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  • About
  • The Global ETD Search service is a free service for researchers to find electronic theses and dissertations. This service is provided by the Networked Digital Library of Theses and Dissertations.
    Our metadata is collected from universities around the world. If you manage a university/consortium/country archive and want to be added, details can be found on the NDLTD website.
41

Population Genetic Structure of the Lesser Long-nosed Bat (Leptonycteris yerbabuenae) in Arizona and Mexico

Ramirez, Judith January 2011 (has links)
The Leptonycteris yerbabuenae is found in southern Arizona, Mexico, Guatemala, and El Salvador. Some females are migratory, mating in southern Mexico, and migrating to maternity roosts in northern Mexico and southern Arizona to give birth. Twelve microsatellite loci markers and the Mitochondrial DNA Control Region (CR) were amplified to examine population structure and phylogenetic relationships among roosts. Twelve polymorphic microsatellite loci were isolated from L. yerbabuenae. A total of sixteen localities in AZ and Mexico were sampled. The mtDNA CR fragment resulted in 102 haplotypes. The phylogenetic analyses resulted in two clades, but no observable geographic structuring. The average FST value across all loci and all sampled localities was 0.022. Program STRUCTURE analyses indicate one population (K=1) throughout the sampling area. These results suggest movement between maternity colonies and transient roosts in Arizona, Sonora, and Chamela, Management recommendations based on these results would be to manage as a single population.
42

Processus d’obduction : quelle ampleur, quelle durée, quelle (s) cause (s) ? Le cas de la branche nord de la Néotéthys en Anatolie et Petit Caucase (Turquie, Arménie) / The obduction process : how big, for how long, why ? The study of the northern branch of Neotethys in NE Anatolia and the Lesser Caucasus (Turkey, Armenia)

Hässig, Marc 24 June 2014 (has links)
Dans de nombreuses chaînes de montagnes, on observe des témoins du processus d’obduction, correspondant au transport de la lithosphère océanique sur la croûte continentale. Le paradoxe intrinsèque de ce phénomène est celui-ci : des roches denses (ρ>3) se retrouvent au-dessus de roches moins denses (ρ≈2,7). Les processus à l’origine de cette bizarrerie tectonique sont encore mal compris. Les ophiolites du Petit Caucase et du NE de l’Anatolie correspondent à un exemple extrême de ce phénomène puisqu’on constate un transport de fragments de lithosphère océanique sur plusieurs centaines de kilomètres, à l’échelle de l’ensemble d’une bordure continentale (>1000 km) vers 90 Ma. En adoptant une stratégie pluridisciplinaire lors de l’étude de ces ophiolites, nous avons pu préciser l’évolution des premiers stades de la fermeture néotéthysienne et en conséquence l’obduction de ces dernières. Ces données suggèrent fortement une mise en place commune de l’ensemble de ces corps ophiolitiques de la région d’étude sous la forme d’une nappe, dont l’épaisseur actuelle est très réduite (quelques kilomètres tout au plus). Ceci en fait l’une des plus grandes nappes ophiolitiques obduites du globe. La modélisation numérique a validé l’hypothèse que la mise en place de cette nappe s’est faite grâce à des conditions thermiques particulières. Elle suggère que l’obduction d’ophiolites vieilles nécessite un état thermique de la lithosphère océanique proche de celui d’une lithosphère jeune (0-40 Ma). / Within many mountain ranges slivers of preserved oceanic lithosphere evidence tectonic processes responsible for their emplacement on top of the continental crust. The first order anomaly inherent to this phenomenon is that dense rocks (ρ>3) end up on top of less dense rocks (ρ≈2.7). The processes responsible for such a tectonic oddity remain uncertain. The ophiolites of the Lesser Caucasus and NE Anatolia are prime examples of this phenomenon, tectonic transport of fragments of oceanic lithosphere is evidenced on the entire continental marge (>1000 km) around 90 Ma. The multidisciplinary approach used throughout the study of the ophiolites of the Lesser Caucasus and NE Anatolian regions yielded clues specify the evolution of the Tethys and consequently the obduction of the ophiolites. This dataset strongly suggests common emplacement of the ophiolites of the study area, resembling a thrust sheet. This would be one of the biggest ophiolite nappe complexes in the world. Numerical modeling validates the hypothesis that emplacement of the ophiolitic nappe is due to particular thermal conditions. It suggests that in order to obduct old oceanic lithosphere obduction it needs to have a thermal state close to that of young oceanic lithosphere (0-40 km). Such a thermal rejuvenation is supposed for the ophiolites of the Caucasus s.l. evidenced by alkaline lavas emplaced on the ophiolite prior to the obduction event during the Late Cretaceous. Resulting seamounts and/or oceanic plateaus upon entery of the subduction zone under Eurasia would block it.
43

