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Scott, Craig Russell. "Physical volcanology, stratigraphy, and lithogeochemistry of an archean volcanic arc : evolution from plume-related volcanism to arc rifting within the SE Abitibi Greenstone Belt, Val d'Or, Quebec, Canada." Thèse, Chicoutimi : Université du Québec à Chicoutimi, 2005. http://theses.uqac.ca.
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Rossouw, Deon. "A technical risk evaluation of the Kantienpan volcanic hosted massive sulphide (VHMS) deposit and its financial viability." Pretoria : [s.n.], 2003. http://upetd.up.ac.za/thesis/available/etd-08132008-094204/.
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Saunders, Katharine Emma. "Micro-analytical studies of the petrogenesis of silicic arc magmas in the Taupo Volcanic Zone and southern Kermadec Arc, New Zealand : a thesis submitted to the Victoria University of Wellington in fulfilment of the requirements for the degree of Doctor of Philosophy in Geology /." ResearchArchive@Victoria e-Thesis, 2009. http://hdl.handle.net/10063/943.
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Ebmeier, Susanna Kathryn. "InSAR measurements of volcano deformation on the Central American Volcanic Arc." Thesis, University of Oxford, 2012. http://ora.ox.ac.uk/objects/uuid:c015fe2a-f4dc-49db-b150-a2ab00ba8f5b.
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Satellite measurements of volcano deformation have the potential to illuminate a wide range of volcanic processes and have provided us with the first opportunity to investigate volcano deformation as an arc-scale process. This thesis presents the results of an Interferometric Synthetic Aperture Radar (InSAR) survey of the Central American Volcanic Arc between 2007 and 2010. My measurements confirm a statistically significant absence of magmatic deformation in Central America relative to other well-studied volcanic arcs. I estimate a minimum detection threshold for deformation at 20 of the arc’s 26 active volcanoes using time series analysis of interferometric phase. I find that the majority (∼80%) of literature measurements of volcano deformation made at other arcs would have been possible with the average magnitude of noise in Central American volcanoes. The absence of measurable magmatic deformation in Central America may therefore be due to factors that limit the geodetic expression of magma movement, including the deep pooling of basalts and high parental melt volatile content. The quantification of measurement uncertainty also allows me to use the lack of deformation at specific erupting volcanoes to make order of magnitude estimations of the minimum depth for magma storage that would not result in measurable deformation. I present measurements and interpretation of non-magmatic deformation associated with edifice development at two Central American volcanoes: Arenal, Costa Rica and Santiaguito, Guatemala. At Arenal, I measure apparently steady slip (∼7 cm/yr) on the volcano’s western flanks, which I attribute to gravity-driven slip on the boundary between lavas emplaced over the past 50 years and older tephras and paleosols. At Santiaguito, I demonstrate the measurement of large-scale (∼10-200 m) topographic change from a small set of large baseline interferograms. Measurements of post-2000 lava fields allow me to estimate extrusion rate, map changes to flow morphology and make simultaneous measurements of lava flow thickness and subsidence rate.
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Hellwig, Bridget M. "The viscosity of dacitic liquids measured at conditions relevant to explosive arc volcanism determing the influence of temperature, silicate composition, and dissolved volatile content /." Diss., Columbia, Mo. : University of Missouri-Columbia, 2006. http://hdl.handle.net/10355/4597.
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Thesis (M.S.)--University of Missouri-Columbia, 2006.The entire dissertation/thesis text is included in the research.pdf file; the official abstract appears in the short.pdf file (which also appears in the research.pdf); a non-technical general description, or public abstract, appears in the public.pdf file. Title from title screen of research.pdf file viewed on (February 7, 2007) Includes bibliographical references.
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NOGUEIRA, LAGES Joao Pedro. "Constrains on mantle, slab and crustal contributions to major volatiles and noble gases along the Andean Volcanic Belt." Doctoral thesis, Università degli Studi di Palermo, 2020. http://hdl.handle.net/10447/395502.
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Berkelhammer, Samuel Ethan. "Initiation of the Wrangell arc: a record of tectonic changes in an arc-transform junction revealed by new geochemistry and geochronology of the ~29–18 Ma Sonya Creek volcanic field, Alaska." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/36236.
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Master of ScienceDepartment of Geology
Matthew E. Brueseke
The Sonya Creek volcanic field (SCVF) contains the oldest in situ magmatic products in the ~29 Ma–modern Wrangell arc (WA) in south-central Alaska. The WA is located within a transition zone between Aleutian subduction to the west and dextral strike-slip tectonics along the Queen Charlotte-Fairweather and Denali-Duke River fault systems to the east. WA magmatism is due to the shallow subduction (11–16°) of the Yakutat microplate. New ⁴⁰Ar/³⁹Ar and U-Pb geochronology of bedrock and modern river sediments shows that SCVF magmatism occurred from ~29–18 Ma. Volcanic units are divided based on field mapping, physical characteristics, geochronology, and new major and trace element geochemistry. A dacite dome yields a ~29 Ma ⁴⁰Ar/³⁹Ar age and was followed by eruptions of basaltic-andesite to dacite lavas and domes (~28–23 Ma Rocker Creek lavas and domes) that record hydrous, subduction-related, calc-alkaline magmatism with an apparent adakite-like component. This was followed by a westward shift to continued subduction-related magmatism without the adakite-like component (e.g., mantle wedge melting), represented by ~23–21 Ma basaltic-andesite to dacite domes and associated diorites (“intermediate domes”). These eruptions were followed by a westward shift in volcanism to anhydrous, transitional, basaltic-andesite to rhyolite lavas of the ~23–18 Ma Sonya Creek shield volcano (Cabin Creek lavas), including a rhyolite ignimbrite unit (~19 Ma Flat Top tuff), recording the influence of local intra-arc extension. The end of SCVF activity was marked by a southward shift in volcanism back to hydrous calc-alkaline lavas at ~22–19 Ma (Young Creek rocks and Border Lavas). SCVF geochemical types are very similar to those from the <5 WA, and no alkaline lavas that characterize the ~18–10 Ma Yukon WA are present. Sr-Nd-Pb-Hf radiogenic isotope data suggest the SCVF data were generated by contamination of a depleted mantle wedge by ~0.2–4% subducted terrigenous sediment, agreeing with geologic evidence from many places along the southern Alaskan margin. Our combined dataset reveals geochemical and spatial transitions through the lifetime of the SCVF, which record changing tectonic processes during the early evolution of the WA. The earliest SCVF phases suggest the initiation of Yakutat microplate subduction. Early SCVF igneous rocks are also chemically similar to hypabyssal intrusive rocks of similar ages that crop out to the west; together these ~29–20 Ma rocks imply that WA initiation occurred over a <100 km belt, ~50–60 km inboard from the modern WA and current loci of arc magmatism that extends from Mt. Drum to Mt. Churchill.
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Underwood, Sandra Jean. "Stable isotope (18 O/16 O and D/H) studies of cascade volcanic arc magmatism." Thesis, Montana State University, 2009. http://etd.lib.montana.edu/etd/2009/underwood/UnderwoodS0509.pdf.
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Dempsey, Scott Robert. "Geochemistry of volcanic rocks from the Sunda Arc." Thesis, Durham University, 2013. http://etheses.dur.ac.uk/6948/.
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Geochemical analyses of igneous rocks can provide valuable information about processes, element fluxes, and rock lithologies not evident at the surface. This is particularly important in subduction zone settings where complex interactions between the subducting plate, mantle wedge and arc crust cannot yet be measured by alternative methods. The Sunda arc, in SE Asia, provides an ideal opportunity to study the effects of subduction in a complex tectonic setting where the basement is poorly exposed and understood. However, in order to do so, magma compositions modified during differentiation in the arc crust must be effectively distinguished from those modified at the source. This study includes a detailed major- and trace element and isotopic (Sr-Nd-Hf-Pb) examination of volcanoes from west Java (Papandayan, Patuha and Galunggung), Central Java (Sumbing), east Java (Kelut) and Bali (Agung), the result of which provides greater insights into petrogenesis both across and along the arc. Contamination in the arc crust is more extensive than previously recognised, particularly in west and central Java where few volcanoes can be used in order to identify subduction and source contributions. In west Java, volcanoes such as Papandayan and Patuha show significant enrichments in isotope ratios above mantle values (e.g. 87Sr/86Sr ~ 0.706, 143Nd/144Nd ~ 0.5125, 208Pb/204Pb ~ 18.91 and 176Hf/177Hf ~ 0.2827) which indicates a terrigneous crustal contaminant. At Sumbing volcano, most magma compositions are similar to those at Merapi and Merbabu, and show strong evidence for the assimilation of carbonate-rich lithologies with some magmas becoming enriched in CaO, Sr and 87Sr/86Sr. Differentiation in volcanoes from east Java and the western part of the Lesser Sunda Islands (Bali, Lombok and Sumbawa) is dominantly controlled by fractional crystallisation, which provides better controls on source compositions. At Kelut, one group of samples show the most ‘depleted’ magma compositions yet discovered on Java, which contain MORB-like values for 143Nd/144Nd and 176Hf/177Hf (0.5130 and 0.2831 respectively). These samples represent the depleted (asthenospheric) mantle and are situated towards the front of the arc in east Java. It is likely that the progressive enrichment further back on the arc (i.e. Leucititic compositions at Ringgit-Besar) include more of an enriched (lithospheric) mantle (SCLM) component derived from the NW margin of Australia during the breakup of Gondwana.
