Dissertations / Theses on the topic 'Géochronologie K-Ar et 40Ar'
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Hevia, Cruz Francisco. "Climatic and landscape evolution of the Azores over the past million years." Electronic Thesis or Diss., université Paris-Saclay, 2023. http://www.theses.fr/2023UPASJ035.
Landscape evolution on volcanic islands is driven by complex interactions between volcano growth and destruction by a variety of processes (explosive eruptions, landslides, riverine erosion, weathering). Major climate changes, may impact the dynamics of degradation processes at different spatial and temporal scales. For example, extreme rain can produce an immediate hydrological response causing important destruction. Changes in weathering rates, sensitive to precipitation and temperature, can trigger changes in soil fertility but also modify global carbon cycling.The Azores volcanic islands provide an ideal setting to study these interactions, with both scientific and societal significance, especially in the context of ongoing global warming. Located in the Central North Atlantic, they are under the influence of major climatic drivers. Most of them had pulses of volcanic activity over the past 1 Myr, a period characterized by high-amplitude glacial-interglacial transitions with major climatic changes. While global climatic variations have been relatively well-studied for this period, reconstructing the atmospheric paleoclimate and its effects at local/regional scales remains challenging. Paleosols (PSs) are fossil soils formed by weathering at surface, and later incorporated into the geological record. Their geochemistry provides valuable insights into past environmental conditions, while the geochronology of volcanic products “bracketing” PSs allows their temporal constraint.In this work, we reconstructed mean annual precipitations (MAP) and air temperature (MAAT) over the last 1 Myr in the Azores region through a combined geochemical-geochronological study of PSs. Two proxies based on PSs’ major element were used: the weathering index (CIA-K) and the Clayeyness, both validated in other volcanic settings. The precise dating of volcanic units by either unspiked K-Ar on lava flow groundmass separates or ⁴⁰Ar/³⁹Ar on single K-feldspar of trachytic fallout evidence “pulses” of soil-formation within only a few kyr. This occurred especially after glacial terminations (MIS 21, 19, 11, 9e, 5e and 1), under wet and warm conditions. Fast paleoenvironmental changes were recorded in PSs’ geochemistry, and MAAT reconstructions (12-28 ᵒC) agree with previously published Sea Surface Temperatures, pointing to a tight ocean-atmosphere teleconnection. Those “pulses” suggest sustained weakening phases for the Azores High, allowing humid air currents (Westerlies) to reach further to the south.Our data also show contrasted rates of vertical soil development (3-180 mm/kyr). Weathering was favored by the structure and texture of parental materials, as PSs formed under lower MAP in pyroclastic deposits than in lava flows (~500 and ~800 mm/yr thresholds). This highlights the influence of fragmentation on weathering’s kinetics due to higher specific surface area. Enhanced weathering at surface and along geological discontinuities may have promoted mechanical weakening, favoring erosion and landslides. Notably, high MAPs (up to 1500 mm/yr) obtained around the Eemian interglacial stage are coincident in time with the initiation of a large slide complex on the southern flank of Pico. Intense precipitation may have led to increased water infiltration favoring enhanced hydromagmatic interactions. Drastic increase in pore pressure may then have triggered the initiation of the flank movement along listric faults that are still active. Current conditions in the Azores are wetter and slightly warmer than during the last Myr. Increased infiltration along faults could partly control subsequent movement and yield to detachment of the outer flank of Pico, with potentially dramatic consequences.More generally, present temperature and humidity increase on volcanic islands points to intense weathering, resulting in fast landscape evolution, increased lixiviation and elementary export and high atmospheric CO₂ uptaking, with local, regional and global impacts
Gaylor, Jonathan. "40Ar/39Ar Dating of the Late Cretaceous." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-01017165.
BROS, REGIS. "Geochimie isotopique (sm-nd, rb-sr, k-ar, u) des argiles du bassin proterozoique de franceville et des reacteurs d'oklo (gabon)." Université Louis Pasteur (Strasbourg) (1971-2008), 1993. http://www.theses.fr/1993STR13059.
