Дисертації з теми "Craton margins"
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Nowicki, Thomas Edward. "Mantle xenoliths from the Abrahamskraal kimberlite : a craton-margin geotherm." Thesis, Rhodes University, 1991. http://hdl.handle.net/10962/d1001557.
Повний текст джерелаDowney, Matthew. "The Structural Geology, Kinematics and Timing of Deformation at the Superior craton margin, Gull Rapids, Manitoba." Thesis, University of Waterloo, 2005. http://hdl.handle.net/10012/1258.
Повний текст джерелаThe Gull Rapids area records a complex tectonic history. The area experienced four generations of Neoarchean ductile and brittle deformation (G1 ? G4) and one of Paleoproterozoic ductile-brittle deformation (G5). G1 deformation produced the main foliation in the map area, as well as local isoclinal folding which may be related to an early shearing event. M1a prograde mid-amphibolite facies metamorphism is contemporaneous with the early stages of G1. Widespread, tight to isoclinal sheath folding during G2 was recorded in the supracrustal assemblage, and is the result of southwest-side-up, dextral shearing during the early shearing event. A ca. 2. 68 Ga widespread phase of granitoid intrusion was emplaced late-G1 to early-G2, and is rich in metamorphic minerals that record conditions of M1b upper-amphibolite facies peak metamorphism. M1b metamorphism, late-G1 to early-G2 deformation, and intrusion of this felsic phase are contemporaneous. M2 retrograde metamorphism to mid-amphibolite facies was recorded sometime after M1b. G1 and G2 structures were re-folded during G3, which was then followed by G4 southwest-side-up, dextral and sinistral shearing, contemporaneous with late pegmatite intrusion at ca. 2. 61 Ga. This was followed by mafic dyke emplacement at ca. 2. 10 Ga, and then by G5 sinistral and dextral shearing and M3 greenschist facies metamorphism or hydrothermal alteration at ca. 1. 80 Ga.
Deformation and metamorphism at Gull Rapids post-dates emplacement and deposition of gneissic and supracrustal rocks, respectively. This deformation and metamorphism, except for G5 and M3, is Neoarchean (ca. 2. 68?2. 61 Ga), and represents a significant movement of crustal blocks: km-scale shearing of the supracrustal assemblage and consequent uplift of the Split Lake Block. Late deformation and metamorphism (G5, M3) may be related to the Paleoproterozoic Trans-Hudson orogeny. The Neoarchean and Paleoproterozoic zircon populations in the geochronological data suggest that the Gull Rapids area largely experienced Neoarchean deformation and metamorphism with a weak Paleoproterozoic overprint. All of the evidence presented above suggests that the Gull Rapids area lies in a part of the Superior Boundary Zone, yet does not lie at the exact margin of the Superior craton, and therefore does not mark the Archean-Proterozoic boundary proper in northeastern Manitoba.
Bagai, Zibisani. "Geodynamic evolution and petrogenesis of the neoarchaean Francistown granite-greenstone complex in NE Botswana, SW margin of the Zimbabwe craton." Doctoral thesis, University of Cape Town, 2009. http://hdl.handle.net/11427/4187.
Повний текст джерелаIncludes bibliographical references.
The Archaean Francistown Granite-Greenstone Complex in NE Botswana is an integral part of the southwestern margin of the Zimbabwe Craton. It includes a suite of geochemically diverse Neoarchaean granitoids and mafic dominated-supracrustal assemblages. All the supracrustal rocks and mafic intrusions have undergone greenschist to lower amphibolite facies metamorphism, but most mafic intrusions have preserved original igneous textures. The Francistown Granite Greenstone Complex likely represents an arc complex that developed along an active continental margin in the Neoarchaean. This thesis presents new geological, geochemical and geochronological data with which to evaluate the crustal evolution of the NE Botswana, and with which to formulate a geodynamic model for better understanding of the Archaean crustal growth flanking the southwestern margin of the Zimbabwe Craton
Esteves, Melina Cristina Borges. "Thermal history and fluid circulation in deformational structures associated with the Bambuí Group at the fold-and-thrust zone, western margin of the São Francisco Craton." Universidade de São Paulo, 2018. http://www.teses.usp.br/teses/disponiveis/44/44143/tde-10092018-135551/.