Fractures, Faults, and Hydrothermal Systems of Puna, Hawaii, and Montserrat, Lesser Antilles

Kenedi, Catherine Lewis January 2010 (has links)
<p>The focus of this work is to use geologic and geophysical methods to better understand the faults and fracture systems at Puna, in southeastern Hawaii, and southern Montserrat, in the Lesser Antilles. The particular interest is understanding and locating the deep fracture networks that are necessary for fluid circulation in hydrothermal systems. The dissertation first presents a study in which identification of large scale faulting places Montserrat into a tectonic context. Then follow studies of Puna and Montserrat that focus on faults and fractures of the deep hydrothermal systems.</p><p>The first chapter consists of the results of the SEA-CALIPSO experiment seismic reflection data, recorded on a 48 channel streamer with the active source as a 2600 in3 airgun. This chapter discusses volcaniclastic debris fans off the east coast of Montserrat and faults off the west coast. The work places Montserrat in a transtensional environment (influenced by oblique subduction) as well as in a complex local stress regime. One conclusion is that the stress regime is inconsistent with the larger arc due to the influence of local magmatism and stress.</p><p>The second chapter is a seismic study of the Puna hydrothermal system (PHS) along the Kilauea Lower East Rift Zone. The PHS occurs at a left step in the rift, where a fracture network has been formed between fault segments. It is a productive geothermal field, extracting steam and reinjecting cooled, condensed fluids. A network of eight borehole seismometers recorded >6000 earthquakes. Most of the earthquakes are very small (< M.2), and shallow (1-3 km depth), likely the result of hydrothermal fluid reinjection. Deeper earthquakes occur along the rift as well as along the south-dipping fault plane that originates from the rift zone.</p><p>Seismic methods applied to the PHS data set, after the initial recording, picking, and locating earthquakes, include a tomographic inversion of the P-wave first arrival data. This model indicates a high seismic velocity under the field that is thought to be an intrusion and the heat source of the hydrothermal system. A shear wave splitting study suggested the PHS fracture system is largely oriented rift-parallel with some orthogonal fractures. Shear wave splitting data also were used in a tomographic inversion for fracture density. The fracture density is high in the PHS, which indicates high permeability and potential for extensive fluid circulation. This has been confirmed by high fluid flow and energy generation. The high fracture density is consistent with the interpretation of a transfer zone between the rift segments where a fracture mesh would be expected. In Puna the transfer zone is a relay ramp.</p><p>The results from the PHS are used as an example to examine the proposed hydrothermal system at St. George's Hill, Montserrat. In southern Montserrat, hot springs and fumaroles suggest a deep hydrothermal system heated by local magmatism. A magnetotelluric study obtained resistivity data that suggest focused alteration under southeastern Montserrat that is likely to be along fault segments. Several faults intersect under SGH, making it the probable center of the hydrothermal system. At Puna, and also Krafla, Iceland, where faults interact is an area of increased permeability, acting as a model to be applied to southern Montserrat. The conclusion is that in both Puna and Montserrat large faults interact to produce local areas of stress transfer that lead to fracturing and permeable networks; these networks allow for high-temperature hydrothermal circulation.</p> / Dissertation
44

The behavioral ecology of Hapalemur griseus griseus : the influences of microhabitat and population density on this small-bodied prosimian folivore

Grassi, Christina 14 March 2011 (has links)
Not available / text
45

Thermoregulation in free-ranging African-endemic small mammals : the rock elephant shrew, Elephantulus myurus and the lesser bushbaby, Galago moholi.