Bablon, Mathilde. "Reconstruction de l'histoire des volcans de l’arc équatorien : contraintes pour l’évolution chronologique de l’arc andin et pour l'évaluation du risque volcanique." Thesis, Université Paris-Saclay (ComUE), 2018. http://www.theses.fr/2018SACLS431/document.
The Ecuadorian arc presents a large number of Quaternary volcanoes. Our ninety new K-Ar ages, carried out on products from twenty volcanic edifices, show that the development of the Quaternary arc began about 1 Ma in northern Ecuador and migrated southward since 600 ka. This migration could be induced by recent change of the slab geometry at depth and by the activation of crustal faults. The magmatic productivity rates are rather homogeneous at the arc scale, and range between 0.1 and 5.6 km³.ka⁻¹. These data highlights that volcanoes grew during sporadic activity pulses separated by quiescence periods. There is no clear correlation between the age of the volcanoes and their emission rates, but the subduction of the Carnegie ridge could favor the magma genesis and explained the increase of the volcanic activity in northern Ecuador during the Quaternary. Erosion rates range between 0.01 and 0.14 km³.ka⁻¹. Youngest volcanic edifices seem to be eroded by a chemical alteration process, while the dismantling of older volcanoes is mostly influenced by physical processes such as glacial abrasion and tectonic activity. Finally, we show that K-Ar ages performed on groundmass or pumice glass shards can be successfully applied to Quaternary volcanic products from the Ecuadorian arc
Renac, Christophe. "Diagenèse des minéraux argileux dans la marge passive cévenole (forage G. P. F. Balazuc 1, France) : structure cristalline, morphologie, composition isotopique, datation K-Ar et inclusions fluides." Poitiers, 1994. http://www.theses.fr/1994POIT2328.
Leibrandt, Sébastien. "Reconstitution de l’évolution morpho-structurale et de la dynamique éruptive du massif du Cantal : relation avec la distribution spatio-temporelle du volcanisme du Massif Central (France)." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112330/document.
The Cantal massif, located in the French Cenozoic volcanic province, is the largest Miocene volcano in Europe. It is mainly composed of volcaniclastic breccias giving impressive dimensions and a shield-like morphology. Field observations, coupled with K-Ar datings, allowed us to reconstruct the morpho-structural evolution, the eruptive dynamics and the volcanic history of the massif. We first constrained a stratigraphic sequence which is identical all around the massif. Then, we show that it exists from chrono-stratigraphic, structural and geomorphologic evidences a 8 x 10 km central caldera ca. 8 Myrs ago occupied by a lake. The sedimentological and morphological study of the main breccia unit, the Large Breccia Flow, led us to define it as one of the largest syn-eruptive debris flow in the world. We estimate its volume at ca. 100 km3. We propose that this debris flow resulted from a major intracaldera lake eruption. The interaction between a juvenile magma and the water of the caldera lake, with a surteyan dynamics, initiated the debris flow that propagated on the external slopes of the volcano at 360° until 25 km from its source. This study opens outlets on one hand to volcanic hazards related to major intracaldera lake eruptions ; on the other hand, we show that it is possible to reconstruct the former source morphology of a several Myrs-old volcaniclastic breccia flow by studying the sedimentological and morphological criterion of its deposit.Furthermore, the combination of new K-Ar datings with field observations allowed us to reconstruct the volcanic history of the Cézallier plateau (site of the youngest volcanic activity in the continental France), of the Aubrac plateau, and also the volcanism along the Sillon Houiller. Consequently, we established the spatio-temporal relationships between the Cantal massif and the adjacent volcanic provinces, highlighting the important role of the Hercynian inherited fractures in the magmas ascent. We thus confirm the spatio-temporal migration toward the north in Auvergne. Finally, the acquisition of 47 new K-Ar ages ranging from 12.8 Ma to 9 ka conveys new time constraints on the chronology of Massif Central volcanism by precising its spatio-temporal distribution
Coulié, Emmanuel. "Chronologie 40Ar/39Ar et K/Ar de la dislocation du plateau éthiopien et de la déchirure continentale à la corne de l'Afrique depuis 30 Ma." Paris 11, 2001. http://www.theses.fr/2001PA112284.