Повний текст джерелаP-T conditions existing at the tectonic event that acted at the fold-and-thrust zone of the western margin of the São Francisco Craton were estimated on the basis of structural, microstructural, petrographic and fluid inclusion study of syntectonic veins. The presence of veins of different generations in the fold-and-thrust zone is evidenced by fluids operating at different scenarios of paleostress throughout the deformation history. The area are composed of weakly deformed rocks of the Bambuí Group recording a metamorphism with conditions ranging from diagenetic to sub-greenschist facies. Two tectonic events were identified by vein geometric arrangement and folded surface, a major early NE-SW compression (D1 - \'sigma\'1 subhorizontal SW-trending and \'sigma\'3 subvertical), related with subhorizontal NW-trending syntectonic veins formed at conditions that have reached at least 140°C and pressures around 200-363 MPa; and later NW-SE compression (D2 - \'sigma\'1 subhorizontal NW-trending and \'sigma\'3 subhorizontal NE-trending), related with subvertical syntectonic cleavage-parallel veins formed at the same range of temperature and pressures between 181-295 MPa. Indication of fluctuations in pressure during these events played a crucial role as fluids significantly influence the mechanical processes, deformation mechanisms and chemical reactions that operate in fold-thrust belts. Fluids show H2O-NaCl-CaCl2 composition where mixing process of different fluids sources (metamorphic and meteoric) are evidenced by evolutive trending of homogenization temperatures and salinities resulting in some variation in salinity (12 against 4 wt.% NaCl eq. for subhorizontal and cleavage-parallel veins respectively). This research confirms that combine the reconstruction of the paleostress states and fluid inclusion studies can provide fundamental information of relationship between fluid flow and tectonic of orogenic terrains contributing to the scientific knowledge about the deformational/metamorphic evolution of the Bambuí Group and the fold-and-thrust zone of the western margin of the São Francisco Craton.
Nethenzheni, Sedzani Shane. "The geochemistry, geochronology and petrogenetic characteristics of two granitic suites on the eastern margin of the Namaqua Sector, Namaqua-Natal Mobile Belt, South Africa." Thesis, University of the Western Cape, 2016. http://hdl.handle.net/11394/5209.
Повний текст джерелаThe group of granites on the eastern margin of the Mesoproterozoic Namaqua sector of the polydeformed and highly metamorphosed Namaqua-Natal Province of southern Africa is known as the Keimoes Suite. The suite includes mixtures of diverse rock types not belonging to a single intrusive series and so it should be subdivided into more than one intrusive suite. The exact definition, extent, distribution and petrogenesis of these granites have been poorly defined in the past, with various authors defining the suite differently due to the lack of proper geochronology and geochemical data. The exact contact between the Namaqua sector and Kaapvaal Craton together with the role of the suite to the Namaqua tectonic evolution is still unclear. The granites of the Keimoes Suite are thought to mark the contact between the Namaqua sector and the Kaapvaal Craton. This study seeks to address the above mentioned problems by making use of new geochronology, isotope, major and trace element geochemistry together with petrography. The granites of the Keimoes Suite were previously grouped based on their degree of deformation. The geochronology, undertaken as part of this study, has proven that this classification is unfounded. The degree of foliation in these granites appears to be largely controlled by the abundance of platy minerals, such as biotite and muscovite, together with the intrusion mechanism, with deformational processes, such as shearing, playing a secondary role. The geochronology, together with geochemistry has helped to redefine the previously defined Keimoes Suite so that two well defined separate suites are recognized and the third is poorly defined due to lack of more samples of that age group. The new classification or grouping of the granites of the eastern Namaqua sector allows a more detailed examination of the tectonic evolution of this region. A member of the 1225 to 1200 Ma early syn-tectonic granites, the Josling Granite, shows a strongly developed foliation and was derived from a depleted source with a relatively low continental crustal component. This granite intruded during the time of arc accretion, and is associated with, and