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1
Appelquist, Karin. "Proterozoic crustal evolution in southcentral Fennoscandia /." Göteborg : Department of Earth Sciences, University of Gotheburg, 2010. http://hdl.handle.net/2077/21530.
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Roberts, Nicholas Michael William. "From crystal to crust : the Proterozoic crustal evolution of southwest Norway." Thesis, University of Leicester, 2010. http://hdl.handle.net/2381/8954.
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The geology of the Suldal Sector, southwest Norway, comprises exposures from three orogenic periods; the Telemarkian, Sveconorwegian and Caledonian. Telemarkian (~1500 Ma) basement rocks are interpreted to be the oldest crust in the region; these are intruded by Sveconorwegian granitoid intrusions (~1070-930 Ma). Crystalline nappe units overlie the Mesoproterozoic basement, and from reconnaissance U-Pb dating and zircon hafnium isotopes, are believed to comprise slices of the Mesoproterozoic Norwegian continental margin. The Telemarkian basement comprises meta-plutonic/volcanic lithologies that represent the deformed upper crustal section of a continental arc - the Suldal Arc; U-Pb dating suggests this arc was active from ~1520 to 1475 Ma. Whole-rock geochemistry and hafnium and oxygen isotopes measured in zircon, suggest that arc magmatism recycled older continental crust (20-50% contribution) that had been mixed with mantle-derived material in the lower crust; the older crustal component comprised late-Palaeoproterozoic sedimentary material derived from the Fennoscandian continent. During the arc’s evolution, dehydration of mafic source magma induced by heat from magmatic underplating, and subsequent melting of dehydrated crust enhanced by asthenospheric upwelling, allowed for the intrusion of iron-enriched tholeiitic magmas. The Suldal arc and by extension, the Telemarkia terrane, represent the last stages of continental crust formation within a retreating accretionary orogen that was active since ~1.8 Ga. Based on whole-rock geochemistry, U-Pb, hafnium and oxygen isotopes in zircon, Sveconorwegian granite suites formed between 1.07 and 0.92 Ga, and are largely derived from ~1.5 Ga mafic lower crust with a limited contribution of juvenile mantle-derived material. The geodynamic setting of granitic magmatism evolved from supra-subduction, to overthickened crust, to thinned crust with possible lithospheric delamination. The varying geochemistry of the granite suites (I- to A-type) is controlled not by geodynamic setting, but dominantly by water content in the magma source. Sveconorwegian deformation in the Suldal Sector is bracketed between ~1069 and ~1047 Ma by intrusions of the Storlivatnet plutonic complex.
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Jahn, Inalee C. "Crustal evolution of the Capricorn Orogen, Western Australia." Thesis, Curtin University, 2018. http://hdl.handle.net/20.500.11937/75146.
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The Capricorn Orogen, Western Australia records the Palaeoproterozoic convergence and collision of the Archaean Yilgarn and Pilbara Cratons during the formation of the West Australian Craton, and over one billion years of subsequent intracontinental crustal reworking. This study uses an integrated analytical study of the isotopic and geochemical systematics in zircon from Capricorn Orogen granites in order to identify the magmatic sources and the fundamental geodynamic processes that have contributed to its crustal evolution.
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Hartnady, Michael Ian Hay. "Crustal Evolution of the Albany-Fraser Orogen, Western Australia." Thesis, Curtin University, 2019. http://hdl.handle.net/20.500.11937/77990.
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This thesis investigates the crustal evolution of the Albany-Fraser Orogen in Western Australia, using U-Pb geochronology, Lu-Hf and oxygen isotope geochemistry of zircon crystals in granitic rocks. The results show that compositional variability of rocks in the region is strongly in uenced by the heterogeneity in the pre-existing crustal substrate. This research therefore demonstrates that mapping spatial Hf isotopic variations in magmatic rocks does not always image deep crustal structure as previously thought.
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Manda, Blackwell Chawala. "Decrypting the crustal evolution of the Mozambique Belt in Malawi." Thesis, University of St Andrews, 2016. http://hdl.handle.net/10023/12469.
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Global paleogeography exerts a first order control on both the deep and surficial components of the Earth system. Temporal and spatial constraints on the Mozambique Belt of Eastern Africa are needed to understand its crustal evolution and its role in assembly of Gondwana. This thesis provides detailed data on the timing, sources and nature of tectono-thermal events responsible for magmatism in the Mozambique Belt in southern Malawi. An integrated approach of petrography, geochemistry, radiogenic isotopes, and single zircon geochronology has been used to determine spatial and temporal constraints and to better constrain models of the assembly of East and West Gondwana, which occurred along the Mozambique Belt. In particular the thesis attempts to address key unresolved questions about the number and timing of accretionary pulses within the orogen. LA-ICP-MS single zircon U-Pb results show tectono-thermal events in four periods: Mesoproterozoic from 1128 ± 30 Ma to 1033 ± 20 Ma; Neoproterozoic (956 ± 12 Ma – 594 ± 65 Ma); Cambrian (530 ± 3 Ma – 515 ± 12 Ma); and Cretaceous (118 ± 2 Ma). Metamorphism is dated from a charnockitic gneiss that yielded a lower intercept age of 515 ± 18 Ma. The granitoids are intermediate to acidic with relative enrichment in LILEs and depletion in HFSEs with moderately negative anomalies in Th, Nb, P, Zr and Ti. REE spider plots show enrichment in LREEs and depleted HREEs with negative Eu anomalies. The meta-granites are largely metaluminous with a few peraluminous, I-type granites belonging to the calc-alkaline series. Radiogenic isotope data reveals slight differences with older, Mesoproterozoic rocks showing positive ɛNd and ɛHf values signifying derivation from depleted mantle material, whilst the younger rocks display negative epsilon values suggestive of crustal material recycling and mixing for their source and origins. Granitoids of southern Malawi display characteristics consistent with derivation in a continental Andean type arc with some aspects of the chemistry resembling tonalite-trondhjemite-granite (TTG) suites mapped in the Mozambique Belt in Kenya, Tanzania, Mozambique, and Antarctica although the data are not sufficiently compelling to assign the Malawi rocks to classic TTGs.
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Robertson, S. "Late Archaean crustal evolution in the Ivisartoq region, southern west Greenland." Thesis, University of Exeter, 1985. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.353048.
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Leftwich, Timothy E. "Geophysical investigations of the crustal structure and evolution of Mars." Columbus, Ohio : Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc%5Fnum=osu1147893346.
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Rippington, Stephen James. "The crustal evolution of Nemegt and Altan Uul, Southern Mongolia." Thesis, University of Leicester, 2008. http://hdl.handle.net/2381/8376.
