Surface manifestations of hydrothermal fluids such as fumaroles and hot springs provide valuable information about the level of activity of a volcano during quiescent period. Geochemical study of gas and spring waters is useful to elaborate geochemical model for magmatic-hydrothermal system. Furthermore, temporal geochemical monitoring of these fluids with time provides a better understanding in processes occurring inside the volcano and can be useful to detect any changes in the activity of the magmatic-hydrothermal system. This thesis investigates two hydrothermal systems at Kelud and Papandayan volcanoes that are located at Java Island in Indonesia. Kelud is considered as one of the most dangerous volcanoes of Java because of its frequent eruptions. After the last eruption that occurred in 1990, a new lake rapidly filled the crater of Kelud volcano. Water samples collected since 1993 are near neutral Na-K chloride fluids and are typical of aged hydrothermal system where the acidity has been completely neutralized by fluid-rock interaction and where the emission of acid magmatic gases has stopped. Two sudden increases in lake temperature in 1996 and 2001 were accompanied by rapid changes in lake water compositions and suggest the existence of two hydrothermal systems feeding the lake: a shallow hydrothermal system dominated by Ca-Mg sulfate waters and a deepest aquifer with neutral alkali chloride waters. From 2001 to 2005, measurements of CO2 emitted by the surface of the lake were performed by using the accumulation chamber method modified in order to work at the surface of a crater lake. Two statistical methods were used to process data: the graphical statistical and stochastic simulation methods. The results of graphical statistical approach showed that two different degassing processes are acting at the lake surface: one corresponding to CO2 fluxes resulting from rising bubbles and the other corresponding to equilibrium diffusion of dissolved CO2 at the water-air surface. Total CO2 emission rate estimated by stochastic simulation ranges from 105 t/day for 2001 to 32 t/day for 2005. Thermal energy released by the lake was also estimated by using an energy balance model with a new constraint using the CO2 flux. The thermal flux decreased from 200 MW (2001) to 100 MW (2002) and then remained stable. Correlation between the chemical data of waters, the fluxes of CO2 and energy show that a constant decrease in the level of activity of the volcano since 1993 occurred although the lake temperature has been stable since 2003. Since the last magmatic eruption that occurred in 1772, phreatic eruptions occur on Papandayan volcano with the last one in 2002. The volcanic material ejected during this eruption is essentially made of altered rocks from within the hydrothermal system. The interaction of acid waters with the host rocks corresponds to an advanced argilic alteration. The chemical compositions of waters from Papandayan volcano and Kelud lake waters are contrasting. Indeed, the spring waters sampled since 1994 are acid sulfate-chloride waters and acid sulfate waters. The chemical and isotopic analyses of gases and waters suggest a significant magmatic contribution in SO2, HCl and HF to the hydrothermal system. The chemical composition of waters sampled after the 2002 eruption have provided information about origin of this eruption. Decrease in chloride concentration and in delta 34S of dissolved sulfates showed that the magmatic contribution in these fluids are less important and that the waters are likely to be formed by the condensation of steam (H2O, H2S) rising from a boiling aquifer.<p><p> / Doctorat en sciences, Spécialisation géologie / info:eu-repo/semantics/nonPublished

La perméabilité est une propriété essentielle notamment pour déterminer la nature explosive des volcans, ainsi que pour de nombreuses autres applications scientifiques et industrielles dans les environnements où l'écoulement du fluide est une préoccupation majeure. Combinant des méthodes expérimentales de déformation des roches en laboratoire, des approches de terrain, de la modélisation numérique, et des analyses systématiques de microstructure, ce travail a mis en évidence le caractère complexe de la formation et la destruction des réseaux poreux dans le magma et des roches volcaniques. La compétition entre les processus dilatants (qui augmentent la porosité) et compactants (qui la diminuent) exerce une influence sur les propriétés de transport des fluides à la fois dans le magma et dans la roche volcanique solidifiée. Ces processus incluent la vésiculation et la croissance des bulles dans le conduit, la rupture et la compression du magma, la fracturation issue du refroidissement et fracturation induite par le transport, ainsi que la déformation pendant ou après la mise en place des matériaux, et la densification par frittage. / The permeability of various volcanic materials is an essential parameter governing the explosive behaviour of volcanic systems, as well as being important in many other scientific and industrial applications in environments where fluid flow is a major concern. Combining experimental rock deformation methods with field measurements, numerical modelling, and systematic analyses of rock microstructure, this work explores the complexities involved in the formation and destruction of porous networks in magma and volcanic rocks, addressing how permeability can evolve in volcanic systems. Competition between dilatant processes (which increase porosity) and compactant processes (which decrease porosity) influences the fluid transport properties both in the conduit-dwelling magma and in solidified edifice rock. These processes include (but are not limited to) vesiculation and bubble growth in the conduit, fracture and compaction of magma, post-emplacement thermal or mechanical fracturing, strain-induced deformation, and viscous sintering.