We present here a new analytical system for 4O_Ar/39_Ar dating that relies onto an original 180ʿ sector multiple collection mass spectrometer with five faraday cups. Results of preliminarily experiments undertaken on geological standard minerals highlight the good behavior of this new instrument for step heating analyses. The age reproducibility of successive steps lead to analytical errors lower than 0. 2 %. Such a system appears today unique on the international plan for 40_Ar/39_Ar routine dating. This new penta-collector MS enabled us to perform highly reproducible 40_Ar/39_Ar dating of Ethiopian volcanics. It is now admitted that continental flood basalt volcanism has a strong relationship with continental break-up. The Ethiopian-Afar plume has been linked to the early opening of the Afar depression, where the propagation of Red Sea and Gulf of Aden within the depression is still an ongoing process. The purposes of this study are to constrain the emplacement and duration of the trap series, and to reconstruct the eruptive chronology of the earlier opening stages, since the initiation of the fracturation. Twenty-eight 40_Ar/39_Ar and 68 K/Ar new ages data have been performed on volcanic series and granitic bodies, sampled on the plateaus (Ethiopian, Yemenite, Somalian) and along their boundaries on the Afar margin. Our results support that the onset of traps volcanism took place around 30 Ma, with a duration lower than 1 Myr. The emplacement of granitic bodies as early as 30 Ma argues for a synchronous initiation of the opening. Finally, all results obtained in this study on both plateau and rifted margin areas helped us to propose a global scheme for the evolution of the Afar depression since 30 Ma
Smietana, Magali. "Pétrologie, géochronologie (K-Ar) et géochimie élémentaire et isotopique (Sr, Nd, Hf, Pb) de laves anciennes de la Réunion : Implications sur la construction de l'édifice volcanique." Phd thesis, Université de la Réunion, 2011. http://tel.archives-ouvertes.fr/tel-00716829.
Smietana, Magali. "Pétrologie, géochronologie (K-Ar) et géochimie élémentaire et isotopique (Sr, Nd, Hf, Pb) de laves anciennes de la Réunion : Implications sur la construction de l’édifice volcanique." Thesis, La Réunion, 2011. http://www.theses.fr/2011LARE0012/document.
The volcanic system of La Reunion is made of the coalescent Piton des Neiges and Piton de la Fournaise edifices. Its formation, associated with the activity of a mantle plume, is characterized by phases of submarine and subaerial growth, followed by a period of destruction, as described in the classical model proposed for Hawaiian Island volcanoes. Previous studies showed that the subaerial activity of La Reunion would have started around 2.2 Ma ago. Geochemical analyses carried out on the products associated with subaerial and submarine volcanism revealed their transitional chemical nature and their peculiar homogeneous isotopic compositions (87Sr/86Sr, 143Nd/144Nd et 176Hf/177Hf) for a hotspot derived magmatism. In this study, we show that some unusual submarine lavas were recently identified below the basal series of Piton de la Fournaise volcano (dredged on the North-East Rift Zone of la Fournaise) and below the subaerial lavas outcropping at the base of the differentiated series of Rivière des Remparts, indicate that the evolution of La Reunion system is probably more complex than previously suggested. The question of the nature and origin of these lavas, together with their implication on the formation of La Reunion, is an issue of major interest in order to better constrain the global evolution of the volcanic system. As a consequence, new petrological, geochemical and geochronological investigations were conducted on the submarine part of La Reunion edifice. They revealed the existence of a geochemically exceptional group of lavas. Its composition is clearly different from common samples of La Reunion and presents (1) an enrichment in incompatible elements and (2) tends toward an enriched EM endmember. These chemical specificities reveal that the source of La Reunion magmatic products is (1) an heterogeneous source affected by (2) variable melting degrees. Moreover, two samples of this new group dated at 3.77 (0,08) and 3.34 (0,07) Ma extend considerably the period of activity of