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This thesis concerns the crustal evolution of Nemegt and Altan Uul in the Gobi Altai mountains of southern Mongolia. Nemegt and Altan Uul consist of polydeformed Palaeozoic rocks uplifted in the Cenozoic at a restraining bend along the active left-lateral Gobi-Tien Shan intra-continental fault system, one of several east-west trending left-lateral intra-continental transpressional fault systems associated with eastward continental extrusion tectonics in Central Asia. The tectonic evolution of southern Mongolia is of particular interest as it forms part of the Central Asian Orogenic Belt, which is the largest area of Phanerozoic continental growth on Earth, and is a natural laboratory for studying processes of continental growth and deformation including terrane accretion, ophiolite obduction, terrane amalgamation, terrane dispersal and crustal reactivation. The uplifted Palaeozoic rocks exposed in Nemegt and Altan Uul offer an opportunity to understand multiple phases of the crustal evolution of southern Mongolia. A series of cross-strike transects of Nemegt and Altan Uul were carried out to document the lithologies and structure of the ranges. Samples were taken along the transects and at several important localities, to constrain the metamorphic petrography of the rocks in the ranges. This data is used to define several distinct east-west trending litho-tectonic sequences in Nemegt and Altan Uul. The ranges have a systematic south to north litho-tectonic variation from greenschist grade meta-volcanic and volcaniclastic rocks, thrust north over a discontinuous ophiolite belt, which is thrust north over greenschist to epidote-amphibolite grade arkosic to mature meta-sedimentary rocks. Four phases of deformation are identified from cross-cutting field relationships and constrained by existing regional data: east-west trending south-dipping cleavage (D1), and north-vergent folds of cleavage and north-directed ductile thrust shear zones (D2) formed during late Carboniferous south to north arc-terrane accretion and ophiolite obduction. East-west and northeast-southwest trending D3 normal faults formed during Cretaceous basin extension. East-west and northwest-southeast trending D4 left-lateral oblique-slip and dip-slip thrust faults formed during Cenozoic transpressional deformation and define the modern mountain ranges. The structures identified are conservatively extrapolated to depth to suggest Nemegt and Altan Uul have a positive flower structure in cross-section. An evolutionary model of Nemegt and Altan Uul suggests that D1 and D2 structures and the ophiolitic rocks in the area may represent south-dipping east-west trending fabrics and rheological weaknesses that have been reactivated in a left-lateral transpressional sense in the Cenozoic.
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Leftwich, Timothy E. "Geopotential investigations of the crustal structure and evolution of Mars." The Ohio State University, 2006. http://rave.ohiolink.edu/etdc/view?acc_num=osu1147893346.
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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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Chapman, Timothy. "Deciphering Igneous and Metamorphic Histories from Exposed Deep Arc Crust, Fiordland, New Zealand: Crustal Differentiation and Evolution." Thesis, The University of Sydney, 2016. http://hdl.handle.net/2123/16751.
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Fiordland, New Zealand, preserves extensive arc plutons, that formed as part of a Cretaceous flare-up event in a long-lived subduction zone forming the proto-Pacific Gondwanan margin. Plutonic rocks of the c. 126–105 Ma Western Fiordland Orthogneiss (WFO) and related Separation Point Suite (SPS), were emplaced syn-tectonically throughout a thickened (>65 km) continental arc. Unique exposures of mid and lower crustal components of the arc provide insights into processes forming Cordilleran margins, which can be used to evaluate and validate inferred deep arc processes. A major difficulty in interpreting such rocks is presented by the extensive overlap of mineral assemblages forming plutonic protoliths and their metamorphic equivalents. However, there is an imperative to correctly distinguish igneous from metamorphic parageneses to interpret plutonic and metamorphic events and establish robustly their roles in forming Cordilleran arcs. This thesis develops a method to distinguish igneous and metamorphic histories utilising mineral trace element chemistries and microstructural relations from exposed lower crustal arc rocks. In deciphering protolith and metamorphic histories constraints on the dynamics of crustal differentiation and evolution are explored using the example from Fiordland.
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Emo, Robert B. "Probing the lower continental crust with the petrology and geochemistry of Queensland xenoliths." Thesis, Queensland University of Technology, 2022. https://eprints.qut.edu.au/232622/1/Robert%20Bernard_Emo_Thesis.pdf.
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This thesis investigated the poorly constrained composition and evolution of the lower continental crust in Queensland through geochemistry, geochronology, and petrological modelling. The analysis of deep crustal rocks brought to the surface by explosive volcanism shows that the lower crust in Queensland is nearly devoid of many geologically significant trace elements. The modelling demonstrates that this lower crust formed through solid-melt interactions at the base of the crust. The combined data show that this depleted, hybridised crust could be more common than previously recognised and that hybridisation is likely a major driver of continent formation.
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Bartlett, Jessica M. "Crustal evolution and metamorphism in the high-grade terrain of South India." Thesis, Open University, 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.262567.
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McDermott, P. F. "Granite petrogenesis and crustal evolution studies in the Damara Pan-African orogenic belt, Namibia." Thesis, Open University, 1986. http://oro.open.ac.uk/57005/.
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Major and trace element data for Damara granitoids distinguish three geochemically distinct granitoid groups, - crustal-melt granitoids, calc-alkaline granitoids and within-plate granitoids. The overwhelming majority of the Oamara granitoids are peraluminous crustal-melt leucogranites which have elevated 87Sr/86Sr ratios (> 0.710) and old model Nd ages (~ 2.0 Ga). Calc-alkaline diorites are metaluminous and have the lowest 87Sr/86Sr ratios (0.704 - 0.707) and model Nd ages (OM) in the range 1.1 -1.7 Ga. Within-plate granitoids are characterised by elevated high-field strength (HFS) abundances and have model Nd ages (OM) in the range 1.1 - 1.6 Ga. All Damara granitoids have model Nd ages (OM) older than about 1.0 Ga suggesting that intracrustal reworking was the dominant process and crustal growth was negligible. Damara granitoids define a hyperbola on an ∈ Sr vs. ∈ Nd diagram but cannot be modelled as simple binary mixtures between old continental crust and depleted mantle end-members. An episodic intracrustal remobilisation model is proposed to explain the hyperbola defined by granitoid data on an ∈ Sr vs. ∈ Nd diagram. Within the 10 km thick Damara metasedimentary pile 87Sr/86Sr ratios increase systematically with depth. This trend is accompanied by a decrease in 143Nd/144Nd ratios. Model Nd ages (CHUR) for the stratigraphically oldest Damara metasediments (Nosib Group) are about 2.0 Ga whereas the younger metasediments (Kuiseb Formation and Nama Group) have model Nd ages (CHUR) about 1.0 Ga reflecting sediment input from younger source terrains. The ratio of model ages (TNdCHUR/TSrBE) is used as an index of intracrustal reworking since it provides a measure of Rb/Sr fractionation (increases) relative to SmlNd fractionation. The older Damara metasediments (Nosib Group) have the highest model age ratios suggesting that their source terrains have suffered the largest amount of intracrustal reworking. However, the rate of intracrustal reworking was greatest in source terrains sampled by the younger Damara metasediments (Kuiseb Formation and Nama Group). This suggests that the rate of intracrustal reworking increased through time in the interval (2.0 - 1.0 Ga) in this segment of continental crust.
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Lilly, Richard Mark. "Magmatic evolution and crustal accretion of the northern Oman-United Arab Emirates ophiolite." Thesis, Cardiff University, 2006. http://orca.cf.ac.uk/56058/.