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Morter, Bethany Kathleen. "Understanding the history of a volcanic arc: linking geochemistry of Cenozoic volcanic cobbles from the Wrangell arc, Alaska, to upper plate and subducting slab tectonic processes." Thesis, Kansas State University, 2017. http://hdl.handle.net/2097/38164.
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Master of ScienceDepartment of Geology
Matthew E. Brueseke
The Wrangell arc (WA) is a ~29 Ma magmatic belt, extending from south-central Alaska into the Yukon Territory, that lies above the edges and leading front of the Yakutat microplate, a buoyant oceanic plateau that is causing shallow subduction (11-16º) in the region. The WA occurs in a transition zone between “normal” Aleutian subduction to the west and dextral strike-slip tectonics to the east, accomplished by the Totschunda, Denali, and Duke River faults. This geologic setting offers a chance to study the interrelations between subduction, strike-slip motion, and slab-edge magmatic processes in a relatively well-exposed arc. We implemented a novel technique of applying geochemical and geochronologic analyses on volcanic cobbles collected from glacio-fluvial systems (rivers, streams, and glaciers) encircling/draining the WA. Our primary objective is to integrate our cobble datasets with the existing bedrock and detrital sand records to develop a comprehensive understanding of WA magmatism through time and space. Our secondary objective is to test the validity of this novel technique for reproducing what is documented from bedrock samples and its potential for utilization in other locations. This study provides new major element data from 215 samples and trace element data from 236 samples collected from 17 major rivers that drain from the modern western and central WA (this study excludes the eastern WA). This study also provides new age data from a total of 119 samples from 10 major rivers. New geochronology of modern detrital volcanic cobbles and sand/zircons reveal that the WA initiated at ~29 Ma and that magmatism migrated northwestward through time. Cobble ages and locations across the arc agree with the northwestward progression of magmatism previously identified by Richter et al. (1990). Forty-seven cobbles are dated <~1 Ma and only nine cobbles are dated 29 – ~20 Ma, whereas there are no cobbles from 17 – ~13 Ma. Geochemical data reveal similarities between our data and that of the <~5 Ma WA defined by Preece and Hart (2004): Trend 1 (transitional-tholeiitic), Trend 2a (calc-alkaline), Trend 2b (calc-alkaline, adakite-like). Therefore, we use the geochemical framework defined in Preece and Hart (2004) to contextualize spatio-temporal trends of magmatism and tectonic implications in the WA during its ~29 m.y. history. Trend 2a and 2b cobbles are spatially and temporally ubiquitous in the WA, indicating that subduction and partial slab melting have been the dominant tectonic processes throughout WA history. Trend 1 cobbles are not found in southwestern WA rivers and are temporally restricted to ~11 – ~6 Ma and <1 Ma, suggesting intra-arc extension has occurred in discrete periods during WA history. These conclusions are confirmed by the existing (Richter et al., 1990; Skulski et al., 1991; 1992; Preece and Hart, 2004; Trop et al., 2012) and new (Berkelhammer, 2017; Weber et al., 2017) bedrock records. Finally, this study shows that the sampled cobble lithologies largely reproduce the known bedrock record in geochemical, temporal, and spatial contexts, which suggests the novel methodology applied here can be used in other locations where field conditions limit access to bedrock.
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Morgado, Bravo Eduardo Esteban. "Contrasting records from mantle to surface of holocene lavas of two nearby arc volcanic complexes: Caburgua-Huelemolle small eruptive centers and Villarrica volcano, Southern Chile|." Tesis, Universidad de Chile, 2015. http://repositorio.uchile.cl/handle/2250/135197.
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Magíster en Ciencias, Mención GeologíaGeólogo
La mayor parte de los centros eruptivos menores de los Andes del sur están ubicados sobre la Zona de Falla Liquiñe-Ofqui (ZFLO), una estructura mayor (>1000 km de extensión) de rumbo NS, y cercanos a volcanes mayores: los estratovolcanes. Sin embargo, las relaciones genéticas entre estos dos tipos de volcanismo es, todavía, pobremente conocido. Esta contribución compara parámetros composicionales y condiciones de presión y temperatura pre- y syn-eruptivas entre las lavas basálticas de los Centros Eruptivos Menores Caburgua-Huelemolle (CEMCH) y la lava andesita-basáltica de la erupción de 1971 del Volcán Villarrica, ubicado a 10 km de los CEMCH. Olivinos y clinopiroxenos se encuentran como fenocristales y formando parte de cúmulos cristalinos de las lavas estudiadas. No muestran marcadas diferencias composicionales, excepto por la composición más dispersa de los clinopiroxenos. Los fenocristales de olivino comúnmente tienen inclusiones de Cr-espinelas. Los fenocristales de plagioclasas se encuentran como fenocristales de 0.7 a 2.0 mm de largo o como microlitos en una matriz sin vidrio. Dos grupos de fenocristales de plagioclasa se identificaron en la lava de 1971 basados en el tamaño de los cristales, texturas de desequilibrio y patrones de zonación. Los microlitos de plagioclasa ocupan ~ 85 % del volumen de la masa fundamental. Las temperaturas pre-eruptivas del reservorio tipo CEMCH está entre 1162 y 1165 ± 6 °C y a presiones entre 7.7 y 14.4 kbar, lo que implica la existencia de un reservorio profundo, fueron obtenidas por geotermobarometría en olivino-clinopiroxeno. Probablemente el reservorio se ubica en el límite corteza manto (10 kbar). Además se obtuvieron escalas de tiempo a partir de los patrones de zonación de los cristales de olivino a partir de condiciones inferidas de un reservorio usando MELTS. Las mínimas escalas de tiempo van entre 11.3 y 78 días y solamente pueden ser explicadas por la presencia de al menos un reservorio en la corteza superior, de otro modo el magma en ascenso se solidificaría antes de llegar a la superficie. Los máximos intervalos de tiempo de la formación de la zonación de los cristales de olivino es de 121 días, lo que representaría el máximo tiempo de residencia en el reservorio de la corteza inferior. Por otro lado, los fenocristales de la lava de 1971 del Volcán Villarrica tienen registros de dos etapas o pausas en el ascenso de magma hasta la superficie: 1,208 ±6 °C y 4.6 - 9.8 kbar (reservorio profundo) y 1,168 - 1,175 ±6 °C y ≤ 0.54 kbar (reservorio de poca profundidad). En este último, un calentamiento previo a la erupción de 1971 del Villarrica es grabado en los bordes más anortítitcos de los fenocristales de plagioclasa. Los tiempos de residencia de los CEMCH, de máximo 121 días, son mucho más cortos que aquellos calculados para el Volcán Villarrica, que sería del orden de décadas. La presencia de la ZFLO bajo los centros eruptivos menores facilitaría el ascenso de magmas y disminuiría el tiempo de residencia de los magmas en la corteza.
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Stannard, Carol A. "Pre-eruptive magma storage conditions at the south Aegean volcanic arc." Thesis, University of East Anglia, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.446169.
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Zellmer, Georg F. "Petrogenetic processes and their timescales beneath Santorini, Aegean Volcanic Arc, Greece." Thesis, Open University, 1999. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.266437.
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Parker, Amy L. "InSAR observations of ground deformation : application to the Cascades Volcanic Arc." Thesis, University of Bristol, 2015. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.687433.
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Interferometric synthetic aperture radar (InSAR) observations of ground deformation play a key role in understanding and monitoring volcanic behaviour throughout the eruption cycle. However, the application of InSAR in volcanic environments remains particularly challenging and better ways of detecting and interpreting commonly observed, low-magnitude deformation signals are required. This thesis approaches this problem in the context of the Cascades Volcanic Arc, where 4 volcanoes are known to have subsided in recent years. Using multi temporal InSAR analysis and large-scale atmospheric models, I develop a new strategy to quantify atmospheric uncertainties a priori for real-time arc-wide volcano monitoring, and improve InSAR measurements at 2 volcanoes in the southern Cascades. At Medicine Lake Volcano, I show that steady subsidence continued at ~10 mm/yr between 2004 - 20 II as recorded since the 1950's. At Lassen Volcanic Center, I carry out the first comprehensive geodetic study and identify subsidence that has decreased in magnitude from >13 mm/yr between 2004 - 2007 to ~8 mm/yr between 2007 - 2010. Long-term volcanic subsidence is a common but poorly understood phenomenon at volcanoes globally. Developing a combined geodetic-thermal model, I present a new way to interpret such deformation signals, and show that cooling and crystallisation of small (<3 km3) magma bodies may result in steady subsidence over decadal time-scales. Applying this model to Medicine Lake Volcano suggests that magma intrusion has occurred more recently than the time of the last eruption ~ 1 ka, and that subsidence may continue for decades. This modelling approach presents a physically reasonable and simple way of coupling geodetic and petrological measurements to provide insight into crustal magma fluxes and the timing of magma intrusion.
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Tarlow, Scott. "Three Dimensional Modeling of mantle melt underneath Lau's Back-Arc spreading center and Tofua Volcanic Arc." OpenSIUC, 2014. https://opensiuc.lib.siu.edu/theses/1482.
