<p> The opening of the Rio Grande Rift of Southern Colorado
resulted in a wide variety of igneous features including the
Spanish Peaks dual stocks, their surrounding radial dyke
system and several proximal enigmatic plugs.</p> <p> Aspects of the crystallization history of two magmas have been studied by using petrographic observations and Crystal Size Distribution (CSD). These were used to examine opaques and feldspars from a rhyolitic dyke in the Spanish
Peaks swarm and augite, olivine, and opaques from a gabbroic
dyke within Huerfano Butte.</p> <p> Augite and opaques from Huerfano Butte reveal a history of no crystal fractionation during emplacement, no size
dependent growth, and constant, continuous nucleation and
growth.</p> <p> Huerfano Butte olivine and Spanish Peaks opaques have
been subjected to resorption and depletion of nucleii. The
resorbed olivine material was probably redeposited as
augite. This could explain why Huerfano Butte augite has a
much higher nucleation density than the other minerals.</p> <p> The phenocrystic feldspars from Spanish Peaks also have a deficit of nucleii, but they lack resorption features. Xenocrystic skeletal feldspars throughout the dyke lack a fines population and show resorption. The absence of fines
is probably due to sorting of grains by density during magma
convection before eruption.</p> / Thesis / Master of Science (MSc)
| Identifer | oai:union.ndltd.org:mcmaster.ca/oai:macsphere.mcmaster.ca:11375/17219 |
| Date | 12 1900 |
| Creators | Durant, Dolores G. |
| Contributors | Clifford, P.M., Geology |
| Source Sets | McMaster University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis |
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