Dissertations / Theses: 'Crustal fluid'

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Barker, Shaun, and sbarker@eos ubc ca. "Dynamics of fluid flow and fluid chemistry during crustal shortening." The Australian National University. Research School of Earth Sciences, 2007. http://thesis.anu.edu.au./public/adt-ANU20090711.074630.

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In this thesis, an integrated structural and chemical approach has been used to investigate the spatial and temporal evolution of fluid chemistry, and fluid flow pathways, during crustal shortening. The Taemas Vein Swarm is hosted in a limestone-shale sequence, the Murrumbidgee Group, in the Eastern Belt of the Lachlan Orogen, in New South Wales, Australia. The Taemas Vein Swarm (TVS) is composed of calcite ± quartz veins, hosted in a series of faults and fractures, which extends over an area of approximately 20 km2. The Murrumbidgee Group is composed of several formations, comprising massive grey micritic limestones, redbed sandstones and shales,and thinly interbedded (1020 cm scale) limestones and shales. ¶ The sedimentary sequence has been folded into a series of upright, open to close folds, and was probably deformed during either mid-late Devonian, or early Carboniferous, crustal shortening. To the east, the Murrumbidgee Group is overthrust by a Silurian volcanic sedimentary sequence along the Deakin-Warroo Fault System. Crosscutting and overprinting relationships demonstrate that vein growth was synchronous with folding, with different vein types related to different fold mechanisms at various stages of fold growth. ¶ Flexural slip folding led to the development of bedding-concordant veins (hereafter called bedding-parallel veins). Flexural flow in semicompetent to incompetent beds caused en echelon extension vein arrays to grow. Decoupling between beds, and dilatancy at fold hinges led to significant vein growth. In addition, fold lock-up led to limb-parallel stretching, and the growth of bedding-orthogonal extension fractures. ¶ Vein growth is inferred to have occurred in a compressional tectonic regime (i.e. sigma3=vertical). Oxygen isotope quartz-calcite thermometry suggests that veins formed at temperatures of 100200 oC. The depth of vein formation may have been between about 5 and 8 km. Vein textures indicate that growth of veins occurred during multiple cycles of permeability enhancement and destruction. Subhorizontal extension fractures, and faults at unfavourable angles for reactivation, imply that fluid pressures exceeded lithostatic levels during the growth of some veins. Coexisting extension and shear fractures imply that differential stress levels varied over time. ¶ Flexural slip continued throughout folding at Taemas, despite some fold limbs being at angles extremely unfavourable for reactivation ( > 60). As folds approached frictional lock-up, flexural slip continued to occur when supralithostatic fluid pressures were developed. Therefore, large, bedding-discordant faults were not developed to accommodate strain during folding, explaining a deficiency of larger faults in the TVS. ¶ Infiltration of overpressured fluids occurred into the base of the Murrumbidgee Group, and was channelled into a distributed mesh of small faults and fractures. At the point that a connected backbone flow network developed in the TVS, highpressure fluids would no longer be available to allow continuing flexural slip on fold limbs approaching lockup. Thereafter, larger faults would develop, which would adjust the fault population in the TVS to a more typical displacement-frequency distribution. This had not occurred in the Taemas area by the time crustal shortening ceased. An abundance of small faults, and fracturing driven by invasion of overpressured fluid, implies that the TVS formed via an earthquake swarm process. ¶ Modern analytical techniques, utilising laser ablation sampling technology, allow high-spatial resolution chemical data to be collected from syntectonic veins. Insights into the role that fluid-mineral interface processes may have on the chemistry of minerals grown in syntectonic veins were provided by an experimental study. Moderate sized ( < 1−5 mm) synthetic calcite crystals were successfully grown to investigate the uptake of rare earth elements (REE) into calcite. Changes in crystal morphology are linked to variable solution chemistry, which has important implications for the interpretation of hydrothermal vein textures. High-spatial resolution chemical analyses of synthetic calcite crystals demonstrate significant fluctuations in REE concentrations over distances of < 200 μm within calcite crystals. Time-equivalent regions on different crystal faces have significantly different REE concentrations, indicating that fluctuations in calcite trace element composition cannot be interpreted exclusively in terms of changing bulk fluid composition. Rare earth element anomalies (Eu/Eu* and Ce/Ce*) are not significantly influenced by compositional zoning, and may be robust indicators of changes in solution bulk chemistry and fluid oxidation state. ¶ Changes in isotopic ratios (13C, 18O and 87Sr/86Sr), and trace element concentrations in veins from the TVS are related to variations in fluid source, flow pathways and chemical conditions (e.g. trace element complexation, precipitation rate, fluid oxidation) during hydrothermal fluid flow. This integrated structural, textural and chemical approach has direct application to the examination of hydrothermal veins in fracture-hosted ore deposits, and may allow the fluid source and/or chemical conditions conducive to the formation of high-grade ore to be discerned. ¶ Vein 18O compositions systematically increase upwards through the Murrumbidgee Group, caused by progressive reaction of an externally derived, low-18O fluid (of probable meteoric origin) with host limestones. Vein 18O and 87Sr/86Sr compositions vary spatially and temporally within the same outcrop, and within individual veins, which is inferred to be caused by the ascent of packages of fluid along constantly changing flow pathways. Fluid-buffered oxygen isotope ratios at the earliest stages of deformation imply that the TVS formed via an invasion percolation process. Fluid pathways are inferred to have changed constantly, with fractures toggleswitching between high-permeability and low-permeability states, due to repeated fracture opening and sealing events.

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Warwick, Alison Julie. "Mineral growth and fluid migration in mid-crustal shear zones." Thesis, University of Plymouth, 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.340287.

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Hopkinson, Laurence. "The role of aqueous fluids in crustal processes at the inter and intra-crystalline level." Thesis, University of Southampton, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.296147.

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4

Porritt, R. W., and S. Yoshioka. "Evidence of Dynamic Crustal Deformation in Tohoku, Japan, From Time-Varying Receiver Functions." AMER GEOPHYSICAL UNION, 2017. http://hdl.handle.net/10150/626288.

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Temporal variation of crustal structure is key to our understanding of Earth processes on human timescales. Often, we expect that the most significant structural variations are caused by strong ground shaking associated with large earthquakes, and recent studies seem to confirm this. Here we test the possibility of using P receiver functions (PRF) to isolate structural variations over time. Synthetic receiver function tests indicate that structural variation could produce PRF changes on the same order of magnitude as random noise or contamination by local earthquakes. Nonetheless, we find significant variability in observed receiver functions over time at several stations located in northeastern Honshu. Immediately following the Tohoku-oki earthquake, we observe high PRF variation clustering spatially, especially in two regions near the beginning and end of the rupture plane. Due to the depth sensitivity of PRF and the timescales over which this variability is observed, we infer this effect is primarily due to fluid migration in volcanic regions and shear stress/strength reorganization. While the noise levels in PRF are high for this type of analysis, by sampling small data sets, the computational cost is lower than other methods, such as ambient noise, thereby making PRF a useful tool for estimating temporal variations in crustal structure.

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Nüchter, Jens Alexander. "The structural record of mid crustal stress and pore fluid pressure changes related to the earthquake cycle." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=983666849.

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Hutnak, Michael. "Heat and fluid flux at a crustal scale : observations and models of coupled transport in young oceanic lithosphere /." Diss., Digital Dissertations Database. Restricted to UC campuses, 2007. http://uclibs.org/PID/11984.

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Salazar, Reinoso Pablo [Verfasser]. "The upper crustal microseismicity image from the North Chilean subduction zone : implications for tectonics and fluid migration / Pablo Salazar Reinoso." Berlin : Freie Universität Berlin, 2011. http://d-nb.info/1025511484/34.

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8

Blereau, Eleanore Renee. "A Petrochronological Investigation of Metamorphic, Melt and Fluid Related Processes in Lower Crustal Rocks from Southwestern Norway and Southern India." Thesis, Curtin, 2017. http://hdl.handle.net/20.500.11937/59704.

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A petrochronological approach permitted quantitative constraints on the duration, conditions and spatio-temporal controls on metamorphism within complex high-grade metamorphic terranes. The effects of prolonged high temperatures on commonly used geochronometers, zircon and monazite, contrasts between terranes. The availability of these minerals and information recorded in lower crustal rocks is highly controlled by lower crustal processes, but the involvement of particular processes is resolvable through the integration of many analytical techniques into a coherent multidisciplinary interpretation.

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Wijns, Christopher P. "Exploring conceptual geodynamic models : numerical method and application to tectonics and fluid flow." University of Western Australia. School of Earth and Geographical Sciences, 2005. http://theses.library.uwa.edu.au/adt-WU2005.0068.

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Geodynamic modelling, via computer simulations, offers an easily controllable method for investigating the behaviour of an Earth system and providing feedback to conceptual models of geological evolution. However, most available computer codes have been developed for engineering or hydrological applications, where strains are small and post-failure deformation is not studied. Such codes cannot simultaneously model large deformation and porous fluid flow. To remedy this situation in the face of tectonic modelling, a numerical approach was developed to incorporate porous fluid flow into an existing high-deformation code called Ellipsis. The resulting software, with these twin capabilities, simulates the evolution of highly deformed tectonic regimes where fluid flow is important, such as in mineral provinces. A realistic description of deformation depends on the accurate characterisation of material properties and the laws governing material behaviour. Aside from the development of appropriate physics, it can be a difficult task to find a set of model parameters, including material properties and initial geometries, that can reproduce some conceptual target. In this context, an interactive system for the rapid exploration of model parameter space, and for the evaluation of all model results, replaces the traditional but time-consuming approach of finding a result via trial and error. The visualisation of all solutions in such a search of parameter space, through simple graphical tools, adds a new degree of understanding to the effects of variations in the parameters, the importance of each parameter in controlling a solution, and the degree of coverage of the parameter space. Two final applications of the software code and interactive parameter search illustrate the power of numerical modelling within the feedback loop to field observations. In the first example, vertical rheological contrasts between the upper and lower crust, most easily related to thermal profiles and mineralogy, exert a greater control over the mode of crustal extension than any other parameters. A weak lower crust promotes large fault spacing with high displacements, often overriding initial close fault spacing, to lead eventually to metamorphic core complex formation. In the second case, specifically tied to the history of compressional orogenies in northern Nevada, exploration of model parameters shows that the natural reactivation of early normal faults in the Proterozoic basement, regardless of basement topography or rheological contrasts, would explain the subsequent elevation and gravitationally-induced thrusting of sedimentary layers over the Carlin gold trend, providing pathways and ponding sites for mineral-bearing fluids.

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Hood, Shawn Bruce. "Mid-crustal Cu-Au mineralisation during episodic pluton emplacement, hydrothermal fluid flow, and ductile deformation at the Minto deposit, YT, Canada." Thesis, University of British Columbia, 2012. http://hdl.handle.net/2429/42818.