the island. These rocks are the oldest samples ever dated at La Reunion. The nature and stratigraphical location of subaerial and submarine samples from Piton des Neiges and Piton de la Fournaise imply a new interpretation of the global evolution of the island. Unlike previous studies, our results indicate that :(1) The differentiated subaerial lavas from Rivière des Remparts, due to their stratigraphical and geographical location underlying Piton de la Fournaise, and by analogy with the Piton des Neiges, cannot be linked to the activity of Piton de la Fournaise. (2) The isotope signature of the submarine lava group from the North-East Rift Zone of Piton de la Fournaise, reveals the heterogeneous character of the mantle source under La Reunion Island, that can be modelled as embedded eclogite in a matrix of spinel lherzolite, (3) The age of this submarine group and its location under the eastern flank of Piton de la Fournaise, imply a more complex model of evolution of La Reunion. Therefore, our geochemical and geochronological data are new arguments suggesting the existence of a third volcanic center on the island. This assumption confirms the previous petrological and geophysical evidence supporting the existence of this volcano at the East of La Reunion, commonly called Les Alizés volcano
Devismes, Damien. "Développement d'un système analytique pour la datation in situ des roches martiennes par la méthode K-Ar." Phd thesis, Université Paris Sud - Paris XI, 2013. http://tel.archives-ouvertes.fr/tel-00954414.
Germa, Aurélie. "Evolution volcano-tectonique de l'île de la Martinique (arc insulaire des Petites Antilles) : nouvelles contraintes géochronologiques et géomorphologiques." Phd thesis, Université Paris Sud - Paris XI, 2008. http://tel.archives-ouvertes.fr/tel-00447342.
Leibrandt, Sébastien. "Reconstitution de l'évolution morpho-structurale et de la dynamique éruptive du massif du Cantal : relation avec la distribution spatio-temporelle du volcanisme du Massif Central (France)." Phd thesis, Université Paris Sud - Paris XI, 2011. http://tel.archives-ouvertes.fr/tel-00703477.
Cadoux, Anita. "Le magmatisme acide Plio-Pleistocène de la MargeTyrrhénienne (Italie Centrale) : Géochronologie,Pétrogénèse et Implications Géodynamiques." Phd thesis, Université Paris Sud - Paris XI, 2005. http://tel.archives-ouvertes.fr/tel-00138852.
basiques et intermédiaires, est à la base de la majorité des modèles géodynamiques. Comparativement, le magmatisme acide, correspondant aux premières manifestations sur la marge Tyrrhénienne est beaucoup pour les édifices de la Province Toscane (San Vincenzo, Roccastrada et Amiata). Pour le volcan de Monte Amiata, de nouvelles données isotopiques Sr-Nd et Pb confirment qu'il est en terme de sources un hybride entre les Province Toscane et Romaine. Nous proposons grâce aux âges obtenus un nouveau scénario pour sa mise en place. L'analyse en composantes principales (ACP) des données isotopiques du Pb de toutes les manifestations acides étudiées dans cette thèse a permis d'identifier les deux composants source à l'origine de ces roches. Le composant le plus important est un pôle mantellique
correspondant à un mélange entre DM et HIMU, tandis que le second, dont le rôle est mineur comparé au premier, est un pôle enrichi de type crustal. Les roches acides les plus au Sud (Pontines) montrent une influence plus forte du composant DM+HIMU. Ainsi, même sur des
roches aussi différenciées et à plus petite échelle (l'Italie centrale), on retrouve la tendance générale propre à l'ensemble de la péninsule Italienne et de la Sicile, dérivée de l'étude isotopique des roches basiques, qui montre un mélange général entre DM et HIMU auquel s'ajoute un composant dérivé de la croûte. L'influence du pôle DM-HIMU est croissante du
Nord au Sud de l'Italie. Etendue à l'échelle de la marge Tyrrhénienne italienne, l'ACP permet d'identifier deux
domaines sources, délimités par une discontinuité lithosphérique majeure de l'Italie centrale, le 41ème Parallèle, dans lesquels les composants évoluent différemment. Les caractéristiques du domaine Nord pourraient être contrôlées par un processus de délamination de la lithosphère inférieure, celles du domaine Sud par un retrait rapide du slab, les deux
phénomènes provoquant une remontée asthénosphérique.