partly responsible for the D₁ deformation and M₁ metamorphism recognized in most of the rocks of the eastern terranes of the Namaqua sector. In terms of age, the syn-tectonic granites of the Augrabies Suite extend from 1200 to 1120 Ma and were largely derived from depleted sources with variable but more substantial amounts of continental crustal components as compared to the early syn-tectonic granite. The granites of this suite intruded during the period of peak D₂ deformation with peak magmatism between 1180 - 1135 Ma, and particularly around 1150 Ma, during the peak of metamorphism (M₂) caused by, and associated with these voluminous intrusions. The Keimoes Suite can now be defined as comprising granites of late- to post-tectonic age relative to the 1.2 - 1.08 Ga Namaquan Orogeny with magmatism occurring on the western side of the Kaapvaal Craton. The 1116 to 1066 Ma Keimoes Suite intruded during the stage of the Namaquan Orogeny in which there was continued indentation of the Kaapvaal Craton into the Namaqua sector with wrenching and shearing causing the development of rifting into which the granites intruded. The Keimoes Suite granites were derived from continental crustal sources and incorporated varying degrees of depleted source components. The intrusives and extrusives of this age occured after the main collisional event between the Namaqua Sector and the Kaapvaal Craton and are associated with the D₃ deformational event, imparting the thermal conditions leading to the M₃ metamorphic event of the rocks within both the Kakamas and Areachap Terranes. The suites mark the suture between the Archean Kaapvaal Craton and the Proterozoic Namaqua sector. The compositions of the granites of the individual suites were mainly controlled by the source with the degree of partial melting exerting a major control. The proportion of entrained peritectic assemblages and accessory minerals played a major role in controlling the compositions of the granites, particularly those of the trace elements. Variations within the compositions of the same suite are due to source heterogeneities. Generally, fractionation processes played a secondary role in influencing the composition of the granites.
Council for Geoscience and National Research Foundation
Loparev, Artiom. "Géométries crustales, évolution paléogéographique et histoire de l'accumulation terrigène des bassins de la marge passive du craton guyanais." Thesis, Toulouse 3, 2020. http://www.theses.fr/2020TOU30170.
Повний текст джерелаThis thesis is a part of "Source to Sink Guyana" project supported by TOTAL and BRGM. Its objective was to establish bases for a Source to Sink study of the Guiana Shield, by studying the geo-dynamic evolution of its passive margin since 200 Ma. These objectives were acquired after seismic data interpretation, crustal cross-sections and paleogeographic maps constructions and terrigeneous accumulation history quantification of the margin. The passive margin of the Guiana Shield is composed of two basins: Guiana/Suriname (GS) and Foz d'Amazonas (FOZ), derived from a Jurassic then Lower Cretaceous diachronous rifting respectively. The study of the subsurface data allowed us to show that the superimposition of the two rifts has shaped the Demerara Shelf into a continental block, thinned twice and surrounded by oceanic crust on three sides. The more oblique rifting of the FOZ basin forms systematically narrower segments and finer syn-rift deposits than in the GS basin. The paleo-geographic evolution of the margin and terrigenous accumulation, over eight intervals of time (from 200 Ma), show a different evolution of the two basins. The lithological distribution of sedimentary systems is homogenized from the Campanian, when both basins reach the late-post-rift stage, during which the distribution is mainly controlled by continental river dynamics. Terrestrial accumulated volumes show however an opposite evolution during Cretaceous in both basins, in connection with the decrease and increase in the drained areas of the major rivers of this region, Paleo-Berbice and Paleo-Tocantins respectively. Siliclastic inputs towards the margin are generally low (between 2 and 11 m/Ma), but alternating with periods of high inputs corresponding to the recreation of the relief on the continent
He, Yanhong. "Ages and geochemistry of the Xiong'er volcanic rocks along the southern margin of the North China Craton implications for the outgrowths of the paleo-mesoproterozoic supercontinent Columbia (Nuna) /." Click to view the E-thesis via HKUTO, 2008. http://sunzi.lib.hku.hk/hkuto/record/B4163424X.