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The genesis of the Minto copper-gold deposit, YT, Canada, has been variously interpreted since its discovery although no existing model accounts for ductile deformation as a control on mineralization. Results from this study show that Minto ore is hosted within ductiley deformed granitoid host rocks emplaced as multiple intrusions into an actively deforming environment, with the variably sheared host rocks separated by incipiently deformed granodiorites essentially barren of mineralisation. Contacts between deformed/mineralized rock and incipiently deformed/barren rock range from abrupt to gradational, and are the product of pre-existing igneous contacts, variably partitioned deformation, or a combination of these. Deformation of granitoids is interpreted to have controlled fluid flow, with associated alteration promoting further deformation and fluid flow. Potassic alteration, in the form of biotite-magnetite, is the dominant alteration associated with mineralisation, and analysis of alteration using isocon diagrams indicates that K, Fe, Si, Cu, Au, and Ag have been added during alteration, although mass has been lost overall due to a relative reduction in Na and Ca. Host rock intrusion, mineralization, and deformation are interpreted via geochronology and crosscutting relationships as ongoing over at least 5 m.a., from about 202 Ma until about 197 Ma, based on U-Pb SHRIMP geochronology of zircons in granitoids and Re-Os ICP-MS geochronology of molybdenite. The trend of mineralisation is now coincident with the strike of foliation on short steep limbs and of axial planes of folded foliation. This geometry may not be representative of original processes, but of remobilization of ore during continued deformation. The above observations, coupled with data from existing studies, strongly suggest Minto is representative of deposit generation within an arc subduction environment at depths not typically considered for copper-gold deposit formation.

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Maggi, Matteo <1981&gt. "The role of the fluid phase in the chemico-mechanical evolution of a mid-crustal shear zone: an example from Alpine Corsica." Doctoral thesis, Alma Mater Studiorum - Università di Bologna, 2011. http://amsdottorato.unibo.it/3773/.

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Moore, Myles Thomas. "Noble Gas and Hydrocarbon Geochemistry of Coalbed Methane Fields from the Illinois Basin." The Ohio State University, 2016. http://rave.ohiolink.edu/etdc/view?acc_num=osu1462561493.

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13

Ballentine, Christopher John. "He, Ne, and Ar isotopes as tracers in crustal fluids." Thesis, University of Cambridge, 1991. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.387053.

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14

Eglinger, Aurélien. "Cycle de l'uranium et évolution tectono-métamorphique de la ceinture orogénique Pan-Africaine du Lufilien (Zambie)." Thesis, Université de Lorraine, 2013. http://www.theses.fr/2013LORR0306/document.

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L'uranium, élément lithophile et incompatible, peut être utilisé en traceur géochimique pour discuter des différents modèles de formation et d'évolution de la croûte continentale. Ce travail de thèse, ciblé sur la ceinture Pan-Africaine du Lufilien en Zambie, caractérise le cycle de l'U et les minéralisations d'U pour ce segment de croûte continentale. Les séries silicoclastiques/évaporitiques de la ceinture du Lufilien, encaissant les minéralisations d'U, se sont déposées en contexte de rift (bassin du Roan) lors de la dislocation du supercontinent Rodinia au Néoprotérozoïque inférieur. Les âges U-Pb des grains de zircon détritique de ces séries métasédimentaires soulignent une source principalement Paléoprotérozoïque. Ces mêmes grains de zircon présentent des signatures isotopiques epsilonHf inférieures au CHUR (entre 0 et -15) et des âges modèles TDM Hf, compris entre ~2.9 et 2.5 Ga. Ces données suggèrent donc la formation d'une croûte continentale précoce, et donc une extraction mantellique de l'U dès la fin de l'Archéen puis une remobilisation par déformation et métamorphisme au cours du Protérozoïque. L'U aurait donc été remobilisé et re-concentré au cours d'orogenèses successives jusqu'au cycle Pan-Africain. Durant ce cycle Pan-Africain, la datation U-Pb et la signature REY (REE et Yttrium) des cristaux d'uraninite caractérisent un premier évènement minéralisateur, daté vers 650 Ma, associé à la circulation de fluides de bassin expulsés des évaporites du Roan, circulant à l'interface socle/couverture, dans ce contexte de rift continental. Un second événement minéralisateur, daté vers 530 Ma et contemporain du pic métamorphique, est assuré par des fluides métamorphiques issus de la dissolution des évaporites, en contexte de subduction/accrétion continentale. Quelques remobilisations tardives de l'U sont observées lors de l'exhumation des roches métamorphiques
Uranium is an incompatible and lithophile element and can be used as a geochemical tracer to discuss the generation and the evolution of continental crust. This thesis, focused on the Pan-African Lufilian belt in Zambia, characterizes the U cycle for this crustal segment. Silici-clastic and evaporitic sediments have been deposited within an intracontinental rift during the dislocation of the Rodinia supercontinent during the early Neoproterozoic. U-Pb ages on detrital zircon grains in these units indicate a dominant Paleoproterozoic provenance. The same zircon grains show subchondritic epsilonHf (between 0 and -15) and yield Hf model ages between ~2.9 and 2.5 Ga. These data suggest that the continental crust was generated before the end of the Archean associated with U extraction from the mantle. This old crust has been reworked by deformation and metamorphism during the Proterozoic. U has been remobilized and re-concentrated during several orogenic cycles until the Pan-African orogeny. During this Pan-African cycle, U-Pb and REY (REE and Yttrium) signatures of uranium oxides indicate a first mineralizing event at ca. 650 Ma during the continental rifting. This event is related to late diagenesis hydrothermal processes at the basement/cover interface with the circulation of basinal brines linked to evaporites of the Roan. The second stage, dated at 530 Ma, is connected to metamorphic highly saline fluid circulations, synchronous to the metamorphic peak of the Lufilian orogeny. These fluids are derived from the Roan evaporite dissolution. Some late uranium remobilizations are described during exhumation of metamorphic rocks and their tectonic accretion in the internal zone of the Lufilian orogenic belt

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Wilkinson, Jamie John. "The origin and evolution of Hercynian crustal fluids, South Cornwall, England." Thesis, University of Southampton, 1989. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.252719.

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Blythe, Lara S. "Understanding Crustal Volatiles : Provenance, Processes and Implications." Doctoral thesis, Uppsala universitet, Berggrundsgeologi, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-171486.

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Knowledge of the provenance of crustal volatiles and the processes by which they are released is extremely important for the dynamics of magmatic systems. Presented here are the results of multiple investigations, which aim to understand magmatic volatile contamination from contrasting but complementary perspectives. The main methodologies used include He and C isotope values and CO2/3He ratios of volcanic gases and fluids; simulation of magma-carbonate interaction using high-pressure high-temperature experimental petrology; X-ray microtomography of vesiculated xenoliths and computer modeling. Findings show that the contribution from upper crustal volatiles can be substantial, and is dependant on the upper crustal lithology on which a volcano lies, as well as the composition of the magma supplied. Carbonate dissolution in particular is strongly controlled by the viscosity of the host magma. The details of the breakdown of vesiculated xenoliths is complex but has wide reaching implications, ranging from the dissemination of crustally derived materials through a magma body to highlighting that crustal volatiles are largely unaccounted for in both individual volcano and global volatile budgets. In synthesizing the conclusions from each of the individual perspectives presented, I propose the contribution of volatiles from crustal sources to play a significant role in many geological systems. This volatile component should be taken into consideration in future research efforts.

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Furtney, Jason. "Some aspects of fluid flow in the earth's crust." Thesis, University of Cambridge, 2007. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.612773.

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Ay, Erkan. "Origin of crustal reflectivity and influence of fluids and fractures on velocity at the Kola superdeep borehole." Laramie, Wyo. : University of Wyoming, 2007. http://proquest.umi.com/pqdweb?did=1453231711&sid=4&Fmt=2&clientId=18949&RQT=309&VName=PQD.

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Kleine, Barbara. "How do fluids move through rocks? : High fluxes of CO2 in the Earth's crust." Licentiate thesis, Stockholms universitet, Institutionen för geologiska vetenskaper, 2012. http://urn.kb.se/resolve?urn=urn:nbn:se:su:diva-84007.

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Metamorphic hydrous, CO2-bearing fluids play a critical role in the global carbon cycle. However, how big this influence is on the global carbon cycle and therefore on global climatic processes, is unknown. The actual amount of CO2 which is released into the atmosphere due to metamorphic processes is still debated. For this purpose, fluid-driven reactions in metamorphic rocks must be studied by tracking fluid-rock interactions along pathways of ancient fluids. In the study presented in this thesis, we study fluid-rock interaction in the southeastern part of the Greek island Syros in the Cycladic Archipelago (Aegean). On Syros fluid-rock interaction is recorded by the preservation of blueschist facies assemblages at greenschist facies conditions along a normal shear zone. Blueschist preservation is caused by a combination of metasomatic addition of SiO2 and Na2O and elevated XCO2 which is maintained by high fluxes of a CO2-bearing, hydrous fluid along the shear zone. This research aims to provide a better understanding of the role of mountain building in the carbon cycle. Flux estimates for climate-forcing fluid components (e.g. carbon) require that their concentration in the fluid, fluid volumes and velocities are known. This will be the focus of future work. Further, whole rock chemistry and the availability of specific minerals will be studied to achieve knowledge about which kind of parameters influence and enhance the propagation of fluids through rocks.

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Morgan, Sally Jane. "High temperature fluid-rock interaction in oceanic crust: a study of fluid inclusions from the Trooso ophiolite and ODP/IODP Hole 1256D." Thesis, University of Leeds, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.493781.

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Fluid inclusions offer the only available samples of uncontaminated sub-seafloor fluids. To date, microthermometry of such fluid inclusions trapped in ocean crust rocks has revealed that fluids of a wide range of salinities exist in both modem and ancient hydrothermal systems. LAICPMS analyses of fluid inclusion chemistry are reported here.

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Mottaghy, Darius Christopher. "Heat transfer processes in the upper crust: influence of structure, fluid flow, and palaeoclimate." [S.l.] : [s.n.], 2007. http://deposit.ddb.de/cgi-bin/dokserv?idn=985669136.

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Fichtel, Katja [Verfasser], Heribert [Akademischer Betreuer] Cypionka, and Ralf [Akademischer Betreuer] Rabus. "Influence of crustal fluids on growth and activity of marine deep biosphere microbial populations / Katja Fichtel. Betreuer: Heribert Cypionka ; Ralf Rabus." Oldenburg : BIS der Universität Oldenburg, 2014. http://d-nb.info/1066873305/34.

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Yuan, Xiaoping. "Extensional collapses in the overpressured frictional upper crust based on limit analysis." Thesis, Paris Sciences et Lettres (ComUE), 2016. http://www.theses.fr/2016PSLEE009/document.