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The Magmatic Evolution and Crustal Accretion of the northern Oman-U.A.E. ophiolite The Oman-United Arab Emirates (U. A.E.) ophiolite is the largest and best-preserved ophiolite complex in the world and has assumed critical importance in guiding ideas as to the functioning of mid-ocean ridge magma chambers and accretion of lower crust formed at a fast-spreading ridge. The portion of the ophiolite within the United Arab Emirates has received much less study than that within the Sultanate of Oman, particularly with regard to its magmatic evolution. Fieldwork has been conducted in co-operation with the British Geological Survey on the ophiolite sections in the U.A.E. Geochemical and field characteristics of these plutonic and extrusive units provide important constraints on the influence subduction-related fluids have on crustal accretion processes. Initial VI magmatic events exhibit a MORB-like composition and record mid-ocean ridge accretion processes which relate to modern crust, forming from steady-state magma chambers. The Khawr Fakkan Block provides the first 'true' MORB mantle source signature to be documented in the Oman-U.A.E. ophiolite, which represents pre-subduction zone influenced oceanic crust and applies constraints to the mechanisms and timing of subduction initiation and propagation. These primary events were followed by V2 magmatic events in a supra subduction zone (SSZ) setting, with plutonic magmatism localised predominantly along major faults. Each subsequent magmatic event exhibits an increase in the subduction related component to the mantle source. The V2, SSZ, magmatic period of the northern Oman-U.A.E. ophiolite can be regarded as an embryonic volcanic arc, which ceased magmatism and was obducted before reaching maturity. The northern Oman-U.A.E. ophiolite records the transition from spreading- to subduction-related volcanism in a SSZ setting within a marginal (fore-arc) basin, representing the change from steady-state to plutonic magmatism. The SSZ signature increases to the north spatially and temporally.
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Finch, Emma. "A crustal lattice solid model : the evolution, geometry and scaling of tectonic extension." Thesis, University of Ulster, 1998. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.274563.
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Hosford, Allegra. "Crustal accretion and evolution at slow and ultra-slow spreading mid-ocean ridges." Thesis, Massachusetts Institute of Technology, 2001. http://hdl.handle.net/1721.1/58441.
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Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric and Planetary Sciences, and the Woods Hole Oceanographic Institution), 2001.Page 250 blank.
Includes bibliographical references.
Half of the ocean crust is formed at spreading centers with total opening rates less than 40 km/Myr. The objective of this Thesis is to investigate temporal variations in active ridge processes and crustal aging at slow-spreading centers by comparing axial crustal structure with that on conjugate flanks of the slow-spreading Mid-Atlantic Ridge (MAR) (full rate, 20 km/Myr) and the ultra-slow spreading Southwest Indian Ridge (SWIR) (full rate, 14 km/Myr). Seismic refraction data collected along the rift valley and flanking rift mountains of the OH-1 segment (35ʻN) at the MAR show that the entire crustal section is constructed within a zone that is less than 5 km wide. Shallow-level hydrothermal circulation within the axial valley is suggested by the rift mountain seismic profiles, which show that the upper crust is 20% thinner and 16% faster along strike than zero-age crust. These effects probably result from fissure sealing within the extrusive crust. Deeper crustal velocities remain relatively constant at the segment midpoint within the first 2 Myr, but are reduced near the segment offsets presumably by faulting and fracturing associated with uplift out of the rift valley.
(cont.) A temporal variation in axial melt supply is suggested by a 15% difference in along-strike crustal thickness between the rift valley and rift mountains, with relatively less melt supplied today than 2 Ma. Crustal accretion at the SWIR appears to occur in a similar manner as at the MAR, although gravity and seismic data indicate that the average crustal thickness is 2-4 km less at theultra-slow spreading SWIR. A 25 Myr record on both flanks of the ridge shows that seafloor spreading has been highly asymmetric through time, with 35% faster crustal accretion on the Antarctic (south) plate. A small-offset non-transform discontinuity between two ridge segments is just as stable as two neighboring transform discontinuities, although a single mantle Bouguer gravity anomaly centered over the non-transform offset indicates that this boundary does not significantly perturb underlying mantle flow. Off-axis magnetic anomalies are recorded with high fidelity despite the very low spreading rates and the absence of a basaltic upper crust in one area. The lower crust may be the dominant off-axis carrier of the magnetic signal, contrary to traditionalmodels of crustal magnetic structure. Morphological and gravity data show evidence of asymmetric crustal accretion across the SWIR ridge axis, with slightly warmer mantletemperatures beneath the slower-spreading African (north) plate.
by Allegra Hosford.
Ph.D.
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Green, Michael Godfrey. "Early Archaean crustal evolution: evidence from ~3.5million year old greenstone successions in the Pilgangoora Belt, Pilbara Craton, Australia." University of Sydney. Geosciences, 2001. http://hdl.handle.net/2123/505.
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In the Pilgangoora Belt of the Pilbara Craton, Australia, the 3517 Ma Coonterunah Group and 3484-3468 Ma Carlindi granitoids underlie the 3458 Ma Warrawoona Group beneath an erosional unconformity, thus providing evidence for ancient emergent continental crust. The basalts either side of the unconformity are remarkably similar, with N-MORB-normalised enrichment factors for LILE, Th, U and LREE greater than those for Ta, Nb, P, Zr, Ti, Y and M-HREE, and initial e(Nd, Hf) compositions which systematically vary with Sm/Nd, Nb/U and Nb/La ratios. Geological and geochemical evidence shows that the Warrawoona Group was erupted onto continental basement, and that these basalts assimilated small amounts of Carlindi granitoid. As the Coonterunah basalts have similar compositions, they probably formed likewise, although they were deposited >60 myr before. Indeed, such a model may be applicable to most other early Pilbara greenstone successions, and so an older continental basement was probably critical for early Pilbara evolution. The geochemical, geological and geophysical characteristics of the Pilbara greenstone successions can be best explained as flood basalt successions deposited onto thin, submerged continental basement. This magmatism was induced by thermal upwelling in the mantle, although the basalts themselves do not have compositions which reflect derivation from an anomalously hot mantle. The Carlindi granitoids probably formed by fusion of young garnet-hornblende-rich sialic crust induced by basaltic volcanism. Early Archaean rocks have Nd-Hf isotope compositions which indicate that the young mantle had differentiated into distinct isotopic domains before 4.0 Ga. Such ancient depletion was associated with an increase of mantle Nb/U ratios to modern values, and hence this event probably reflects the extraction of an amount of continental crust equivalent to its modern mass from the primitive mantle before 3.5 Ga. Thus, a steady-state model of crustal growth is favoured whereby post ~4.0 Ga continental additions have been balanced by recycling back into the mantle, with no net global flux of continental crust at modern subduction zones. It is also proposed that the decoupling of initial e(Nd) and e(Hf) from its typical covariant behaviour was related to the formation of continental crust, perhaps by widespread formation of TTG magmas.
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Guan, Hong, and 關鴻. "Fuping complex and its significance in early precambrian crustal evolution of Sino-Korean craton." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2000. http://hub.hku.hk/bib/B42575588.
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Zhao, Xinfu, and 赵新福. "Paleoproterozoic crustal evolution and Fe-Cu metallogeny of the western Yangtze Block, SW China." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2010. http://hub.hku.hk/bib/B43572261.
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Opare-Addo, Emmanuel. "Aspects of Early Proterozoic granitoids and migmatites in southern Ghana : implications for crustal evolution." Thesis, University of Cambridge, 1992. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.240966.
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Miller, James Fisher. "Granite petrogenesis in the Cordillera Real, Bolivia and crustal evolution in the Central Andes." Thesis, Open University, 1988. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.292357.
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Keaney, Gemma Maria Jacinta. "Experimental study of the evolution of permeability in rocks under simulated crustal stress conditions." Thesis, University College London (University of London), 2000. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.392134.
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Guan, Hong. "Fuping complex and its significance in early precambrian crustal evolution of Sino-Korean craton." Click to view the E-thesis via HKUTO, 2000. http://sunzi.lib.hku.hk/hkuto/record/B42575588.