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Valu Fa and Eastern Lau `s (two regions along Lau's back-arc spreading center) observed axial morphology suggest that Valu Fa is more magmatically robust than Eastern Lau despite Eastern Lau's spreading rate nearly doubling Valu Fa's. Early geochemical [Pearce et al., 1994] and geophysical [Martinez and Taylor, 2002] studies predict a gradational decrease in melting moving north from Valu Fa to Eastern Lau, but more recent geochemical and seismic observations ([Escrig, .et al 2009]; [Dunn and Martinez, 2011]; [Dunn et al., 2011]) show a sharper stepwise decrease in melting as the spreading center's ridge axis sweeps away from the Tofua Volcanic-Arc. As the ridge sweeps away from the volcanic-arc, the influence of the slab hydrated mantle in the melting structure of the ridge decreases. Furthermore, Eastern Lau produces a thinner crust than expected for a robust spreading center. 2-D numerical studies [Harmon and Blackmon, 2010] show a gradational decrease in melting from Valu Fa to Eastern Lau but with no corresponding thinning of Eastern Lau's crust. To understand the melting dynamics underneath Lau's back-arc spreading center and the Tofua Volcanic-Arc implementing the effects of 3-D mantle flow and slab hydration appears to be required. To explain the observed geochemical and seismic observations, three 3-D numerical were performed, using a community developed mantle convection solver (CitcomS). The first model shows that observed geometric and surface kinematic boundary conditions cause a steep gradational increase in relative melting area (anhydrous) moving northward with increasing spreading rate along the ridge axis from Valu Fa to Eastern Lau caused by a northwestern along axis mantle flow. A peak in the relative melting area appears particularly close to Eastern Lau where crust is thinnest. These predictions run in opposition to the observations. The second model shows including a viscosity reduction in the mantle wedge due to slab hydration causes a more subdued relative melting increase with spreading rate and "saddle" shaped decrease in relative melting area north of 20.9°S. This saddle shaped melting structure is caused by a reversal in along axis flow towards the southeast, which takes hot mantle from Eastern Lau and transports it underneath Valu Fa accounting for the anomalously thin crust observed at Eastern Lau. Finally, introducing a hydrated solidus increases the melt production under Valu Fau and causes a stepwise decrease in melt production at Eastern Lau due to its decreased proximity to the slab-hydrated region, consistent with the observed geochemical and seismic studies.
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Hollis, Steven Philip. "Evolution and mineralization of volcanic arc sequences : Tyrone Igneous Complex, Northern Ireland." Thesis, University of Southampton, 2012. https://eprints.soton.ac.uk/359062/.
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The Tyrone Igneous Complex of Northern Ireland forms an integral part of the Grampian-Taconic orogen, linking the well documented sectors of Scotland, western Ireland and Newfoundland. The orogen records the accretion of a series of peri-Laurentian affinity arcs, ophiolites and microcontinental blocks to the Laurentian margin between the Late Cambrian and Middle Ordovician. The Tyrone Igneous Complex is broadly divisible into two distinct units: the c. 484-480 Ma ophiolitic Tyrone Plutonic Group and the structurally overlying c. 475-469 Ma arc-related Tyrone Volcanic Group. Both were intruded by a synvolcanogenic and syncollisional, to postcollisional high-level ensialic intrusive suite between c. 470 and 464 Ma associated with their coeval obduction to an outboard peri-Laurentian microcontinental block, the Tyrone Central Inlier, at c. 470 Ma. The Tyrone Plutonic Group is principally composed of amphibolite-facies layered and isotropic gabbros, sheeted dolerite dykes and rare pillow lavas. Tholeiitic suprasubduction affinity geochemical characteristics, Nd- isotope constraints, zircon inheritance, and the presence of late Fe-Ti enriched post-obduction dykes suggest the Tyrone Plutonic Group formed above a N-dipping subduction zone by the propagation of a spreading centre into a microcontinental block. The Tyrone Volcanic Group is characterized by mafic to intermediate lavas, tuffs, rhyolite, banded chert, ironstone and argillaceous sedimentary rocks cut by numerous high-level synvolcanogenic intrusive rocks. Geochemical signatures are consistent with formation in an evolving peri-Laurentian island-arc which underwent several episodes of rifting. High LILE and LREE enrichment, calc- alkaline geochemical signatures and strongly negative εNd t values suggest the Tyrone arc was at least partially founded on a fragment of microcontinental crust, which may have rifted off the Tyrone Central Inlier during the formation of the Tyrone Plutonic Group. Stong temporal, stratigraphic, and geochemical correlations with elements within the Annieopsquotch Accretionary Tract of Newfoundland suggest the Tyrone Igneous Complex represents a third phase of arc-ophiolite obuction in the Irish Caledonides during the Grampian-Taconic orogeny and may potentially host significant VMS mineralization. Through a combination of field mapping and petrochemistry several stratigraphic horizons have been identified in the Tyrone Igneous Complex, favourable for the formation and preservation of VMS deposits. Each is closely associated with hydrothermal alteration, synvolcanogenic faults and high-level synvolcanogenic intrusions of dolerite, gabbro, diorite and tonalite. Episodic rifting is recorded by the eruption of: abundant non-arc type Fe-Ti enriched eMORB (‘icelandite’), island-arc tholeiite, OIB-like alkali basalt, high-temperature tholeiitic rhyolites with flat to U-shaped REE profiles, and high-Zr rhyolites, within the calc-alkaline dominated sequence. Rift related mafic lavas occur in the hangingwall to VMS-style mineralization and are closely associated with ironstones (often Au-bearing) and/or argillaceous sedimentary rocks representing volcanic quiescence. Extensive hydrothermal alteration, characterized by Na-depletion, high Ba/Sr, Bi, Sb, Ni, CCPI, AI and variable MgO and CaO, allows specific target areas to be identified. In the lower bimodal-mafic Tyrone arc and backarc, hydrothermal alteration is associated with Zn-Cu mineralized float. Pb-Zn-Cu-Au mineralization occurs in silicified auriferous rhyolite domes/flows and/or volcaniclastic rocks of the syncollisional bimodal-felsic upper Tyrone arc. Ophiolite hosted Cu mineralization is characterized by chalcopyrite stringers hosted in sheeted dyke sequences.
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Murray, Natalie A. "Deep Diagenesis in Tephra-Rich Sediments from The Lesser Antilles Volcanic Arc." University of Akron / OhioLINK, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=akron1462881686.
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Blein, Olivier. "Les séquences magmatiques d'arc du Paléozoïque supérieur et Trias du Nevada (Etats-Unis d'Amérique) et de Colombie britannique (Canada) : structure, pétrologie et géochimie : implications dans l'évolution géodynamique des Cordillères nord-américaines et des processus d'accrétion continentale." Phd thesis, Grenoble 1, 1996. http://www.theses.fr/1996GRE10077.
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Le continent nord-américain présente sur sa bordure pacifique un domaine constitué par l'accrétion du Paléozoïque supérieur au Cénozoïque de fragments lithosphériques: les Cordillères nord-américaines. Ces fragments lithosphériques sont caractérisés par des séquences volcaniques d'arc ou de bassin océanique. Les séquences volcaniques d'arc paléozoïques supérieurs et du Trias ont longtemps été considérées comme un seul arc. Depuis une dizaine d'années, des équipes françaises ont montré que les séquences d'arc du Paléozoïque et du Trias des Klamath orientales et de Sierra Nevada (Californie du nord) étaient établies respectivement sur une lithosphère océanique et un bloc continental. Dans le Nevada occidental, les séquences d'arcs du Paléozoïque supérieur affleurent dans deux régions distinctes : Black Rock Desert et Excelsior Mountains. Dans le Black Rock Desert, la séquence permo-triasique de Bilk Creek ressemble en tout point à celle des Klamath orientales et des Blue Mountains. Il s'agit d'un magmatisme d'arc permo-triasique continu, reposant sur des calcaires permiens inférieurs à affinité téthysienne. Ce magmatisme dériverait d'une source mantellique de type-Morb. Dans les excelsior mountains, la formation Black Dyke est constituée de laves et de pyroclastites recouvertes en concordance par des turbidites volcanoclastiques. Cette activité volcanique se produit au Permien inférieur autour de 276 ma. Ce magmatisme d'arc présente de nombreuses similitudes avec celui de Sierra Nevada. Dans les deux cas, il s'agit d'un magmatisme : (i) exclusivement permien ; (ii) caracterisé par des roches volcaniques calco-alcalines ; et (iii) caracterisé par de faibles valeurs d'epsilon Nd#(#t#=#2#7#5#m#a#) comprises entre -1,5 et +5,5. Cet arc est séparé du continent nord-américain par un domaine océanique, le bassin de Golconda. En Sierra Nevada, cet arc paléozoïque est établi sur une séquence sédimentaire du Palézoïque inférieur tectonisée. Les faibles valeurs de l'epsilon Nd#(#t#) des roches magmatiques de Sierra Nevada et des Excelsior Mountains suggèrent que les magmas dérivent d'une source mantellique, contaminée par une vieille croûte continentale, probablement protérozoïque. Ces magmas subissent au cours de leur remontée et leur stockage dans des chambres des assimilations de matériel crustal lors de leur fractionnement et de leur cristallisation. Le Paléozoïque supérieur volcanique et sédimentaire d'arc de Sierra Nevada et des Excelsior Mountains est plissé, puis recouvert en discordance par des sédiments respectivement du Trias ou du Jurassique. Ces déformations et cette discordance sont liées à la phase orogénique Sonoma, induite par la collision de cet arc avec la marge nord-américaine. Après l'accrétion de cet arc, un magmatisme calco-alcalin à shoshonitique se développe au Trias en bordure du craton. Sa diversité reflète des variations dans la nature et l'épaisseur de la croûte qui forme la marge occidentale cratonique américaine et sur laquelle s'édifie cet arc de type andin
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Dissler, Eric. "Evolution geodynamique cadomienne du nord-cotentin (massif armoricain)." Caen, 1987. http://www.theses.fr/1987CAEN2048.