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Dans ce manuscrit nous développons l'approche cinématique 2D du calcul à la rupture pour examinerles effondrements en extension (ou failles normales) de la croûte supérieure cassante qui résultent desurpressions de fluides. Les sujets d'intérêt liés à la déformation en extension sont (1) les roles de lapression des fluides, des processus de surface, et des propriétés des matériaux et des failles sur lastabilité des structures d'extension; (2) la formation de failles normales à faible pendage et de failleslistriques; (3) la distribution de la déformation au dessus d'un glissement à faible pendage; et (4)l'influence de l'adoucissement mécanique des failles et des processus de sédimentation sur cettedistribution.Cette approche mécanique est vérifiée par la théorie du prisme critique de Coulomb, et la généralise pour étudier la topographie complexe de la péninsule de Mejillones dans le Nord du Chili. Cetteapproche est aussi appliquée à l'instabilité gravitaire dans le delta du Niger en reliant les structurescompressives en bas de pente aux structure extensives en amont par un détachement profond. Nousprédisons des surpressions de fluides beaucoup plus élevée que celles obtenues par application duprisme de Coulomb. Enfin, cette méthodologie est appliquée à l'étude de la forme de failles normalesreliant un détachement profond à la surface. Dans le cas du delta du Niger, nous montrons que lesfailles à faible pendage et les failles listriques impliquent que la profondeur de rétention des fluides estfaible. La version séquentielle de l'analyse limite ouvre de nouvelles voies pour suivre l'évolutionstructurale dans le temps du jeu sur les failles normales. Les simulations montrent en particulier qu'unefaille normale tourne vers des pendage plus faibles au fur et à mesure de la dénudation du mur, formantune région qui passe du mur au toit de la faille active en rotation. La prédiction de cette région estillustrée par des expériences analogiques et des exemples de terrain
This manuscript develops a 2D kinematic approach of Limit Analysis to examine the extensionalfailures in the brittle, upper crust resulting from fluid overpressures and normal faulting. There aremany interesting topics related to the extensional deformation such as (1) the roles of fluid pressure,topographic process, material and fault properties on the stability of extensional structures; (2) theformation of low-angle and listric normal fault; (3) the deformation pattern due to slip on a low-anglefault; and (4) the influence of fault softening and sedimentation processes on this deformation pattern.This mechanical approach applied to wedge prototypes is validated by the critical Coulomb wedge(CCW) theory, and it generalizes the CCW theory to investigate the complex topography on theMejillones peninsula, Northern Chile. Additionally, this approach is also applied to investigate gravityinstability of Niger Delta by linking down-slope compressional to up-slope extensional failures througha deep detachment. We predict much higher fluid overpressures than that of the CCW theory. Finally,this Limit Analysis methodology is applied to investigate the shape of normal fault linking a lowdetachment to the surface. The application to Niger Delta implies that the formation of very low-angleand strongly listric faults results from a shallow fluid-retention depth. The sequential version of LimitAnalysis opens new ways to envision the structural evolution through time resulting from normalfaulting. The simulations show that the normal fault rotates during extension, forming a region of Footto-Hanging Wall (FHW) where the material in the footwall is sheared upon entering the hanging wall.The creation of the FHW region is illustrated by sandbox experiments and field examples

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Zirner, Aurelia [Verfasser]. "Fluid driven processes in the crust - the formation of anorthositic dykes in the Troodos ophiolite (Cyprus) / Aurelia Zirner." Bonn : Universitäts- und Landesbibliothek Bonn, 2017. http://d-nb.info/1149154020/34.

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Louis-Napoléon, Aurélie. "Modélisation d'instabilités gravitaires au sein de la croûte partiellement fondue par une méthode de Volume-Of-Fluid." Thesis, Toulouse, INPT, 2020. http://www.theses.fr/2020INPT0124.

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Les instabilités gravitaires au sein des racines orogéniques partiellement fondues peuvent être à l'origine du développement de dômes de migmatites. Non seulement ces dômes peuvent concentrer des matériaux d’intérêt économique, mais une meilleure compréhension de leur formation présente un intérêt fort dans la connaissance de l’évolution et de la différenciation de la croûte terrestre. Bien que les forces horizontales peuvent être impliquées dans la formation de dômes, l’objectif de cette thèse consistait à regarder uniquement l’influence des forces verticales en étudiant la convection et le diapirisme. Pour cela, nous avions le choix entre deux codes, basés sur la méthode numérique de Volume-Of-Fluid (VOF): JADIM (code de l'IMFT) et OpenFOAM (open-source). Nous avons dans un premier temps montré que la méthode VOF est adaptée à la modélisation des instabilités gravitaires en comparant les résultats obtenus avec i) ceux de la littérature concernant les instabilités de Rayleigh-Taylor et de Rayleigh-Bénard, ii) ceux donnés par le code de géodynamique ASPECT. Nous avons trouvé que JADIM et OpenFOAM fournissent des résultats en bon accord avec ceux de la littérature et conservent mieux la masse qu'ASPECT. Nous avons choisi OpenFOAM pour la suite de ce travail car il est plus rapide que JADIM. Ensuite, nous avons appliqué la méthode VOF au contexte de formation des dômes de migmatites, en considérant plus particulièrement le cas de l'île de Naxos (Grèce). Ces dômes se sont formés entre 24 et 16 millions d'années et présentent une structure imbriquée de sous- dômes de 2 km dans un dôme majeur de 10 km. Des datations sur zircon ont montré que les roches ont subi une alternance de température d'une période de 2 Ma. Ces dômes sont intéressants car ils se sont formés récemment dans l'histoire de la Terre dans une zone orogénique, ils sont donc mieux préservés que les dômes plus anciens. Nous avons cherché à montrer que ces structures peuvent résulter d'épisodes convectif et diapirique. Nous avons d'abord considéré la croûte chaude comme un système constitué de trois couches horizontales. Ce système ne permet pas de former des dômes imbriqués par convection et diapirisme. En effet, les dômes formés au cours de la simulation sont détruits par la convection. Nous avons donc complexifié le système. Nous avons pris en compte le chauffage interne, la fusion partielle, la dépendance des rhéologies sur la température et le taux de déformation, et avons ajouté des hétérogénéités compositionnelles (inclusions). Tous ces éléments ont fait l'objet de tests paramétriques et nous permettent finalement de proposer deux scénarios pour expliquer la formation des dômes de Naxos : le premier fait émerger des diapirs composés d'inclusions au dessus de cellules convectives locales, formées lors de la ségrégation des inclusions lourdes et légères, tandis que le second scénario permet aux inclusions de s'élever pendant la disparition de la cellule convective globale pour former des dômes lors du refroidissement du système. Toutefois, ces scénarios n'excluent pas le rôle de forces latérales extérieures à la fin de l'orogène pour expliquer l'exhumation des dômes. Plus généralement, nous avons trouvé que les caractéristiques des dômes (taille et homogénéité) sont déterminées par leur mode de formation (présence d'inclusions, de convection ...). L'analyse dimensionnelle des systèmes avec fusion partielle nous a permis de distinguer plusieurs régimes convectifs et de déterminer les paramètres nécessaires à la sédimentation (vers le haut et vers la bas) des inclusions lors d'une convection crustale
Gravity instabilities within partially molten orogenic roots may form migmatite domes. Not only can these domes concentrate materials of economic interest, but they also bring a better understanding of the evolution and differentiation of Earth's crust. Although horizontal forces can be involved in the formation of domes, the objective of this thesis was to look only at the influence of vertical forces by studying convection and diapirism. We had at our disposal two numerical codes based on Volume-Of-Fluid methods (VOF): JADIM (IMFT code) and OpenFOAM (open-source). We first showed that the VOF method is suitable for the modeling of gravity instabilities. Therefore we compared the results obtained with JADIM and OpenFOAM with i) theoretical, experimental and numerical results from the literature of RayleighTaylor and Rayleigh-Bénard instabilities and with ii) the results of the geodynamic code ASPECT . We found that JADIM and OpenFOAM provide results in good agreement with those in the literature and conserve mass better than ASPECT. We chose OpenFOAM for the rest of this work because it is faster than JADIM. Then, we applied the VOF method to the context of the migmatite domes from Naxos island (Greece). These domes were formed between 24 and 16 Ma and feature nested structures of 2 km sub-domes in a 10 km major dome. Zircon dating has shown that the rocks have undergone a temperature alternation with a 2 Ma period. These domes are interesting because they are recent and thus better preserved than older domes. We have tried to show that they can result from a combination of convective and diapiric episodes. We first considered the hot orogenic crust as a system made of 3 horizontal layers with temperature dependent viscosity. We showed that both in 2D and 3D, we cannot reproduce nested domes: the simulated domes are destroyed by convection when it appears. Therefore we made the system more complex. We took into account internal heating and partial melting which allow to achieve low viscosities. In addition, we added the strain-rate dependency of the rheology, as well as compositional heterogeneities (inclusions). All these factors were subjected to parametric tests, which finally allow us to propose two scenarios explaining the formation of the Naxos domes. The first scenario takes into account a nonlinear rheology and heavy and light inclusions, making it possible to generate local convection: convection and diapirism are then simultaneous, and diapirs emerge above the convective cells. The second scenario takes into account partial melting, but the progressive cooling of the system is the key mechanism that allows light inclusions to rise and form domes. However, both these scenarios do not exclude the role of external lateral forces at the end of the orogen on the remaining exhumation. More generally, we have found that the characteristics of the domes (size and homogeneity) are determined by their mode of formation (presence of inclusions, convection ...) The dimensional analysis of systems with partial melting allows us to distinguish several convective regimes and to determine the parameters necessary for the sedimentation (upwards and downwards) of inclusions during crustal convection

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26

Higashino, Fumiko. "Infiltration process of brine in the deep crust constrained from multi-scale major and trace element zonings in high-grade metamorphic rocks." 京都大学 (Kyoto University), 2016. http://hdl.handle.net/2433/215324.

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Laurie, Angelique. "The formation of Earth’s early felsic continental crust by water-present eclogite melting." Thesis, Stellenbosch : Stellenbosch University, 2013. http://hdl.handle.net/10019.1/80214.

