Geology and 40-argon/39-argon geochronology of the mid-miocene high rock caldera complex, northwest Nevada
Abstract/Contents
- Abstract
- Large igneous provinces are characterized by eruption of > 100,000 cubic km of magma over time scales of less than a few million years. Although most studies of large igneous provinces focus on flood basalt magmatism, there is increasing evidence that voluminous eruptions of silicic ignimbrites and lavas occur contemporaneous with global flood basalt magmatism. Estimated volumes of silicic magma range from 1 to 6% of the volume of coeval flood basalt lavas. Although these volumes are significant, poor preservation has resulted in relatively few detailed geologic investigations of cogenetic silicic deposits in large igneous provinces. In this dissertation, I investigate silicic caldera-forming eruptions that are contemporaneous with eruptions of the youngest and best exposed continental flood basalt province on Earth, the Columbia River flood basalt province, located in the northwestern United States. I present new 40-Argon/39-Argon ages and geologic evidence for silicic volcanism in northwest Nevada and southern Oregon at the High Rock Caldera Complex (HRCC). The HRCC consists of the products of four major overlapping calderas, 24- to 40-km in diameter, which collapsed between 16.4 and 15.7 Ma, shortly after initiation of flood basalt eruptions at Steens Mountain at ca. 16.7 Ma. Regionally, silicic volcanism that was contemporaneous with the peak flood basalt eruption interval between 16.7 and 15.0 Ma was more voluminous and occurred over a wider area than previously recognized. The most voluminous silicic eruptions were early and peralkaline, occurring at HRCC and McDermitt Caldera. The largest calderas are located along a narrow NNE trend near the transition between continental and accreted oceanic crust, and occur peripheral to zones of intense basaltic diking. I present a new model in which flood basalt magmas that intruded along the edge of the western margin of continental North American craton controlled the timing, location, and composition of 16.6 to 15.0 Ma silicic calderas at the HRCC and McDermitt Caldera. I also present evidence for the Steens basalt being the source for peralkaline rhyolite magmatism at the HRCC. These new findings are important because they agree with observations from other large igneous provinces that these massive eruptive events are predominantly bimodal. These observations require modification of models for the initiation of the Snake River Plain-related silicic magmatism.
Description
| Type of resource | text |
|---|---|
| Form | electronic; electronic resource; remote |
| Extent | 1 online resource. |
| Publication date | 2012 |
| Issuance | monographic |
| Language | English |
Creators/Contributors
| Associated with | Coble, Matthew A | |
|---|---|---|
| Associated with | Stanford University, Department of Geological and Environmental Sciences. | |
| Primary advisor | Mahood, Gail A, 1957- | |
| Thesis advisor | Mahood, Gail A, 1957- | |
| Thesis advisor | Grove, Marty, 1958- | |
| Thesis advisor | Miller, Elizabeth | |
| Advisor | Grove, Marty, 1958- | |
| Advisor | Miller, Elizabeth |
Subjects
| Genre | Theses |
|---|
Bibliographic information
| Statement of responsibility | Matthew A. Coble. |
|---|---|
| Note | Submitted to the Department of Geological and Environmental Sciences. |
| Thesis | Ph.D. Stanford University 2012 |
| Location | electronic resource |
Access conditions
- Copyright
- © 2012 by Matthew A. Coble
- License
- This work is licensed under a Creative Commons Attribution Non Commercial 3.0 Unported license (CC BY-NC).
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