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The role of subduction fluids in generating compositionally diverse basalts in the Cascadia subduction zone /Rowe, Michael C. January 1900 (has links)
Thesis (Ph. D.)--Oregon State University, 2006. / Printout. Includes bibliographical references (leaves 224-238). Also available on the World Wide Web.
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Volcaniclastic sedimentation in a caradocian marginal basin, North WalesOrton, Geoff January 1988 (has links)
No description available.
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Reaction phenomena between Karroo Dolerite and cave sandstone xenoliths in the Bird's River complexKenyon, A K January 1976 (has links)
Mapping of the north-eastern portion of the Bird1s River Complex revealed that two large xenoliths composed of pyroclastic rocks and sandstone of the Cave Sandstone Stage have reacted with the dolerite. All the reaction phenomena normally associated with Karroo Dolerite are encountered. These are: (a) Metasomatism during the stage of iron enrichment of the dolerite with the production of a pyroxene-plagioclase metasomatic granophyre (b) Metasomatism during the stage of alkali enrichment of the dolerite with the production of a potassium feldspar adinole C c) Assimilation 'vi th the production of contaminated doleri tes Cd) Fusion 'vi th the production of glassy rocks including buchi tes (e) The production of rheomorphic veins
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A study of two soils derived from volcanic ash in southwestern British Columbia and a review and determination of ash distribution in western CanadaSneddon, J. I. January 1973 (has links)
Four papers are presented in this thesis each one reporting
on studies relating to volcanic ash with special reference to soils. The first paper reviews a) some of the phenomena relating to the ejection and deposition of ash that are important in interpreting the significance of its occurrence, b) the significance of ash layers to workers in the Quaternary, c) the techniques available for the characterization and recognition of tephra, d) the literature on ash deposits in western Canada and compiles the noted occurrences. In addition this paper presents the data from a study to determine the amount of ash retained by soils within and beyond the major areas of deposition indicated in the literature. The presence of ash in soils was found to be widespread though the amounts present may be limited for identification purposes, in some cases. The second paper describes two soils derived from Bridge River volcanic ash and their underlying paleosols and presents selected physical and chemical analyses. The analyses indicate that in the youthful soils studied the physical properties of the ash soils are inherited from the parent material. The colloidal and chemical properties are initially imparted by organic matter with some influence from ash weathering products especially aluminum. Shallow surface additions of volcanic ash
to soils influence soil properties to varying degrees depending on pedogenic environment and depth of material. The third paper evaluates a number of methods that have been used to identify podzolic B horizons and the influence of surface additions of volcanic ash on the podzolic characteristics of soils. Pyrophosphate, pyrophosphate dithionite, citrate dithionite bicarbonate extractions, phosphate sorption capacity and pH-dependent cation exchange capacity determinations all highlighted the podzol B horizons while acid ammonium oxalate extractions and pH determined in NaF did not. The presence of surface additions of Bridge River ash may influence acid ammonium Oxalate or NaF criteria but it was not found to reduce the value of the other diagnostic criteria examined in this study. The final paper studies the amorphous material and clay mineral characteristics of the two aforementioned soils and examines some of the methods of extraction and isolation of clay materials in soils. All of the chemical treatments applied to the soils were found to result in some dissolution of secondary and primary soil materials. The treatments used to extract amorphous materials indicated that the Si to Al ratios of extracted materials was greater than 2. As this value approaches 2 the formation of allophane and imogolite will take place. This situation is indicated as having taken place in isolated capillaries as evidenced by the limited occurrence of imogolite-like material. Chlorite is the dominant clay mineral in the ash soils and is believed to be the weathering product of primary biotite, horneblende and pyroxene. / Land and Food Systems, Faculty of / Graduate
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Petrology, geochemistry and geochronology of Neoproterozoic volcanic rocks of the Punagarh and Sindreth Groups, Rajasthan, northwest IndiaVan Lente, Belinda 28 January 2009 (has links)
M.Sc. / Please refer to full text to view abstract
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CONSTRAINING THE POTENTIAL RESPIRATORY HEALTH HAZARD FROM LARGE VOLCANIC ERUPTIONSTOPRAK, FUNDA O. 05 October 2007 (has links)
No description available.
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Thermal Barrier Coatings Resistant to Glassy DepositsDrexler, Julie 16 December 2011 (has links)
No description available.
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Improving Countermeasure Strategies against Volcanic Ash Risks due to Large Eruptions / 大規模噴火時の火山灰災害に対する対策方法の改善Haris, Rahadianto 25 March 2024 (has links)
京都大学 / 新制・課程博士 / 博士(情報学) / 甲第25434号 / 情博第872号 / 京都大学大学院情報学研究科社会情報学専攻 / (主査)教授 多々納 裕一, 教授 矢守 克也, 教授 井口 正人 / 学位規則第4条第1項該当 / Doctor of Informatics / Kyoto University / DGAM
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The physical volcanology and geochemistry of the Nsuze group, Pongola supergroup, of northern KwaZulu-Natal and southeastern Mpumalanga.Grant, Claire Elizabeth. January 2003 (has links)
The Nsuze Group forms the lower,
predominantly volcanic succession of the
Pongola Supergroup. The 2.9Ga Nsuze Group
outcrops in southeastern Mpumalanga, northern
KwaZulu-Natal and Swaziland. The volcanic
rocks of the Nsuze Group are basalts, basaltic
andesites, andesites, dacites and rhyolites
preserved as both lava and pyroclastic deposits.
The oldest volcanic sequence of the Nsuze Group
is the basaltic Wagondrift Formation. The
younger Bivane Subgroup represents the main
volcanic component of the Nsuze Group. The
White River Section represents a complex
volcanic history of magma storage, fractionation,
and eruption, supplied by a multi-level system of
magma chambers. The basaltic and basaltic
andesite rocks of the White Mfolozi Inlier
represent the steady and non-violent eruption of
lavas from related volcanic centres. The Nsuze
Group rocks have been metamorphosed by high
heat flow burial metamorphism to lower
greenschist facies. Geochemically, elements
display well-defined fractionation trends, with
evident sub-trends within each phase group of
samples. These sub-trends are related to the
fractionation of key minerals, in particular
plagioclase. The REE patterns show that
evolution of magma was largely controlled by
the fractionation of plagioclase. All REE
patterns show LREE enrichment relative to the
HREE. The Wagondrift Formation was derived
from a more depleted source than the younger
Bivane Subgroup volcanic rocks and exhibits a
within-plate tectonic signature. The volcanic
rocks of the Bivane Subgroup in the White River
Section and the White Mfolozi Inlier are
geochemically similar. The volcanic rocks of the
Bivane Subgroup of both the White River
Section and the White Mfolozi Inlier have a
subduction zone tectonic signature, in particular
a Ta-Nb negative anomaly. Tectonic
discrimination diagrams suggest an enriched
source related to a continental-arc setting. The
geochemistry suggests an eclogitic source for the
Nsuze Group volcanic rocks. The formation of
eclogite in the mantle requires subduction of
basaltic material. Archaean models for
subduction-like processes include decoupling of
oceanic crust and subsequent underplating of the
continental lithosphere, and low-angle
subduction which minimises the effect of the
mantle wedge. It is possible that a combination
of these processes resulted in an enriched
eclogitic source for the magmas of the Nsuze
Group. / Thesis (M.Sc.)-University of Natal, Durban, 2003.
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Early high Cascade silicic volcanism : analysis of the McKenzie Canyon and Lower Bridge tuffEungard, Daniel W. 31 July 2012 (has links)
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 km�� 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. / Graduation date: 2013
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