Chergach stone, chondrite, H5 transient to Impact melt breccia Erg Chech, Northern Mali Fall: July 2007 Recently cut samples of the Chergach meteorite show clear signs of impact melt brecciation. The endcut pictured weighs 13.10g 36.7g endcut of an impact melt breccia from the Erg Chech fall Thinslide scan of an IMB sample. (photo courtesy of Dr. Beda Hofmann, Natural History Museum Bern) Ilmenit-chromite, incident light, sample in oil immersion, image width 0.3 mm (photo courtesy of Dr. Beda Hofmann, Natural History Museum Bern) Iron-troilite, segregated eutectic melt, incident light, sample in oil immersion, image width 0.3 mm (photo courtesy of Dr. Beda Hofmann, Natural History Museum Bern) The ash grey matrix is intersected by broad impact melt veins reaching several centimeters width. These IM veins enclose heavily shocked maskelynite rich clasts indicating a catastrophic collision event that played a major role in the history of Chergach material. The image shows a 22.51g endcut displaying a distinct black impact melt vein separating several clasts in different shock stages Melted NiFe aggregate projecting from the fusion crust of a 440.90g individual of the Chergach fall. The metal shows a gun blue flow lined fusion crust that is partly eroded by the plasma jet stream on the apex. The interesting feature is situated at the bottom of a shallow regmaglypt and measures 12mm at its longest axis 261g individual of the Chergach meteorite. Approx. 100kg of a recent fall in northern Mali have been reported. According to A. Habibi the new material originates from a recent fall at "Chergach" which is the Algerian name for the Erg Chech. The fall occured in July 2007. The Chergach or "Mali" material, as it has been dubbed by some sellers, can be clearly distinguished from e.g. Benguerir, Amgala, Bensour and Bassikounou by comparing broken or cut surfaces. As can be seen in the comparisons above and below Chergach ("Mali") has a dark ash grey color with meandering unevenly distributed blueish areas that often enclose dark grey and light grey patches. The difference in color to Bassikounou which is of brighter, saffron grey is obvious. Chergach ("Mali") is clearly brecciated and shows impact melt clasts embedded in about 5% of the samples studied so far. Chergach ("Mali") shows less black shock veining which is common in Bassikounou samples. Unless the Bassikounou fall did not drop a second hitherto unknown lithology these two are clearly separate events. Matrix comparison of Chergach (left) and Bassikounou (right). The darker lithology of this polished cut section that clearly shows the brecciation of the Chergach material. Photo courtesy of Christian Anger According to other reports the material was supposed to be connected to a fireball sighting in September/October 2006 at the Agerian-Mali border several weeks previous to the Bassikounou event. Not much is known yet on this event either. Eyewitnesses reported a single bolide exploding over the city of Adrar in Algeria and descending in numerous glowing fragments towards Mali territory. However the measuring of short lived radionuclids of the Chergach material determined the fall to July 2007. It can therefore not be connected with the Adrar event but represents a fall of its own. Approx. trajectory of the sept./Oct. 2006 bolide passing the city of Adrar in Algeria towards North Mali. The distance from Adrar to the possible fall site at the Algerian-Mali border is more than 400 miles. In most cases the bright flight of meteroids cover much less distance but a bright trajectory this length would have been not completely unlikely. 21.4gm sample of the Erg Chech meteorite displaying an ash grey matrix and a small number of submilimeter chondrules. The pictured sample contains no obvious shock fractures. NMR scale cube is 1cm each side Return to the "Meteorite Article Archive".     © 2001-2010 NigerMeteoriteRecon