10-16 Characterization of Three Unclassified NWA Meteorites Using Thin Section Microscopy

Session: Undergraduate and Graduate Geoscience Student Showcase (Posters)

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Abstract:

The Northwest Africa (NWA) designation has been given to thousands of meteorites found in and around the Sahara Desert. Predominantly purchased with minimal record keeping during the Sahara Gold Rush of the 1990s and 2000s, many of these meteorites are understudied and have never received official classification. These meteorites include the unofficially named NWA 140, NWA 185, and NWA 195. This research aims to provide a baseline characterization of these three meteorites in order to lay a foundation for future classification. Through the use of optical microscopy, thin sections are analyzed in both plane polarized and cross polarized light. Samples are studied and characterized according to petrologic type, metal content, shock stage.

All three samples are believed to possess petrographic type of six due to poor chondrule definition and a highly recrystallized matrix. Similarly, each meteorite has an average chondrule diameter close to 0.7 millimeters, resulting in theorized low iron content for all three. All meteorites are believed to possess a shock stage of at least five due to the presence of strong mosaicism and planar deformation features in each sample. Through these observations, all three meteorites are deemed to be L6 ordinary chondrites. Weathering grade is also observed for each meteorite. NWA 140 and NWA 185 are believed to possess a weathering grade of six due to extensive silicate oxidation. NWA 195 is believed to possess a weathering grade of two to four due to moderate metal oxidation and minimal silicate oxidation.

It is possible that lower levels of iron correspond with less dramatic depths within a parent body as part of a proto-differentiation phenomenon. This could suggest that the high petrographic type of these samples is a result not of great depth within their parent bodies but rather, large parent body size. In addition, the high amounts of shock experienced by each meteorite could be a result of larger parent bodies and therefore larger amounts of stress involved in collisions. It is therefore possible that the three NWA meteorites studied once belonged to large parent bodies of masses nearly large enough to result in differentiation. Further research, including chemical analysis, will aid in further developing an understanding of these meteorites and the celestial histories they preserve.

Geological Society of America Abstracts with Programs. Vol. 58, No. 1, 2026

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