Mineralbestand und Strukturen der Graphit- und Sulfideinschlüsse in Eisenmeteoriten
1965; Elsevier BV; Volume: 29; Issue: 10 Linguagem: Inglês
10.1016/0016-7037(65)90116-x
ISSN1872-9533
Autores Tópico(s)Geomagnetism and Paleomagnetism Studies
ResumoDetailed studies of more than fifty nodules from fifteen iron meteorites were performed in reflected light and with the microprobe. They were taken from the meteorites Bethany, Braunau, Canon Diablo, Cape York, Charcas, Corizatillo, Dalgaranga, Delegate. Hoba West, N'Goureyma, Obernkirchen, Odessa, Russel Gulch,Toluca (Xiquipilco) and Trenton. According to the mineralogical composition the following different groups of nodules wore identified: (1) Graphite nodules with traces of sulphides. (2) Graphite-troilite nodules. (3) Troilito nodules devoid of graphite. Graphite nodules are comparatively rare, and composed mainly of graphite together with schreibersite, cohenite and traces of sphalerite. The majority of graphite occurs as idiomorphic or compact cliftonite crystals. No genetical relationship have been found to exist between cliftonite and diamond on the one hand, and cliftonite and iron carbides in the other. A graphite nodule from Cañon Diablo contains besides cliftonite another younger feathery graphite generation. Graphite-troilite nodules are very complicated both in mineralogical composition and textures. In this group the following graphite generations were observed: (a) cliftonite, (b) crescentic graphite similar to "retorte graphite", (c) separate grains preferably oriented // (0001) of troilite, (d) palmetten graphite, (e) small graphite spherulites, (f) big spherules with troilito nuclii. The meteorites Bethany, Braunau and N'Goureyma suffered cosmic heating causing certain changes in the mineralogical composition of their nodules. Mechanical deformation and recrystallization textures due to cosmic collisions and meteorite impacts are described in detail.
Referência(s)