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Zhao, Xinfu. "Paleoproterozoic crustal evolution and Fe-Cu metallogeny of the western Yangtze Block, SW China." Click to view the E-thesis via HKUTO, 2010. http://sunzi.lib.hku.hk/hkuto/record/B43572261.
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Hapugoda, Hapugoda Udage Sarath. "Late Archaean and Early Proterozoic crustal evolution of the Georgetown Block, Northeast Queensland, Australia /." St. Lucia, Qld, 2002. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe16503.pdf.
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Siegel, Coralie. "Heat-producing element enrichment in granitic rocks, the role of crustal composition and evolution." Thesis, Queensland University of Technology, 2015. https://eprints.qut.edu.au/85344/1/Coralie_Siegel_Thesis.pdf.
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This study greatly enhanced our knowledge of the potential for geothermal energy development in Queensland as a viable clean energy source in the coming decades. Key outcomes of the project were understanding the first-order controls on the concentration of the heat-producing elements: uranium, thorium and potassium in granitic rocks, and constraining where rocks with the greatest heat-producing potential lie at depth in Queensland. Importantly, new temperature and heat flow maps for southwest Queensland were developed that will greatly assist future exploration efforts.
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Chopin, Francis. "Evolution du flux de matière, de l'architecture et de la rhéologie d'un prisme d'accrétion crustal." Strasbourg, 2010. https://tel.archives-ouvertes.fr/tel-00592281.
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L’évolution tectono-métamorphique d’un prisme d’accrétion orogénique est abordée à l’aide d’une étude géologique multiméthode. Le dôme d’Orlica-Śnieżnik (Sudètes) est situé au front d’un butoir rigide. Sa formation est expliquée par l’influx de croûte continentale subductée jusqu’à 50-60km de profondeur dans un prisme d’accrétion. La racine ainsi formée comprend une croûte inférieure felsique avec quelques lentilles basiques partiellement fondues en profondeur et séparées de la croûte moyenne (metasédiments) par une couche rigide d’orthogneiss. Cette infrastructure rhéologiquement hétérogène est remaniée au front du butoir par des plissements plurikilométriques de longueurs d’onde variables. Ils permettent des échanges verticaux aboutissant à l’exhumation des différents niveaux crustaux. La croissance du dôme par plissement s’achève par le décoiffement de la superstructure associé à un amincissement ductile et à un remplissage des bassins syn-orogéniques adjacents. Cette étude montre la formation et l’évolution conjuguée des différents niveaux crustaux notamment lors de l’enfouissement le long de la zone de subduction. Ici, la déformation dans les orthogneiss est localisée et permet le transport passif de larges portions de roches peu déformées et rigides. Ceci est expliqué par un changement dans le mécanisme de recristallisation d’un fluage- dislocation vers un glissement aux joints de grains. Initié par la croissance de phases interstitielles dans les agrégats monominéraux. Cette évolution est aussi observée dans les migmatites formant le cœur des anticlinaux proches du butoir. Ils permettent l’adoucissement rhéologique nécessaire au fluage dans le prisme d’accrétionEvolution of flow, framework and rheology of an orogenic accretionnary wedge is assessed with a multimethod geological investigation. The Orlica-Śnieżnik Dome (Sudetes) is situated in front of a rigid indenter. Its structure is explained by an influx of continental crust until 50-60 km depth in an accretionnary wedge. The incipient root is composed of lower crustal felsic material partially melted with smaller pieces of basic rocks. Structurally above it lies an intermediate level of weakly deformed metagranite and metasediments of the middle crust. This rheologicaly heterogeneous layered infrastructure is subsequently reworked in front of the rigid buttress developing multi-scale wave-length crustal upright folds. It permits vertical material transfers between different crustal levels that is responsible for the growing dome. It is achieved by the detachment of the superstructure, ductile thinning and by infill of syn-orogenic basins. This study highlights the shared evolution of the different crustal levels, in particular during influx and burial along the subducting plate. Here, the deformation in eclogites metagranites is localized and allows to passively transport large pieces of weakly deformed rocks into the apex of the corner. This localization is explained by a switch in the mode of recrystallisation from dislocation creep to grain boundary sliding diffusion creep which is chemically enhanced by nucleation of interstitial phases in monomineralic aggregates. This switch in mode of deformation is also observed in migmatites in front of the butress during exhumation. It permits the weakening of the rocks that is necessary to explain flow in the whole felsic corner
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Hopper, Derek J. "Crustal evolution of paleo- to mesoproterozoic rocks in the Peake and Denison Ranges, South Australia /." [St. Lucia, Qld.], 2001. http://www.library.uq.edu.au/pdfserve.php?image=thesisabs/absthe18288.pdf.
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Curtis, Michael L. "The structural and kinematic evolution of an upper crustal transpression zone : the Lusitanian Basin, Portugal." Thesis, Durham University, 1993. http://etheses.dur.ac.uk/5680/.
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The Lusitanian Basin forms a long (250km), narrow (50-100km), NE-SW trending outcrop of inverted Mesozoic carbonates and elastics. The outcrop of the Mesozoic sequence is flanked by two Neogene sub-basins, the contact between which is commonly faulted indicating that the Lusitanian basin underwent inversion during the Miocene. This inversion was achieved by reactivation of Jurassic extensional faults, which were originally formed above reactivated Hercynian basement faults during the Atlantic rifting event. The Serra de Montejunto/Candeeiros fault system (SMCF) forms the eastern boundary to this inverted zone, and is dominated by the NNE trending Serra dos Candeeiros fault (SCF). Towards the northern end of this fault system is a complex, uplifted, 15x20km fault bounded block, the Candeeiros block. At the southern termination of the SMCF, the fault orientation changes abruptly from NNE to ENE. This change in fault orientation coincides with the Serra de Montejunto mountain range, a narrow zone of tectonic uplift. Detailed studies of the main fault zones and adjacent wall rock deformation, allows the kinematics and strain to be characterised. These studies have revealed a complex history of Miocene to Recent reactivation along the boundaries of the Candeeiros block. Initial reactivation of the cross-faults of the block was synthetic to the sinistral SCF. Initial sinistral motion along the cross-faults was superimposed by a late period of dextral transpression, as evidenced by the inverted Alvados pull-apart basin preserved along the Alvados/Minde cross-faults. Dextral transpressive strains along the cross faults of the Candeeiros block, appear to be intimately related to the southerly directed extrusion and anti-clockwise rotation of the block. Structural relationships suggest up to 30 of rotation has occurred. Rotation of the Candeeiros Block is believed to be associated with the change from sinistral simple shear to sinistral transpression along the SCF, during the Late Miocene. The Serra de Montejunto region also displays a complex kinematic history, initiated by N-S shortening across the range, which was superseded by a late stage of sinistral transpression. This transpressive phase manifests itself as both simple and complex transpressive strains. The overall structural geometry of the region is that of a flower structure, formed in a major restraining bend at the termination of the SMCF. The kinematic and deformation style of the early Miocene reactivation in both the Candeeiros and Montejunto regions are consistent with the application of a N-S regional shortening direction, or σ(_1), on the pre-existing Jurassic age structure of the areas. This initial phase of deformation is overprinted by a distinct late phase of deformation related to sinistral transpression along the SCF, which was probably responsible for the inversion of the Lusitanian Basin. The orientation, and chronology of the regional shortening directions responsible for the evolution of the SMCF are in agreement with the relative plate motion history for Africa-Europe (Dewey et al., 1989).A comparison of instrumental seismicity and neotectonic surface faults associated with the SMCF, suggests that the basin is undergoing basement driven sinistral deformation, which is decoupled from the cover sequence by a thick evaporate sequence. The sinistral displacement along the proposed concealed, steep, basement faults appears to be transferred laterally along the sub-horizontal evaporite horizon, for up to 20km, to the steep cover faults of the SMCF.
