Portland State University. Department of Geology
Date of Award
Master of Science (M.S.) in Geology
1 online resource (ix, 84 pages)
To understand the occurrence and distribution of carbide minerals in ordinary chondrites, thirty meteorites were examined, twenty-eight ordinary chondrites and two iron meteorites. The occurrence of carbide, textures, and chemical compositions were examined in the 7 carbide-bearing meteorites. Two formation methods for carbide have been presented in previous research. These are aqueous alteration and shock heating, and they are examined for validity in this thesis. Additionally, one other formation method for carbide formation through impact and brecciation is put forth and examined. Textural differences between the carbide-magnetite assemblages (CMAs) observed by Krot et al., (1997) and those seen in this study are compared regarding possible evidence for aqueous alteration. Different carbide minerals (haxonite and cohenite) were distinguished using a correction method on linescan data obtained through a scanning election microscope. Cooling rates, formation temperatures, and closure temperatures from carbide associated taenites closely match that of petrographic type 3 material from ordinary chondrites. Carbide is not found in shock melt, and shock blackened areas are less likely to contain carbide. It is unlikely that the heat source that formed carbides exceeded that of petrographic type 3 as too much heat would equilibrate the type 3 material as well as carbide minerals or prevent them from forming.
Farley, Karla Rae, "Distribution and Origin of Carbide in Ordinary Chondrites" (2019). Dissertations and Theses. Paper 5040.