La réduction du risque volcanique dans les départements ultramarins français s’inscrit dans une réflexion plus globale de gestion visant la caractérisation des enjeux et la diminution de leur vulnérabilité. Les îles de la Guadeloupe, la Martinique et la Réunion sont exposées à une multitude de risques naturels de par leur situation géographique et leur caractère insulaire. S’appuyant sur une approche comparative, aussi bien spatiale que temporelle, cette thèse de géographie propose une analyse des rapports des hommes à leur territoire marqué par la présence d’une menace latente : le volcanisme. Dans cette perspective, le risque est appréhendé, non comme un élément extérieur, mais comme un processus de construction sociale. A partir des scénarios éruptifs envisagés par les experts, ce diagnostic évalue, en amont de toute crise, les connaissances, les représentations et les comportements annoncés des populations exposées au risque. Il envisage les déterminants influents, tels le type de volcanisme, l’histoire éruptive ou l’identité des sociétéscréoles. Recenser les distorsions et cerner les réponses inadaptées permet d’envisager des outils d’information préventive plus efficients. Dans la lignée de travaux s’attachant à des thématiques similaires, cette recherche met en exergue la dimension de la composante humaine au coeur de la gestion des risques qu’on a qualifié un peu trop rapidement de "naturels". Au final, nous pointons les atouts à renforcer, les méconnaissances ou croyances à rectifier et les caractéristiques immuables des sociétés créoles, à prendre en compte pour une gestion de crise volcanique optimisée dans le futur. / Reduction of volcanic risk en the French overseas departments is part of a more global management issues for the evaluation and reduction of their vulnerability. Indeed, the islands of Guadeloupe, Martinique and Reunion are exposed to a multitude of natural hazards due to their geographical location and insular character. This thesis provides an analysis of how humans relate to their environment. It is based on a comparative approach, both spatial and temporal, given thepresence of a latent threat: volcanism. In this perspective, the risk is understood, not as an external element, but as a socially constructed process. Experts are developing scenarios to see how exposed populations may react to volcanic eruptions, asking what the local knowledges, representations, and possible behaviors are - considering key factors, such as the type of eruption, volcanic history, and the identity of Creole societies. Finally, this study, in line with work focusing on similar themes, highlights the human dimension in risk management. It takes into account the strengths and weaknesses, including the unique characteristics of Creole societies, necessary for optimal management of volcanic crisis in the future.

Diploma thesis deals with geological, petrological and geochemical studies of neovolcanic rocks of the SW part of the Most Basin in the area of Tušimice power plant open pit. There are two lava flows affected by coal mining in northern part of the mine. Petrological and geochemical studies with K-Ar dating relatively recent rocks in mostly weatherworn volcanic rocks showed, that they can be classified as Ti-rich basaltic rocks without olivine (tephrites), which belong to the main volcanic phase in the evolution of the Eger graben. It was evidenced geologicaly and with K-Ar dating, that studied rocks were seperated from underlying beda by hiatus which caused erosion of volcanic rocks as well as crystalline bedrock. Mmajor and trace elements composition of co-magmactic volcanics showed that rock were derived from two slightly different sources of upper mantle. Composition of two samples indicates the formation from low degree of partial melting strongly metasomatic asthenospheric mantle. Chemical features of volcanic rocks show that mantle source was comparamble to recent OIB basalts. Last sample arose from less metasomatized and depth distincted mantle which was affected by higher level of partial melting. Melts from which crystallized both rocks were minimaly affected by asimilation or...