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Behn, Mark Dietrich 1974. "The evolution of lithospheric deformation and crustal structure from continental margins to oceanic spreading centers." Thesis, Massachusetts Institute of Technology, 2002. http://hdl.handle.net/1721.1/29061.
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Thesis (Ph. D.)--Joint Program in Oceanography (Massachusetts Institute of Technology, Dept. of Earth, Atmospheric, and Planetary Science; and the Woods Hole Oceanographic Institution), 2002.Includes bibliographical references (p. 221-243).
This thesis investigates the evolution of lithospheric deformation and crustal structure from continental margins to mid-ocean ridges. The first part (Ch. 2) examines the style of segmentation along the U.S. East Coast Margin and investigates the relationship between incipient margin structure and segmentation at the modem Mid-Atlantic Ridge. The second part (Chs. 3-5) focuses on the mechanics of faulting in extending lithosphere. In Ch. 3, I show that the incorporation of a strain-rate softening rheology in continuum models results in localized zones of high strain rate that are not imposed a priori and develop in response to the rheology and boundary conditions. I then use this approach to quantify the effects of thermal state, crustal thickness, and crustal rheology on the predicted style of extension deformation. The mechanics of fault initiation and propagation along mid-ocean ridge segments is investigated in Ch. 4. Two modes of fault development are identified: Mode C faults that initiate near the center of a segment and Mode E faults that initiate at the segment ends. Numerical results from Ch. 5 predict that over time scales longer than a typical earthquake cycle transform faults behave as zones of significant weakness.
(cont.) Furthermore, these models indicate that Mode E faults formed at the inside-corner of a ridge-transform intersection will experience preferential growth relative to faults formed at the conjugate outside-corner due to their proximity to the weak transform zone. Finally, the last part of this thesis (Ch. 6) presents a new method to quantify the relationship between the seismic velocity and composition of igneous rocks. A direct relationship is derived to relate Vp to major element composition and typical velocity-depth profiles are used to calculate compositional bounds for the lower continental, margin, and oceanic crust.
by Mark Dietrich Behn.
Ph.D.
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Green, Michael Godfrey. "Early Archaean crustal evolution: evidence from ~3.5million year old greenstone successions in the Pilgangoora Belt, Pilbara Craton, Australia." Thesis, The University of Sydney, 2001. http://hdl.handle.net/2123/505.
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In the Pilgangoora Belt of the Pilbara Craton, Australia, the 3517 Ma Coonterunah Group and 3484-3468 Ma Carlindi granitoids underlie the 3458 Ma Warrawoona Group beneath an erosional unconformity, thus providing evidence for ancient emergent continental crust. The basalts either side of the unconformity are remarkably similar, with N-MORB-normalised enrichment factors for LILE, Th, U and LREE greater than those for Ta, Nb, P, Zr, Ti, Y and M-HREE, and initial e(Nd, Hf) compositions which systematically vary with Sm/Nd, Nb/U and Nb/La ratios. Geological and geochemical evidence shows that the Warrawoona Group was erupted onto continental basement, and that these basalts assimilated small amounts of Carlindi granitoid. As the Coonterunah basalts have similar compositions, they probably formed likewise, although they were deposited >60 myr before. Indeed, such a model may be applicable to most other early Pilbara greenstone successions, and so an older continental basement was probably critical for early Pilbara evolution. The geochemical, geological and geophysical characteristics of the Pilbara greenstone successions can be best explained as flood basalt successions deposited onto thin, submerged continental basement. This magmatism was induced by thermal upwelling in the mantle, although the basalts themselves do not have compositions which reflect derivation from an anomalously hot mantle. The Carlindi granitoids probably formed by fusion of young garnet-hornblende-rich sialic crust induced by basaltic volcanism. Early Archaean rocks have Nd-Hf isotope compositions which indicate that the young mantle had differentiated into distinct isotopic domains before 4.0 Ga. Such ancient depletion was associated with an increase of mantle Nb/U ratios to modern values, and hence this event probably reflects the extraction of an amount of continental crust equivalent to its modern mass from the primitive mantle before 3.5 Ga. Thus, a steady-state model of crustal growth is favoured whereby post ~4.0 Ga continental additions have been balanced by recycling back into the mantle, with no net global flux of continental crust at modern subduction zones. It is also proposed that the decoupling of initial e(Nd) and e(Hf) from its typical covariant behaviour was related to the formation of continental crust, perhaps by widespread formation of TTG magmas.
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Pimentel, Marcio Martins. "Late Proterozoic crustal evolution of the Tocantins Province in central Brazil : an isotopic and geochemical study." Thesis, University of Oxford, 1990. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.280038.
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Collier, Richard E. Ll. "Sedimentary facies evolution in Continental fault-bounded basins formed by crustal extension : the Corinth Basin, Greece." Thesis, University of Leeds, 1988. http://etheses.whiterose.ac.uk/2616/.
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Characteristic half-graben and graben geometries are generated by extensional tectonics. The sedimentary infill to such basins reflects their structural evolution. The actively extending basins of central Greece have provided an opportunity to study the mechanisms that control sediment distribution and the resultant facies patterns and geometries produced in such environments. The modern and precedent Neogene to Quaternary sediments studied, and their controlling processes, provide predictive templates for the analysis of controls acting upon ancient extensional basin fills. On a basinwide scale, facies patterns are controlled by the geometry of major basin-controlling normal faults and by the structural level of the basin - determining alluvial, lacustrine or marine environments. Increments of movement on normal faults tilt and vertically displace the depositional surface, producing facies responses in terms of fluvial/submarine channel avulsion or preferential migration into topographic lows, lake or sea coastline advance or retreat across the depositional slope, and the progradation of clastic wedges off fault scarps and uplifted areas. The time-averaged product in the stratigraphic record is typically of clinoforms developed preferentially against basin margin faults and axial channel systems concentrated in the structurally constrained depocentre(s). Such gross morphologies are seen in the Lower Pliocene early rift history of the Corinth asymmetric graben; conglomerate-dominated fan deltas and alluvial fans prograded laterally into the basin. The progradation of an ophiolite-derived, fluvio-deltaic system along the basin axis illustrates the competition of sediment supply rates with tectonic subsidence rates in determining facies geometries. A number of other controls on sediment distribution are variously important through time within extensional basins, in addition to structuration and sediment supply rates (itself a function of hinterland litho-type and structural evolution). These include eustatic and climatic variation and compactional subsidence rates. The Corinth Isthmus has been studied with the aim of establishing the interaction of concurrent tectonic and eustatic relative base-level changes. Computer-modelling of the migration of a coastline through theoretical stratigraphic sections illustrates the effects of varying rates of change of sea-level, tectonic subsidence (or uplift) and deposition with time. Incorporation of the global sea-level curve for the Late Quaternary into such models reasonably predicts observed facies geometries in the Late Pleistocene and Holocene of the Isthmus. U-series disequilibrium dating of corals from the Corinth Canal area has constrained transgressive beach sub-sequences as reflecting c. 100,000 year wavelength eustatic cycles. After subtraction of depositional levels constrained in time and space against the sea-level curve, an average net uplift rate is derived for the central Isthmus of more than 0.3m per 1000 years. The areal distribution of Late Pleistocene marine facies in the southern Corinth Basin is principally controlled by the structural form and evolution at time of deposition. Subsequent tilt block faulting in an alluvial environment illustrates how intrabasinal fault block morphologies may generate axial and lateral sediment transport systems analagous to those on a basinwide scale. The competition between process rates is emphasized. Three- dimensional sedimentary facies patterns within evolving syn-rift basins are shown to be dependent upon the interaction of three principal factors: a) the rate of tectonic displacements through time, on both basinwide and local fault block scales, b) the rate of sea-level change through time (or lake-level change, whether determined by tectonic or climatic means), and c) the rate of deposition at any locality, itself a function of hinterland structure and lithology, climate and depositional geometries.
