Download or read book Petrogenesis of Compositionally Distinct Silicic Volcanoes in the Three Sisters Region of the Oregon Cascade Range written by Brittain E. Hill and published by . This book was released on 1991 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Three Sisters region of the Oregon High Cascades has developed three compositionally and petrogenetically distinct silicic (i.e., SiO2 [greater than or equal to] 58%) magma systems within the last 600 k.y. These silicic systems evolved from the same High Cascade mafic magma system and developed in the same 20x30 km area of the arc, but did not interact. The Broken Top system (BT) evolved to 71% SiO2 through a combination of plag + px + Fe-Ti oxides ± ap (PPFA) fractionation and 20%-35% mixing of rhyolitic (74% SiO2) crustal melts. In contrast, part of the Three Sisters system (3S) evolved to 66% SiO2 through PPFA fractionation alone, while other parts evolved to 66% SiO2 through PPFA fractionation coupled with [greater than or equal to} 40% mixing of rhyolitic ([greater than or equal to]72% SiO2) crustal melts. The 3S system was intermittently active from [less than or equal to] 340 ka to 2 ka. The petrogenesis of intermediate composition rocks at Middle Sister (340 ka, 100 ka) was controlled by PPFA fractionation to [less than or equal to] 66% SiO2. Rhyolite (72%-76% SiO2) was first erupted in the 3S system at [approximately] 100 ka, at the start of South Sister (SS) volcanism. Major and trace element abundances preclude derivation of 3S rhyolite through crystal fractionation, but are consistent with 20-30% dehydration melting of mafic amphibolite. The petrogenesis of intermediate composition rocks at SS was controlled by PPFA fractionation coupled with 30-40% rhyolitic magma mixing. However, the rhyolitic magma mixed into an essentially mafic system, which limited intermediate differentiation at SS to [less than or equal to] 66% SiO2. The BT system was active from [approximately] 600 ka to at least 200 ka. Major and trace element abundances preclude derivation of BT rhyolite (74% SiO2) through crystal fractionation, but are consistent with [approximately] 30% dehydration melting of older tonalitic intrusions. BT petrogenesis was controlled by PPFA fractionation accompanied by 10-20% mixing of rhyolitic magmas to [approximately] 63% SiO2, with [approximately] 30% rhyolite mixing from 63% to 71% SiO2. In contrast to the 3S system, differentiation proceeded beyond 66% SiO2 because rhyolitic magma was mixed into a more evolved ([approximately] 60%-65% SiO2) system. The observed temporal and spatial variations in petrogenesis were not controlled by regional changes in tectonic setting, crustal thickness or crustal composition. However, small-scale changes in the magnitude of crustal extension occurred in this area, and are thought to have controlled petrogenesis by localizing mid-crustal mafic magmatism and thus crustal heat flow.
Download or read book Quaternary Magmatism in the Cascades written by Wes Hildreth and published by . This book was released on 2007 with total page 148 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 Oregon Geology written by and published by . This book was released on 1992 with total page 306 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Quaternary Period in the United States written by A.R. Gillespie and published by Elsevier. This book was released on 2003-12-17 with total page 595 pages. Available in PDF, EPUB and Kindle. Book excerpt: This book reviews advances in understanding of the past ca. two million years of Earth history - the Quaternary Period - in the United States. It begins with sections on ice and water - as glaciers, permafrost, oceans, rivers, lakes, and aquifers. Six chapters are devoted to the high-latitude Pleistocene ice sheets, to mountain glaciations of the western United States, and to permafrost studies. Other chapters discuss ice-age lakes, caves, sea-level fluctuations, and riverine landscapes. With a chapter on landscape evolution models, the book turns to essays on geologic processes. Two chapters discuss soils and their responses to climate, and wind-blown sediments. Two more describe volcanoes and earthquakes, and the use of Quaternary geology to understand the hazards they pose. The next part of the book is on plants and animals. Five chapters consider the Quaternary history of vegetation in the United States. Other chapters treat forcing functions and vegetation response at different spatial and temporal scales, the role of fire as a catalyst of vegetation change during rapid climate shifts, and the use of tree rings in inferring age and past hydroclimatic conditions. Three chapters address vertebrate paleontology and the extinctions of large mammals at the end of the last glaciation, beetle assemblages and the inferences they permit about past conditions, and the peopling of North America. A final chapter addresses the numerical modeling of Quaternary climates, and the role paleoclimatic studies and climatic modeling has in predicting future response of the Earth's climate system to the changes we have wrought.