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La structuration actuelle des terrains brioveriens resulte en grande partie de l'evolution tectono-metamorphique varisque. La chaine cadomienne accuse une vergence nord-ouest. L'identification geochimique des series volcaniques brioveriennes revele une affinite tholeitique generalisee. Une tendance calcoalcaline s'exprime en revanche au sein du batholite de la hague. L'enchainement des premieres etapes de l'evolution geodynamique cadomienne est ainsi etablie, le magmatisme du brioverien inferieur traduisant le fonctionnement d'un dispositif arcs insulaires-bassins marginaux de type marge ouest du pacifique, installe sur des lambeaux de croute pentevrienne
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Cafaggi, Sara. "Temporal and geochemical characterization of the Negros de Aras (northern Chile) monogenetic volcanic field." Master's thesis, Alma Mater Studiorum - Università di Bologna, 2021.
Find full textAbstract:
Negros de Aras is a monogenetic volcanic field located in the Central Volcanic Zone of the Andes in northern Chile, 26 km towards the north from active Socompa volcano, at a zone dominated by N-S trending faults. It is formed by lava flows and subordinate scoria cone, dated between < 1.5 and 0.6 ± 0.4 Ma, referable to six formations. Geochemically, lava flows display a range from 54.28 to 64.47 wt.% SiO2, respectively and show a compatible trending of major elements as Fe2O3, TiO2, MgO, whereas K2O and Na2O present an incompatible trending. Trace elements display elevated Sr/Y and La/Yb ratios, high Sr values, depleted Y and HREE values, absence of an Eu anomaly, Nb and Ti negative anomalies, and relative enrichment LILE and LREE. The geochemical features suggest that the magma has fractionated garnet ± amphibole in its origin, with a low degree of contamination during its ascents to the surface. Besides, considering the small-volume magma batches, it is possible to suggest that the magmas did not have any prolonged stopping on the ascent to the surface. The content of volatiles dissolved, and the ascent rate of these magmas played an essential role in the definition and the change of dominant eruptive styles.
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Dufek, Josef D. "The ascent and eruption of arc magmas : a physical examination of the genesis, rates, and dynamics of silicic volcanism /." Thesis, Connect to this title online; UW restricted, 2006. http://hdl.handle.net/1773/6697.
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Tebar, Henry J. "Petrology and geochemistry of volcanic rocks from the Pocdol Mountains, Bicol Arc (Philippines)." Thesis, University of Canterbury. Geology, 1988. http://hdl.handle.net/10092/9408.
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The Pocdol Mountains are part of the Bicol arc-- a SE-trending calcalkaline volcanic belt adjacent to the Philippine Trench. Recent volcano-stratigraphic studies and five new K-Ar ages have delineated seven lithostratigraphic units in the Pocdol Mountains. The rocks are grouped into : (i) a Western Pocdol Mountains (WPM) series, and (ii) an Eastern Pocdol Mountains (EPM) series. WPM eruptives comprise Early Pliocene basaltic tuff breccias and lavas (Malobago volcanics) and Middle to Late Pleistocene (0.478-0.065 Ma) andesitic lavas and tuff breccias (Lison and Kayabon volcanics). EPM volcanism produced (i) Middle Pliocene dacitic tuff breccias and minor lavas and the Matacla Dome (Suminandig volcanics). The stratified unit is intercalated with lenses of siltstones and sandstones (Rangas conglomerate), and was later (0.065 Ma) intruded by the Rangas microdiorite; (ii) Middle Pliocene to Early Pleistocene andesi tic tuff breccias, laharic breccias and lavas (Pangas volcanics), which were erupted mostly from four flank vents, with associated igneous intrusives (Pangas intrusives), and (iii) Late Pleistocene to Recent andesitic lavas, tuff breccias and lahars of the Cawayan volcanics (<0.04 Ma) and basaltic tephras and minor lavas of the Pulog volcanics (<0.03 Ma).
The rocks are plagioclase-phyric, with minor clino- and orthopyroxene, titanomagnetite and hornblende. Olivine is only found in the Malobago volcanics. Glomerophyric and pilotaxitic textures are common, and most phenocrysts show normal or oscillatory zonation. Disequilibrium features are rare. The inferred crystallisation sequence of WPM lavas is titanomagnetite-olivine-pyroxene-amphibole, accompanied by plagioclase. EPM rocks have the same order of crystallisation as WPM lavas, except that olivine was not involved. Overall mineralogy of the lavas suggests a low pressure (<9 kb) crystallisation and estimated equilibration temperatures from coexisting two pyroxenes range from 1006°C to 1135°C. The absence of ilmenite phases precludes an estimate of oxygen fugacity. WPM lavas comprise medium-K high-Al basalt to medium-K and high-K andesite, whereas the EPM rocks consist of low-K basaltic andesite to medium-K andesite and dacite. Major oxide and trace element variations indicate two possible parental liquids, each generating the WPM and EPM series; the EPM lavas also show two fractionation trends : a dacite and an andesite crystallisation paths. WPM lavas generally contain greater abundances of large-ion lithophile (LIL) and high field strength (HFS) ions, but they have lower concentrations of ferromagnesian elements. Low Mg/(Mg+Fe²), Ni and Cr values in both series suggest that the liquids are not in equilibrium with mantle peridotite.
Both WPM and EPM lavas are considered to have been derived by closed-system low pressure POAM fractionation (Gill, 1981) of a basaltic source, that may have been generated by higher degrees of partial melting within the mantle wedge and/or the subducted slab, together with some degree of enrichment from the downgoing slab. Stratigraphic criteria and least-squares mixing models indicate that by precipitating plagioclase, orthopyroxene, titanomagnetite and clinopyroxene, both Lison and Kayabon andesites (WPM series) were probably derived from a high-alumina basaltic source (Malobago volcanics), whereas the Suminandig, Pangas and Cawayan volcanics (EPM series) originate from a low-K basaltic andesite liquid (Pulog volcanics). However, if it is assumed that a dacitic melt was sitting on top of the EPM reservoir, then it is necessary to invoke liquid fractionation (McBirney et al., 1985), whereby the more fractionated liquids move upward and are collected at the roof of the chamber, due to density stratification in the magma reservoir.
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Freymuth, Heye. "The role of the oceanic crust in the genesis of volcanic arc magmas." Thesis, University of Bristol, 2014. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.684749.
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Volcanic arc magmas are usually thought to receive components from three different sources: the subarc mantle, fluids derived from the subducted oceanic crust and lithospheric mantle, and melts derived from subducted sediments. This thesis re-evaluates this model based on isotopic data for magmas from the Izu, New Britain and Mariana arcs. High (230Th/232Th) ratios of up to 2.5 and U excess over Th in samples from the Izu and New Britain arcs are shown to be inconsistent with a derivation from subducted sediments or the sub-arc mantle and are instead argued to reflect a contribution of a melt of the mafic oceanic crust. In addition to Th, the magmas require a number of incompatible elements to be added to the sub-arc mantle. Many of these elements have traditionally been interpreted to be derived from a melt of subducted sediments. Yet, radiogenic Nd and Hf isotopes in these samples do not indicate the presence of a sediment melt. In order to explain this discrepancy, a model is presented in which the component previously identified as sediment melt is a mixture of a sediment melt and a melt of the mafic oceanic crust. Mo isotopes are suggested as a novel tracer for subduction components in volcanic arc magmas and a potential tracer for deep recycling of material transported into the mantle beyond subduction zones. Mo isotope ratios are presented for samples from oceanic sediments, the altered top part of the mafic oceanic crust, and volcanic arc magmas from the Mariana arc, thus defining input and output parameters for a subduction zone. Mo is shown to be preferentially transported in an isotopically distinct fluid derived from the subducted slab. Fluid addition leads to values of 0'98Mo in the Mariana arc lavas ~0.1-0.3 %0 higher than in MORB.
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De, Joux Alexandra. "Cosmos greenstone terrane : insights into an Archaean volcanic arc, associated with komatiite-hosted nickel sulphide mineralisation, from U-Pb dating, volcanic stratigraphy and geochemistry." Thesis, University of Edinburgh, 2014. http://hdl.handle.net/1842/8918.