Mzilikazi, Nomakwezi. January 2005 (has links)
Endothermy in birds and mammals is invariably associated with homeothermy. However, homeothermy can only be maintained if sufficient energy is obtained to meet the animals' maintenance budget. In mammals, daily torpor and hibernation have evolved to conserve energy when energy inputs from the environment are insufficient to meet maintenance requirements. Several studies have suggested that daily torpor and hibernation do not represent distinct physiological responses but are components of a continuum of heterothermy. Under laboratory conditions, even within phylogenetically ancient eutherian mammals, such as elephant shrews, it is unclear whether daily torpor or hibernation is used. Furthermore, an interpretation of the torpor patterns observed under laboratory conditions is complicated by the fact that torpor patterns often differ between laboratory and free-ranging conditions. Within the more recent mammal lineages, torpor has been observed in strepsirrhine primates. The occurrence of torpor in strepsirrhines is interesting as it pertains to arguments relating to the colonization of Madagascar by strepsirrhine primates as well as implications for human physiology. The first aim of this study was to investigate and quantify parameters that characterize torpor in a phylogenetically ancient eutherian mammal (Macroscelidae: Elephantulus myurus) under free-ranging conditions. This was done mainly to resolve whether daily torpor and hibernation were physiologically discrete responses. The second aim was to investigate torpor occurrence in a more recently evolved eutherian mammal (Primates: Galago moholi). The objective was to gain insights into the phylogenetic distribution of torpor and to provide a physiological verification of torpor occurrence in a mainland strepsirrhine relative to arguments about the colonization of Madagascar. I measured body temperatures in three monthly cycles between May 2001 - May 2002 in 22 free-ranging E. myurus. I recorded a total of 467 torpor bouts throughout the study period. The elephant shrews were capable of daily torpor throughout the year, with torpor most prevalent during winter and correlated with ambient temperature, photoperiod and invertebrate abundance. Only two torpor bouts were observed during summer. I suggest that although torpor use was most prevalent during winter, summer torpor might also be important for energy conservation in this species during drought years. This highlights the need for long-term physiological data in free-ranging animals. The mean torpor Tbmin and the mean bout length for the whole year were in the range expected for daily heterotherms. However, there was some marginal overlap with hibernation characteristics; a few torpor bouts were longer than 24 hrs in duration indicating that the animals were capable of opportunistically extending torpor bouts longer than 24 hours in response to unpredictable energetic shortfalls. Tbmin also decreased below 10°C. However, a consideration of behavioural and ecological factors argues against hibernation in E. myurus. Instead, these results support the idea of a physiological continuum for heterothermy. A return to normothermic body temperatures requires considerable energy expenditure, and this is perceived to be one of the major disadvantages of torpor. E. myurus offset the high cost of arousal from low body temperatures by using exogenous passive heating. This is achieved by coupling of the timing of arousal with ambient temperature cycles. Laboratory studies that quantify torpor energetics are usually conducted under constant temperature conditions and are likely to underestimate the energetic benefits accrued through the use of ambient temperature cycles during arousal. Torpor is often displayed during the animal's rest phase. However, nocturnal small mammals that utilize passive heating to assist arousal from torpor may enter torpor during the nighttime, thus effectively advancing the onset of the rest phase. I investigated the functional significance of daily and seasonal rhythms of body temperature in normothermic and torpid free-ranging E. myurus. Daily patterns of Tb, in normothermic