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Buchan, A. Craig. "Tectonic evolution of the Bayankhongor Ophiolite, Central Mongolia : implications for the Palaeozoic crustal growth of Central Asia." Thesis, University of Leicester, 2001. http://hdl.handle.net/2381/30444.
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The Bayankhongor ophiolite marks the closure of an ocean separating two microcontinents: the Baidrag complex with the Burd Gol accretionary complex to the south, and a northern continent which forms the basement for the Hangai region. Subduction was towards the SW with NE-directed ophiolite obduction onto a passive margin represented by the Dzag zone. Geochemical and Nd isotope studies of the ophiolitic rocks suggest that they were derived from a heterogeneous mantle source composed of a depleted N-MORB and enriched E-MORB component. A model for the tectonic setting of the ophiolitic rocks is presented in which the N-MORB rocks represent melts produced at a mid-ocean ridge, whilst the E-MORB rocks represent off-axis flows or melts produced at transform ridge intersections. Basalts from the Delb Khairkhan melange have island arc-like chemistry and provide evidence that the ophiolite may have been trapped within a supra-subduction setting prior to obduction. New 207Pb/206Pb zircon evaporation ages for granites and rhyolite dykes that intrude the ophiolite and its neighbouring lithotectonic units, suggest that the ophiolite was obducted at c. 540 Ma at the beginning of a collisional event that lasted until c. 450 Ma. The new data combined with that of previous studies indicate regional correlation of isotopic ages north-westward from Bayankhongor to southern Tuva. These data record oceanic crust formation at c. 570 Ma, followed by approximately 30 million years of subduction-accretion that culminated in obduction of ophiolites, collision related metamorphism, and magmatism in the period c.540-450 Ma. Correlation of isotopic-age data for the ophiolites of western Mongolia and southern Tuva suggest that the ophiolites define a major collisional suture in the Central Asian Orogenic Belt which helps define the southern and western margins of the Hangai continental block.
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Guntoro, Agus. "Tectonic evolution and crustal structure of the Central Indonesian Region : from geology, gravity and other geophysical data." Thesis, University College London (University of London), 1995. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.307471.
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Grimes, Craig B. "Duration, rates, and patterns of crustal growth at slow-spreading mid-ocean ridges using zircon to investigate the evolution of in situ ocean crust /." Laramie, Wyo. : University of Wyoming, 2008. http://proquest.umi.com/pqdweb?did=1799840381&sid=1&Fmt=2&clientId=18949&RQT=309&VName=PQD.
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Parks, Jane Elizabeth. "Crustal evolution of Grenville terranes in the central and southern Appalachians : the Pb isotope perspective for Grenville tectonics /." Thesis, This resource online, 1993. http://scholar.lib.vt.edu/theses/available/etd-06162009-063235/.
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Chopin, F. "Evolution du flux de matière, de l'architecture et de la rhéologie d'un prisme d'accrétion crustal (Dôme d'Orlica-Śnieżnik, Sudètes)." Phd thesis, Université de Strasbourg, 2010. http://tel.archives-ouvertes.fr/tel-00592281.
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L'évolution du flux de matière, de l'architecture et de la rhéologie d'un prisme d'accrétion orogénique au cours du temps est abordée à l'aide d'une étude géologique multiméthode. Le dôme d'Orlica-Śnieżnik dans les Sudètes est situé au front d'un butoir rigide. La formation de ce dôme est expliquée par l'influx de croûte continentale felsique issue de la marge passive subductée jusqu'à 50-60km de profondeur dans un prisme d'accrétion d'échelle crustale. La racine ainsi formée comprend une croûte inférieure felsique avec quelques lentilles basiques partiellement fondues en profondeur et séparées de la croûte moyenne (metasédiments, metavolcanites) par une couche rigide d'orthogneiss peu déformée. Cette infrastructure rhéologiquement hétérogène résultant du remplissage du prisme est fortement remaniée au front du butoir par des plissements plurikilométriques de longueurs d'onde variables. Ceux-ci permettent des échanges verticaux aboutissant à l'exhumation des différents niveaux crustaux de l'infrastructure. La croissance du dôme par plissement au front du butoir s'achève par le décoiffement de la suprastructure associé à un amincissement ductile localisé et à un remplissage des bassins syn-orogéniques adjacents. Cette étude montre bien la formation et l'évolution conjuguée des différents niveaux crustaux en particulier lors de l'enfouissement le long de la zone de subduction au sein du prisme. Ici, la déformation dans les orthogneiss est très localisée et permet le transport passif de larges portions de roches peu déformées et rigides. Ceci est expliqué par un changement dans le mécanisme de recristallisation des roches quartzo feldspathiques d'un fluage- dislocation intense vers un glissement aux joints de grains. Ce changement est initié par la croissance de phases interstitielles dans les agrégats monominéraux. Ce type d'évolution dans un gradient prograde éclogitique est aussi observé dans les migmatites formant le cœur des anticlinaux proches du butoir. Ils permettent l'adoucissement rhéologique nécessaire au fluage dans le prisme d'accrétion crustal.
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Kazimoto, Emmanuel Owden [Verfasser]. "Crustal evolution and hydrothermal gold mineralization in the Katuma Block of the Paleoproterozoic Ubendian Belt, Tanzania / Emmanuel Owden Kazimoto." Kiel : Universitätsbibliothek Kiel, 2014. http://d-nb.info/1053326122/34.
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Clerc, Camille. "EVOLUTION DU DOMAINE NORD-PYRENEEN AU CRETACE. AMINCISSEMENT CRUSTAL EXTREME ET THERMICITE ELEVEE: UN ANALOGUE POUR LES MARGES PASSIVES." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2012. http://tel.archives-ouvertes.fr/tel-00787952.
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Cette thèse présente une analyse structurale et thermique des marges passives crétacées inversées dans la Zone Nord Pyrénéenne (ZNP). L'application du paléothermomètre RSCM (spectrométrie Raman de la matière carbonée) sur plus de cent échantillons répartis à travers la ZNP permet de préciser l'évolution thermique de la déchirure continentale. Un métamorphisme de haute température (450 à >600°C) se développe particulièrement au droit de zones ou la croûte continentale est extrêmement amincie voire éliminée. Les sédiments pré- et syn-rift sont marqués par une intense déformation ductile. L'analyse à l'EBSD des fabriques minérales indique une déformation de Haute-température contemporaine du métamorphisme HT-BP. Les conditions de mise en place crustale des péridotites et leur exhumation localisée sont examinées dans les localités d'Urdach, Saraillé-Tos de la Coustette, Moncaup, Lherz, Caussou-Bestiac et Salvezines. Les résultats indiquent un boudinage de la croûte continentale au cours du processus de rifting. Des décollements de couverture, principalement localisés dans les évaporites triasiques conduisent à la superposition directe des sédiments pré-rift sur le manteau exhumé. La notion nouvelle de soutirage crustal est introduite pour désigner ce processus dans lequel l'écoulement gravitaire ne joue pas un rôle principal. La caractérisation sédimentologique, pétrographique et isotopique (O et C) des différentes formations de brèches et ophicalcites observées à proximité des corps de péridotites permet de reconstituer les étapes de l'exhumation du manteau en pied de marge. Enfin de nouvelles datations permettent de mieux contraindre le calendrier des évènements successifs.