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Thesis (PhD)--Stellenbosch University, 2013.
ENGLISH ABSTRACT: The sodic and leucocratic Tonalite, Trondhjemite and Granodiorite (TTG) granitoid series of rocks characterise Paleo- to Meso- Archaean felsic continental crust, yet are uncommon in the post-Archaean rock record. Consequently, petrogenetic studies on these rocks provide valuable insight into the creation and evolution of Earth’s early continental crust. The highpressure (HP)-type of Archaean TTG magmas are particularly important in this regard as their geochemistry requires that they are formed by high-pressure melting of a garnet-rich eclogitic source. This has been interpreted as evidence for the formation of these magmas by anatexis of the upper portions of slabs within Archaean subduction zones. In general, TTG magmas have been assumed to arise through fluid-absent partial melting of metamafic source rocks. Therefore, very little experimental data on fluid-present eclogite melting to produce Archaean TTG exist, despite the fact that water drives magmatism in modern arcs. Consequently, this study experimentally investigates the role of fluid-present partial melting of eclogite-facies metabasaltic rock in the production of Paleo- to Meso-Archaean HP-type TTG melts. Experiments are conducted between 1.6 GPa and 3.0 GPa and 700 ºC and 900 ºC using natural and synthetic eclogite, and gel starting materials of low-K2O basaltic composition. Partial melting of the natural and synthetic eclogite occurred between 850 ºC and 870 ºC at pressures above 1.8 GPa, and the melting reaction is characterised by the breakdown of sodic clinopyroxene, quartz and water: Qtz + Cpx1 + H2O ± Grt1 = Melt + Cpx2 ± Grt2. The experimental melts have the compositions of sodic peraluminous trondhjemites and have compositions that are similar to the major, trace and rare earth element composition of HPtype Archaean TTG. This study suggests that fluid-present eclogite melting is a viable petrogenetic model for this component of Paleo- to Meso-Archaean TTG crust. The nature of the wet low-K2O eclogite-facies metamafic rock solidus has been experimentally defined and inflects towards higher temperatures at the position of the plagioclase-out reaction. Therefore, the results indicate that a crystalline starting material is necessary to define this solidus to avoid metastable melting beyond temperatures of the Pl + H2O + Qtz solidus at pressures above plagioclase stability. Furthermore, this study uses numerical and metamorphic models to demonstrate that for reasonable Archaean mantle wedge temperatures within a potential Archaean subduction zone, the bulk of the water produced by metamorphic reactions within the slabs is captured by an anatectic zone near the slab surface. Therefore, this geodynamic model may account for HP-type Archaean TTG production and additionally provides constraints for likely Archaean subduction. The shape of the relevant fluid-present solidus is similar to the shape of the pressure-temperature paths followed by upper levels of the proposed Archaean subducting slab, which makes water-fluxed slab anatexis is very dependant on the temperature in the mantle wedge. I propose that cooling of the upper mantle by only a small amount during the late Archaean ended fluid-present melting of the slab. This allowed slab water to migrate into the wedge and produce intermediate composition magmatism which has since been associated with subduction zones.
AFRIKAANSE OPSOMMING: Die reeks natruimhoudende en leukokraties Tonaliet, Trondhjemiet en Granodioriet (TTG) felsiese stollingsgesteentes is kenmerkend in die Paleo- tot Meso-Argeïkum felsiese kontinentale kors, maar is ongewoon in die post-Argeïese rots rekord. Gevolglik, petrogenetiese studies op hierdie rotse verskaf waardevolle insig in die skepping en evolusie van die aarde se vroeë kontinentale kors. Die hoë-druk (HD)-tipe van die Argeïkum TTG magmas is veral belangrik in hierdie verband as hulle geochemie vereis dat hulle gevorm word deur hoë druk smelting van 'n granaat-ryk eklogitiese bron. Dit word interpreteer as bewys vir die vorming van hierdie magmas deur smelting van die boonste gedeeltes van die blaaie in Argeïese subduksie sones. TTG magmas in die algemeen, is veronderstel om op te staan deur middel van water-afwesig gedeeltelike smelting van metamafiese bron rotse. Daarom bestaan baie min eksperimentele data op water-teenwoordig eklogiet smelting om Argeïkum TTG te produseer, ten spyte van die feit dat water magmatisme dryf in moderne boë. Gevolglik is hierdie studie ‘n eksperimentele ondersoek in die rol van water-teenwoordig gedeeltelike smelting van eklogiet-fasies metamafiese rots in die produksie van Paleo- tot Meso-Argeïkum HD-tipe TTG smelte. Eksperimente word uitgevoer tussen 1.6 GPa en 3.0 GPa en 700 ºC en 900 ºC met behulp van natuurlike en sintetiese eklogiet, en gel begin materiaal van lae-K2O basaltiese samestelling. Gedeeltelike smelting van die natuurlike en sintetiese eklogiet het plaasgevind tussen 850 ºC en 870 ºC te druk bo 1.8 GPa, en die smeltings reaksie is gekenmerk deur die afbreek van natruimhoudende klinopirokseen, kwarts en water: Qtz + Cpx1 + H2O ± Grt1 = Smelt + Cpx2 ± Grt2. Die eksperimentele smelte het die komposisies van natruimhoudende trondhjemites en is soortgelyk aan die hoof-, spoor- en seldsame aard element samestelling van HD-tipe Argeïkum TTG. Hierdie studie dui daarop dat water-teenwoordig eklogiet smelting 'n lewensvatbare petrogenetiese model is vir hierdie komponent van Paleo- tot Meso-Argeïkum TTG kors. Die aard van die nat lae-K2O eklogietfasies metamafiese rock solidus is eksperimenteel gedefinieër en beweeg na hoër temperature by die posisie van die plagioklaas-out reaksie. Daarom dui die resultate daarop dat 'n kristallyne materiaal nodig is om hierdie solidus te definieër en metastabiele smelting buite temperature van die Pl + H2O + Qtz solidus druk bo plagioklaas stabiliteit te vermy. Verder maak hierdie studie gebruik van numeriese en metamorfiese modelle om aan te dui dat die grootste deel van die water geproduseer deur metamorfiese reaksies binne die blaaie bestaan vir redelike Argeïkum mantel wig temperature binne 'n potensiële Argeïkum subduksie sone, en word opgevang deur 'n smelting sone naby die blad oppervlak. Daarom kan hierdie geodinamies model rekenskap gee vir HD-tipe Argeïkum TTG produksie en dit bied ook die beperkinge vir waarskynlik Argeïese subduksie. Die vorm van die betrokke waterteenwoordig solidus is soortgelyk aan die vorm van die druk-temperatuur paaie gevolg deur die boonste vlakke van die voorgestelde Argeïkum subderende blad, wat water-vloeiing blad smeltingbaie afhanklik maak van die temperatuur in die mantel wig. Ons stel voor dat afkoeling van die boonste mantel met slegs 'n klein hoeveelheid gedurende die laat Argeïese, die water-vloeiing smelting van die blad beëindig. Dit het toegelaat dat die blad water in die wig migreer en intermediêre samestelling magmatisme produseer wat sedert geassosieer word met subduksie sones.

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Siebenaller, Luc. "Circulations fluides au cours de l'effondrement d'un prisme d'accrétion crustal : l'exemple du "Metamorphic Core Complex" de l'île de Naxos (Cyclades, Grèce)." Thesis, Nancy 1, 2008. http://www.theses.fr/2008NAN10139/document.

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Cette thèse a pour objectif de caractériser les circulations de fluides en contexte d’effondrement d’un prisme d’accrétion crustal. Le Metamorphic Core Complex (MCC) de Naxos comprend un système de détachement/décollement caractérisé par mylonites, ultramylonites, cataclasites et failles normales dont les relations géométriques témoignent du litage rhéologique de la croûte continentale. La chimie des inclusions fluides déterminée par l’analyse microthermométrique, la spectroscopie RAMAN, l’ablation laser couplée à l’analyse spectroscopique (LA-ICP-MS), le « crush-leach », et les signatures isotopiques C et H des inclusions fluides permettent d’identifier trois grands types de fluides (1) des fluides salés riche en métaux, ii) des fluides aquo-carboniques en équilibre avec les encaissants métamorphiques, et iii) des fluides aqueux, probablement d’origine météorique. Ces données indiquent que la croûte est subdivisée en deux réservoirs séparés par la transition fragile-ductile. Les fluides météoriques circulent en association avec la déformation fragile de la croûte supérieure alors que les fluides salés et les fluides aquo-carboniques circulent en relation avec la déformation ductile. La géométrie de ces réservoirs évolue lors de la formation du MCC, conjointement avec l’exhumation et le refroidissement des roches métamorphiques. Le passage des roches du réservoir ductile au réservoir fragile est associée à un changement depuis un gradient géothermique élevé (60-100°C/km) vers un gradient géothermique plus faible (35-60°C/km). La transition fragile-ductile correspond ainsi à la fois à une limite rhéologique corrélée à une limite thermique et une limite de perméabilité
The aim of this thesis is to characterize fluid circulations in the context of the collapse of a crustal accretionary belt. The Naxos Metamorphic Core Complex comprises a detachment/decollement system characterized by mylonites, ultramylonites, cataclasites and normal faults with structural relationships reflecting the rheological layering at the crustal scale. Fluid inclusion chemistry is determined by microthermometry, Raman spectroscopy; laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS), crush-leach and stable isotopes (C and H) analyses. These data characterize three different types of fluids: (1) high salinity fluids with a high metal content and high Th, (2) aqueous-carbonic fluids in equilibrium with the wall rocks and (3) aqueous probably surface-derived fluids. These data indicate that the crust is subdivided into two crustal reservoirs separated by the brittle/ductile transition. Surface-derived aqueous fluids circulate in association with the brittle deformation within the upper crust whereas aqueous-carbonic and high salinity fluids circulate in relation with ductile deformation. The characteristics of the trapped fluids indicate that as rocks have passed through the ductile/brittle transition they undergo a drastic change in geothermal gradient from 60 to 100°C/km within a lithostatic pressure regime to 35-60°C/km within a hydrostatic pressure regime. This implies that the fluid circulations are closely related to the rheological layering within the crust and its evolution during crustal extension. The ductile/brittle transition corresponds to a rheological boundary correlated to a thermal boundary and impermeable cap

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Wiersberg, Thomas. "Edelgase als Tracer für Wechselwirkungen von Krusten- und Mantelfluiden mit diamantführenden Gesteinen des östlichen Baltischen Schildes." Phd thesis, Universität Potsdam, 2001. http://opus.kobv.de/ubp/volltexte/2005/27/.

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In der vorliegenden Arbeit werden anhand der Edelgaszusammensetzung von Kimberliten und Lamproiten sowie ihrer gesteinsbildenden Minerale die Wechselwirkungen dieser Gesteine mit Fluiden diskutiert. Die untersuchten Proben stammen vom östlichen Baltischen Schild, vom Kola-Kraton (Poria Guba und Kandalaksha) und vom karelischen Kraton (Kostamuksha). Edelgasanalysen nach thermischer oder mechanischer Gasextraktion von 23 Gesamtgesteinsproben und 15 Mineralseparaten ergeben folgendes Bild: Helium- und Neon-Isotopendaten der Fluideinschlüsse von Lamproiten aus Kostamuksha lassen auf den Einfluss einer fluiden Phase krustaler Herkunft schliessen. Diese Wechselwirkungen fanden wahrscheinlich schon während des Magmenaufstiegs statt, denn spätere Einflüsse krustaler Fluide auf die Lamproite und ihr Nebengestein (Quarzit) sind gering, wie anhand der C/³⁶Ar-Zusammensetzung gezeigt wird. Auch sind die mit verschiedenen Datierungsmethoden (Rb-Sr, Sm-Nd, K-Ar) an Mineralseparaten und teilweise an Gesamtgestein ermittelten Alter konsistent und machen eine metamorphe Überprägung unwahrscheinlich. Aufgrund der Verteilung der primordialen Edelgasisotope zwischen Fluideinschlüssen und Gesteinsmatrix ist ein langsamer Magmenaufstieg anzunehmen, was die Möglichkeit der Kontamination mit einem krustalen Fluid während des Magmenaufstiegs erhöht.

