Download or read book Geology and Petrologic Evolution of the Silicic to Intermediate Volcanic Rocks Underneath Steens Mountain Basalt SE Oregon written by Vera W. Langer and published by . This book was released on 1992 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt: Steens Mountain in SE Oregon is part of the northern Basin and Range Province, and represents a horst tilted about 100 to the west that is bounded to the east by a high angle, NNE trending normal fault. The minimum displacement is about 1200 m. Volcanic rocks, exposed along the eastern escarpment, range from basalt to high-silica rhyolite. By establishing a stratigraphy and determining chemical variations in the volcanic rock sequence underlying Steens Mountain Basalt, it was possible to evaluate the origin of this volcanism and the role of crustal contamination, explain its chemical variation with time, and relate the chemical evolution to extensional processes. The necessary chemical data were obtained by X-ray fluorescence, electron microprobe, and instrumental neutron activation analyses; field mapping provided information about stratigraphy and structure. The oldest units are lake sediments which are overlain by a volcanic rock sequence that proceeded from early rhyolitic tuffs to rhyolitic lava flows, dacites, andesites, and culminated with the eruption of Steens Mountain Basalt (S MB). All stratigraphic units are tilted to the NW or SW to various degrees. Early sediments and rhyolitic tuffs are tilted as much as 25°; whereas younger andesites (15° tilt), and SMB (5-10° tilt) overlie the older units unconformably. The stratigraphy and mapped unconformities indicate that active, volcanic episodes alternated with episodes of erosion and block tilting. Tilting events are thought to be connected to extensional tectonics, and the maximum extension for the Steens Mountain area is estimated to be 30%. Relationships between basalt, andesites, dacites, and rhyolites of the Steens Mountain volcanic suite are complex. Crystal fractionation alone cannot relate the different rocks to each other. Trace element chemistry of intermediate compositions requires fractional crystsllization plus large degrees of assimilation and magma mixing. Magma mixing is also suggested by different plagioclase populations and zoningpatterns in plagioclase and dinopyroxene phenocrysts from intermediate rock compositions. The role of assimilation is greater in the andesites and that of mixing in the dacites. The silicic mixing partner has to be extremely low in rare earth elements. Rhyolites are not directly related to the rest of the suite, but are related to each other by crystal fractionation. They most likely evolved from a partial melt of depleted crust (probably lower crust) by fractionation. Assimilation coupled with fractionation and simple magma mixing are typical magma processes for major metaluminous volcanic suites in the Basin and Range and elsewhere. These processes decrease the density of stagnated basaltic melts and subsequently increase their buoyancy. Extension triggers the ascent of mafic magma, but small amounts of extension alone do not increase the mean crustal density enough for basalts to rise to the surface. Increasing the crustal density by injection of mafic plutons and extension is able to produce a shift in volcanism from intermediate to more basaltic compositions as seen at Steens Mountain, where the influence of crustal material decreases upwards in the volcanic sequence.
Download or read book Oregon Geology written by and published by . This book was released on 1996 with total page 314 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Volcanoes to Vineyards written by Jim E. O'Connor and published by Geological Society of America. This book was released on 2009 with total page 886 pages. Available in PDF, EPUB and Kindle. Book excerpt: "This volume contains guides for 34 geological field trips offered in conjunction with the October 2009 GSA Annual Meeting in Portland, Oregon. Showcasing the region's geological diversity, the peer-reviewed papers included here span topics ranging from accreted terrains and mantle plumes to volcanoes, floods, and vineyard terroir. Locations visited throughout Oregon, Washington, and Idaho encompass Astoria to Zillah. More than just a series of maps, the accompanying descriptions, observations, and conclusions offer new insights to the geologic processes and history of the Pacific Northwest - insights that will inspire readers to put their boots on the evidence as they develop their own understanding of this remarkable and dynamic corner of the world."--Publisher's description.
Download or read book The Columbia River Flood Basalt Province written by Stephen P. Reidel and published by Geological Society of America. This book was released on 2013-09-13 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Miocene Columbia River flood basalt province covers ~210,000 km2 of the Pacific Northwest of the United States, and forms part of a larger volcanic region that also includes contemporaneous silicic centers in northern Nevada, the basaltic and time-transgressive rhyolitic volcanic fields of the Snake River Plain and Yellowstone plateau, and the High Lava Plains of central Oregon. The Columbia River flood basalt province is accessible and well exposed, making it one of the best-studied flood basalt provinces worldwide, and it serves as a model for understanding the stratigraphic development and petrogenesis of large igneous provinces through time. This volume details our current knowledge of the stratigraphy and physical volcanology; extent, volume, and age of the lava flows; the tectonic setting and history of the province; the petrogenesis of the lavas; and hydrogeology of the basalt aquifers.