E. myurus suggested polyphasic Tb patterns that nevertheless indicated a rest phase coincident with the daytime. I suggested that the principal benefit of a flexible daily rhythm of Tb, is that it facilitated torpor use during the nighttime and arousal by passive exogenous heating using ambient temperature cycles. It has been suggested that the evolution of endothermy precluded the need for homeothermic mammals to be sensitive to Ta cycles because they could maintain physiological function despite fluctuations in the ambient temperature. Elephant shrews utilize passive heating and provide excellent models with which to investigate whether mammals can entrain their body temperature rhythms to ambient temperature cycles. I experimentally tested whether food restricted E. myurus can entrain torpor cycles to shifts in the Ta cycle while holding the light-dark cycle constant. Food restriction and short photoperiod were only sufficient to induce torpor in E. myurus if photoperiod and Ta, cycles are in phase with each other. Shifting the cold T, into the photophase prevented the expression of torpor. I concluded that the body temperature rhythm is most probably tightly coupled with the photoperiod cycle and that although Ta and photoperiod usually act synergistically in nature, photoperiod is probably the stronger zeitgeber. The evolution of endothermy is thought to have been facilitated by the advent of endothermic energy sources such as brown adipose tissue (BAT), the principal site of nonshivering thermogenesis (NST). Rock elephant shrews are amongst the smallest members of the Afrotheria, the most basal of the eutherian lineage. I determined whether the phylogenetic placement of E. myurus and reliance on passive heating might result in a decreased capacity for NST relative to other eutherians. I investigated the capacity for NST in winter acclimated E. myurus by measuring the thermogenic response to noradrenalin (NA) injection. I used phylogenetically independent analyses to compare E. myurus NST capacity with other eutherians. E. myurus had an NST capacity that was no different from other eutherian mammals. Although they displayed a NST capacity that was 74% of that expected on the basis of body mass, this value was not significantly different from phylogenetically independent allometric predictions. Although heterothermy is almost always considered in the context of how the environment affects function , its use may offer insights into topics such as island biogeography and species dispersal. For example, there have been suggestions that heterothermy might have played an important role in the successful colonization of Madagascar by strepsirrhine primates. To my knowledge no studies exist as yet that provide a physiological verification of this suggestion. Currently no data exist on thermoregulation and heterothermy in any free-ranging African strepsirrhines. The lesser bushbaby, Galago moholi, is a small nocturnal strepsirrhine primate that experiences severe winters and drastic food reduction during winter and is a candidate employer of torpor. I measured body temperatures of 11 free-ranging lesser bushbabies, Galago moholi, captured at different times between February 2002 - September 2003. I did not record any incidents of heterothermy throughout the study period. Why does G. moholi not employ heterothermy? I consider several alternatives; phylogenetic placement, physiological and ecological factors that might preclude the use of torpor in this species. I suggest that the breeding pattern observed in G. moholi obviates torpor use whilst increasing fecundity, which would be adaptive if the animals are confronted with high predation risks. Much is currently known about the advantages of torpor use. This study highlights the need to consider and investigate those physiological, ecological and phylogenetic factors that might constrain species from utilizinq heterothermy. Furthermore, this study highlights the potential for thermoregulatory studies to offer insights into topics as widely separated as evolution of endothermy to species dispersal and island biogeography. / Thesis (Ph.D.)-University of KwaZulu-Natal, Pietermaritzburg, 2005.
46