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Hoal, Brian Garner. "Proterozoic crustal evolution of the Awasib Mountain terrain, southern Namibia, with speical reference to the volcanic Haiber flats formation." Doctoral thesis, University of Cape Town, 1989. http://hdl.handle.net/11427/21889.
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Bibliography: pages 245-257.The middle to late Proterozoic Awasib Mountain terrain (AMT) straddles the boundary between the Rehoboth and Gordonia subprovinces in southern Namibia. The AMT is made up of two major crustal components, the older of which is correlated with the Namaqualand Metamorphic Complex (NMC), and the younger with the Sinclair Sequence.
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Clerc, Camille. "Evolution du domaine nord-pyrénéen au Crétacé : amincissement crustal extrême et thermicite élevée : un analogue pour les marges passives." Paris 6, 2012. http://www.theses.fr/2012PA066572.
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Cette thèse présente une analyse structurale et thermique des marges passives crétacées inversées dans la Zone Nord Pyrénéenne (ZNP). L’application du paléothermomètre RSCM (spectrométrie Raman de la matière carbonée) sur plus de cent échantillons répartis à travers la ZNP permet de préciser l’évolution thermique de la déchirure continentale. Un métamorphisme de haute température (450 à >600°C) se développe particulièrement au droit de zones ou la croûte continentale est extrêmement amincie voire éliminée. Les sédiments pré- et syn-rift sont marqués par une intense déformation ductile. L’analyse à l’EBSD des fabriques minérales indique une déformation de Haute-température contemporaine du métamorphisme HT-BP. Les conditions de mise en place crustale des péridotites et leur exhumation localisée sont examinées dans les localités d’Urdach, Saraillé-Tos de la Coustette, Moncaup, Lherz, Caussou-Bestiac et Salvezines. Les résultats indiquent un boudinage de la croûte continentale au cours du processus de rifting. Des décollements de couverture, principalement localisés dans les évaporites triasiques conduisent à la superposition directe des sédiments pré-rift sur le manteau exhumé. La notion nouvelle de soutirage crustal est introduite pour désigner ce processus dans lequel l’écoulement gravitaire ne joue pas un rôle principal. La caractérisation sédimentologique, pétrographique et isotopique (O et C) des différentes formations de brèches et ophicalcites observées à proximité des corps de péridotites permet de reconstituer les étapes de l’exhumation du manteau en pied de marge. Enfin de nouvelles datations permettent de mieux contraindre le calendrier des évènements successifsBased on fieldwork and modern analytical technics, this work presents an overview of the Mid-Cretaceous hyper-extended rift system exposed in the northern part of the Pyrenean mountain range. Its inversion during the Pyrenean orogeny allows for precious observations of the deep-seated processes occurring at the foot of distal margins. Some peculiar aspects characterizing the pre-Alpine hyper-extended domain are examined throughout the 400km long suture that is fossilized in the North Pyrenean Zone (NPZ). The High Temperature/Low Pressure (HT/LP) thermal imprint of the extensional event is studied thanks to a dataset of more than hundred peak temperature measurement by Raman spectroscopy of the carbonaceous material (RSCM). The pre- and syn-rift metasediments are characterized by an intense ductile deformation. Field and EBSD investigations of the mechanisms of deformation reveal ductile and syn-metamorphic processes. The emplacement conditions of the peridotite into crustal levels and localized exhumation is examined in the key-localities of Urdach, Saraillé-Tos de la Coustette, Moncaup, Lherz, Caussou-Bestiac and Salvezines, The results indicate an early boudinage of the crust during the rifting process, resulting in the direct superposition of pre-rift sediments on top of mantle peridotites. Field, textural and isotopic characterization of the various ophicalcite and breccias found in the vicinity of the peridotite outcrops allow to decipher their exhumation history. New Ar-Ar geochronological results allow to precise the temporal evolution of the NPZ
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Green, Michael Godfrey. "Early archaean crustal evolution evidence from 3̃.5 billion year old greenstone successions in the Pilgangoora Belt, Pilbara Craton, Australia /." Connect to full text, 2001. http://hdl.handle.net/2123/505.
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Thesis (Ph. D.)--University of Sydney, 2002.Title from title screen (viewed Apr. 23, 2008). Submitted in fulfilment of the requirements for the degree of Doctor of Philosophy to the School of Geosciences, Division of Geology and Geophysics. Degree awarded 2002; thesis submitted 2001. Includes bibliography. Also available in print form.
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Wiemer, Daniel. "Tectonic evolution of the Early Archaean Doolena Gap Greenstone Belt, East Pilbara Terrane, Western Australia." Thesis, Queensland University of Technology, 2017. https://eprints.qut.edu.au/102985/1/Daniel_Wiemer_Thesis.pdf.
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This thesis examined how the oldest core of the Australian continent formed more than 3.5 billion years ago. Unraveling the complex tectonic and petrologic history of ancient rocks of the East Pilbara in Western Australia provided important new insights into how and why continents developed on our hot, young planet. A multifaceted methodology of field-based structural geology, uranium-lead (U-Pb) dating of zircon, whole-rock geochemistry, and petrology improved our understanding of early Archaean mass and heat transfer, including the history of the associated planetary surface environment, which hosted some of the earliest life on Earth.
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Parent, Andrew Michael. "Pre-Mt. Simon Seismic Sequences Below West-Central Indiana: Local Interpretation and Regional Significance." Wright State University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=wright149606295325976.
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Simpson, Clayton A. "Constraints on proterozoic crustal evolution from an isotopic and geochemical study of clastic sediments of the Gawler Craton, South Australia /." Title page, contents and abstract only, 1994. http://web4.library.adelaide.edu.au/theses/09SB/09sbs613.pdf.
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Thesis (B. Sc.(Hons.))--University of Adelaide, Dept. of Geology and Geophysics, 1995.Map sheets: Lincoln (SI 53-11) 1:250 000 Tumby Bay (SI 53-6129) 1:100 000. Includes bibliographical references.
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Wasilewski, Benjamin. "Geochronology, Petrogenesis and Crustal Evolution of the Saglek-Hebron Complex (Northern Labrador): Over One Billion Years of Archean Geological History." Thesis, Université d'Ottawa / University of Ottawa, 2019. http://hdl.handle.net/10393/39617.