This dissertation is a comprehensive summary of four papers on the development and application of new strategies for locating tremor and relocating events in earthquake catalogs. In the first paper, two new strategies for relocating events in a catalog are introduced. The seismicity pattern of an earthquake catalog is often used to delineate seismically active faults. However, the delineation is often hindered by the diffuseness of earthquake locations in the catalog. To reduce the diffuseness and simplify the seismicity pattern, a relocation and a collapsing method are developed and applied. The relocation method uses the catalog event density as an a priori constraint for relocations in a Bayesian inversion. The catalog event density is expressed in terms of the combined probability distribution of all events in the catalog. The collapsing method uses the same catalog density as an attractor for focusing the seismicity in an iterative scheme. These two strategies are applied to an aftershock sequence after a pair of earthquakes which occurred in southwest Iceland, 2008. The seismicity pattern is simplified by application of the methods and the faults of the mainshocks are delineated by the reworked catalog. In the second paper, the spatial distribution of seismicity of the Hengill region, southwest Iceland is analyzed. The relocation and collapsing methods developed in the first paper and a non-linear relocation strategy using empirical traveltime tables are used to process a catalog collected by the Icelandic Meteorological Office. The reworked catalog reproduces details of the spatial distribution of seismicity that independently emerges from relative relocations of a small subset of the catalog events. The processed catalog is then used to estimate the depth to the brittle-ductile transition. The estimates show that in general the northern part of the area, dominated by volcanic processes, has a shallower depth than the southern part, where tectonic deformation predominates. In the third and the fourth papers, two back-projection methods using inter-station cross correlations are proposed for locating tremor sources. For the first method, double correlations, defined as the cross correlations of correlations from two station pairs sharing a common reference station, are back projected. For the second method, the products of correlation envelopes from a group of stations sharing a common reference station are back projected. Back projecting these combinations of correlations, instead of single correlations, suppresses random noise and reduces the strong geometrical signature caused by the station configuration. These two methods are tested with volcanic tremor at Katla volcano, Iceland. The inferred source locations agree with surface observations related to volcanic events which occurred during the tremor period.

La faune des bousiers des hautes montagnes du Mexique a été encore très peu étudiée. Des travaux ponctuels avaient été réalisés pour certaines montagnes, mais une analyse approfondie et simultanée de plusieurs massifs montagneux n'avait jamais été faite auparavant, en particulier avec une double approche, écologique et historique. Les chaînes montagneuses sont des systèmes extrêmement favorables pour analyser les influences biogéographiques et les interactions écologiques dans les assemblages d'espèces. L'objectif de cette thèse est de décrire et d'analyser la distribution et la richesse des Scarabaeinae, Geotrupinae et Aphodiinae de quatre massifs volcaniques dans la partie Est du Système Volcanique Transversal (SVT), qui se trouve dans la Zone de Transition Mexicaine (ZTM). Les zones de transition sont des régions remarquables où différentes lignées évolutives coexistent. Les montagnes échantillonnées sont La Malinche, le Cofre de Perote, le Pico de Orizaba et la Sierra Negra. Il s'agit de volcans situés dans la partie Est du SVT. La Malinche est séparée des trois autres volcans, lesquels présentent une certaine connectivité entre eux. L'importance de notre travail est basée sur le fait qu'il s'agit aussi du premier échantillonnage systématique effectué simultanément au Pico de Orizaba, à la Sierra Negra et à La Malinche, assorti d'une approche écologique et biogéographique. Pour chaque massif, nous avons utilisé trois techniques complémentaires d'échantillonnage : pièges appâtés avec des excréments, une collecte directe dans les stations et l'excavation des terriers des gauphres (rongeurs) pour y trouver les coléoptères associés à leurs déjections. Pour chaque volcan l'échantillonnage a été conduit à deux niveaux d'altitude, aux environ de 2800 m et à environ 3400 m, en prenant en compte les