Die Gasextraktion aus Mineralseparaten erfolgte thermisch, wodurch eine Freisetzung der Gase ausschließlich aus Fluideinschlüssen nicht möglich ist. Hierbei zeigen Amphibol und Klinopyroxen, separiert aus Kostamuksha-Lamproiten, in ihrer Neon-Isotopenzusammensetzung im Vergleich zur krustalen Zusammensetzung (Kennedy et al., 1990) ein leicht erhöhtes Verhältnis von ²⁰Ne/²²Ne, was ein Hinweis auf Mantel-Neon sein könnte. Kalifeldspäte, Quarz und Karbonate enthalten dagegen nur Neon krustaler Zusammensetzung. Phlogopite haben sehr kleine Verhältnisse von ²⁰Ne/²²Ne und ²¹Ne/²²Ne, zurückzuführen auf in-situ-Produktion von ²²Ne in Folge von U- und Th-Zerfallsprozessen.

Wie unterschiedliche thermische Entgasungsmuster für ⁴⁰Ar und ³⁶Ar zeigen, ist ³⁶Ar in Fluideinschlüssen konzentriert. Das ⁴⁰Ar/³⁶Ar-Isotopenverhältnis der Fluideinschlüsse von Lamproiten aus Kostamuksha ist antikorreliert mit der durch thermische Extraktion bestimmten Gesamtmenge an ³⁶Ar. Argon aus Fluideinschlüssen setzt sich daher aus zwei Komponenten zusammen: Einer Komponente mit atmosphärischer Argon-Isotopenzusammensetzung und einer krustalen Komponente mit einem Isotopenverhältnis ⁴⁰Ar/³⁶Ar > 6000. Diffusion von radiogenem ⁴⁰Ar aus der Kristallmatrix in die Fluideinschlüsse spielt keine wesentliche Rolle.

Kimberlite aus Poria Guba und Kandalaksha zeigen anhand der Helium- und z. T. auch der Neon-Isotopenzusammensetzung eine Mantelkomponente in den Fluideinschlüssen an. Bei einem angenommenen ²⁰Ne/²²Ne-Isotopenverhältnis von 12,5 in der Mantelquelle ergibt sich ein ²¹Ne/²²Ne-Isotopenverhältnis von 0,073 ± 0,011 sowie ein ³He/⁴He-Isotopenverhältnis, welches im Vergleich zum subkontinentalem Mantel (Dunai und Baur, 1995) stärker radiogen geprägt ist. Solche Isotopensignaturen sind mit höheren Konzentrationen an Uran und Thorium in der Mantelquelle der Kimberlite zu erklären.

Rb-Sr- und Sm-Nd-Altersbestimmungen erfolgten von russischer Seite (Belyatskii et al., 1997; Nikitina et al., 1999) und ergeben ein Alter von 1,23 Ga für den Lamproitvulkanismus in Kostamuksha. Eigene K-Ar-Datierungen an Phlogopiten und Kalifeldspäten stimmen mit einem Alter von 1193 ± 20 Ma fast mit den Rb-Sr- und Sm-Nd-Altern überein. Die K-Ar-Datierung an einem Phlogopit aus Poria Guba, separiert aus dem Kimberlit PGK 12a, ergibt ein Alter von 396 Ma, ebenfalls in guter Übereinstimmung mit Rb-Sr-und Sm-Nd-Altern (ca. 400 Ma, Lokhov, pers. Mitteilung). K-Ar-Altersbestimmungen an Gesamtgestein aus Poria Guba erbrachten kein schlüssiges Alter. Die Rb-Sr- und Sm-Nd-Alter des Lamproitmagmatismus in Poria Guba betragen 1,72 Ga (Nikitina et al., 1999).

Vergleiche von gemessenen mit berechneten Edelgaskonzentrationen aus in-situ-Produktion zeigen weiterhin, dass in Abhängigkeit vom Alter der Probe Diffusionsprozesse stattgefunden haben, die zu unterschiedlichen und z. T. erheblichen Verlusten an Helium und Neon führten. Diffusionsverluste an Argon sind dagegen kaum signifikant. Unterschiedliche Diffusionsverluste in Abhängigkeit von Alter und betrachtetem Edelgas zeigen auch die primordialen Edelgase.
In the present thesis, interactions of kimberlites and lamproites as well as their constituent minerals with fluids are discussed based on noble gas compositions. The samples originate from the eastern Baltic Shield, more specifically from the Kola craton (Poria Guba and Kandalaksha) and the Karelia craton (Kostamuksha). Gas was extracted by stepwise heating and crushing from 23 whole rock samples and 15 mineral separates. These two techniques allow differential extraction of gas from fluid inclusions (crushing technique) and from the bulk sample (stepwise heating). The noble gas analyses provide the following information:

Helium and neon isotopic compositions of fluid inclusions in lamproites reveal the presence of a crustal fluid phase. Fluid interaction probably ocurred already during the process of magma ascent. Interaction after lamproite emplacement seems unlikely. The lamproites and their host rock differ in the degree of fluid-rock interaction, as demonstrated by the C/³⁶Ar composition. In addition, various dating methods (Rb-Sr, Sm-Nd, K-Ar) yield almost the same age within analytical error. Thus, a metamorphic overprint can be excluded. The distribution of primordial noble gases between fluid inclusions and crystal lattice suggests a relatively slow magma ascent, making an interaction of the lamproitic magma with crustal fluids even more likely. Since noble gases from mineral separates were extracted only by the stepwise heating method, gases stored in fluid inclusions could not be released separately.

Amphibole and clinopyroxene separates yielded a higher ²⁰Ne/²²Ne ratio in comparison to crustal composition (Kennedy et al., 1990). This presumably is an indication of a mantle derived fluid phase. On the other hand, neon isotopic composition of K-feldspar, quartz and carbonate separates are indistinguishable from the crustal composition. In comparison to other mineral separates, phlogopite yields very low ratios of ²⁰Ne/²²Ne and ²¹Ne/²²Ne due to in situ production of ²²Ne, which is a result of nuclear reactions.

The distinct thermal gas release patterns of ⁴⁰Ar and ³⁶Ar indicates that ³⁶Ar is concentrated in fluid inclusions. The ⁴⁰Ar/³⁶Ar isotopic ratio in fluid inclusions shows a negative correlation with the total amount of ³⁶Ar released by thermal extraction. Therefore, argon from fluid inclusions is a simple 2-component mixture of air and a crustal component with an ⁴⁰Ar/³⁶Ar ratio > 6000. It can be shown that diffusion of ⁴⁰Ar from the matrix into fluid inclusions is negligible.

In contrast to lamproites, whole rock kimberlite samples from Poria Guba and Kandalaksha show clear evidence in helium and, to a certain extentalso in neon isotope ratios, of interaction with a mantle derived fluid phase. Assuming a ²⁰Ne/²²Ne ratio of 12.5 for the mantle endmember, a ²¹Ne/²² Ne ratio of 0.073 ± 0.011 can be calculated. Likewise, the resulting ³He/⁴He ratio is more strongly influenced by radiogenic helium in comparison to the mean subcontinental mantle (Dunai und Baur, 1995). Such behaviour reflects higher concentrations of uranium and thorium in the magma source of kimberlites than the subcontinental mantle.

Rb-Sr and Sm-Nd age determinations (Belyatskii et al., 1997; Nikitina et al., 1999) yield 1.23 Ga for the lamproite magmatism in Kostamuksha. K-Ar dating of phlogopite and K-feldspar provides similar ages (1.19 Ga). K-Ar dating of a single phlogopite separate from the Kimberlite sample PGK12a from Poria Guba, yields an age of 396 Ma which corresponds well with Rb-Sr and Sm-Nd ages.

Depending on sample age, distinct and partly extensive diffusive loss of helium and neon has occurred, as shown by comparison of measured and calculated concentrations of in situ produced isotopes. Diffusion loss is negligible for argon. This is also strongly supported by primordial noble gas composition.

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Zoporowski, Anna [Verfasser]. "Dynamical and Mechanistic Effects of High Pressure Fluids in the Earth's Crust / Anna Zoporowski. Mathematisch-Naturwissenschaftliche Fakultät." Bonn : Universitäts- und Landesbibliothek Bonn, 2012. http://d-nb.info/1021444855/34.

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Ichiki, Masahiro. "Resistivity Structures of a Subduction Zone and a Seismically Active Area - Some Evidence of Fluid and its Role in the Earth's Crust and the Uppermost Mantle." 京都大学 (Kyoto University), 1999. http://hdl.handle.net/2433/181956.

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32

Baese, Rauno [Verfasser]. "Fluid-rock interaction processes during subduction and exhumation of oceanic crust: Constraints from jadeitites in serpentinites, eclogite veins in blueschists and tectonic breccias formed during uplift / Rauno Baese." Kiel : Universitätsbibliothek Kiel, 2013. http://d-nb.info/1030604762/34.

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Abily, Bénédicte. "Caractéristiques pétrographique, géochimique et structurale de la section crustale profonde de l'ophiolite d'Oman : Implications pour la genèse des magmas et le fonctionnement des chambres magmatiques à l'aplomb d'un centre d'expansion océanique." Phd thesis, Université Paul Sabatier - Toulouse III, 2011. http://tel.archives-ouvertes.fr/tel-00627553.

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Ce travail repose sur (1) une étude de terrain des cumulats lités de l'ophiolite d'Oman, notamment dans plusieurs massifs où cette unité restait largement inexplorée, (2) une étude pétrographique et géochimique (microsonde électronique et LA-ICP-MS) d'environ 700 échantillons et (3) une simulation en laboratoire de la cristallisation de magmas boninitiques en présence d'eau. La cinquantaine de faciès pétrographiques définie, gabbroïques et ultrabasiques, est indispensable pour décrire rigoureusement la croûte profonde omanaise. Cette variété lithologique est révélatrice de la très grande variabilité des paramètres intensifs (P, T°, PH2O ...) et extensifs (composition) lors de la cristallisation des magmas au sein des chambres magmatiques à l'aplomb d'un centre d'expansion océanique. L'orthopyroxène précoce dans les cumulats primitifs (XMg > 80 %) est beaucoup plus commun que ce qui était proposé jusqu'à présent, ce qui remet en cause certaines idées reçues concernant l'origine de l'ophiolite. Je démontre que cette variété lithologique, l'abondance d'orthopyroxène, et d'autres caractéristiques pétrographiques et géochimiques des cumulats d'Oman s'expliquent par le mélange, dans des proportions variables, de deux principaux magmas : un d'affinité tholéiitique issu de la fusion d'une source asthénosphérique " N-MORB ", et un d'affinité andésitique à boninitique issu de la fusion hydratée d'une source lithosphérique déprimée. Ces deux magmas ont circulé dans des chenaux mantelliques (" filons ") avant d'alimenter les chambres. Le rôle de " mélangeur " des chambres magmatiques est ainsi confirmé. La contribution relative de ces deux magmas évolue au cours de l'ascension de diapirs asthénosphériques dans la lithosphère. Des variations abruptes de la pression partielle d'eau sont également indispensables pour rendre compte de l'ensemble de mes observations. Je montre aussi que les failles syn-accrétions, dont l'importance en Oman restait largement sousévaluée, sont un vecteur principal de la pénétration de fluides hydrothermaux jusque dans la croûte profonde en cours de cristallisation. Mon étude me permet également de mieux contraindre l'origine, encore très discutée, des intrusions " wehrlitiques " et de la zone de transition dunitique.