Download or read book Dissertation Abstracts International written by and published by . This book was released on 1992 with total page 786 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Petrochemical Evolution of High Cascade Volcanic Rocks in the Three Sisters Region Oregon written by Scott Stevens Hughes and published by . This book was released on 1982 with total page 398 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Early High Cascade Silicic Volcanism written by Daniel W. Eungard and published by . This book was released on 2012 with total page 273 pages. Available in PDF, EPUB and Kindle. Book excerpt: Silicic volcanism in the central Oregon Cascade range has decreased in both the size and frequency of eruptions from its initiation at ~40 Ma to present. The reasons for this reduction in silicic volcanism are poorly constrained. Studies of the petrogenesis of these magmas have the potential for addressing this question by providing insight into the processes responsible for producing and erupting silicic magmas. This study focuses on two extensive and well-preserved ash-flow tuffs from within the ~4-8 Ma Deschutes Formation of central Oregon, which formed after the transition from Western Cascade volcanism to the modern High Cascade. Documentation of outcrop extent, outcrop thickness, clast properties, and samples provide the means to estimate a source location, minimum erupted volumes, and to constrain eruptive processes. Major and trace element chemistry of glass and minerals constrain the petrogenesis and chemical evolution of the system. The tuffs selected for this study, the Lower Bridge and McKenzie Canyon, are the first known silicic units originating from the Cascade Arc following the reorganization from Western Cascade to High Cascade Volcanism at ~8 Ma. These eruptions were significant in producing a minimum of ~5 km3 DRE each within a relatively short timeframe. These tuffs are sourced from some vent or edifices related to the Three Sisters Volcanic Complex, and capture an early phase of the volcanic history of that region. The chemical composition of the tuffs indicates that the Lower Bridge erupted predominately rhyolitic magma with dacitic magma occurring only in small quantities in the latest stage of the eruption while McKenzie Canyon Tuff erupted first as a rhyolite and transitioned to a basaltic andesite with co-mingling and incomplete mixing of the two magma types. Major and trace element concentrations in minerals and glass indicate that the basaltic andesite and rhyolite of the McKenzie Canyon Tuff were well convected and stored in separate chambers. Geothermometry of the magmas indicate that the rhyolites are considerably warmer (~850°) than typical arc rhyolites. Trace element compositions indicate that both the Lower Bridge and McKenzie Canyon Tuff experienced mixing between a mantle derived basaltic melt and a rhyolitic partial melt derived from gabbroic crust. Rhyolites of the Lower Bridge Tuff incorporate 30-50% partial melt following 0->60% fractionation of mantle derived melts. The McKenzie Canyon Tuff incorporates 50-100% of a partial melt of a mafic crust with up to 15% post mixing fractionation. The results of this study suggest that production of voluminous silicic magmas within the Cascade Arc crust requires both fractionation of incoming melts from the mantle together with mixing with partial melts of the crust. This provides a potential explanation for the decrease in silicic melt production rates from the Western Cascades to the High Cascades related to declining subduction rate. As convergence along the Cascade margin became more oblique during the Neogene, the consequent slowing rate of mantle melt production will result in a net cooling of the crust, inhibiting the production of rhyolitic partial melts. Without these partial melts to provide the rhyolitic end member to the system, the system will evolve to the mafic melt and fractionation dominated regime that has existed along Cascadia throughout the Quaternary.
Download or read book Petrography and Petrology of Volcanic Rocks in the Mount Jefferson Area High Cascade Range Oregon written by Robert C. Greene and published by . This book was released on 1968 with total page 60 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Bibliography and Index of Geology written by and published by . This book was released on 1992 with total page 1404 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Deep Crustal and Mantle Inputs to North Sister Volcano Oregon High Cascade Range written by Mariek Schmidt and published by . This book was released on 2005 with total page 394 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Central Oregon High Cascade Range is an anomalously mafic segment of the Cascade Arc due to ongoing intra-arc extension, which allows most magmas to traverse the crust without stalling and evolving to more evolved compositions. North Sister, a composite volcano in this arc segment, has produced a seemingly monotonous basaltic andesite (52.5-54.0% SiO2) that is depleted in incompatible elements from [aprroximately] 320 ka until 15 ka. This dissertation addresses the volcanic development of North Sister Volcano and deep crustal processes that produced its basaltic andesite. Stratigraphic variation signaling changes in eruptive style, unconformable contacts, 40Ar/39 dating, and geochemical correlations divide North Sister's eruptive history into four stages: (1) the early shield, (2) the subglacial stage, (3) the upper shield stage, and (4) the stratocone stage. Lastly, the north-striking,>1 11-km Matthieu Lakes Fissure (MLF) transected North Sister in three splays. North Sister's eruptive stages correspond to four compositional groups that record a general decrease in compatible elements such as Ni (112 to 35 ppm), while incompatible elements are constant or generally decrease (e.g. Ba 302 to 247 ppm) through time. Isotopic variations at North Sister are small, but systematic; Sr and Nd isotopic ratios become more mantle-like with time. Petrologic modeling places the generation of North Sister's basaltic andesite in the deep crust by a) deciphering upper crustal re-equilibration; b) mixing a primitive, low K tholeiite (LKT) with a silicic, Al-rich partial melt of 5-30 million year old crust; and c) high recharge rates by mantle-derived LKTs and interaction with a refractory crust. The Sr and Nd isotopic ratios of primitive basalts from the Cascade Range define four segments of the arc that reflect separate isotopic reservoirs and mantle melting regimes and correlate with major crustal domains. These segments are 1) north, Mt. Meager to Glacier Peak; 2) Columbia, Mt. Rainier to Mt. Jefferson; 3) central, the North Sister to Medicine Lake, and 4) south, Mt. Shasta to Mt. Lassen. The central segment has Basin and Range in the backarc and is the most restricted in bulk and isotopic composition.