Von der Glückseligkeit, alles zu wissen die Erforschung der Natur als religiöse Praxis in der frühen Neuzeit

Trepp, Anne-Charlott January 2006 (has links)
Zugl.: Göttingen, Univ., Habil.-Schr., 2006
47

Využívání méně obvyklých sportovních her ve výuce tělesné výchovy na středních školách v okrese České Budějovice\\ / Usage of less common sport games during physical education lessons in secondary schools in České Budějovice district

WERNEROVÁ, Tereza January 2011 (has links)
This diploma thesis is focused on the usage of less common sport games during physical education lessons in secondary schools in České Budějovice district. The first part of this diploma thesis is dedicated to the theoretical knowledge of the topic. The practical part presents the results of questionnaire survey in six secondary schools selected by stratified sampling method. The frequency of usage of less common sport games during physical education lessons has been found out. According to students? answers different sport games were played comparing to teachers? answers. The both groups prefered the ,,big sport games?? than the less common sport games. The choice of sport games depended on school type. This phenomenon could be explained by different sex ratio in various school types.
48

Composition chimique des sédiments entrant dans la zone de subduction des Petites Antilles

Carpentier, Marion 26 October 2007 (has links)
Les laves provenant de l’arc des Petites Antilles sont caractérisées par une grande variabilité chimique et leurs compositions isotopiques suggèrent une contribution variable de matériel crustal ancien dans leur genèse. L’arc des Petites Antilles est également caractérisé par une zonation chimique nord-sud, les laves des îles du sud présentant généralement des signatures isotopiques crustales plus fortes que celles des îles du nord. Nous avons tenté dans cette étude d’établir s’il existe des variations de la composition chimique des sédiments entrant en subduction le long de l’arc, et si d’éventuels changements de leur composition peuvent expliquer les variations chimiques observées au sein des laves. Pour ce faire, nous avons réalisé une étude géochimique approfondie (majeurs, traces, isotopes du Sr, du Nd, de l’Hf et du Pb) du flux sédimentaire potentiellement entrant dans la zone de subduction à différentes latitudes. L’échantillonnage comprend des sédiments forés au niveau des sites 543 (nord de l’arc) et 144 (extrême sud de l’arc) lors des campagnes DSDP 78A et 14 respectivement, et des sédiments provenant de l’île de la Barbade (sud de l’arc). <p>Les échantillons présentent une grande hétérogénéité lithologique correspondant globalement à un mélange en proportion variable entre une composante détritique et une composante biogénique (siliceuse ou carbonatée). De plus, au niveau du site 144, des niveaux très riches en matière organique (black shales) datant du Cénomanien supérieur au Santonien (~ 95 à 84 Ma) ont été forés. Ces formations correspondent à l’enregistrement des Oceanic Anoxic Events 2 et 3. Nous avons montré que la « dilution » variable de la fraction détritique par la composante biogénique est le facteur qui contrôle largement les variations de concentrations en éléments traces observées. De plus, nous avons révélé un enrichissement en U extrêmement important au sein des black shales du site 144. Les signatures isotopiques de l’Hf, du Nd et du Pb sont dominées par la composante détritique, alors que celle du Sr, dans le cas d’échantillons riches en carbonates est dominée par celle de l’eau de mer. Les sédiments des trois sites présentent des compositions isotopiques du Pb fortement radiogéniques par rapports aux sédiments océaniques « classiques », que nous avons associées à une forte contribution de matériel issu de l’altération des cratons guyanais et brésilien dans la composante détritique. De plus, la décroissance radioactive de l’U dans les black shales du site 144 a généré des rapports 206-207Pb/204Pb extrêmement radiogéniques. <p>Un mélange entre le manteau appauvri et les sédiments du site 543 reproduit les compositions isotopiques des laves de la partie nord de l’arc. Pour la partie sud de l’arc un mélange entre les sédiments les plus radiogéniques en Pb du site 144 et le manteau appauvri explique les compositions des laves des îles de la Martinique à Grenade. Une contribution croissante des black shales du nord vers le sud est nécessaire, et est de plus en accord avec l’augmentation du nord vers le sud de l’âge du plancher océanique subduit. Enfin, quelques sédiments de l’île de la Barbade présentent certaines caractéristiques compatibles avec leur implication dans la genèse des laves de la partie sud de l’arc.<p> / Doctorat en sciences, Spécialisation géologie / info:eu-repo/semantics/nonPublished
49

Kalínago. Français et amérindiens dans les Petites Antilles au XVIIe siècle / Kalínago. Amerindians and French in the Lesser Antilles during the seventeenth century