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34

Wilckens, Frederike Kristina [Verfasser], Simone A. [Akademischer Betreuer] Kasemann, Simone A. [Gutachter] Kasemann, and Wolfgang [Gutachter] Bach. "Isotopic signatures in hydrothermal vent fluids and the oceanic crust : tracing of sub-seafloor magmatic and hydrothermal processes / Frederike Kristina Wilckens ; Gutachter: Simone A. Kasemann, Wolfgang Bach ; Betreuer: Simone A. Kasemann." Bremen : Staats- und Universitätsbibliothek Bremen, 2017. http://d-nb.info/115700704X/34.

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35

Grasso, Jean-Robert. "Fluides et instabilités sismiques : implications pour le comportement mécanique de la croûte supérieure." Phd thesis, Grenoble 1, 1993. http://tel.archives-ouvertes.fr/tel-00703292.

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Sur la base des faibles variations de contraintes poroélastiques qui sont à l'origine de la séismicité déclenchée localement par la baisse de pression du gisement de Lacq, on tente dans le chapitre 3 d'évaluer les échelles spatiales des connections fluides dans la croûte supérieure à l'aide de la migration des fronts de pression induits. Les séismes associés à la mise en eau d'une retenue artificielle (M 4-5, Monteynard, Vercors, France) permettent par exemple de cartographier des failles sismiques potentielles au sud de l'agglomération grenobloise, les séismes induits jouant alors le rôle de jauges de contrainte. Dans la région de Lacq, à l'aide de modélisations analytiques des transferts de contraintes visco-élastiques et poro-élastiques, on montre qu'on ne peut rejeter a-priori des interactions entre l'extraction du champ de Lacq, les séismes majeurs de la faille Nord-Pyrénéenne distants d'une trentaine de kilomètres, et les séismes locaux à l'aplomb du champ d'hydrocarbure. Le chapitre 4 constitue une synthèse des mécanismes d'instabilités sismiques déclenchées par les exploitations d'hydrocarbures. On isole trois classes de mécanismes de déclenchements des séismes correspondant à des types d'exploitations et à des réponses sismiques (taille-temps-espaces) bien différenciés: augmentation de pression due à l'injection de fluide; baisse de pression due à extraction de fluide, déficit de masse lors d'extraction massive. Les mécanismes de ruptures sont en accord avec les lois de contraintes effectives, et s'expliquent soit par des transferts poroélastiques soit par des compensations isostasiques. Si la sismicité induite par les extractions de fluides reste marginale par rapport au nombre de gisements exploités, la surveillance sismique fine effectuée sur les gisements montre que de nombreux petits séismes (M < 3) sont présents et permettent un suivi in-situ du comportement des réservoirs au cours de l'exploitation. Notre approche de la séismicité à l'aide des séismes induits par des activités humaines montre les limites des lois de la mécanique classique qui, si elles permettent de comprendre et d'évaluer les seuils critiques qui déclenchent les instabilités sismiques, ne peuvent expliquer ni la durée des phénomènes d'instabilités qui sont entretenus durant de nombreuses années ni la taille des instabilités sismiques (Mmax 7). Sur la base des cas mondiaux de séismicité induite on propose la notion de Systèmes Critiques Auto Organisés Induits où l'on peut observer la genèse, la pérennité et la disparition de systèmes critiques dans un contexte, proposé par ailleurs, d'état critique auto-organisé pour l'ensemble de la croûte supérieure.

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36

Rigaudier, Thomas. "Analyse isotopique des inclusions fluides des matériaux de la croûte terrestre : caractérisation des sources des fluides et reconstitutions paléoclimatiques." Phd thesis, Université Claude Bernard - Lyon I, 2010. http://tel.archives-ouvertes.fr/tel-00733643.

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Un des enjeux majeurs en Science de la Terre ces dernières décennies est de comprendre les interactions entre les différentes enveloppes terrestres. Le but poursuivi par ce travail est d'aborder quelques aspects de ces interactions du point de vue des cycles géochimiques des éléments volatils H2O et CO2 en se basant sur l'étude des inclusions fluides piégées dans des roches variées de la croûte terrestre, depuis sa surface jusqu'à l'interface croûte-manteau. La première partie de mon travail présente des travaux expérimentaux effectués sur de la halite. L'étude du fractionnement isotopique de l'oxygène et des cinétiques d'équilibration entre H2O et CO2 lors de l'évaporation de saumures a montré l'importance des corrections à effectuer sur les mesures isotopiques de l'oxygène pour des solutions de haute salinité. L'élaboration d'un protocole expérimental de précipitation de halite en milieu contrôlé a permis de mettre en évidence le potentiel des inclusions fluides pour les reconstitutions paléoclimatiques. La combinaison des données microthermométriques et des compositions isotopiques de l'hydrogène et de l'oxygène des inclusions aqueuses permet d'estimer les sources et la température de l'eau de formation de la halite ainsi que la vitesse du vent à l'interface eau-air pendant la croissance du cristal. Cette méthode a été ensuite appliquée aux dépôts de halite de Sicile datés du Messinien. La deuxième partie de mon travail est consacrée à l'identification des compositions chimiques et des sources des fluides circulant dans la croûte et à l'interface croûte-manteau à travers l'analyse des compositions isotopiques des inclusions fluides des granites et granulites.

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37

Barker, Shaun. "Dynamics of fluid flow and fluid chemistry during crustal shortening." Phd thesis, 2007. http://hdl.handle.net/1885/49303.

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In this thesis, an integrated structural and chemical approach has been used to investigate the spatial and temporal evolution of fluid chemistry, and fluid flow pathways, during crustal shortening. The Taemas Vein Swarm is hosted in a limestone-shale sequence, the Murrumbidgee Group, in the Eastern Belt of the Lachlan Orogen, in New South Wales, Australia. The Taemas Vein Swarm (TVS) is composed of calcite ± quartz veins, hosted in a series of faults and fractures, which extends over an area of approximately 20 km2. The Murrumbidgee Group is composed of several formations, comprising massive grey micritic limestones, redbed sandstones and shales,and thinly interbedded (10–20 cm scale) limestones and shales. ¶ ...

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38

Kay, B. V. "Testing the uncover paradigm: crustal fluid pathways in the Curnamona Province." Thesis, 2017. http://hdl.handle.net/2440/128253.

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This item is only available electronically.
In July 2017, scale-reduction was undertaken to improve the bandwidth and resolution of the AusLAMP defined Curnamona Conductor (Robertson et al., 2016) by way of a broadband magnetotelluric profile with site spacing of 2 km, extending from the Erudina Domain across the Mudguard and Quinyambie Domains in the Curnamona Province. A fossil fluid pathway has been identified from the lower mid crustal conductor to the near surface situated near a topographic basement high. The upper crustal conductor has been further delineated beneath the Quinyambie Domain to within 5 km of the surface situated alongside a major crustal feature.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2017

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39

Soeffky, P. "Delineating the deep crustal fluid link between the Paralana Enhanced Geothermal System and the Beverley Uranium Mine using magnetotellurics." Thesis, 2012. http://hdl.handle.net/2440/95486.

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This item is only available electronically.
The global demand for clean energy alternatives is constantly increasing, creating significant interest for more sustainable energy resources such as uranium and geothermal. Australia is host to over 25% of the world's known uranium resources as well as having significant geothermal potential. The Mount Painter Domain, in the Northern Flinders Ranges in South Australia, is in a region of anomalously high heat flow generated by radiogenic decay of uranium and thorium rich granites. Two distinct uranium deposits have formed from dissolved uranium carried from the ranges by fluids, being deposited where reduction in sediment pH precipitates uranium. In May 2012 a magnetotelluric profile was collected, extending from the Northern Flinders Ranges to the Lake Frome embayment to help constrain existing resistivity models. Precipitation of uranium at the Beverley Mine site is anomalous as no surface water flow is present, suggesting the presence of subsurface processes. This pathway is linked to a 50m conductive body at the brittle-ductile boundary of the mid-crust, directly under the Paralana geothermal prospect. 3D modelling of the Paralana geothermal prospect suggests deep conductive features connecting with features at the surface.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Earth and Environmental Sciences, 2012

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40

Nüchter, Jens Alexander [Verfasser]. "The structural record of mid crustal stress and pore fluid pressure changes related to the earthquake cycle / Jens Alexander Nüchter." 2007. http://d-nb.info/983666849/34.

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41

Hensch, Martin [Verfasser]. "On the interrelation of fluid induced seismicity and crustal deformation at the Columbo submarine volcano (Aegean Sea, Greece) / vorgelegt von Martin Hensch." 2009. http://d-nb.info/1000297624/34.

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42

Robin, Catherine M. I. "Diapirism on Venus and the Early Earth and The thermal effect of fluid flows in AECL's Tunnel Sealing Experiment." Thesis, 2010. http://hdl.handle.net/1807/24863.

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Flow instabilities occur at all scales in planetary systems. In this thesis we examine three cases of such instabilities, on three very different length scales. In the first part, we test the idea that Archean granite-greenstone belts (GGBs) form by crustal diapirism, or Rayleigh-Taylor instabilities. GGBs are characterized by large granitic domes (50-100 km in diameter) embedded in narrow keel-shaped greenstones. They are ubiquitous in Archean (> 2.5 Ga) terrains, but rare thereafter. We performed finite element calculations for a visco-elastic, temperature-dependent, non-Newtonian crust under conditions appropriate for the Archean, which show that dense low-viscosity volcanics overlying a felsic basement will overturn diapirically in as little as 10 Ma, displacing as much as 60 % of the volcanics to the lower crust. This surprisingly fast overturn rate suggests that diapiric overturn dominated crustal tectonics in the hot conditions of the Early Earth, becoming less important as the Earth cooled. Moreover, the deposition of large volumes of wet basaltic volcanics to the lower crust may provide the source for the formation of the distinctly Archean granitic rocks which dominate Earth's oldest continents. The second part examines the origin of Venusian coronae, circular volcanic features unique to Venus. Coronae are thought to result from small instabilities (diapirs) from the core-mantle boundary, which are typical of stagnant-lid convection. However, most young coronae are located in a region surrounded by long-lived hotspots, typical of a more active style of mantle convection. Using analogue experiments in corn syrup heated from below, we show that the co-existence of diapirs and long-lived mantle plumes are a direct consequence of the catastrophic overturn of the cold Venusian lithosphere thought to have occurred ~ 700 Ma ago. In the last part we analyze the thermal effect of fluid flow through a full-scale experiment testing clay and concrete tunnel seals in a Deep Geological Repository for nuclear was finite element software, we were able to show that the formation of fissures in the heated chamber between the two seals effectively limited heat flow, and could explain the discrepancy between the predicted and measured temperatures.

