 3.4 b.y. to only 1.7 b.y., evidence of multiple late impact events and reflecting the diversity of components mixed into the final breccia assemblage. Cosmogenic radionuclide studies indicate that exposure at a depth of ~30 cm in the regolith lasted 500–1000 m.y., which was followed by a relatively short Moon–Earth transit of ~80 t.y (Nishiizumi, 2003). Thereafter, the meteorite was moderately weathered during an extended terrestrial residence lasting an additional ~80 t.y.

Dar al Gani 262 is likely paired with DaG 996 (12.3 g), DaG 1042 (801.43 g), and DaG 1048 (0.801 g). It is very close in its chemistry and mineralogy to the lunar meteorite pairing of QUE 93069 and QUE 94269, and has similarities in ejection times, Moon–Earth transit times, and terrestrial ages as well. This suggests the possibility of a common ejection event for all of these meteorites. Two other lunar highland meteorites, MAC 88104/5 and Y-86032, also share close similarities with DaG 262.

The specimen pictured above is a 0.09 g fragment showing a black shock vein filled with microscopic bubbles running vertically along the left edge. The photo below shows the complete mass of DaG 262 and its interior after sectioning.

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