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The Saglek-Hebron Complex (SHC) in Northern Labrador represents one of the oldest terrains on Earth and it is closely related to the Archean Itsaq Gneiss Complex (IGC) in Greenland. The SHC is a typical granite-greenstone terrain that recorded over one billion years of magmatic history between ~3900 Ma and ~2700 Ma. Our geochronological and geochemical study shows that the SHC includes five generations of trondhjemite-tonalite-granodiorite suites (TTG): the ~3870 Ma Iqaluk gneiss, the ~3750 Ma Uivak I gneiss, the ~3600 Ma Uivak II gneiss, the newly described ~3300 Ma Iluilik gneiss, and the ~3220 Ma Lister gneiss. These granitoid units are mostly consist of trondhjemite and tonalite with only rare granodiorites that appear to define a distinct unit formed at ~3330 Ma and newly defined as the Iluilik gneiss. The Iluilik granodiorite appears to be derived from a Hadean mafic crust as supported by its combined whole-rock geochemical composition, its positive µ142Nd value of +6, and its low εHf= -6 and εNd= -3, at 3300 Ma. SHC granites were emplaced throughout the Archean, from 3800 to 2700 Ma, but are predominant in the Neoarchean. They appear to have been mainly formed from the reworking of the SHC TTG, as supported by their low εHf and εNd initial values of respectively -16 and -11 at 2700 Ma. The granitoids include numerous enclaves of supracrustal rocks from various size, up to a few kilometers in scale, consisting of metavolcanic metasedimentary rocks. Previous work has suggested that they were formed at two different ages, with the younger Upernavik supracrustal unit deposited around 3400 Ma and the older Nulliak supracrustal assemblage deposited at around 3750 Ma. We show that both units are comparatively geochemically homogeneous with no distinction between the mafic and ultramafic rocks from both supracrustal assemblages. They mainly consist of mafic metavolcanic amphibolites with tholeiitic affinities, consistent with more depleted mafic and more enriched compositions produced by magmatic differentiation. Their complementary Eu anomaly and whole-rock geochemistry suggest that they formed from fractional crystallization of gabbroic assemblage that derived from similar if not the same parental magma. The mafic metavolcanic rocks are also often associated with ultramafic rocks that we divided into two distinct units, respectively referred as the high-Fe and the low-Fe ultramafic rocks, characterized by different FeO contents and Al/Ti ratio. They both represent olivine-rich cumulative rocks derived from distinct parental komatiitic basalt magmas. Our interpretation contrasts with previous work suggesting that the SHC ultramafic rocks were komatiites and slivers of residual lithospheric mantle. Most SHC TTG exhibit a positive 142Nd anomaly, as high as µ142Nd = +15, suggesting a source formed by differentiation in the Hadean. This 142Nd isotopic composition is similar to the Nulliak supracrustal rocks that exhibit on average a µ142Nd of +10. TTG is generally considered to derive from a mafic precursor. This study therefore shows that mafic crustal source of the SHC Eoarchean TTG, potentially the Nulliak metabasalts, derives from an ancient highly depleted mantle, described as the Saglek mantle, sharing a similar early history as the mantle reservoir involved in the formation of the ancient Itsaq terrane of southwest Greenland. The Saglek depleted mantle is interpreted to have formed at ~4400 Ma, exhibit highly depleted signature with a 147Sm/144Nd ratio of 0.221-0.240.
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Li, Jiangyu. "Proterozoic crustal evolution of NE Australia during the supercontinent Nuna Assembly: new insights from a coupled thermochronological and geophysical study." Thesis, Curtin University, 2021. http://hdl.handle.net/20.500.11937/89292.
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This thesis primary focus on the NE Australian Craton, with particular interests in the Protozoic rocks of the Mount Isa and Georgetown inliers, to resolve the crustal evolution record across this region that reflects on tectonic processes and crustal history related to the assembly of the supercontinent Nuna.
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Barbosa, Maria Fernanda Novo. "Estimativa de espessura crustal na Prov?ncia Borborema (NE/Brasil) atrav?s de fun??o do receptor." Universidade Federal do Rio Grande do Norte, 2008. http://repositorio.ufrn.br:8080/jspui/handle/123456789/18744.
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Previous issue date: 2008-06-13Conselho Nacional de Desenvolvimento Cient?fico e Tecnol?gico
Crustal thickness and VP/VS estimates are essential to the studies of subsurface geological structures and also to the understanding of the regional tectonic evolution of a given area. In this dissertation, we use the Langston?s (1979) Receiver Function Method using teleseismic events reaching the seismographic station with angles close to the vertical. In this method, the information of the geologic structures close to the station is isolated so that effects related to the instrument response and source mechanics are not present. The resulting time series obtained after the deconvolution between horizontal components contains the larger amplitude referring to the P arrival, followed by smaller arrival caused by the reverberation and conversion of the P-wave at the base of the crust. We also used the HK-Stacking after Zhu & Kanamori (2000) to obtain crustal thickness and Vp/VS estimates. This method works stacking receiver functions so that the best estimates of crustal thickness and Vp/VS are found when the direct P, the Ps wave and the first multiple are coherently stacked. We used five broadband seismographic stations distributed over the Borborema Province, NE Brazil. Crustal thickness and Vp/VS estimates are consistent with the crust-mantle interface obtained using gravity data. We also identified crutal thickening in the NW portion of the province, close to Sobral/CE. Towards the center-north portion of the province, there is an evident crustal thinning which coincides with a geological feature consisting of an alignment of sedimentary basins known as the Cariris-Potiguar trend. Towards the NE portion of the province, in Sol?nea/PB and Agrestina/PE regions, occurs a crustal thickening and a systematic increase in the VP/VS values which suggest the presence of mafic rocks in the lower crust also consistent with the hypothesis of underplating in the region
A estimativa da espessura da crosta terrestre e raz?o VP/VS s?o essenciais para o detalhamento de estruturas e fei??es geol?gicas, al?m de corroborarem para o entendimento da evolu??o tect?nica regional. Neste trabalho, utiliza-se o m?todo da Fun??o do Receptor de Langston (1979) com eventos teless?smicos que incidem sob uma esta??o sismogr?fica com um ?ngulo pr?ximo da vertical. ? necess?rio o isolamento de informa??es das estruturas pr?ximas ao receptor, eliminando informa??es relacionadas ? resposta do instrumento, e ao mecanismo da fonte. O sismograma sint?tico obtido ap?s uma deconvolu??o entre as componentes horizontais possui um pico maior referente ? onda P, seguido por picos menores da onda Ps e m?ltiplas. A Onda Ps ? considerada como onda P convertida em onda S refratada na descontinuidade Moho. Para o c?lculo das estimativas de espessura crustal e raz?es Vp/VS utilizou-se o procedimento HK-Stacking de Zhu & Kanamori (2000). Esse m?todo trabalha com o empilhamento das fun??es do receptor. As melhores estimativas de espessura crustal e raz?o VP/VS s?o encontradas quando as tr?s fases P, Ps e primeira m?ltipla s?o empilhadas coerentemente. Foram utilizadas cinco esta??es sismogr?ficas banda-larga distribu?das estrategicamente pela Prov?ncia Borborema, nordeste do Brasil. As estimativas de espessura crustal e raz?o VP/VS s?o consistentes com o modelo atual da interface crosta-manto usados pela gravimetria. Foi identificado um espessamento crustal na por??o NW da prov?ncia, pr?ximo de Sobral/CE, na borda leste da Bacia do Parna?ba. Em dire??o a por??o centro-norte da Prov?ncia Borborema ? evidente um afinamento crustal, coincidente com a fei??o geol?gica que consiste de um alinhamento de bacias sedimentares conhecido como o trend Cariris-Potiguar. Na por??o NE, nas regi?es de Sol?nea/PB e Agrestina/PE, ocorre um espessamento crustal e aumento da raz?o VP/VS sugerindo presen?a de rochas mais m?ficas na crosta inferior, consistente com a hip?tese de underplating na regi?o