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43

Eckert, Andreas [Verfasser]. "3D multi-scale finite element analysis of the crustal state of stress in the Western US and the Eastern California Shear Zone, and implications for stress - fluid flow interactions for the Coso geothermal field / von Andreas Eckert." 2007. http://d-nb.info/986722170/34.

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44

Williams, Morgan John. "Tracing Fluids from Seafloor to Deep Subduction Environments: An In-situ Geochemical Investigation of Fluid-Mobile Elements in Oceanic Crust." Phd thesis, 2019. http://hdl.handle.net/1885/165238.

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Hydration reactions within the oceanic crust incorporate significant amounts of water and incompatible and volatile elements from the Earth's surface into the oceanic lithosphere. During subduction, the altered oceanic crust releases a sequence of metamorphic dehydration fluids, which carry with them a significant portion of the fluid-mobile element inventory. Together, fluid cycling and plate tectonics enable geochemical interaction between the outer regions of our planet and its inner depths. However, aqueous fluids are transient and cannot be observed directly in deeper geological environments. Instead, the nature of fluids must be reconstructed from mineral records. This thesis focuses on the use of in-situ and small-scale geochemical analysis of different mineral generations and intra-mineral zonation to resolve the nature and evolution of fluids in oceanic and subduction environments. Noble gas, halogen and SHRIMP oxygen isotope analyses are supplemented with routine analytical methods including SEM, EPMA, and LA-ICP-MS. Boron isotope analysis with SHRIMP II is also tested and developed, allowing precise investigation of natural suites of metamorphic tourmaline. The first part of the thesis documents a geochemical investigation of hydrated lithologies from the upper detachment surface of the Atlantis Massif using samples collected during IODP Expedition 357. In-situ analyses of lizardite-chrysotile serpentinites reveal that multi-stage serpentinization is linked to shifts in δ18O, and that significant isotopic and trace element heterogeneity between polymorphs and serpentinization stages is present at the microscale. Individual SHRIMP analyses have δ18O ranging from 0 to 6‰, and serpentine generations within individual samples have mean δ18O of -0.2 to +4.4‰. Ranges in oxygen isotope composition are similar between sites, and give consistently high estimates for serpentinization temperatures during all stages of hydration (up to 350°C). Halogen and noble gas abundances of serpentinites, hydrated gabbro and talc-amphibole-chlorite schists from the Massif are lower than previously investigated lizardite-chrysotile serpentinites. Serpentinites contain 28-430 μg/g of Cl, and exhibit 40Ar/36Ar up to 538. Amphibole exerts a strong control on halogen abundances in talc schists. Noble gases are fractionated from seawater abundance patterns, and record a variety of processes including radiogenic ingrowth (He), addition of excess Ar and fractionation related to mineral trapping at different alteration temperature. Oxygen isotope ratios and trace element, halogen and noble gas abundances attest to generally high fluid fluxes and dominant high temperature of serpentinization at the Atlantis Massif. The second part of the thesis investigates metamorphic fluid-rock interaction within a section of subducted upper oceanic crust in the UHP Lago di Cignana Unit and underlying Zermatt-Saas serpentinites near Valtournenche (NW Italian Alps). This study reveals previously undocumented trends and shifts in garnet δ18O, serpentine δ18O and tourmaline 11B. Evidence for multiple stages of metasomatism near peak metamorphic conditions is preserved within a select few samples where outer garnet growth zones exhibit major element, trace element and isotopic shifts (up to 15‰ zonation in δ18O) which require infiltration of externally derived fluids. Multiple stages of fluid infiltration are identified. In two samples fluid derived from serpentinized ultramafic lithologies can be confidently identified as a metasomatic agent, likely preceded by fluids derived from nearby mafic units. Unit-scale tourmaline δ11B heterogeneity is observed, with differences of up to 10‰ observed over the cm to dm-scale; variations of similar magnitude are observed within individual samples. Individual tourmalines exhibit zonation in δ11B to slightly higher values (minor) and lower values (most pronounced in calcschists). Variations in sample-mean tourmaline δ11B may largely reflect protolithic δ11B diversity, slightly modified through dehydration reactions towards lighter δ11B. Significant boron isotopic heterogeneity is preserved near the slab interface even at sub-arc conditions. Together these investigations provide novel insights into seafloor hydration and subduction dehydration of the altered oceanic crust, and demonstrate the utility of microscale oxygen isotope analyses coupled with complementary geochemical tracers to provide detailed constraints on hydrothermal alteration conditions and fluid sources in seafloor and subduction settings.

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45

Marquis, Guy. "Geophysical studies of saline fluids in the deep crust." Thesis, 1992. https://dspace.library.uvic.ca//handle/1828/9586.

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Geophysical studies have shown that the lower continental crust, especially in Phanerozoic areas, is commonly more conductive and reflective and has a lower seismic velocity than what is expected from the composition of xenoliths and exposed lower crustal terrains. These anomalous in situ properties can be explained by the presence of small amounts of free aqueous fluids in the intergranular space. A compilation of lower crustal geophysical data shows a correlation between electrical resistivity and seismic velocity, in agreement with physical properties models of porous rocks, as well as a general decrease of inferred porosity with geological age. Correlations with geothermal data also show that the reflective and conductive layers usually have their tops near the 400-450°C isotherms suggesting an association with the brittle-ductile transition. The rheology at depth might have an effect on the trapping of the fluids that are in textural equilibrium pores in the ductile crust. Alternatively metamorphic reactions may constrain free fluids to below this depth. Model for the effects of porosity in textural equilibrium pores on seismic and electrical properties of rocks have been developed, and are also in good agreement with the data compilation. Re-processed LITHOPROBE South Cordillera magnetotelluric and seismic reflection data in the Intermontane Belt support a coincidence between the top of low resistivity and high reflectivity of the crust at depths of about 20 km in the west, and about 15 km in the east of the Belt, corresponding to temperatures around 450°C. Two models for reconciling the low vertical permeability required for maintaining the porosity at depth with the interconnection required to reduce the electrical resistivity are presented: one involves the deformation of equilibrium pores by small deviatoric stresses that pinch off the vertical interconnection, the other the flattening and alignment of pores by lower crustal shear processes. A difficulty is recognized in reconciling free aqueous fluids in the lower crust with the expected retrograde metamorphism that should take up any free water. This processes can be avoided if the fluids are of high salinity. High-salinity fluids are in liquid phase in the lower crust, not in supercritical phase as often thought.
Graduate

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46

Blatter, Daniel. "Constraining fluid properties in the mantle and crust using Bayesian inversion of electromagnetic data." Thesis, 2020. https://doi.org/10.7916/d8-b6nw-b545.

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Recent advances in computational power, as well as the hard work of a handful of brilliant scientists, have made Bayesian inversion of geophysical observations possible. This development is highly significant, as it permits the quantification of uncertainty, not only on the inverted model parameters, but also on related properties of interest. This dissertation focuses on the application of a particular kind of Bayesian inversion – trans-dimensional Markov chain Monte Carlo – to electromagnetic data, specifically airborne transient electromagnetic, magnetotelluric, and surface-towed controlled source electromagnetic data. In chapters 2-4, these data, both real and synthetic, are inverted for 1D models of subsurface electrical resistivity. In chapter 5, magnetotelluric data are inverted for 2D models of resistivity – the first time, to the best of my knowledge, that trans-dimensional Bayesian inversion of magnetotelluric data for 2D models has been achieved. In each instance, the uncertainty on bulk resistivity provided by the Bayesian inversion is used to estimate uncertainty on related subsurface properties, including pore fluid resistivity and salinity, porosity, melt fraction, melt volatile content, and bulk mantle volatile inventory. Chapter 1 introduces the topic of Bayesian inversion of electromagnetic data. Chapter 2 concerns trans-dimensional Bayesian inversion of airborne transient electromagnetic data. These data were collected above Taylor Glacier in the McMurdo Dry Valleys region of Antarctica in 2011, and were inverted using deterministic inverse methods to image a conductive channel beneath the glacier, interpreted as a package of brine-saturated sediments. The Bayesian inversion of these data confirms the existence of a conductive channel and provides quantitative uncertainties on the resistivity as a function of depth. These uncertainties are used in conjunction with Archie’s Law to estimate uncertainty on the resistivity of the pore fluids in the sediments. Additionally, the Kullback-Leibler divergence – a statistical measure of the dissimilarity of two distributions – is introduced as a measure of how much influence the observations have on the model parameters as a function of depth. The utility of Bayesian inversion in estimating the noise floor necessary to effectively resolve model structure is demonstrated. In chapter 3, a joint Bayesian framework for inverting electromagnetic data is introduced. A modified version of the algorithm utilized in chapter 2 is applied to jointly invert marine magnetotelluric and surface-towed controlled source electromagnetic data. These data were collected offshore New Jersey in 2015 to image a freshwater aquifer in the continental shelf. Deterministic inversions of this data clearly image a resistive body at depths consistent with low salinity from bore hole measurements collocated with the electromagnetic survey. The Bayesian inversion of this data set again confirms the existence of the resistive region while further providing uncertainty on the inverted resistivity with depth. In some instances, bimodality in the posterior distribution is found, demonstrating the importance of Bayesian inverse methods for fully exploring the model space. The uncertainty on bulk resistivity is used in conjunction with Archie’s Law and the porosity from bore hole measurements in a Monte Carlo framework to estimate uncertainty in the salinity of the pore water as a function of depth for three well locations. These estimates match well with measured salinities at these locations, validating the use of the Bayesian posterior in the context of a Monte Carlo framework to estimate uncertainty on related physical properties. In chapter 4, seafloor magnetotelluric data are again inverted for 1D models of subsurface resistivity, this time to image a conductive channel at the base of the lithosphere. The data are a subset of a deployment of 50 Broadband MT instruments on the seafloor above the Cocos plate offshore Nicaragua. Deterministic inversions of this data revealed a conductive structure at 45-70 km depth, beneath the Cocos plate. This earlier analysis concluded that melt was required at the lithosphere-asthenosphere boundary (LAB) to explain the inverted resistivity, but the deterministic inverse tools available at the time did not permit quantitative uncertainties – on the conductive anomaly itself, the requirement for partial melt, the degree of partial melt, or the degree of mantle hydration. Bayesian inversion of data from two magnetotelluric sites confirm that the conductor is indeed robust, and that melt is required by nearly 100% of the models that fit the data. Further, the resistivity uncertainty from the Bayesian inversion is used in conjunction with petrological modeling of partial melting in the mantle and an estimated probability distribution for temperature to place constraints on the degree of partial melt and mantle volatile (water and carbon) inventory over the depth range 45-63 km. This analysis concludes that large melt fractions and either high temperatures or a high degree of mantle hydration are likely needed to explain the resistivities produced by the Bayesian inversion, potentially explaining the mechanism for plate sliding that enables plate tectonics. Finally, chapter 5 introduces 2D trans-dimensional Bayesian inversion of magnetotelluric data, for the first time to my knowledge. A Gaussian Process-parametrized, trans-dimensional Markov chain Monte Carlo algorithm is used with MARE2DEM to invert synthetic data as well as field data from the Gemini data set from the Gulf of Mexico. For Bayesian inversion to be computationally feasible beyond inverting for 1D models, the cost of forward modeling must be reduced, as well as the number of model parameters that the algorithm must sample over. The first challenge is addressed through high performance computing. The forward modeling is performed on a cluster. In addition, we implement parallel tempering, where multiple Markov chains are run in parallel and swap models at each iteration, vastly increasing the rate at which the model space is explored and sampled. The curse of dimensionality is addressed by utilizing a Machine Learning technique known as a Gaussian Process to represent the model with far fewer parameters than required in a typical discrete finite difference or finite element representation of the subsurface. The Bayesian inversion of the Gemini data successfully recovers the model structure obtained by deterministic inversion of the same data, but additionally provides uncertainty on bulk resistivity. This thesis demonstrates the power and utility of Bayesian inversion to move beyond single estimates of subsurface resistivity. Not only does the work in this dissertation show that Bayesian inversion can provide uncertainty on inverted resistivity, it shows that these inverted uncertainties can be used to place quantitative constraints on parameters related to bulk resistivity. This is crucial to rendering the information obtained from inversion of electromagnetic data useful to disciplines far beyond electromagnetic geophysics.