Roux, Benoît 13 September 2019 (has links)
L’histoire des expansions européennes est peuplée d’ethnonymes dont l’évocation seule suffit à figurer les confins de la civilisation et à résumer les espoirs déçus des empires coloniaux. Autant de noms exotiques que l’on prononce, tels des emblèmes de la résistance indigène opposée à tout effort de conquête. Caraïbes est de ceux-là qui, sitôt entrés dans les chroniques européennes, ont été érigés en légende. Or, au-delà des discours hérités et convenus, que savons-nous de ces Indiens, de leurs logiques, de leurs pratiques, de leurs représentations sociales, ou des relations qu’ils entretiennent avec les Français au XVIIe siècle ? À dire vrai, fort peu de choses. Ces questions, bien que sorties des mortes-eaux de l’histoire coloniale, n’ont suscité que peu d’intérêt. Elles n’ont été qu’effleurées dans des monographies insulaires, ou dans des ouvrages consacrés à l’occupation archéologique de l’archipel. C’est en écho à ce constat un peu trop vite entériné qu’a pris forme le projet d’écrire une histoire de la cohabitation entre Français et Caraïbes au XVIIe siècle. La présente recherche aspire donc non seulement à apporter un éclairage sur ce chapitre, mais également à désenclaver des histoires généralement séparées dans la production scientifique. Aussi, souhaitons-nous que cette enquête, à l’intersection des histoires coloniales et indigènes, conduise à revoir nos grilles d’analyse, en tenant compte des réflexions développées par l’ethnologie et l’archéologie, afin d’éviter les écueils de l’histoire-récit. Les circulations et les échanges entre Indiens, Européens et Africains, où prime le facteur humain, seront par conséquent au cœur de l’intrigue. / In the stories of European expansion, many ethnonyms are synonymous with barbarism (as opposed to civilization) or with the failure of the colonial empire. These “exotic” demonyms became the symbols of the resistance of the natives against any attempt of conquest. “Caraïbes” (Caribs) is one of the names which became legendary as soon as it appeared in the European chronicles. But beyond the inherited and agreed discourses, what do we know about these Caribs, their logics, their practices, their social representations, or their relations with the French settlers during the seventeenth century? It must be acknowledged we know next to nothing about these Indians, despite the historiographical revival in the field of colonial history over the last decades. The Caribs have only been touched upon in monographs concerned with such or such island, or in books focusing on archaeological occupation of the archipelago. On the basis of these observations, this doctoral thesis explores the history of the cohabitation between the French and the Caribs in the seventeenth century. It also attempts to open up stories which have generally been studied separately although they all belong to the same scientific field. Such project, at the intersection of colonial and native history, will therefore take into account archaeological and ethnological research in order to avoid the pitfalls of story-telling. As a consequence, the circulation and exchanges between Amerindians, Europeans and Africans, in which the human factor prevailed, will be an essential field of investigation.
50

Storage conditions and dynamics of magma reservoirs feeding the major pumiceous eruptions of Dominica (Lesser Antilles Arc) / Dynamiques des zones de stockage à l’origine des grandes éruptions ponceuses de la Dominique (Arc des Petites Antilles)