Повний текст джерелаHe, Yanhong, and 何艷紅. "Ages and geochemistry of the Xiong'er volcanic rocks along the southern margin of the North China Craton: implications for the outgrowths of the paleo-mesoproterozoicsupercontinent Columbia (Nuna)." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2008. http://hub.hku.hk/bib/B4163424X.
Повний текст джерелаDavenport, Kathy. "Continental Tectonics from Dense Array Seismic Imaging: Intraplate Seismicity in Virginia and a Steep Cratonic Margin in Idaho." Diss., Virginia Tech, 2016. http://hdl.handle.net/10919/72976.
Повний текст джерелаPh. D.
Durham, Rachel Lauren. "POTENTIAL FIELD MODELING ACROSS THE NEODYMIUM LINE DEFINING THE PALEOPROTEROZOIC-MESOPROTEROZOIC BOUNDARY OF THE SOUTHEASTERN MARGIN OF LAURENTIA." UKnowledge, 2017. http://uknowledge.uky.edu/ees_etds/53.
Повний текст джерелаVanadia, David S. "Mapping the Outer Margin of the Serpent Mound Impact Structure to Assess the Outer Limit of Deformation: Adams, Highland, and Pike Counties, Ohio." Ohio University / OhioLINK, 2017. http://rave.ohiolink.edu/etdc/view?acc_num=ohiou1503092648273144.
Повний текст джерелаBrommer, Axel. "Strukturelle Entwicklung und Petrogenese des nördlichen Kristallingürtels der Shackleton Range, Antarktis: Proterozoische und Ross-orogene Krustendynamik am Rand des Ostantarktischen Kratons = Structural evolution and petrogenesis of the northern crystalline belt of the Shackleton Range, Antarctica: Proterozoic and Ross-orogenic crustal dynamics along the margin of the East Antarctic Craton /." Bremerhaven : Alfred-Wegener-Inst. für Polar- und Meeresforschung, 1998. http://www.gbv.de/dms/bs/toc/252821556.pdf.
Повний текст джерелаSpence, Joshua S. "1750-1710 Ma orogenesis along the eastern margin of the North Australian Craton." Thesis, 2021. https://researchonline.jcu.edu.au/75973/1/JCU_75973_Spence_2021_thesis.pdf.
Повний текст джерелаBailie, Russell Hope. "Mesoproterozoic volcanism, metallogenesis and tectonic evolution along the western margin of the Kaapvaal Craton." Thesis, 2010. http://hdl.handle.net/10210/3298.
Повний текст джерелаThe western margin of the Archean Kaapvaal Craton, at its contact with the polydeformed and metamorphosed Proterozoic Namaqua Province, is host to four volcanosedimentary successions of Mesoproterozoic age (1.1-1.3 Ga) that occur in close spatial and temporal association to each other. These are the Areachap Group, the Leerkrans Formation of the Wilgenhoutsdrif Group and the two volcanosedimentary successions that comprise the Koras Group. There has been protracted debate as to the exact nature, origin, age and tectonic evolution of these successions, particularly as they occur immediately adjacent to an important crustal suture. A comprehensive whole rock and isotope geochemical study, complemented by zircon-based geochronology where necessary, was thus carried out to characterize and compare the volcanic rocks associated with these four successions. The results are used to assess the role of the four volcanosedimentary successions during the development of the Mesoproterozoic suture between the Kaapvaal Craton and the Namaqua Province during the ~1.2-1.0 Ga Namaquan Orogeny. The geochemical study of the Areachap Group examined a suite of lithologies from different locations along the ~280km long outcrop belt, with the aim of testing the lateral continuity and integrity of this highly metamorphosed and deformed succession. As the bulk of the samples collected were from diamond drill core intersecting volcanogenic massive sulphide (VMS) Zn-Cu deposits it was only appropriate to extend the investigation to assess the metallogenesis and relation of these deposits to their host rock sequences. This included a survey of the sulphur isotope composition of sulphides and sulphates that comprise the Zn-Cu deposits. Furthermore, the architecture and origin of the world-class Copperton deposit, the largest Zn-Cu deposit of the Areachap Group, was examined. For this purpose, available literature