Mount Tazerzait

standby for mount tazerzait photo
Fell August 21, 1991
18° 42′ N., 4° 48′ E. On an August afternoon, a seven-year-old Tuareg boy witnessed the fall of a 110 kg stone in Tahoua, Republic of Niger. This is a uniquely unshocked (S1) meteorite with high porosity and large vugs containing crystals of silicates, troilite, and FeNi-metal. Mount Tazerzait shares many similarities with the meteorite Baszkówka; some of these are the low shock stage of S1, unusually high porosity, crystal growth inside vugs, very long cosmic-ray exposure age (~61 and ~76 m.y., respectively), noble gas abundance, chemical composition, and date of fall. These similarities suggest that both meteorites might be members of a meteor stream ejected from the same source region on their parent body. Additionally, the L5 meteorite named Tjerebon, from Java, Indonesia, may be another member of this meteor stream.

A proposed model for the development of high porosities in meteorites was presented in an article by Przylibski et al. in MAPS, vol. 38, #6 (2003). In their paper, ‘Petrology of the Baszkówka L5 chondrite: A record of surface-forming processes on the parent body’, the authors describe how an early collision of two thinly-crusted, molten planetesimals occurred within the first two million years of Solar System history. This collision produced a hot cloud of low-density chondritic material, which thereafter, slowly accreted onto the surface of the larger body. This homogeneous material was then loosely welded together by hot, plastic metal and sulfides. Material that remained near the surface of the planetesimal developed ubiquitous impact-generated microcracks resulting in the highest total porosities, such as is found in the ordinary chondrites Baszkówka, Miller (20%), NWA 2380 (18.7%), and Sahara 98034 (16.1 [±2.0] %), while those meteorites with somewhat less porosity such as Mount Tazerzait (12.6%) were more deeply buried and experienced more complete compaction ((Sasso et al., 2009). These meteorites did not experience further recrystallization, and therefore, their petrography reflects the conditions that existed during the earliest period of solar system history.

These meteorites likely originated on a separate parent body than that of other L chondrites, one on which a low shock history has preserved the primary porosity. The growth of euhedral crystals inside the pores might have been created during equilibration involving solutions originally present on the Mount Tazerzait–Baszkówka parent body. The above specimen is a 37.8 g cut fragment with a polished face showing the high porosity of this meteorite.

For additional information on the Mount Tazerzait meteorite, read the article by Dr. Svend Buhl on the Meteorite Recon website—‘Mount Tazerzait Meteorite: Unlocking an eventful past’.

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