Solaro-Müller, Clara 31 January 2017 (has links)
Les grandes éruptions explosives (10 to 1000 km3/eruption) ont été l’un des sujets principaux d’étude de la volcanologie moderne car elles représentent des éruptions de grand impact sur la nature et sur les installations humaines sur Terre. Les pétrologues ont démontré que la proportion de cristaux dans les produits de ces éruptions peut être utilisée pour étudier les dynamiques pré-éruptives de la plomberie magmatique et contraindre les échelles de temps des processus magmatiques. Plus précisément, de nombreuses études ont prouvé que ces cristaux peuvent être remobilisés en des temps courts de 10 à 100 ans avant l’éruption, ce qui rend ces systèmes significativement dynamiques. Plusieurs éruptions ignimbritiques d’un volume de l’ordre de la dizaine de km3 ont été reconnues en Dominique (Arc des Petites Antilles). Nous présentons ici, sur la base d’une étude stratigraphique détaillée, une étude pétrologique des ponces de la phase plinienne qui débute les trois éruptions ponceuses majeures de la Dominique : Layou (~51kyrs cal BP), Roseau (~33kyrs cal BP) et Grand Fond (~24kyrs cal BP). En combinant une étude pétrologique des produits naturels et des produits issus des travaux de pétrologie expérimentale, nous proposons un modèle complet des réservoirs à l’origine des trois éruptions. Les magmas sont des dacites à forte teneur en cristaux (~30%), comprenant plagioclases, orthopyroxènes, clinopyroxènes, amphiboles et oxydes. Les expériences d’équilibre de phases sur ces dacites ont permis de contraindre les conditions de stockage à 850°C, 400 MPa (16 km), ~ΔNNO+1 et une teneur en eau pré-éruptive de ~6-8 wt % pour les trois éruptions. Les orthopyroxènes ont été utilisés pour étudier les dynamiques pré-éruptives du système magmatique. Par une analyse systématique (« Crystal system analysis ») de leur zonation nous avons défini différents environnements magmatiques et leur connections. Les échelles de temps des dynamiques pré-éruptives sont calculées par modélisation de l’interdiffusion Fe-Mg dans les orthopyroxènes. Les caractéristiques chimiques et texturales des orthopyroxènes montrent que ~80-85% des cristaux sont non-zonés, tandis que 15-20% présentent une zonation multiple, normale ou inverse, avec prévalence de cette dernière. Les cristaux non zonés représentent l’environnement magmatique principal, alors que les zonés suggèrent une perturbation pré-éruptive du réservoir. Le « crystal system analysis » appliqué à ces derniers suggère la présence de 4 environnements magmatiques (MEs), avec un mouvement principal des cristaux vers des MEs de compositions moins évoluées, lié à la zonation inverse des cristaux. Cependant, la composition des inclusions vitreuses des orthopyroxènes, montre que les différents MEs sont en équilibre avec un verre de même composition. Ces considérations, couplées aux résultats d’équilibres de phases, nous permettent de définir le réservoir comme un environnement fortement cristallisé (~30%), modérément froid (~850°C) et fortement oxydé (~ΔNNO+1) possédant 80-85% de cristaux non-zonés, remobilisé par un réchauffement de 25-30°C produit par l’injection d’un magma plus chaud sous-jacent. La modélisation de l’interdiffusion Fe-Mg dans les orthopyroxènes indique que le réchauffement s’est produit ~10 ans avant chaque éruption. Ce processus crée la zonation inverse retrouvée dans 15-20% des orthopyroxènes et développe un panache thermique interne au réservoir qui est responsable de l’hétérogénéité cristalline retrouvée dans les échantillons / Large silicic eruptions (tens to hundreds of km3/eruption) have been a main subject of study for modern volcanology as they represent volcanic events of great impact on environment and human settlement on Earth. Petrologists have demonstrated that the crystal “cargo” of these eruptions can be used to unravel the pre-eruptive dynamic of their magmatic plumbing system and constrain timescales of the related magmatic processes. Specifically, several studies have proved that this “crystal cargo” can be remobilized and brought to eruption in short timescales of decades to centuries, making these systems more dynamic than previously believed.Several ignimbritic eruptions with a volume of the order of ~10 km3 have been recognized in Dominica (Lesser Antilles arc). On the basis of a detailed chronostratigraphy of the deposits, we present an integrated petrological study of the plinian fallout deposit of the latest three ignimbritic eruptions of Layou (~51kyrs cal BP), Roseau (~33kyrs cal BP) and Grand Fond (~24kyrs cal BP). We combine natural and experimental petrology to investigate the prevailing storage conditions within the reservoir that fed each eruption. Whole rocks are all dacites with crystal contents of ~30%, comprising plagioclase (An50-78), orthopyroxene (En47-63), clinopyroxene (Wo44-45), amphibole (Mg# 0.52-0.60) and Fe-Ti oxide (Mag71-75 and Ilm86-87) and rhyolitic residual melt. Pre-eruptive storage conditions of 850 (±5) °C, 400 MPa (16 km depth), ~ΔNNO+1 and melt water content of ~6-8wt% were determined for all studied eruptions through phase equilibria experiments. Orthopyroxenes were used to investigate the architecture and pre-eruptive dynamics of the plumbing system through a crystal system analysis (CSA) combined to a Fe-Mg diffusion modelling. Textural and chemical features of analysed orthopyroxenes prove that for all eruptions ~80-85% of crystals are unzoned while 15-20% present clear normal, reverse and multiple zoning, with reverse zoning being prevalent. Unzoned crystals represent the main magmatic environment (ME) while reverse zoned ones suggest a pre-eruptive perturbation of the reservoir. 4 MEs are evidenced, with a main movement of crystals towards MEs of less evolved composition, linked with the observed reverse zoning. Nevertheless, major element composition of orthopyroxene-hosted melt inclusions shows that all MEs are in equilibrium with the same melt. Combining results on natural and experimental petrology we can define the reservoirs as a highly crystalline (~30%), moderately cold (850°C) and highly oxidized (~ΔNNO+1) environment with 80-85% of unzoned orthopyroxenes, and 15-20% of zoned orthopyroxenes recording a heating process of 25-30°C, possibly produced by an underplating hotter magma that is responsible of the rejuvenation of the reservoir. By modelling the diffusional relaxation of Fe-Mg chemical gradient on zoned orthopyroxenes, we argue that this heating occurs in short timescales of ~10 years prior to each eruption. This heating process develops, over the considered eruptive time, a plume heating geometry able to bring together, on the scale of the hand sample, crystals of different magmatic environments (MEs)

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