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The Neoarchaean Agnew-Wiluna greenstone belt (AWB) of the Kalgoorlie Terrane, within the Eastern Goldfields Superterrane (EGS) of the Yilgarn Craton, Western Australia, contains several world-class, komatiite-hosted, nickel-sulphide ore bodies. These are commonly associated with felsic volcanic successions, many of which are considered to have a tonalite-trondhjemite-dacite (TTD) affinity. The Cosmos greenstone sequence lies on the western edge of the AWB and this previously unstudied mineralised volcanic succession contrasts markedly in age, geochemistry, emplacement mechanisms and probable tectonic setting to that of the majority of the AWB and wider EGS. Detailed subsurface mapping has shown that the footwall to the Cosmos mineralised ultramafic sequence consists of an intricate succession of both fragmental and coherent extrusive lithologies, ranging from basaltic andesites through to rhyolites, plus later-formed felsic and basaltic intrusions. The occurrence of thick sequences of amygdaloidal intermediate lavas intercalated with extensive sequences of dacite lapilli tuff, coupled with the absence of marine sediments or hydrovolcanic products, indicates the succession was formed in a subaerial environment. Chemical composition of the non-ultramafic lithologies is typified by a high-K calc-alkaline to shoshonite signature, indicative of formation in a volcanic arc setting. Assimilation-fractional crystallisation modelling has shown that at least two compositionally distinct sources must be invoked to explain the observed basaltic andesite to rhyolite magma suite. High resolution U-Pb dating of several units within the succession underpins stratigraphic relationships established in the field and indicates that the emplacement of the Cosmos succession took place between ~2736 Ma and ~2653 Ma, making it significantly older and longer-lived than most other greenstone successions within the Kalgoorlie Terrane. Extrusive periodic volcanism spanned ~50 Myrs with three cycles of bimodal intermediate/felsic and ultramafic volcanism occurring between ~2736 Ma and ~2685 Ma. Periodic intrusive activity, related to the local granite plutonism, lasted for a further ~32 Myrs or until ~2653 Ma. The Cosmos succession either represents a separate, older terrane in its own right or it has an autochthonous relationship with the AWB but volcanism initiated much earlier in this region than currently considered. Dating of the Cosmos succession has demonstrated that high-resolution geochronology within individual greenstone successions can be achieved and provides more robust platforms for interpreting the evolution of ancient mineralised volcanic successions. The geochemical affinity of the Cosmos succession indicates a subduction zone was operating in the Kalgoorlie Terrane by ~2736 Ma, much earlier than considered in current regional geodynamic models. The Cosmos volcanic succession provides further evidence that plate tectonics was in operation during the Neoarchaean, contrary to some recently proposed tectonic models.
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Stachler, Aris-Edda [Verfasser]. "Das CRISPR-Cas-System von Haloferax volcanii: CRISPRi und Autoimmunität / Aris-Edda Stachler." Ulm : Universität Ulm, 2017. http://d-nb.info/1140118145/34.
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Weller, Jennifer N. "Bayesian Inference In Forecasting Volcanic Hazards: An Example From Armenia." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000485.
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Kiyosugi, Koji. "Temporal and Spatial Analysis of Monogenetic Volcanic Fields." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4101.
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Achieving an understanding of the nature of monogenetic volcanic fields depends on identification of the spatial and temporal patterns of volcanism in these fields, and their relationships to structures mapped in the shallow crust and inferred in the deep crust and mantle through interpretation of geochemical, radiometric and geophysical data.
We investigate the spatial and temporal distributions of volcanism in the Abu Monogenetic Volcano Group, Southwest Japan. E-W elongated volcano distribution, which is identified by a nonparametric kernel method, is found to be consistent with the spatial extent of P-wave velocity anomalies in the lower crust and upper mantle, supporting the idea that the spatial density map of volcanic vents reflects the geometry of a mantle diapir. Estimated basalt supply to the lower crust is constant. This observation and the spatial distribution of volcanic vents suggest stability of magma productivity and essentially constant two-dimensional size of the source mantle diapir.
We mapped conduits, dike segments, and sills in the San Rafael sub-volcanic field, Utah, where the shallowest part of a Pliocene magmatic system is exceptionally well exposed. The distribution of conduits matches the major features of dike distribution, including development of clusters and distribution of outliers. The comparison of San Rafael conduit distribution and the distributions of volcanoes in several recently active volcanic fields supports the use of statistical models, such as nonparametric kernel methods, in probabilistic hazard assessment for distributed volcanism.
We developed a new recurrence rate calculation method that uses a Monte Carlo procedure to better reflect and understand the impact of uncertainties of radiometric age determinations on uncertainty of recurrence rate estimates for volcanic activity in the Abu, Yucca Mountain Region, and Izu-Tobu volcanic fields. Results suggest that the recurrence rates of volcanic fields can change by more than one order of magnitude on time scales of several hundred thousand to several million years. This suggests that magma generation rate beneath volcanic fields may change over these time scales. Also, recurrence rate varies more than one order of magnitude between these volcanic fields, consistent with the idea that distributed volcanism may be influenced by both the rate of magma generation and the potential for dike interaction during ascent.
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Handley, Heather K. "Geochemical and Sr-Nd-Hf-O isotopic constraints on volcanic petrogenesis at the Sunda Arc, Indonesia." Thesis, Durham University, 2006. http://etheses.dur.ac.uk/2670/.
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The Sunda island arc of Indonesia formed as a result of the northward subduction of the Indo- Australian Plate beneath the Eurasian Plate. Along-arc variations in the composition and thickness of the overriding Eurasian plate and variation in the type and amount of sediment deposited on the subducting plate create differential effects on Sunda arc lava geochemistry. Detailed study of volcanic rocks from Salak, Gede Volcanic Complex (GVC) in West Java and Ijen Volcanic Complex (IVC) in East Java was carried out in order to establish the relative importance and contributions of various potential source components and composition-modifying processes at individual volcanic centres, prior to investigating petrogenetic variation along the arc. Differentiation processes play a major role in modifying the geochemical composition of Sunda arc magmas. However, the relative importance and traceable impact of the different processes varies at each volcanic centre. Fractional crystallisation of a typical Javan island arc mineral assemblage exerts the largest control on major and trace element composition of the volcanic rocks. Distinct intra-volcanic complex differentiation trends at rvc and Salak are spatially controlled and are explained by independent conduits and multiple magma reservoirs at different depths in the crust - linked to sub-volcanic structure. Shallow level contamination by typical upper-crustal continental material is insignificant during magmatic differentiation at Salak, GVC and IVC. However, at Salak there is some evidence for assimilation of material similar in composition to the volcanic rocks. Deep fractionation of a phase in which HFSE and HREE are compatible (e.g. amphibole) is inferred in the evolution of most Javan magmas. Magmatism at Salak, GVC and IVC is the product of shallow, relatively homogeneous, fertile, Indian Ocean MORB-like mantle that has been enriched by slab- derived component(s) sourced from the altered oceanic crust and subducted sediment. Hf and Nd isotope ratios of Javan lavas show that the subducted sedimentary source component is heterogeneous and reflects spatial variations in sediment compositions on the down-going plate along the Java Trench. A progressive eastward increase in Sr isotope ratio of volcanic rocks across West and Central Java broadly correlates with inferred lithospheric thickness. A significant change in crustal architecture (i.e. thickness) occurs between Central and East Java. This transition may represent the south-eastern boundary of Sundaland (pre-Tertiary arc basement).
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Holbik, Sven P. "Arc Crust-Magma Interaction in the Andean Southern Volcanic Zone from Thermobarometry, Mineral Composition, Radiogenic Isotope and Rare Earth Element Systematics of the Azufre-Planchon-Peteroa Volcanic Complex, Chile." FIU Digital Commons, 2014. http://digitalcommons.fiu.edu/etd/1524.
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The Andean Southern Volcanic Zone (SVZ) is a vast and complex continental arc that has been studied extensively to provide an understanding of arc-magma genesis, the origin and chemical evolution of the continental crust, and geochemical compositions of volcanic products. The present study focuses on distinguishing the magma/sub-arc crustal interaction of eruptive products from the Azufre-Planchon-Peteroa (APP 35°15’S) volcanic center and other major centers in the Central SVZ (CSVZ 37°S - 42°S), Transitional SVZ (TSVZ 34.3-37.0°S), and Northern SVZ (NSVZ 33°S - 34°30’S). New Hf and Nd isotopic and trace element data for SVZ centers are consistent with former studies that these magmas experienced variable depths of crystal fractionation, and that crustal assimilation is restricted to the lower crustal depths with an apparent role of garnet. Thermobarometric calculations applied to magma compositions constrain the depth of magma separation from mantle sources in all segments of the SVZ to(70-90 km). Magmatic separation at the APP complex occurs at an average depth of ~50 km which is confined to the mantle lithosphere and the base of the crust suggesting localized thermal abrasion both reservoirs. Thermobarometric calculations indicate that CSVZ primary magmas arise from a similar average depth of (~54 km) which confines magma separation to the asthenospheric mantle. The northwards along-arc Sr-Nd-Hf isotopic data and LREE enrichment accompanied with HREE depletion of SVZ mafic magmas correlates well with northward increasing crustal thickness and decreasing primary melt separation from mantle source regions indicating an increased involvement of lower crustal components in SVZ magma petrogenesis.
The study concludes that the development of mature subduction zones over millions of years of continuous magmatism requires that mafic arc derived melts stagnate at lower crustal levels due to density similarities and emplace at lower crustal depths. Basaltic underplating creates localized hot zone environments below major magmatic centers. These regions of high temperature/partial melting, and equilibration with underplated mafic rocks provides the mechanism that controls trace element and isotopic variability of primary magmas of the TSVZ and NSVZ from their baseline CSVZ-like precursors.
