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Thesis (M.S.)--Virginia Polytechnic Institute, 1961. / Vita. Abstract. Includes bibliographical references (leaves 58-59). Also available via the Internet.

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Thermobarometry, detailed petrography, electron microprobe analysis, and fluid inclusion microthermometry were used to quantify the history of a high grade Proterozoic terrane exposed within the northeastern Colorado Front Range. Pressure-temperature calculations identified two blocks from different crustal levels exposed adjacent to one another within the Poudre Canyon west of Fort Collins. They are the eastern, higher pressure, block (HPB; 734 degree C, 7.1 kbar) and the western, lower pressure, block (LPB; 655 degree C, 5.2 kbar). The blocks followed a clockwise uplift path and were juxtaposed by ductile shear near the end of the decompressive stage of uplift. Final assembly of the separate blocks to the same crustal level was constrained by mineralogic and textural considerations and by the isochores of identical low density carbon dioxide inclusions trapped by both blocks. Both blocks experienced peak metamorphism within the sillimanite-K-feldspar zone accompanied by partial melting, are characterized by stromatic migmatites, and show textural evidence for localized reactions related to decompression and cooling. Differences between the blocks include the type of melt-generating reactions and the pronounced late muscovite in the LPB. Gibbs' Method calculations indicate that local (outcrop scale) textural and mineralogical differences between HPB Mg-enriched pelites are caused by small differences in bulk composition and locally variable H2O content. The quartzo-feldspathic biotite gneisses in the LPB generated migmatites by wet melting, whereas the pelitic schists and gneisses in the HPB generated migmatites by dehydration melting of muscovite and biotite. Biotite dehydration melting enriched the leucosomes in HPB pelitic migmatites in K-feldspar and garnet. The minor presence of late muscovite in the HPB relative to the LPB was controlled by the different positions of their uplift paths relative to the muscovite breakdown reaction. / Ph. D.

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The purpose of the present investigation was to undertake a systematic study of cordierite compositions to determine to what extent the ultimate refractoriness and use temperature could be increased by the addition of zirconia without increasing the thermal expansion above 4.0 x 10⁻⁶ cm./cm./°c. A procedure has been presented for making the compound cordierite. Several raw batch compositions which can be expected to produce a high percentage of relatively pure cordierite on a one-fire basis are given. Data are presented tabulating the coefficients of thermal expansion of cordierite specimens containing increasing percentages of zirconia, the thermal shock resistance of these same specimens, the pyrometric cone equivalents of those specimens which possessed expansions lower than 4.0 x 10⁻⁶, and the effect of firing temperature on the absorption and distortion of a specimen possessing the maximum allowable thermal expansion. The results of the investigation indicate that zirconia does not materially extend the short firing range of cordierite compositions and the refractoriness of cordierite is not increased by the addition of zirconia at least in amounts up to 40%. It was found that a 70% cordierite-30% zirconia body could be used at a temperature of 1300°c without warping or undergoing shrinkage. / Master of Science