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47

Scicchitano, Maria Rosa. "Oxygen isotopes as tracers and stopwatches for rock-fluid interaction in the crust: New analytical and experimental developments." Phd thesis, 2018. http://hdl.handle.net/1885/144939.

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Metamorphism is the dominant transformation mechanism of rocks in most of the Earth’s lithosphere and it is driven by variations in temperature, pressure, deformation and influx of chemically active fluids. Fluids play a crucial role in affecting many physical and chemical processes. It is therefore essential to unravel their nature and source(s) and the extent of their infiltration to fully understand crustal evolution. Oxygen isotopes are one of the most robust tools used to obtain such information. Because fluid-rock interactions can occur at different stages of metamorphism, metamorphic rocks often preserve complex textures. A thorough understanding of rock-fluid interactions is however limited by the ability to resolve oxygen isotopic variations recorded at the microscale and by the robustness of oxygen isotopic signatures measured in nature. This challenge is addressed in this study by presenting new analytical and experimental developments concerning oxygen isotopes at the microscale and with implications for serpentinisation processes and oxygen diffusion in garnet. Serpentinised peridotites are important in recycling fluids and elements from ocean floor to mantle through seafloor metamorphism and subduction. This project represents the first investigation of (i) oxygen isotopes in serpentine minerals by ion microprobes and (ii) matrix bias effects related to Mg/Fe variations in olivine during oxygen isotope analysis by SHRIMP. Serpentine isotopic measurements were calibrated against the oxygen compositions of chemically homogeneous samples of antigorite, chrysotile and lizardite analysed by laser fluorination. Each serpentine mineral was analysed by SHRIMP to assess its homogeneity compared to San Carlos olivine, and potential matrix bias and crystal orientation effects. Matrix bias between antigorite/olivine and antigorite/lizardite was up to +3‰ and -1‰, respectively. Crystal orientation effects were identified only in chrysotile. Matrix bias effects in olivine were investigated by referencing isotopic measurements of ten chemically homogenous olivine standards (Fo74 to Fo100) to San Carlos olivine (Fo91). A matrix bias up to -2.0‰ was observed in olivine with Fo > Fo92. The new standards and protocols were used to unravel the nature and source(s) of serpentinising fluid(s) in (i) a UHP serpentinite with multiple serpentine generations, (ii) a serpentinised dunite with zoned olivine grains surrounded by lizardite. Variations in the oxygen isotopic composition of garnet can be used to unravel the P-T-t-fluid evolution of numerous crustal rocks. However, the correct interpretation of measured oxygen isotopic heterogeneities and the understanding of rates and timescales of rock-fluid interactions require the knowledge of oxygen diffusion rates in garnet, which are yet poorly constrained. This work presents new high-P piston cylinder experiments performed in dry and wet conditions (T = 900-1600°C, P = 1.0-2.5 GPa) and 1 atm dry experiments (T = 1500-1600°C) using YAG and pyrope garnets. The recovered crystals were analysed in step-scanning and depth profiling mode by SHRIMP and in step-scanning mode by nanoSIMS. Mixing and edge effects during SHRIMP depth profiling were evaluated. The obtained results suggest no effects of chemical composition and pressure on oxygen diffusivity in garnet. The Arrhenius relation determined in this study predicts oxygen diffusivities faster than any previous calibration.

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48

Mottaghy, Darius Christopher [Verfasser]. "Heat transfer processes in the upper crust: influence of structure, fluid flow, and palaeoclimate / vorgelegt von Darius Christopher Mottaghy." 2007. http://d-nb.info/985669136/34.

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49

Boulahanis, Bridgit. "Seismic studies of interactions between the accretionary, tectonic, fluid flow, and sedimentary processes that impact the evolution of oceanic lithosphere." Thesis, 2021. https://doi.org/10.7916/d8-4739-e945.

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The oceanic lithosphere makes up approximately two-thirds of the surface of the earth. Oceanic crust, which is underlain by lithospheric mantle, is formed at mid-ocean ridges and is shaped by a combination of igneous accretionary processes at and near the ridge axis, and post-emplacement tectonic and hydrothermal processes as it evolves. Through time the crust is covered by sediments, sealing it from the overlying ocean, which influences hydrothermal circulation and cooling in the lithosphere below. Finally, oceanic lithosphere is subsumed at subduction zones. In this thesis I utilize seismic data to investigate the oceanic lithosphere from formation to near subduction using seismic datasets from the East Pacific Rise (EPR) and the Juan de Fuca (JdF) plate. In my first chapter I investigate the hypothesis that eustatic sea level fluctuations induced by the glacial cycles of the Pleistocene influence mantle-melting at mid-ocean ridges (MORs) using a unique bathymetry and crustal thickness dataset derived from a 3D multi-channel seismic (MCS) investigation of the East Pacific Rise from 9°42’ to 57’N. The results of this study show variations in crustal thickness and bathymetry at timescales associated with Pleistocene glacial cycles, supporting the inference that mantle melt supply to MOR may be modulated by sea level variations. Further investigations of the hypothesis that sea level variations may influence MOR dynamics are presented in appendices one and two. In appendix one I explore whether variations at the timescales of glacial cycles are apparent in MCS datasets from the intermediate spreading JdF ridge as well as bathymetry data from the fast spreading EPR. In appendix two I present a case study in which I re-examine the crustal thickness and bathymetry data from the northern EPR presented in chapter one in order to assess how fine-scale segmentation of the ridge axis appears in data, and compare different methodological approaches to describing MOR generated topography. In my second chapter I present results from a wide-angle controlled source seismic experiment conducted along a transect crossing the JdF plate from ~20 km east of the axis at the Endeavour segment of the JdF ridge to the Cascadia margin off of Washington state. I utilize a joint refraction-reflection traveltime inversion to generate a two-dimensional tomographic Vp model of the sediments, crust and upper mantle. Analysis of this Vp model, along with characterization of the basement topography along the transect, reveals three intervals (spanning millions of years) of distinct crust and upper mantle properties indicating a spatially heterogeneous JdF plate which is interpreted as inherited from changes in the mode of accretion at the paleo-JdF ridge, differences in plate interior processes, and deformation near the subduction zone. In my third chapter I present results of a MCS study of the sediment section conducted along a transect spanning ~350 km along the Cascadia margin from offshore southern Oregon to offshore Washington state. In this study I utilize prestack depth migrated MCS data to describe the reflectivity of the sediment section and invert for impedance and density. I also present results of amplitude variation with angle of incidence analysis conducted using pre-stack seismic gathers. Results indicate along margin variations in the characteristics of the sediments as well as complex changes in the stress state along the Cascadia margin. Synthesis of these analyses provides an in-depth assessment of patterns of sedimentation and properties of the sediment section as it experiences the effects of the onset of subduction.

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Tian, Zhu. "Tracing on-axis diffuse fluids by chalcophile elements distribution in upper oceanic crust at Pito Deep, East Pacific Rise." Thesis, 2016. http://hdl.handle.net/1828/7646.

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Abstract:

Mid-ocean ridge hydrothermal systems play an important role in the cycling of energy and mass between the solid earth and oceans. The on-axis low-temperature diffuse fluids (temperature lower than ~100 °C) carry ~90% of the on-axis heat fluxes, but diffuse fluids generation is poorly constrained. This study uses the abundance of the chalcophile elements, which form metal-sulphides in the rock record, to test models for diffuse fluids generation. These include mixing between seawater and high-temperature hydrothermal fluids and conductive cooling of high- temperature hydrothermal fluids. This thesis determined the concentrations of the elements of interest (As, Mo, Ag, Cd, Sn, and Tl) in geological reference materials using standard addition method in ICP-MS. These values were used to calibrate the analysis of samples from Pito Deep to trace the abundance of these elements within the upper oceanic crust. The results show that the Zn, Cu, As, Ag, Cd, Tl, and Pb are generally depleted in sheeted dikes and enriched in the lava unit and/or the transition zone, which is consistent with previous studies on fast-spreading EPR crust at Hole 504B, Hess Deep and Hole 1256D. The enrichment of these elements in the lava unit and/or the transition zone suggests that cooling high-temperature hydrothermal fluids to form diffuse fluids occurred in this iii iv area of the oceanic crust. Molybdenum and Sb are added into all units of the crust by recharging seawater. The concentrations of chalcophile elements in diffuse fluids were calculated by a mass balance. The results of this study favored a diffuse fluids generation model that involves mixing of seawater and high-temperature hydrothermal fluids. Results also show that the observed concentrations of Mo and Sb requires extra input source besides recharging seawater and oceanic crust, possibly particulates in seawater.
Graduate
juliatian2013@gmail.com

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Dissertations / Theses on the topic 'Crustal fluid'

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