deux versants de chaque montagne, au vent (humide) et sous le vent (sec). L'échantillonnage a été réalisé durant trois années consécutives (2011 à 2013), pendant la saison des pluies (juin, juillet, août). Après la collecte et l'identification des coléoptères, nous avons comparé les affinités biogéographiques des communautés de bousiers de chaque massif. Les différences de composition et d'abondance ont montré que les affinités néarctiques, paléoaméricaines et mésoaméricaines de montagne prédominent dans ces massifs. L'abondance et la richesse étaient maximales aux altitudes moyennes et sur les versants au vent. La colonisation horizontale par les espèces est prédominantepour ces volcans. Plusieurs espèces nouvelles pour la science ont été découvertes grâce à ce travail : trois coléoptères coprophages (un Onthophagus et deux Aphodius), ainsi que six espèces nouvelles d'acariens phorétiques. D'une manière générale, les espèces montagnardes ont une dispersion ensuivant les chaines de montagnes ou l'Altiplano (Haut Plateau). Les espèces d'origine néotropicale présentent une distribution plus large et se trouvent plutôt à plus basse altitude. Quelques espèces avec des affinités pour le Haut Plateau se retrouvent à La Malinche sur le versant sous le vent et à une altitude moyenne. Les résultats ont permis de mieux définir la répartition des genres néarctiques, paléoaméricains et mésoaméricains de montagne dans le SVT, principalement pour les Aphodiinae. Ce travail constitue une base solide pour la connaissance de la distribution de cette faune dans ces massifs montagneux qui n'avaient jamais été étudiés en profondeur au Mexique. / High mountains' dung beetles fauna was still little studied. Punctual works have been done for some mountains, but a deep and simultaneous analysis that includes several mountains has never been done before, especially with a dual approach, ecological and historical. Mountain ranges are extremely favorable systems to analyze biogeographic influences and ecological interactions in species assemblages. This thesis objective is to describe and analyze the richness and distribution of Scarabaeinae, Geotrupinae and Aphodiinae of four volcanoes in the eastern part of the Trans- Mexican Volcanic Belt (TMVB), located in the Mexican Transition Zone (MTZ). Transition zones are remarkable regions where different evolutionary lineages coexist. Sampled mountains are La Malinche, Cofre de PEROTE, Pico de Orizaba and Sierra Negra. These volcanoes are located in the Eastern part of the TMVB. Malinche is separated from the other three mountains which have certain connectivity between them. The importance of our work is based on the fact that it is the first systematic and simultaneous sampling performed at Pico de Orizaba, Sierra Negra and La Malinche, with both an ecological and biogeographic approach. For each mountain, we used three complementary sampling techniques, baited traps with feces, direct collection at each of the stations, and excavation of pocket gopher's burrows, to find the dung beetles associated with their droppings. For each mountain, the sampling was conducted at two altitude levels, one about 2800 meters and another one of about 3400 meters, taking into account both sides of each mountain, windward (wet) and leeward (dry). Sampling was conducted during rainy season (June to August) for three consecutive years (2011-2013). After the collection and identification of beetles, the biogeographic affinities of the dung beetles' communities of each mountain were compared. The differences in composition and abundance showed that the predominant pattern affinities are the Nearctic, Mountain Paleomaerican and Mountain Mesoamerican patterns. Abundance and richness was higher in the middle elevations and in the windward side. Horizontal colonization is predominant in these four volcanoes. Tree new dung beetles' species for science were discovered thanks to this work (one Onthophagus and two Aphodiinae) as well as six phoretic mite new species. In general, montane species have a dispersion following the mountain ranges or the high lands of the High Plateau. Species with a Neotropical affinity were found to have a wider distribution and found instead at the low altitude range. The High Plateau affinity species were found mainly at the leeward side and at the lower altitude range in La Malinche. These results have helped to define the distribution of Nearctic, Montane Paleoamerican and Montane Mesoamerican genera in the SVT, mainly for Aphodiinae. This work provides a solid basis of knowledge of the distribution of this fauna in these four mountains, which had never been studied extensively in Mexico.

