Petrology and geochemistry of Late Cretaceous and Tertiary Epizonal Plutons in the vicinity of Taylor Park, Gunnison, Colorado / by Mark A. Ouimette.
| Author/creator | Ouimette, Mark A., 1955- author. |
| Other author | Lawrence, David P., 1943- degree supervisor. |
| Other author | East Carolina University. Department of Geology. |
| Format | Theses and dissertations |
| Production | 1991. |
| Description | viii, 57 leaves : illustrations ; 28 cm |
| Supplemental Content | Access via ScholarShip |
| Subjects |
| Summary | Petrography, mineral chemistry and geochemistry of eight Late Cretaceous and Tertiary stocks in the vicinity of Taylor Park, eastern Gunnison County, Colorado indicate that they are mildly peraluminous and calc-alkaline. Six are hypabyssal rhyolitic to dacitic porphyries, one is an equigranular granodiorite and one is a microgranular rhyolite. The porphyries are the Hillerton Rhyolite (TCH), Gold Hill Dacite (TGH), Pitkin Rhyolite (TCP), South Matchless Mountain Rhyolite (SMM), Wheelbarrow Gulch Dacite (WG) and Dustin Gulch Dacite (DGD). TGH and DGD have a rhyolite phase along their western contacts. The porphyries have mediumgrained phenocrysts. Quartz phenocryst are embayed, bipyramidal crystals, some with coronas. Plagioclase occurs as zoned and unzoned phenocrysts and monomineralic glomerocrysts. Zoned plagioclase has sodic andesine (An₃₆) cores and calcic oligoclase (An₂₇) margins. Unzoned plagioclase is calcic andesine (An₄₅). Orthoclase phenocrysts are generally subhedral to euhedral Or₍₉₇₋₈₃₎. Hornblende is sparsely distributed, generally euhedral and actinolitic. include euhedral titanite, zircon, magnetite and pyrite. The groundmass is composed of microcrystalline quartz, alkali feldspar and plagioclase. The Seeton Mine Granodiorite (SMG) contains mediumgrained phenocrysts. Euhedral phenocrysts are titanite and actinolitic hornblende. Anhedral phenocrysts are biotite, andesine (An₃₇) , orthoclase (Or₉₀) and quartz. The Buck Gulch stock (BG) is an equigranular microcrystalline rhyolite composed of quartz, sanidine (Or₉₃) and sodic plagioclase (An₉Or₁Ab₉₀) . Medium-grained biotite is sparsely present. DGD yields a K/Ar hornblende date of 76.3 (+/- 1.7) Ma. K/Ar biotite dates are 41.4 (+/- 0.9) Ma for TCH and 39.7 (+/- 0.9) Ma for SMG. The Tertiary stocks probably represent cupolas that extend upward from a buried granitic batholith, inferred on the basis of a gravity low in the area between Tomichi Dome and Italian Mountain. The batholith probably fed stratovolcanoes like those in the San Juan and West Elk Mountains during Oligoc̈ne time. The stocks are comagmatic and their compositions reflect various degrees of mixing and differentiation. |
| General note | Submitted to the faculty of the Department of Geology. |
| General note | Advisor: David P. Lawrence |
| Dissertation note | M.S. East Carolina University 1991 |
| Bibliography note | Includes bibliographical references (leaves 38-42). |
| Genre/form | dissertations. |
| Genre/form | Academic theses. |
| Genre/form | Academic theses. |
| Genre/form | Thèses et écrits académiques. |