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Kraus, Stefan. "Magmatic dyke systems of the South Shetland Islands volcanic arc (West Antarctica) reflections of the geodynamic history /." Diss., [S.l.] : [s.n.], 2005. http://edoc.ub.uni-muenchen.de/archive/00003827/.
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Shimoda, Hajime. "Origin of the Setouchi Volcanic Rocks in SW Japan Arc : Constraints from Pb-Nd-Sr Isotope Geochemistry." Kyoto University, 1996. http://hdl.handle.net/2433/160842.
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本文データは平成22年度国立国会図書館の学位論文(博士)のデジタル化実施により作成された画像ファイルを基にpdf変換したものであるKyoto University (京都大学)
0048
新制・課程博士
博士(人間・環境学)
甲第6565号
人博第10号
8||105(吉田南総合図書館)
新制||人||3(附属図書館)
UT51-96-W409
京都大学大学院人間・環境学研究科人間・環境学専攻
(主査)教授 石坂 恭一, 教授 堀 智孝, 教授 巽 好幸
学位規則第4条第1項該当
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Paulson, Benjamin D. DeBari Susan M. "Magmatic processes in the Jurassic Bonanza arc : insights from the Alberni region of Vancouver Island, Canada /." Online version, 2010. http://content.wwu.edu/cdm4/item_viewer.php?CISOROOT=/theses&CISOPTR=331&CISOBOX=1&REC=3.
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Petriello, John A. Jr. "Thicknesses and Density-Current Velocities of a Low-Aspect Ratio Ignimbrite at the Pululagua Volcanic Complex, Ecuador, Derived from Ground Penetrating Radar." Scholar Commons, 2007. http://scholarcommons.usf.edu/etd/3819.
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The thinning trend of a low-aspect ratio ignimbrite (LARI) in a direction of increasing topographic relief at the Pululagua Volcanic Complex, Ecuador, is established by correlating continuous ground penetrating radar (GPR) profiles and radar reflector behavior with stratigraphic measurements and unit behavior. Minimum density-current and vertical (cross-sectional) velocity analyses of the LARIs parent pyroclastic density-current are performed by analyzing the exchange of kinetic energy for potential energy in an upslope direction. Continuous GPR profiles were acquired in a direction of increasing topographic relief with the intent of identifying the LARI within the GPR record and examining the relationships between the LARI and the underlying paleo-topographical surface. Stratigraphic measurements recorded throughout the field area demonstrate that the LARI thins 7.5 m in an upslope direction (over 480 m distance and 95 m elevation). Stratigraphic measurements enable correlations with GPR profiles, resulting in LARI identification. By utilizing GPR derived paleo-topographical surface elevations, minimum flow velocities of the LARI-producing parent pyroclastic density-current at the base of upslope flow are shown to be at least 25 m/s. Vertical velocity analyses based on the identification of internal GPR reflectors, interpreted as flow streamlines, yield pyroclastic surge-like cross-sectional velocity profiles of the LARIs parent density-current. Maximum density-current velocities at the base of upslope flow reach 24 m/s and diminish toward the base of the current.
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Leonard, Michelle. "Vent-Fault Spatial Study of Selected Volcanic Fields of Southwestern North America and Mexico." Scholar Commons, 2012. http://scholarcommons.usf.edu/etd/4125.
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Of fundamental concern in volcanic hazard and risk assessment studies of volcanic systems is what role crustal structures might play in the ascent of magma through the crust. What are the processes that govern the spatial distribution and timing of eruptions, especially in populated areas or near sensitive facilities? Many studies have drawn the conclusion that faults play a critical role as easily–exploitable crustal weaknesses along which magma can ascend. Great care must be used when assuming a causative relationship between patterns of vents and faults especially when such relationships may be incorporated into hazard assessment models or other forecasting tools. This thesis presents a quantitative analysis of vent and fault populations in seven actively–faulted volcanic fields to test whether or not spatial relationships exist between faults and volcanic features. The data generated in this study include map distances acquired by measuring existing geologic maps produced by other scientists. Statistical methods were adapted from a similar study by Paterson and Schmidt (1999) which involved the analysis of pluton–to–fault distances. The data show that statistical spatial correlations exist between vents and faults in only two of the seven volcanic fields in this study. As a general observation, most vents cluster far from faults in these populations, which could be explained by a variety of natural phenomenon such as suppression of faulting from increased magmatism and magma source geometry differences. Although data some of the data show a spatial correlation, it does not necessarily imply a genetic relationship.
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Hannon, Jeffrey S. "Reconstructing the Generation, Evolution, and Migration of Arc Magmatism using the Whole-rock Geochemistry of Bentonites: A Case Study from the Cretaceous Idaho-Farallon Arc System." University of Cincinnati / OhioLINK, 2020. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1613745220524224.
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Sowerbutts, Alison A. "Coeval extension, sedimentation and arc-volcanism along the Oligo-Miocene Sardinian Rift." Thesis, University of Edinburgh, 1997. http://hdl.handle.net/1842/14461.
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The Oligo-Miocene Sardinian Rift is an intra-arc basin which formed in response to multiphase extension and transtension on several orientations of normal and strike-slip faults. Rifting occurred during and after the separation and rotation of the Corsica-Sardinia microplate from Eurasia, coeval with northwestward dipping subduction of Neotethyan oceanic crust beneath the islands. The Sardinian rift comprises many semi-independent sub-basins which are filled with complex arrangements of non-marine and marine, siliciclastic, carbonate and marlstone sediments plus subduction-derived extrusive and pyroclastic volcanic rocks. Exposures in the Sardinian Rift provide a rare opportunity to study the evolution of, and processes active within intra-arc and back-arc basins. Field observations from along the Oligo-Miocene Sardinian Rift are presented and placed within a new chronostratigraphic framework. A tectono-stratigraphic synthesis of the Sardinian Rift has implications for the Oligo-Miocene tectonic development of the Western Mediterranean and for extensional settings in general. Geochemical analysis of volcanic-arc rocks provides clues as to what happens at depth when continental arc magmatism and extension are combined. Rifting commenced in the mid-late Oligocene, coeval with the eruption of the first volcanic-arc rocks, whilst the Sardinia-Corsica microplate was attached to Eurasia. The resultant proto-Sardinian rift formed with considerable along-strike variability. It consisted of a N-S segment in northern Sardinia which was cross-cut by NE-SW trending, elongate transtensional sub-basins. In southern Sardinia, the main rift segment was oriented NW-SE with separate E-W trending grabens dissecting the southernmost pre-rift basement. Geometries within continental clastic sediments shed from local topographic highs and basinward lacustrine limestones suggest that the first phase of extension was short-lived (
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Heydolph, Ken [Verfasser]. "Spatial variations in the geochemistry of arc volcanism in Central America / Ken Heydolph." Kiel : Universitätsbibliothek Kiel, 2010. http://d-nb.info/1019983507/34.
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van, Alderwerelt Brennan Martin Edelman de Roo. "Diverse monogenetic volcanism across the main arc of the central Andes, northern Chile." Diss., University of Iowa, 2017. https://ir.uiowa.edu/etd/5668.
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Instances of fault-controlled monogenetic volcanism across the subduction arc of the Central Andes at ~ 23°S illuminate the nature of different parental melts being delivered to the crust. Evidence of magmatic history is preserved in bulk rock geochemistry, the content of melt inclusions, and mineral compositions. Volcanism in this region is dominated by felsic and intermediates lavas as the thickened crust (55 – 65 km) and vast volumes (> 500,000 km3) of mid-crustal magma beneath the Altiplano-Puna high plateau region prevent mafic magmas from reaching the surface (Davidson & De Silva, 1991; Beck et al., 1996; Perkins et al., 2016). However, small volumes of relatively undifferentiated lava have been delivered from the lower crust to the surface along zones of crustal weakness without extensive processing by crustal assimilation and/or extended storage in sub-volcanic magma chambers. Monogenetic eruptions of less-differentiated lava provide important constraints on compositions normally obscured by crustal processing in the Central Andes.
Basaltic andesite sampled within the frontal arc (Cerro Overo maar) is a regional mafic end-member and approximates the composition of parental arc magmas derived from partially-molten lower crustal regions where mantle-derived magmas interact with the surrounding lithosphere and undergo density differentiation (MASH zones). Basaltic olivine-hosted melt inclusions from Cerro Overo provide a glimpse of less-evolved melt composition from this region and suggest mobilization of MASH magma by injection of basaltic melt. Basaltic andesite sampled from the eastern (back) margin of the frontal arc (Puntas Negras – El Laco) is another regional mafic endmember, representing a mantle-derived magma composition that is transitional between subduction arc magmatism and intraplate magmatism of the back-arc. The internal crystal architecture revealed by major and trace element zoning of olivine phenocrysts indicates Cerro Overo magma experienced continuous ascent, while Puntas Negras magma experienced a brief period of stalling or storage near the brittle-ductile transition zone (~ 25 km). Aphyric intermediate monogenetic lavas sampled west of (before) the frontal arc display Adakite-like signatures (e.g. high Sr/Y and Sm/Yb) represent small amounts of melt generated with a significant contribution from direct melting of the metabasaltic slab or delaminated lithospheric root at high pressure. These three magmatic regimes sampled at monogenetic centers approximate different end-member compositions being delivered to the lower crust of the Central Andes from which the range of intermediate main arc volcanism in the Altiplano-Puna region is ultimately derived.