Lama, Chafik. "Apport de la méthode K-ar à la compréhension de l'histoire géologique des granitoïdes birimiens du Liptako (Niger Occidental) et des leucogranites à deux micas de Tagragra d'AKKA (Anti-Atlas Occidental, Maroc)." Vandoeuvre-les-Nancy, INPL, 1993. http://www.theses.fr/1993INPL062N.
Sasseville, Christian. "Géochronologie K-Ar et transfert de matière le long de systèmes de failles et de fractures dans la lithosphère continentale : Cas du système de rift Saint-Laurent en relation avec le domaine allochtone des Appalaches (Québec, Canada)." Strasbourg 1, 2008. http://www.theses.fr/2008STR1GE10.
Janin, Myriam. "Le plateau Amsterdam-St. Paul : caractérisation du point chaud éponyme et évolution de son interaction avec la dorsale Sud-est Indienne." Brest, 2010. https://tel.archives-ouvertes.fr/tel-00592036.
The Amsterdam-St Paul plateau (ASP) is an oceanic plateau built from the interaction between ASP hotspot and the Southeast Indian ridge. P volcanic chain, called the chain of the dead Poets (CDP), lies to its northward and related to the hotspot intraplate activity. Their study reveals that ASP plume composition comes from oceanic crust and pelagic sediments recycled in the mantle through a 1,5Ga subduction process, ASP plume activity is pulsatile and occurs preferentially on weakness zones. The CDP construction results thus from (1) the plume pulses and (2) the diffuse divergent boundary between the Capricorn and Australian plates. K-Ar datings reveal that this volcanic chain is made of two generations of seamounts: (1) an old one, of about 9Ma and made of large edifices which had probably a sub-aerial period and (2) a young one, younger than 2Ma, and made of small edifices related to some pounded plume pulse material. In addition, ASP plume has an own motion of about 1-2 cm/yr to the south-west. The ASP plateau lavas compositions (major and trace elements and Sr-Nd-Pb-Hf isotopes) show en important variability and reveal that the underlying mantle is heterogeneous. It is made of a depleted mantle with lower continental crust strips in the form of garnet-plagioclase granulites, probably delaminated during the Gondwana breakup. The lower continental crust s one of the hypotheses for DUPAL anomaly origin and our data support this assumption
Al, Kwatli Mohamad Amer. "Evolution volcano-tectonique du nord de la plaque arabique (la syrie) : cadre géodynamique, chronologie K-Ar, caractères géochimiques et éléments de cartographie (SIG et télédétection)." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112079.
