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dc.date.accessioned2023-06-05T17:48:17Z
dc.date.available2023-06-05T17:48:17Z
dc.date.issuedn.d.
dc.identifier.urihttps://repository.tcu.edu/handle/116099117/58928
dc.descriptionNotes on Dar al Gani 262, the first lunar from the Sahara. M702.1
dc.relationOscar Monnig Papers (MS 124)
dc.rightsPrior written permission from TCU Special Collections required to use any document or photograph.
dc.sourceSeries III, Box 06, Dar Al Gani 262, 2001 folder
dc.subjectMeteorite
dc.subjectDar al Gani meteorites
dc.subjectLunar meteorite
dc.subjectAnorthositic breccia
dc.titleDAR AL GANI 262: THE FIRST Lunar meteorite FROM THE SAHARA.
dc.typeDocument
dc.description.transcriptionDAR AL GANI 262: THE FIRST Lunar meteorite FROM THE SAHARA. A. Bischoff and D. Weber, Institut für Planetologie, Westfälische Wilhelms- Universität Münster, Wilhelm-Klemm-Strasse 10. 48149 Münster, Germany. On April 10, 1997, we received the exciting message that (probably) the first Lunar meteorite has beep found in the Sahara. The first studies in the days following the discovery revealed that Dar al Gani 262 is indeed the thirteenth Lunar meteorite: a polymict anorthositic lunar highland breccia. Dar al Gani 262 was found March 23, 1997. in the Libyan part of the Sahara. A single fragment weighing 513 g was recovered. Thus, Dar al Gani 262 is one of the largest Lunar meteorites. The surface of a thin slice is shown in Fig. I. Dar al Gani 262 is a polymict lunar highland breccia containing abundant light-colored clasts embedded in a tough fine- grained matrix. Some of the lithic clasts reach a size of ~I cm. Mineralogy: Two polished thin sections were prepared (PL97062. PL97063). The rock is moderately weathered and contains several fractures filled with terrestrial calcite and, occasionally. Ba-sultate. In addition tc these filled fractures. abundant impact melt veins cut across the entire thin sections. Concerning the clast population, Dar al Cani 262 contains clasts very similar to other lunar highland regolith breccias (e.g., 1.2]. 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. Matic components like matic crystalline melt breccias as found in other Lunar meteorites are extremely rare. Within the fine-grained matrix of the breccia and within the shock veins, Fe.Ni-metal particles with variable Ni concentrations (5-26 w1%) occur. The matrix of Dar al Gani 262 is well consolidated and the porosity is approximately zero. Plagioclase in the bulk rock is anorthite (mostly An,gs). Olivine and low-Ca pyroxene are variable in composition (Fazo-7, and F$26-63 respec-tively). Ilmenite, troilite, and Ti-,Cr-spinel were identified as accessory phases. 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 impact melt breccias, anorthositic breccias, and impact melt spherules). Dar al Gani 262 contains maskelynite-rich clasts (anorthosites) not observed in OUE 93069. However. since these clasts occur close to fragments in which feldspar shows only weak undulatory ex-tinction, in situ formation of maskelynite can be ruled out. Most olivines show planar fractures; in several cases mosaics 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 were certainly formed after lithification. Summary: As already indicated by the description of the major litholo-gies. the rock is 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 (prelimi-nary) chemical data may constrain possible areas of the Moon from which the breccia was derived. The source area of Dar al Gani 262 must be a high-land terrain lacking significant matic 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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  • Records of the Monnig Meteorite Gallery [2247]
    The files are arranged alphabetically, usually according to the location of discovery of the meteorite. The files contain correspondence and research material on the meteorites in the collection.

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