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Kilgore, Wayne Walter. "Seismic and Geodetic Investigation of the 1996-1998 Earthquake Swarm at Strandline Lake, Alaska." Scholar Commons, 2010. https://scholarcommons.usf.edu/etd/1681.
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Microearthquake (< M3.0) swarms occur frequently in volcanic environments, but do not always culminate in an eruption. Such non-eruptive swarms may be caused by stresses induced by magma intrusion, hydrothermal fluid circulation, or regional tectonic processes, such as slow-slip earthquakes. Strandline Lake, located 30 km northeast of Mount Spurr volcano in south-central Alaska, experienced an intense earthquake swarm between August 1996 and August 1998. The Alaska Volcano Observatory (AVO) catalog indicates that a total of 2,999 earthquakes were detected during the swarm period, with a maximum magnitude of Mw 3.1 and a depth range of 0-30 km below sea level (with the majority of catalog hypocenters located between 5-10 km BSL). The cumulative seismic moment of the swarm was 2.03e15 N-m, equivalent to a cumulative magnitude of Mw 4.2. Because of the swarm's distance from the nearest Holocene volcanic vent, seismic monitoring was poor and gas and GPS data do not exist for the swarm period. However, combined waveforms from a dense seismic network on Mount Spurr and from several regional seismic stations allow reanalysis of the swarm earthquakes. I first developed a new 1-D velocity model for the Strandline Lake region by re-picking and inverting precise arrival times for 27 large Strandline Lake earthquakes. The new velocity model reduced the average RMS for these earthquakes from 0.16 to 0.11s, and the average horizontal and vertical location errors from 3.3 to 2.5 km and 4.7 to 3.0 km, respectively. Depths of the 27 earthquakes ranged from 10.5 to 22.1 km with an average depth of 16.6 km. A moderately high b-value of 1.33 was determined for the swarm period, possibly indicative of magmatic activity. However, a similarly high b-value of 1.25 was calculated for the background period. 28 well-constrained fault plane solutions for both swarm and background earthquakes indicate a diverse mixture of strike-slip, dip-slip, and reverse faulting beneath Strandline Lake. Finally, five Interferometric Synthetic Aperture Radar (InSAR) images spanning the swarm period unambiguously show no evidence of surface deformation. While a shallow volcanic intrusion appears to be an unlikely cause of the Strandline Lake swarm based on the new well-constrained earthquake depths and the absence of strong surface deformation, the depth range of 10.5 to 22.1 km BSL for relocated earthquakes and the high degree of FPS heterogeneity for this swarm are similar to an earthquake swarm beneath Lake Tahoe, California in 2003 caused by a deep intrusion near the base of the crust (Smith et al, 2004). This similarity suggests that a deep crustal magmatic intrusion could have occurred beneath the Strandline Lake area in 1996-1998 and may have been responsible for the resulting microearthquake activity.
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Watson, Thomas LaPoint Dennis John. "Volcanism and sedimentation new insight into arc-related volcanism and sediment deposition in a synkinematic Paleoproterozoic basin, Rosebel Gold Mine, northeastern Suriname /." Chapel Hill, N.C. : University of North Carolina at Chapel Hill, 2008. http://dc.lib.unc.edu/u?/etd,1565.
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Thesis (M.S.)--University of North Carolina at Chapel Hill, 2008.Title from electronic title page (viewed Sep. 16, 2008). "... in partial fulfillment of the requirements for the degree of Master of Science in the Department of Geological Sciences." Discipline: Geology; Department/School: Geological Sciences.
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Tormey, Daniel Richard. "Geology and geochemistry of the active Azufre-Planchon-Peteroa volcanic center (351̊5' S, southern Andes) : implications for Cordilleran arc magmatism." Thesis, Massachusetts Institute of Technology, 1989. http://hdl.handle.net/1721.1/39953.
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Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Sciences, 1989.Includes bibliographical references (v. 2, leaves 314-331).
by Daniel Richard Tormey.
Ph.D.
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Hintz, Amanda Rachelle. "Physical Volcanology and Hazard Analysis of a Young Monogenetic Volcanic Field: Black Rock Desert, Utah." [Tampa, Fla] : University of South Florida, 2008. http://purl.fcla.edu/usf/dc/et/SFE0002716.
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Thomas, Kelly Jean. "Volcanology and petrology of submarine volcanoes of the New Hebrides island arc." Thesis, Queensland University of Technology, 2011. https://eprints.qut.edu.au/45480/1/Kelly_Thomas_Thesis.pdf.
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The New Hebrides Island Arc, an intra-oceanic island chain in the southwest Pacific, is formed by subduction of the Indo-Australian Plate beneath the Pacific Plate. The southern end of the New Hebrides Island Arc is an ideal location to study the magmatic and tectonic interaction of an emerging island arc as this part of the island chain is less than 3 million years old. A tectonically complex island arc, it exhibits a change in relative subduction rate from ~12cm/yr to 6 cm/yr before transitioning to a left-lateral strike slip zone at its southern end. Two submarine volcanic fields, Gemini-Oscostar and Volsmar, occur at this transition from normal arc subduction to sinistral strike slip movement. Multi-beam bathymetry and dredge samples collected during the 2004 CoTroVE cruise onboard the RV Southern Surveyor help define the relationship between magmatism and tectonics, and the source for these two submarine volcanic fields. Gemini-Oscostar volcanic field (GOVF), dominated by northwest-oriented normal faults, has mature polygenetic stratovolcanoes with evidence for explosive subaqueous eruptions and homogeneous monogenetic scoria cones. Volsmar volcanic field (VVF), located 30 km south of GOVF, exhibits a conjugate set of northwest and eastwest-oriented normal faults, with two polygenetic stratovolcanoes and numerous monogenetic scoria cones. A deep water caldera provides evidence for explosive eruptions at 1500m below sea level in the VVF. Both volcanic fields are dominated by low-K island arc tholeiites and basaltic andesites with calcalkalic andesite and dacite being found only in the GOVF. Geochemical signatures of both volcanic fields continue the along-arc trend of decreasing K2O with both volcanic fields being similar to the New Hebrides central chain lavas. Lavas from both fields display a slight depletion in high field strength elements and heavy rare earth elements, and slight enrichments in large-ion lithophile elements and light rare earth elements with respect to N-MORB mantle. Sr and Nd isotope data correlate with heavy rare earth and high field strength element data to show that both fields are derived from depleted mantle. Pb isotopes define Pacific MORB mantle sources and are consistent with isotopic variation along the New Hebrides Island Arc. Pb isotopes show no evidence for sediment contamination; the subduction component enrichment is therefore a slab-derived enrichment. There is a subtle spatial variation in source chemistry which sees a northerly trend of decreasing enrichment of slab-derived fluids.
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Villa, Contardo Víctor Alejandro. "Morfología de estructuras volcánicas cenozoicas de los Andes Centrales entre los 25° y 26° S, Chile." Tesis, Universidad de Chile, 2013. http://www.repositorio.uchile.cl/handle/2250/114119.
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GeólogoA partir de la observación de imágenes satelitales y de la utilización de modelos de elevación digital (ASTER GDEM con resolución de 30 m) se determinan parámetros morfométricos de edificios volcánicos (altura absoluta, volumen, área basal y de la cima, diámetros basal y de cima, pendientes promedio y máxima) y razones entre estos parámetros (razón de aspecto y entre este valor versus diámetro cima/diámetro basal) para los 6 conjuntos de volcanes definidos entre los paralelos 25º y 26º S, el meridiano 69ºW, y la frontera entre Chile y Argentina, unidades que representan la evolución del arco volcánico en la zona, en el lapso Oligoceno Holoceno. Existen diferencias morfométricas en valores de altura absoluta y volumen de los conjuntos de volcanes 3 y 4 (Mioceno medio a superior y Mioceno superior Plioceno inferior, respectivamente): mientras el Conjunto Volcánico 3 exhibe una población importante de volcanes compuestos relativamente mayores en la zona, el Conjunto Volcánico 4 presenta una población considerable de conos simples y volcanes compuestos de menor tamaño. Estas diferencias podrían tener relación con la profundidad, duración y distribución de las cámaras magmáticas en cada conjunto. Por otro lado, es posible establecer una secuencia evolutiva para las morfologías volcánicas: a partir de conos simples de <0,1 km3, se desarrollan conos de mayor tamaño (por crecimiento a través de un solo centro de emisión), volcanes compuestos (por colapsos de conos simples y volcanes compuestos, y por migraciones en los centros de emisión). Cuando los procesos migratorios en una zona particular persisten en el tiempo, ocurren complejos volcánicos, que representan la máxima evolución de las morfologías volcánicas en la zona. Las tres morfologías se observan generalmente bien preservadas en todos los conjuntos volcánicos, lo que evidencia que los colapsos volcánicos son el principal proceso de degradación de volcanes en la zona desde hace 25 Ma. Se identifican 7 edificios volcánicos en la zona con depósitos de avalanchas asociados. El origen de estos colapsos es en general mixto (volcánico y tectónico) para los volcanes colapsados, lo que implica una posible latencia de las cámaras magmáticas durante el crecimiento y destrucción de estos volcanes.