The Cainozoic volcanic activity in the Arabian plate offers an excellent opportunity to study the intra-plate volcanism related to a complex tectonic setting. After the emplacement of the Yemeni-Ethiopian continental flood basalt plateau, ~ 31 Ma, since the Late Oligocene, widespread volcanic activity has erupted, accompanying the separation of the Arabian-Nubian Shield (development of Red Sea rifting) and the convergence between the Arabian and Eurasian plates (building of the Bitlis-Zagros thrust belts). In the northern part of the Arabian platform, the Syrian volcanism has taken place in a general compressional context, surrounding the Palmyride fold belt and adjacent to other deformation zones (e.g. the Euphrates graben and Dead Sea fault system). This thesis focuses on the volcano-tectonic evolution of the northern part of the Arabia plate, particularly in Syria, and essentially combines geochronological, geochemical, and morpho-structural studies, in addition to supplementary geophysical models. Our morpho-structural analyses of the Harrat Ash Shaam volcanic province (HASV) to the south of Palmyride, digitally characterise more than 800 monogenic volcanic cones placed in Syria, Jordan, and Saudi Arabia. These new data, together with the availability of sediment thickness data, give rise to a new volcano-tectonic approach. This study shows that the consistent negative correlation between the intensity of volcanism and basement depth is influenced by the tectonic setting. The normative analysis of the distribution of volcanic cones in relation to sediment thicknesses is critical when comparing the extension of tectonics in different zones. Remote sensing imagery, field work and our > 40 new K-Ar ages dataset ranging from ~0.05 million years (Ma) to ~18 Ma allow us to precise the Syria volcano-tectonic evolution through time. Regarding the youngest lava flows of HASV, the integration of the results makes it possible to suggest a chronological model for the alteration processes in relation to Quaternary palaeoclimatic changes. We reconstruct the volcano-tectonic evolution in Syria during the Cainozoic, and suggest different extension styles to explain the volcanism. It started during the Late Oligocene and the Early Miocene, between ~26 Ma and ~16 Ma to the South of Palmyride at HASV in an extensional tectonic context. From the Miocene to the Quaternary, between ~19 Ma and ~0.08 Ma, the volcanism developed to the North under second order extension tectonic conditions. Since the Mid-Miocene, the compression has increased and the magma erupted in relation with a possible counter-clockwise rotation tectonic relative motion. South of Palmyride it corresponds to the widespread eruptive phase during the last 13 Ma. To the North, this phase, linked to rotational tectonics appears concentrated in superficies and time; it corresponds to the Homs plateau, NW Palmyride, between 6.3 and 4.3 Ma. We suggest a new volcano-tectonic evolution model for the HASV. It highlights the essential role of lithosphere heterogeneity beneath Lebanon, in particular the anti Lebanon Mountains and Palmyride thrust belts, in triggering the Mid-Miocene volcanism. Our geophysical models estimate mean lithosphere – asthenosphere boundaries at about 150 km depth. According to geochemical data, the zone of shallowest depth ~110 km, W of HASV, could be the result of a thermal anomaly, instead of an asthenospheric upwelling. Geochemically, the Cainozoic Syrian lavas are alkaline and subalkaline rocks, typical of magma emitted in continental intraplate contexts. They are basanites and tephrites, basalts, basaltic andesites, basaltic trachyandesites, and trachybasalts. Thirty samples from different Syrian volcanic provinces show significant variation in terms of incompatible trace element signatures. Crustal contamination plays a negligible role in the process of magma genesis, as does crystal fractionation, essentially restricted to olivine and clinopyroxene. Our results show that the Syrian lava has been generated by variable rates of partial melting from different levels of a locally heterogeneous lithospheric mantle. The LREE/MREE ratio not only illustrates how the degree of partial melting was changed spatially and temporally during the last ~18 Ma, but it also illustrates how the degree and style of extension tectonics changed through time
Boulesteix, Thomas. "Age, récurrence et mécanismes de déstabilisation des flancs des volcans océaniques d'après l'exemple de Tenerife (iles Canaries)." Thesis, Paris 11, 2011. http://www.theses.fr/2011PA112174/document.
