CR7 or Meta-CR
(CR-like in MetBull 86; CR-an in MetBull DB)
Found March 2000
20° 45.8' N., 10° 26.5' E.
A single mass of 3,636 g was found by a German team in the Ténéré region of the Sahara Desert in north-central Niger, specifically, at a location known as Grein. Provisionally named Te-1, it was classified by J. Otto and A. Ruh (Universitat Freiburg) as a metal-rich, coarse-grained, primitive achondrite. Olivine grains are mostly 0.10.4 mm in size, but larger grains occur. They commonly exhibit triple-junctions, consistent with recrystallization. Large poikilitic pyroxene grains are present, as well as small agglomerates of crystals, sometimes called "Sammelkristalle", which usually form during melting and recrystallization processes. Unlike chondrules, these structures are composed primarily of plagioclase poikilitically enclosing minor olivines and pyroxenes, and are often accompanied by FeNi-metal. Te-1 is a freshly fallen meteorite with a weathering grade of W0, and it has a shock stage of S12.
This primitive achondrite has a chemical and mineral composition unlike that of any other meteorite. It has an O-isotopic composition distinct from any other achondrite group, plotting within the CR-field, and interestingly, very near to that of the ungrouped basaltic meteorite NWA 011. Oxygen isotopes are similar to those of the lodranite/acapulcoite parent body but are not an exact match. The mineral composition and noble gas content of Te-1 are very similar to that of the brachinites and the brachinite-like meteorite, Divnoe; moreover, the olivine and pyroxene compositions are nearly identical to those of Brachina. Furthermore, the composition of chromite and metal in Te-1 is also indicative of a very close relationship with Divnoe. These varied characteristics are most consistent with the grouping of Te-1 as a brachinite-like primitive achondrite. See the Tafassasset page for further information.
Te-1 has a CRE age of 45 m.y. The specimen shown above is a 1.72 g partial slice with fresh fusion crust on one end. The photo below shows the main mass of Te-1 with an end slice removed.