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Weaver, Stephanie, and Stephanie Weaver. "Mantle Heterogeneity and the Origins of Primitive Arc Lavas: An Experimental Study with a Focus on the Trans-Mexican Volcanic Belt." Thesis, University of Oregon, 2012. http://hdl.handle.net/1794/12547.
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Primitive, mantle-derived magmas provide important clues about the formation and equilibration conditions of magmas at depth. In subduction zones, it is uncommon for primitive magmas to ascend through the shallow mantle and crust without undergoing chemical modification. Instead, magmas commonly differentiate through fractional crystallization, crustal assimilation, or magma mixing. Those rare primitive lavas that do erupt along a volcanic arc are useful for elucidating subduction-related processes within the mantle wedge (~30–80 km depth) and are the focus of this research.
I used piston-cylinder apparatuses to investigate the high-pressure, high-temperature, H2O-undersaturated phase equilibria for several primitive compositions that have erupted at volcanic arcs. I aimed to reveal the permissible residual mantle mineralogy, as well as the P-T- H2O conditions over which the putative mantle melts last equilibrated before erupting. My work focuses on the Trans-Mexican Volcanic Belt (TMVB), where primitive compositions span a range of SiO2, total alkalies (K2O+Na2O), magmatic H2O, and incompatible trace element enrichments. Variations among these components are presumed to result from melting heterogeneous mantle that has been affected, to varying degrees, by a subduction component. Chapter III focuses on the phase equilibria of a Mexican basaltic andesite and an Aleutian basalt. Results show that hydrous basaltic andesite equilibrated with harzburgite in the shallow mantle, whereas the basalt equilibrated with lherzolite. The former appears more common in continental arcs and the latter in intraoceanic arcs. Chapter IV focuses on two alkaline lavas of varying K2O content from the TMVB that are transitional between potassic, hydrous minette and H2O-poor intraplate alkali basalt. Experimental phase relations and trace element modeling reveals that melting and/or mixing of peridotite and clinopyroxene-rich veins are likely involved in producing these transitional lava types.
These experimental data are integrated with other petrologic and geophysical data to provide an along-arc perspective of mantle-melt equilibration in the TMVB. Primitive melts appear to commonly equilibrate with chemically heterogeneous mantle at depths above the "hot nose" of the mantle wedge. It is apparent that the shallow mantle wedge is a key component for understanding the geochemical complexities of subduction zone magmas.
This dissertation includes previously published and unpublished co-authored material.
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Jacques, Guillaume [Verfasser]. "Causes of along- and across-arc geochemical variations in the Southern Volcanic Zone (33°-43°S) in Chile and Argentina / Guillaume Jacques." Kiel : Universitätsbibliothek Kiel, 2017. http://d-nb.info/1138979899/34.
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Heath, Emily. "Genesis and evolution of calc-alkaline magmas at Soufriere volcano, St Vincent, Lesser Antilles arc." Thesis, Lancaster University, 1997. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.360643.
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Soufriere of St. Vincent is the most active subaerial volcano in the Lesser Antilles arc, and is composed of basalts and basaltic andesites. Eruptive style has tended to alternate between predominantly effusive and explosive, although magma compositions show no systematic variations with time. New Ar-Ar and 14C dates help to constrain the geological evolution of the (- 0.6 Ma) volcano. Parental, possibly primary, magmas at Soufriere had MgO contents exceeding 12 wt.% (mg# 75) and were probably nepheline-normative. They may be representative of the parental magmas of the calc-alkaline suites of the Lesser Antilles arc. The source mantle probably resembled that of N-MORB, prior to metasomatic enrichment by hydrous slab-derived fluids, containing contributions from subducted sediments and oceanic crust. Parental magmas last equilibrated with the mantle at - 17 kbar pressure, with temperatures greater than 1130·C and f02 exceeding FMQ +1. Near-primary basaltic lavas were only erupted during the earliest (Pre-Somma) phase of volcanism. Basaltic andesites (and occasional andesites) were produced by fractionation of 01 + spinel + cpx + plag ± opx over a range of crustal pressures (5-10kbar), at temperatures mainly in the range 1000 - 1l00·C. The total amount of crystallization was some 76 wt. %, and amphibole was apparently not a fractionating phase. There is conflicting evidence as to the pre-eruptive water contents of Soufriere magmas; phenocryst compositions suggest H20 > 3 wt. %, whereas various projections into phase diagrams are more consistent with relatively anhydrous magmas. Magma mixing did not apparently play a significant role in the evolution of most Soufriere magmas, and fractional crystallization was not accompanied by crustal assimilation, judging from trace element and Sr-Nd isotope systematics. New U-Th mineral isochrons suggest that magmas resided for tens of thousands of years within the crust, which requires rather stable thermodynamic conditions in the magma chamber(s) beneath Soufriere.
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Martin, Kristin Terese. "Limitations of the Advection-Diffusion Equation for Modeling Tephra Fallout: 1992 Eruption of Cerro Negro Volcano, Nicaragua." [Tampa, Fla.] : University of South Florida, 2004. http://purl.fcla.edu/fcla/etd/SFE0000581.
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Billur, Basak. "Geology And Petrology Of Beypazari Granitoids: Yassikaya Sector." Master's thesis, METU, 2004. http://etd.lib.metu.edu.tr/upload/12605577/index.pdf.
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Beypazari Granitoid is a low temperature and shallow-seated batholite intruded the Tepeköy metamorphic rocks of the Central Sakarya Terrane. Composition of the granitoid varies from granite to diorite. The granitoid is unconformably overlain by Palaeocene and Eocene rock units. Thus the age is probably Late Cretaceous. The Beypazari Granitoid comprises mafic microgranular enclaves. The granitoid mainly consists of quartz, plagioclase, orthoclase and minor amphibole, biotite, chlorite, zircon, sphene, apatite, and opaque minerals. Plagioclase shows sericitation whereas biotite and hornblende, chloritization. Holocrystalline and hypidiomorphic are characteristic textures of the granitoid. Geochemically, the Beypazari Granitoid is calc-alkaline, metaluminous and I-type. REE data indicate that it may have been generated from a source similar to the upper continental crust. The trace element data of the Beypazari Granitoid suggest a volcanic arc tectonic setting. The possible mechanism of Beypazari granitoid is the northdipping subduction of Neo-Tethyan northern branch under Sakarya continent during Late Cretaceous. The Beypazari Granitoid may be related with Galatean volcanic arc granitoids.
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Aravena, Noemí Diego José. "Balance comparativo de volumen de edificios volcanicos en la zona volcánica sur." Tesis, Universidad de Chile, 2016. http://repositorio.uchile.cl/handle/2250/143707.
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Magíster en Ciencias, Mención GeologíaEn el margen occidental de Sudamérica desde los 33º S hasta los 46º S, ocurre una subducción oblicua dextral entre la placa de nazca y la placa sudamericana. Esta configuración tiene como resultado una cadena volcánica de 1.900 km de largo, contexto ideal para el desarrollo de sistemas geotermales de tipo volcánico. El objetivo principal de este estudio es identificar correlaciones entre propiedades volcanológicas y geotermales del arco activo en la ZVS. Para esto, se analizan las características volcanológicas, geotérmicas y estructurales del arco volcánico activo con énfasis en un balance volumétrico de los edificios volcánicos, los que son utilizados para inferir tasas de flujo magmático bajo el arco activo. Adicionalmente, se miden propiedades físico-termales de las principales unidades geológicas que componen el basamento y relleno de la cuenca de Cura-Mallín entre los 37.5º y 38.5º S; incluyendo densidad, conductividad termal y producción de calor radiogénico. Tras este análisis se realiza una modelación numérica de la estructura termal bajo el arco activo. En base al balance volumétrico y el análisis de características geoquímicas y tectónicas del arco se definen 8 segmentos, los que indican tasas de flujo magmático regional de 2 a 8 (km3/km/Ma). Se distinguen dos tendencias respecto a la proporción de material explosivo versus efusivo: (1) Depósitos de toba, ignimbritas y cenizas de composición basáltica a riolítica que son generalmente menores a un 30% del volumen del edificio volcánico actual, (2) tobas e ignimbritas de composición dacítica a riolítica cuyo volumen cuadruplica el de los edificios volcánicos actuales. Este comportamiento bimodal de la proporción extrusivo/efusivo es consistente con evidencia que sugiere que son necesarios dos tipos de flujo magmático para la ocurrencia de grandes erupciones volcánicas: (1) de largo plazo y regional (más profundo), con magnitudes del orden de 0.0002 a 0.0003 [km3/ka], similar a tasas de emplazamiento estimadas para plutones de volumen menor a 100 ka, y (2) episódicos y localizados, con magnitudes que superan al menos en un orden a las de largo plazo y se asemejan a tasas de emplazamiento calculadas para intrusivos de más de 100 km3. La estructura termal modelada en la corteza a los 38º S es consistente con la ocurrencia de anomalías geofísicas que sugieren la ocurrencia de magmatismo a 25-35 km de profundidad. La geometría de la corteza continental y la conductividad termo-dependiente cumplen un rol fundamental en la distribución de temperaturas en la corteza inferior. En la corteza superior, la generación de calor radiogénico incrementa el flujo calórico hasta en un 30%, lo que sumado a la generación de calor en zonas de falla puede dar lugar a fusión parcial de corteza.