Download or read book Masters Theses in the Pure and Applied Sciences written by Sade H Shafer and published by Springer Science & Business Media. This book was released on 1995 with total page 440 pages. Available in PDF, EPUB and Kindle. Book excerpt: Cited in Sheehy, Chen, and Hurt . Volume 38 (thesis year 1993) reports a total of 13,787 thesis titles from 22 Canadian and 164 US universities. As in previous volumes, thesis titles are arranged by discipline and by university within each discipline. Any accredited university or college with a grad
Download or read book Revisions to the Cenozoic Stratigraphy of Harney Basin Southeastern Oregon written by George Walton Walker and published by . This book was released on 1979 with total page 46 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geology of Oregon written by Ewart Merlin Baldwin and published by . This book was released on 1976 with total page 168 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Tectonic and Magmatic Evolution of the Snake River Plain Volcanic Province written by Bill Bonnichsen and published by Idaho Geological Survey. This book was released on 2002 with total page 508 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geologic Mapping and Petrochemical Stratigraphy of Southern Warner Valley Southern Oregon USA written by Michelle May Dooley and published by . This book was released on 2010 with total page 192 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Geologic Setting of the John Day Country Grant County Oregon written by Thomas P. Thayer and published by Good Press. This book was released on 2023-10-25 with total page 39 pages. Available in PDF, EPUB and Kindle. Book excerpt: In 'The Geologic Setting of the John Day Country: Grant County, Oregon,' Thomas P. Thayer provides a comprehensive analysis of the geological features of this specific region, exploring the various rock formations, fossil records, and landscape evolution. Thayer's scientific approach is evident throughout the book, as he delves into the intricate details of the geology while making the information accessible to readers of all backgrounds. The book is a valuable resource for geologists, environmental scientists, and anyone interested in the natural history of the area. Thayer's writing style is clear and concise, making it easy for readers to grasp complex geological concepts. Thomas P. Thayer, a renowned geologist with years of field experience, brings a wealth of knowledge to this book. His passion for the subject matter is evident in the meticulous research and attention to detail present in the text. Thayer's expertise in the field makes him a trusted authority on the geology of Grant County, Oregon. I highly recommend 'The Geologic Setting of the John Day Country' to anyone seeking a deeper understanding of the geological history of the region. Thayer's expert analysis and engaging writing style make this book a must-read for scholars, researchers, and nature enthusiasts alike.
Download or read book From Terranes to Terrains written by Adam M. Booth and published by Geological Society of America. This book was released on 2021-11-10 with total page pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Proterozoic Nuna to Pleistocene Megafloods written by Mark D. McFaddan and published by Geological Society of America. This book was released on 2024-05-23 with total page 250 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Colebrooke Schist of Southwestern Oregon and Its Relation to the Tectonic Evolution of the Region written by Robert Griffin Coleman and published by . This book was released on 1972 with total page 458 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geology of Oregon written by Elizabeth L. Orr and published by . This book was released on 1992 with total page 270 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geology and Mineral Deposits of the Coyote Hills Mining District Lake County Oregon written by Thomas Holbeck Thomas and published by . This book was released on 1981 with total page 274 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Coyote Hills are located about 46 kilometers north-northwest of Lakeview, Oregon, within the Basin and Range physiographic province. These hills represent a complex volcanic center of bimodal calc-alkaline igneous activity. The oldest rocks recorded in the Tertiary succession are horn-blende- bearing andesite and aphanitic basalt flows, laharic breccias, conglomerates, tuffaceous sandstones, and lithic wackes of the late Eocene to early Oligocene Lower Andesite formation. During middle to early late Oligocene time, voluminous eruptions of predominately basaltic andesite formed a large shield volcano. This unit, the Upper Basalt formation, was followed, after a short hiatus, by the Coyote Hills rhyolite of late Oligocene to early Miocene age. The Coyote Hills rhyolite represents a complex spectrum of multi-phase silicic volcanism and comagmatic near-surface plutonism. Magma compositions varied from dacite to rhyolite and include lava flows, volcanic plugs, a flow dome complex, and a hypabyssal quartz monzonite intrusion. Volcanic activity that post-dates formation of the bimodal Coyote Hills complex culminated with the lower slopes of the shield volcano onlapped by the middle Miocene Steens Basalt, the late middle to early late Miocene Plush tuff, and the late Miocene to early Pliocene Upper basalt. A prominent northwest and northeast-trending fault and fracture system formed after emplacement of the Coyote Hills rhyolite, and as early as late Oligocene to early Miocene in time. Basin and Range faults post-date the Steens Basalt and have caused some minor displacement of the younger rocks. Penecontemporaneous with silicic volcanism of the Coyote Hills rhyolite was a period of hydrothermal activity. Fluids ascended favorable structures, altered the surrounding country rocks, and deposited minor quantities of epithermal gold-silver-copper-mercury-molybdenum - lead , and zinc in structurally controlled quartz-pyrite veinlets and as disseminations. Because of the association of mineralization with silicic volcanics in time and space, it is concluded that the two processes were genetically related. The hydrothermal system in the Coyote Hills is related to the late stages of silicic volcanism. Evidence for a genetic relation includes the close association of rock type, and chemical and mineral zonations within the district. Geological and geochemical evidence that includes rock type and alteration patterns, and mineral and trace element zonations, collectively suggest that only the highest level of the hydrothermal system has been exposed. It is entirely possible that a large vein or disseminated-type deposit containing both base and precious metals is present at depth.
Download or read book Oregon Geology written by Elizabeth L. Orr and published by . This book was released on 2012 with total page 308 pages. Available in PDF, EPUB and Kindle. Book excerpt: Easy-to-read, rhyming text depicts different animals dancing.
Download or read book The Columbia River Basalt Group in the Spokane Quadrangle Washington Idaho and Montana written by Allan B. Griggs and published by . This book was released on 1976 with total page 54 pages. Available in PDF, EPUB and Kindle. Book excerpt:
