Lunar Meteorite - DaG 262

Saharas first lunar meteorite DAG 262 / Dar al Gani 262 was found on March 23, 1997, in the Libyan part of the Sahara, by a German scientist. A single fragment weighing 513 g was recovered . The lunar material is a polymict lunar highland breccia containing abundantlight-coloured clasts embedded in a tough fine-grained matrix. Some of the lithic clasts reach a size of about 1 cm.

Mineralogy: Impact melt veins and pockets are abundant. Concerning the class population Dar al Gani 262 contains very similar clasts like other lunar highland regolith breccias: Recrystallized anorthositic rocks and breccias, granulitic lithologies, and feldspathic fine-grained to microporphyritic crystalline impact melt breccias are the most abundant rock types. Dar al Gani 262 contains several glass fragments (partly recrystallized) and two (devitrified) glass spherules. Within the fine-grained matrix of the breccia and within the shock veins Fe,Ni-metal particles with variable Ni concentrations (5-26 wt%) occur. The matrix of Dar al Gani 262 is well consolidated and the porosity isapproximately zero.Plagioclase in the bulk rock is anorthite (mostly An>95). Olivine and low-Ca pyroxene are variable in composition (Fa20-71 and Fs26-63,respectively). As accessory phases ilmenite, troilite, and Ti-,Cr-spinel were identified.

Shock effects: As is the case for all polymict impact breccias, the lithic and mineral clasts belong to an unknown number of shock events and show various degrees of shock. Most of the shock features result from processes that occurred prior to breccia lithification and shock-induced ejection from the Moon (e.g., formation of impactmelt breccias, anorthositic breccias, and impact melt spherules). Dar al Gani 262 contains maskelynite-rich clasts (anorthosites) not observed in QUE 93069. However, since these clasts occur close to fragments in which feldspar shows only weak undulatory extinction, insitu formation of maskelynite can be ruled out. Most olivines show planar fractures; in several cases mosaicism can be observed. These shock features indicate that the bulk rock must have been shocked to 15-20 GPa [3,4]. The impact melt veins that cut across all lithologies werecertainly formed after lithification.Summary: As already indicated by the description of the major lithologies the rockis highly feldspathic. Preliminary X-ray bulk chemical analysis revealed the following concentrations (in wt%): Mg: 2.4, Al: 15.2 Si: 20.3, Ca: 13.1, Fe: 3.5. Based on these data Dar al Gani 262 would have the highest Al- and Ca-concentrations among the lunar meteorites (cf. [2]). The Ca-value, however, is probably influenced by the presence of terrestrial calcite that fills several cracks of the meteorite. The mineralogical and (preliminary) chemical data may constrain possible areas ofthe Moon from which the breccia was derived. The source area of Dar al Gani 262 must be a highland terrain lacking significantmafic impact melts or mare components.References: [1] Bischoff A. (1996), Meteoritics Planet. Sci., 31, 849. [2] Palme H. et al. (1991), GCA, 55, 3105. [3] Stöffler D. et al. (1991), GCA, 55 3845. [4] Bischoff A. and Stöffler D. (1992), Eur. J. Mineral., 4, 707.


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Erich H Haiderer