La caractérisation granulaire de dépôts hétérométriques organisés en paquets glissés implique une démarche systématique afin d'optimiser l'extraction de données et de les rendre comparables. La quantification des rapports structures-fractions granulaires a permis de mettre en évidence des cinématiques localisées, inscrites dans des cinématiques d'ordre I. Les rides de Tutupaca, le lobe distal du Pichu-Pichu, l'effondrement du Misti au Pérou; la levée latérale du Cheix et le charriage distal de Perrier aux Mt Dore ; les transformations de Meager au Canada, de la Qda San Lazaro au Pérou, de Pardines en France ont été quantifiés. Héritage volcanique, ségrégations granulaires, cataclases syn-tectoniques sont des précurseurs aux modifications matricielles, à l'origine des transformations distales en lahars. Les données ainsi comparées permettent de proposer des classifications sédimentologiques distinguant les effondrements proximaux des transformations par les fluides ( hydrothermaux, eau). Seules quelques équations regroupent l'ensemble de ces dépôts. / The sedimentology of heterogeneous granular deposits, such as debris avalanches deposits require a systematic method to describe and compare data. The relationships between the localized structures and granular distributions show that the localized granular kinematics follow with the larger kinematic structural order. Structures and sedimentology are studied and quantified at the following debris avalanche deposits: the ridged avalanche units at Tutupaca (s. Peru), the distal lobe of the Pichu-Pichu debris avalanche (Arequipa, Peru), a lateral levee of a deposit at Cheix (Sancy volcano, France), a thrusted distal lobe at Perrier (Mt Dore, France). Debris avalanche - lahar transformations are studied at Mt Meager (Canada), Qda San Lazaro (Misti, Peru), Pardines (Mt Dore, France). The inherited granular distribution, the granular segregation, the syn-tectonic cataclasis are precursor stages to the distal matrix transformations. Sedimentological classifications are produced that differentiate the proximal collapse from later transformations caused by fluids (gas, water). Some equations are common for these heterogeneous deposits.

Two mid-Miocene (16.5-15 Ma) rhyolite volcanic centers in eastern Oregon, the Buchanan rhyolite complex and Dooley Mountain rhyolite complex, were investigated to characterize eruptive units through field and laboratory analysis. Results of petrographic and geochemical analysis add to field observations to differentiate and discriminate the eruptive units. Additionally, new geochemical data are used to correlate stratigraphically younger and older basalt and ash-flow tuff units with regional eruptive units to constrain the eruptive periods with modern Ar-Ar age dates. Previous work at the Buchanan rhyolite complex was limited to regional mapping (Piper et al., 1939; Greene et al., 1972) and brief mention of the possibility of multiple eruptive units (Walker, 1979). Observed stratigraphic relationships and geochemical analysis were used to identify eight distinct eruptive units and create a geologic map of their distribution. Slight differences in trace element enrichment are seen in mantle normalized values of Ba, Sr, P, Ti and Nd-Zr-Hf and are used to differentiate eruptive units. New geochemical analyses are used to correlate the overlying Buchanan ash-flow tuff (Brown and McLean, 1980) and two underlying mafic units to the Wildcat Creek ash-flow tuff (~15.9 Ma, Hooper et al., 2002) and flows of the Upper Steens Basalt (~16.57 Ma, Brueseke et al., 2007), respectively, bracketing the eruptive age of the Buchanan rhyolite complex to between ~16.5 and ~15.9 Ma (Brueseke et al., 2007; Hooper et al., 2002). The Dooley Mountain rhyolite complex was thoroughly mapped by the U.S. Geological Survey (Evans, 1992) and geochemically differentiated in a previous Portland State University M.S. thesis (Whitson, 1988); however, discrepancies between published interpretations and field observations necessitated modern geochemical data and revisions to geologic interpretations. Field and laboratory studies indicate that the Dooley Mountain rhyolite complex consists of multiple eruptive units that were effusive domes and flows with associated explosive eruptions subordinate in volume. At least four geochemically distinct eruptive units are described with variations in Ba, Sr, Zr and Nb. Picture Gorge Basalt flows and Dinner Creek Tuff units found within the study area both overlay and underlie the Dooley Mountain rhyolite complex. These stratigraphic relationships are consistent with the one existing Ar-Ar age date 15.59±0.04 Ma (Hess, 2014) for the Dooley rhyolite complex, bracketing the eruptive period between ~16.0 and ~15.2 Ma (Streck et al., 2015; Barry et al., 2013). The findings of this study indicate that the Buchanan rhyolite complex and the Dooley Mountain rhyolite complex are the westernmost and northernmost rhyolite complexes among the earliest (16-16.5 Ma) mid-Miocene rhyolites associated with initiation of Yellowstone hot spot related volcanism.