Download or read book The Nature and Origin of the Intermediate and Silicic Rocks and Their Mafic Inclusions at South Sister Volcano Central High Cascades written by Jonathan D. Price and published by . This book was released on 1993 with total page 338 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Geology and Petrology of South Sister Volcano High Cascade Range Oregon written by James Gregory Clark and published by . This book was released on 1983 with total page 470 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book A Tale of Three Sisters written by Shaun Andrew Marcott and published by . This book was released on 2005 with total page 184 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book The Origin of Composition Gaps at South Sister Volcano High Cascades Central Oregon written by Scott Travis Dreher and published by . This book was released on 1996 with total page 264 pages. Available in PDF, EPUB and Kindle. Book excerpt:
Download or read book Diverse Mid Miocene Silicic Volcanism Associated with the Yellowstone Newberry Thermal Anomaly written by Matthew E. Brueseke and published by . This book was released on 2008 with total page 18 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Santa Rosa?Calico volcanic field (SC) of northern Nevada is a complex, multi-vent mid-Miocene eruptive complex that formed in response to regional lithospheric extension and flood basalt volcanism. Santa Rosa?Calico volcanism initiated at ~16.7 Ma, concurrent with regional Steens?Columbia River flood basalt activity and is characterized by a complete compositional spectrum of basalt through high-silica rhyolite. To better understand the relationships between upwelling mafic magmatism, coeval extension, and magmatic system development on the Oregon Plateau we have conducted the first comprehensive study of Santa Rosa?Calico silicic volcanism. Detailed stratigraphic-based field sampling and mapping illustrate that silicic activity in this volcanic field was primarily focused along its eastern and western margins. At least five texturally distinct silicic units are found in the western Santa Rosa?Calico volcanic field, including abundant lava flows, near vent deposits, and shallow intrusive bodies. Similar physical features are found in the eastern portion of the volcanic field where four physically distinct units are present. The western and eastern Santa Rosa?Calico units are characterized by abundant macro- and microscopic disequilibrium textures, reflecting a complex petrogenetic history. Additionally, unlike other mid-Miocene Oregon Plateau volcanic fields (e.g. McDermitt), the Santa Rosa?Calico volcanic field is characterized by a paucity of caldera-forming volcanism. Only the Cold Springs tuff, which crops out across the central portion of the volcanic field, was caldera-derived. Major and trace element geochemical variations are present within and between eastern and western Santa Rosa?Calico silicic units and these chemical differences, coupled with the observed disequilibrium textures, illustrate the action of open-system petrogenetic processes and melt derivation from heterogeneous source materials. The processes and styles of Santa Rosa?Calico silicic magmatism are linked to three primary factors, local focusing of and thermal and material contributions from the regional flood basalt event, lithospheric extension within the northern portion of the Northern Nevada rift, and interaction of mid-Miocene silicic magmas with pre-Santa Rosa?Calico lithosphere. Similar processes and styles of mid-Miocene silicic volcanism likely occurred across the Oregon Plateau in regions characterized by both focused lithospheric extension and localized mafic magmatism.
Download or read book Field trip Guide to Mafic Volcanism of the Cascade Range in Central Oregon written by and published by . This book was released on 2017 with total page 94 pages. Available in PDF, EPUB and Kindle. Book excerpt: The Cascade Range in central Oregon has been shaped by tectonics, volcanism, and hydrology, as well as geomorphic forces that include glaciations. As a result of the rich interplay between these forces, mafic volcanism here can have surprising manifestations, which include relatively large tephra footprints and extensive lava flows, as well as water shortages, transportation and agricultural disruption, and forest fires. Although the focus of this multidisciplinary field trip will be on mafic volcanism, we will also look at the hydrology, geomorphology, and ecology of the area, and we will examine how these elements both influence and are influenced by mafic volcanism. We will see mafic volcanic rocks at the Sand Mountain volcanic field and in the Santiam Pass area, at McKenzie Pass, and in the southern Bend region. In addition, this field trip will occur during a total solar eclipse, the first one visible in the United States in more than 25 years (and the first seen in the conterminous United States in more than 37 years). The Cascade Range is the result of subduction of the Juan de Fuca plate underneath the North American plate. This north-south-trending volcanic mountain range is immediately downwind of the Pacific Ocean, a huge source of moisture. As moisture is blown eastward from the Pacific on prevailing winds, it encounters the Cascade Range in Oregon, and the resulting orographic lift and corresponding rain shadow is one of the strongest precipitation gradients in the conterminous United States. We will see how the products of the volcanoes in the central Oregon Cascades have had a profound influence on groundwater flow and, thus, on the distribution of Pacific moisture. We will also see the influence that mafic volcanism has had on landscape evolution, vegetation development, and general hydrology.