The growth of oceanic volcanoes is frequently punctuated by large flank collapses, which can generate voluminous debris avalanches and destructive tsunamis. The causes, the mechanisms and the consequences of such instabilities, crucial for risk assessment, remain poorly understood.Tenerife (Canary Islands, Spain) is a target of particular interest to study such phenomena. Its recent evolution includes the development of a large silicic central volcano and a prominent volcanic ridge along a main NE-SW trending rift zone (NERZ). During the last Myr, these volcanic systems have been truncated by three large flank collapses, the base of which is partly accessible through underground water mining galleries.This thesis develops a systematic analysis of the relationships between volcanic construction and recurrent flank instabilities along the NERZ. Our approach includes field investigations at the surface and in the galleries to identify and sample the volcanic units affected by each landslide and the successions filling their scar; unspiked K/Ar dating (Cassignol-Gillot technique) on fresh separated groundmass to constrain precisely the timing of the landslides; 3-D morphological reconstructions to estimate the volume of the edifices and landslides structures; and whole-rock geochemical analyses to characterize the compositional evolution of the magma prior to and after each collapse event.Our new results show the intermittent functioning of the various sections of the NERZ with a recurrent pattern comprising:(1) The rapid construction of a large volcanic edifice. The resulting load favors the creation of superficial storage levels, the associated evolution of the magma and the eruption of viscous differentiated terms, favoring local inflation of the structure and its destabilization(2) The collapse of a flank of the NERZ, dated at ca. 840 ka, 525 ka, and 175 ka (Güimar, La Orotava and Icod, events respectively)(3) An immediate eruptive response, implying the rapid emptying (<50kyr) of the feeding system and the filling of the landslide scars under tens of km3 of lava.(4) The subsequent displacement of volcanic activity towards the less mature sectors (lower thickness/lower lithostatic pressure).We show here that loading/unloading processes have a strong influence on the development of gravitational instabilities and the evolution of the magma feeding systems on such large intraplate volcanic islands
Favier, Alexiane. "Évolution spatio-temporelle de l'hydrothermalisme dans la plaque supérieure de l'arc des Petites Antilles en Guadeloupe : applications aux systèmes géothermaux." Thesis, Antilles, 2019. http://www.theses.fr/2019ANTI0401.
To further develop high-enthalpy geothermal energy in Lesser Antilles arc, it is necessary to identify possible new key targets, and to better understand the modes of fluids and heat transfers in geothermal reservoirs. The objective of this work is thus to characterize the spatio-temporal evolution of hydrothermalism at the upper plate of the arc in Guadeloupe with a multidisciplinary approach (combined structural, geochemical, mineralogical, petrological and geochronological analyses) focussed on the oldest volcanic complexes of the archipelago. In the north of Basse-Terre Island reveals an arc metamorphism developed under sub-Greenschist facies. The standard thermal state of the arc crust in Guadeloupe thus established shows a brittle-ductile transition located at depths of 3 to 4 km. An exhumed geothermal paleo-reservoir, identified at the south of Basse-Terre Island, indicates a hydrothermal metamorphism developed under Greenschist facies synchronous with the development of schistose corridors and attests for both vertical and lateral hydrothermal fluid transfers at depths between 2 and 3 km. Comparison of the age of the volcanic activity and Ar-Ar dating of the high-temperature hydrothermal phases allows us to estimate a maximum operating time of the paleo-reservoir at 650 ka. Finally, the discovery, the analysis and the K-Ar dating of a new hydrothermal breccia, within the active geothermal system, reveals a link between current geothermal activity and volcanic activity of the Soufrière, interpreted as a distal epithermal system. Our results lead to a conceptual model for the operation of a high-energy geothermal reservoir in the context of an active arc
Janin, Myriam. "Le plateau d'Amsterdam-St Paul : Caractérisation du point chaud éponyme et évolution de son interaction avec la dorsale Sud-est indienne." Phd thesis, Université de Bretagne occidentale - Brest, 2010. http://tel.archives-ouvertes.fr/tel-00592036.