The ‘giant’ Tambogrande volcanogenic massive sulphide (VMS) deposits within the Cretaceous Lancones basin of northwestern Perú are some of the largest Cu-Zn-Au-Ag-bearing massive sulphide deposits known. Limited research has been done on these deposits, hence the ore forming setting in which they developed and the key criteria that permitted such anomalous accumulation of base-metal sulphides are not understood. Based on field relationships in the host volcanic rocks and U-Pb geochronology, the deposits formed during the early stages of arc development in the latest Early Cretaceous and were related to an extensional and arc-rift phase (~105-100 Ma, phase 1). During this time, bimodal, primitive basalt-dominant volcanic rocks were erupted in a relatively deep marginal basin. Phase 1 rhyolite is tholeiitic, M-type, and considered to have formed from relatively high temperature, small batch magmas. The high heat flow and extensional setting extant during the initial stages of arc development were essential components for forming a VMS hydrothermal system. The subsequent phase 2 (~99-91 Ma) volcanic sequence comprises more evolved mafic rocks and similar, but more depleted, felsic rocks erupted in a relatively shallow marine setting. Phase 2 is interpreted to represent late-stage arc volcanism during a waning extensional regime and marked the transition to contractional tectonism. The Tambogrande deposits are particularly unusual amongst the ‘giant’ class of VMS deposits in that deposition largely occurred as seafloor mound-type and not by replacement of existing strata. Paleomorphology of the local depositional setting was defined by seafloor depressions controlled by syn-volcanic faults and rhyolitic volcanism. The depressions were the main controls on distribution and geometry of the deposits and, due to inherently confined hydrothermal venting, enhanced the efficiency of sulphide deposition. Geochemical and radiogenic isotope data indicate that the rhyolites in the VMS deposits were high temperature partial melts of the juvenile arc crust that had inherited the isotopic signatures of continental crust. Moreover, Pb isotope data suggest the metal budget was sourced almost wholly from mafic volcanic strata. Therefore, unlike the implications of many conventional models, the felsic volcanic rocks at Tambogrande are interpreted to have only played a passive role in VMS formation. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

Lead isotope compositions have been obtained from five major volcanic and intrusive rock suites and several ore deposits on Vancouver Island. Lead, uranium and thorium concentrations and strontium isotope ratios have been obtained for a subset of these samples. The rock suites examined are the Paleozoic Sicker Group, Triassic Karmutsen Formation, Jurassic Island Intrusions and Bonanza Group volcanic rocks, and the Eocene Catface intrusions. Isotope geochemistry of the Sicker Group is consistent with the interpretation that it formed as an island arc. Relatively high 207pb/204pb ratios indicate sediment involvement in the subduction process, which suggests that the Sicker Group formed close to a continent. Buttle Lake ore deposits display decreasingly radiogenic lead isotope ratios with time, suggesting that the associated magmas become increasingly primitive. This supports the hypothesis that these deposits formed during the establishment of rifting in a back-arc environment. Karmutsen Formation flood basalts display isotopic mixing between an ocean island-type mantle source and average crust. Isotopic evidence is used to support a Northern Hemisphere origin for these basalts. Mixing is apparent in the lead and strontium isotope signatures of the Island Intrusions and Bonanza Group volcanic rocks, between depleted mantle and crustal (possibly trench sediments) components. This is consistent with formation of these rocks in an island arc environment. Eocene Catface intrusions have relatively high 207pb/204pb indicating that crustal material was involved in their formation. There are two groups of plutons corresponding to an east belt and west belt classification. Galena from the Zeballos mining camp related to the Eocene Zeballos pluton indicates that the mineralization was derived from the pluton. Galena lead isotope data from Vancouver Island may be interpreted in a general way by comparison with data from deposits elsewhere of known age and origin. No single growth curve model can be applied. Lead isotope characteristics of Vancouver Island are clearly different from those of the North American craton, reflecting the oceanic affinities of this terrane. A new technique has been developed to compare 207pb/204pb ratios between samples with differing 206pb/204pb ratios. The procedure projects 207pb/204pb ratios along suitable isochrons until they intersect a reference value of 206pb/204pb. This technique can be used for interpreting lead isotope data from old terranes, in which lead and uranium may have undergone loss or gain, and if lead and uranium abundances have not been measured. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate