The purpose of this study was to provide both a detailed geochemical analysis of the lithologies that comprise the Glacier Peak volcanic terrain and to summarize the small amounts of past research which has been completed on this Cascade volcano. A broad and extensive literature search indicates this area was previously unstudied in modern petrochemical terms. This study is a detailed petrochemical description and analysis of the mineral phases and the textures present in the various units in the Glacier Peak area (tephra, lava, breccia, and tuff). A scanning electron microprobe study of the scoriaceous basaltic lapilli of the White Chuck cinder cone, indicates that the contemporaneous basaltic cone is comprised of two or more compositional groups. One group is higher in calcium and iron than the other group. These distinct groups, in the lapilli tephra, may imply that the recent cone was built by a multitude of eruptions which variedslightly in composition over time.Through microprobe techniques and computer point-counting methods, the petrochemistry of the Glacier Peak and Gamma Ridge lava flows and the modal distributions of minerals present were determined. The micropobe data was checked for stochiometry and plotted on triangular variation diagrams. Histograms show the distribution along plagioclase binary, solid-solution series (NaAlS13O8 - CaA1Si208). Standard triangular variation diagrams were used to show the composition of the pyroxenes present in the samples (othopyroxene or clinopyroxene). A bimodal distribution of both the pyroxene and the plagioclase exists.The data and observations made in this thesis study, (1) support the sequence of the Glacier Peak magmatic events (i.e., the late Miocene to Pliocene Gamma Ridge hypersthene-augite dacite flows, the Pleistocene Glacier Peak hypersthene dacite flows, and the recent, basaltic, White Chuck cinder cone tephra eruptions), and (2) suggests changing magmatic conditions which would result in the observed disequilibrium features common throughout the Glacier Peak volcanic series (i.e., resorbed and relict crystals, normal and reverse zoning features, cognate clotting and polymodal distribution of plagioclase compositions).Finally, from these observations made on the sequence of the magmatic events of the Glacier Peak series and the conclusions from the analyzed compositions of these volcanic rocks, which suggest changing magmatic conditions, a generalized magmatic model (introduced by Eichelberger, 1977) has been applied to the Glacier Peak series. This model involves injection of basaltic magma into a more silicic magma chamber and results in a hybridized magma. This would be the Glacier Peak magma and would result in the petrological characteristics which imply disequilibrium conditions.
| Identifer | oai:union.ndltd.org:BSU/oai:cardinalscholar.bsu.edu:handle/183169 |
| Date | January 1986 |
| Creators | Calderone, Gina Marie |
| Contributors | Sans, John R. |
| Source Sets | Ball State University |
| Detected Language | English |
| Format | xiii, 255 leaves : ill. ; 28 cm. |
| Source | Virtual Press |
| Coverage | n-us-wa |
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