Dibacto, Kamwa Stéphane. "Dynamique de construction et démantèlement des volcans tertiaires et quaternaires des Carpates par des approches géomorphologiques et géochronologiques Growth and erosion constraints of the East Carpathians volcanoes by numerical models: tectonic and climatic implications Eruptive history of the Late Quaternary Ciomadul (Csomád) volcano, East Carpathians, part II: magma output rates Eruptive history of the Late Quaternary Ciomadul (Csomád) volcano, East Carpathians I: timing of lava dome activity constrained by the unspiked K-Ar method." Thesis, université Paris-Saclay, 2020. http://www.theses.fr/2020UPASS144.
In this PhD thesis, 47 new ages have been obtained by the Cassignol-Gillot technique. The very good reproducibility of the ages obtained in this study, added to a strict consistency observed between the volcanic edifices, support the use of the K-Ar method in the dating of the East Carpathian lavas (Călimani-Gurghiu-Harghita) and ignimbrite deposits of the North Hungarian (Mátra and Bükk Mts. [western Carpathians]). In the Eastern part, this new geochronological dataset has been combined with geomorphological analyses to constrain the volcanic history as well as to compute construction and erosion rates of those volcanoes. In parallel, in the western part geochronological dataset has been combined with available paleomagnetic data to refine their stratigraphy. The East Carpathian volcanic range experienced an along-arc, Late Miocene to Quaternary migration of eruptive activity. Here, a novel and complex methodology are presented that yields new geochronological and geomorphological constraints on the evolution of the 20 volcanic edifices. New unspiked K-Ar ages either constrain their lifespan (6.79- 6.47 Ma for Seaca-Tătarca; 5.47- 4.61 Ma for Vârghiş) or date the youngest volcanic activity (central Călimani). For Ciomadul volcanic complex composed by a dozen of lava domes, which hosts the recent volcanic activity since the last 1 Ma, its activity has been constrained between 704± 18 ka and 28 ± 1 ka with several quiescence periods. In parallel, numerical reconstructions of volcanic paleo-topographies were performed to quantify their shape at the end of their construction stage. The inferred initial volcano size shows a wide range (3±3 to 592±115 km³), making up the four main successive volcanic segments (910, 880, 279 and 165 km³ for Călimani, Gurghiu,North Harghita and South Harghita segment, respectively) totalizing 2300 km³. Volume and age constraints allowed computing an average growth rate of 200 km³/Ma for the whole range, characterized by an initial moderate growth rate (137 km³/Ma) of the older volcanoes (11-3.6 Ma) followed by a lower growth rate (28 km³/Ma) obtained for the Plio-Quaternary volcanoes. Comparing reconstructed and current topographies yielded a total eroded volume of 524±125 km³, defining averaged denudation of 22% and a 20 m/Ma erosion rate. Erosion rates for major climatic periods were computed, which highlight the contrasting climatic contexts since 11 Ma. The highest erosion rate (38 m/Ma) occurred during a transitional moderate subtropical continental climate period (9.5-8.2 Ma). An intermediate erosion rate (14m/Ma) characterized a moderate continental climate period (8.2-6.8 Ma) when conditions became less humid. The lowest erosion rate (7 m/Ma) reflects the prevailing continental but occasionally semi-arid climate (6.8-5.8 Ma). The highest erosion rate (28m/Ma) was obtained for Plio-Quaternary times during the interglacial/glacial cycles. Such a quantitative morphometric and geochronological approach demonstrates its efficiency to study volcanic dynamism, including both constructional and erosional processes, through time. In the western part of the Carpathian range, the new ages obtained on the lava flows of Börzsöny made it possible to constraint its period of activity between 14.27 - 15.11 Ma. For the Miocene ignimbrite of Bükk foreland, the new K-Ar results range between 12.7 - 16.5 Ma
Sasseville, Christian. "Géochronologie K-Ar et transfert de matière le long de systèmes de failles et de fractures dans la lithosphère continentale : cas du système de rift Saint-Laurent en relation avec le domaine allochtone des Appalaches (Québec, Canada)." Thèse, 2009. http://www.archipel.uqam.ca/1937/1/D1778.pdf.