data were collated and complemented by new geochemical and geochronological information. Sm-Nd isotopic systematics and U-Pb zircon ages suggest a coeval origin and close genetic link between the metavolcanic rocks of the Leerkrans Formation of the Wilgenhoutsdrif Group and the Areachap Group. Both successions record the establishment of an eastward-directed subduction zone on the western margin of the Kaapvaal Craton. The Areachap Group represents the highly metamorphosed and deformed remnants of a Mesoproterozoic (ca. 1.30-1.24 Ga) volcanic arc that was accreted onto the western margin of the Kaapvaal Craton at ~1.22-1.20 Ga, during the early stages of the Namaquan Orogeny. The igneous protoliths within the Areachap Group are low- to medium-K tholeiitic to calc-alkaline in composition ranging in composition from basaltic through to rhyolitic. Tholeiitic basalts, represented by volumetrically minor amphibolites within the succession have Sm-Nd isotopic characteristics indicative of derivation from a depleted mantle source as denoted by their positive Nd(t) values. The lithogeochemical results highlight the fact that, despite differences in lithological architecture on a local scale, the Areachap Group exhibits coherent geochemical characteristics along its entire strike length.
Anderson, Jade Rachel. "Metamorphic and isotopic characterisation of Proterozoic belts at the margins of the North and West Australian Cratons." Thesis, 2015. http://hdl.handle.net/2440/106136.
Повний текст джерелаThesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Physical Sciences, 2015.
Trenouth, C. W. "An insight into the lowtemperature thermal evolution of the covered eastern Gawler Craton margin: the Stuart Shelf basement." Thesis, 2015. http://hdl.handle.net/2440/118240.
Повний текст джерелаMulti-method thermochronology applied to the eastern Gawler Craton, beneath the Stuart Shelf cover (Olympic Dam Domain, South Australia), reveals multiple episodes of exhumation. Modelled data from Apatite Fission Track (AFT) analysis identifies four time periods where the eastern Gawler Craton basement experienced cooling into AFT closure temperatures (~60-120°C); at1050 ± 55 Ma (Mesoproterozoic), 439 ± 14 Ma (late Ordovician-Silurian), 304 ±36 Ma (mid-Carboniferous-mid Permian) and 245 ± 52 Ma (late Permian-early Jurassic). In addition, the Carboniferous and Jurassic peaks are supported by zircon (ZHe) and apatite (AHe) (U-Th-Sm)/ He results. The Ordovician peak is interpreted as resulting from the final pulses of the Delamerian Orogeny partially, mixed with the first pulses of the Alice Springs Orogeny. The Carboniferous-Permian event is linked with widespread exhumation likely due to the final pulses of the Alice Springs Orogeny (~300Ma). The preserved Mesoproterozoic event presents new AFT data in the area and coincides with some recent studies. However, it occurs only in samples obtained from the Gawler Range Volcanics and more prominent in core depth shallower than 500m. The late Permian-early Jurassic event is comparable to events believed have to stemmed from hydrothermal events. This event compliments AFT studies in the northern Flinders Ranges. The Late Ordovician-Silurian and Carboniferous-early Permian AFT pulses confirm events seen in studies of surrounding regions. Other geochronological studies around the Olympic Dam area indicate that this pulse either results from a localised hydrothermal event or distal effects of the Musgravian Orogeny. The Jurassic event suggests that the hydrothermal effect on AFT ages may be a more widespread event and not just localised to the northern Flinders Ranges as previously thought. The Ordovician event represents mixing between Delamerian and Alice Springs Orogenies. The Carboniferous-Permian event represents late distal effects of the Alice Springs Orogeny. These events match those of surrounding regions.
Thesis (B.Sc.(Hons)) -- University of Adelaide, School of Physical Sciences, 2015
Hogan, Eric Gordon. "Sedimentologic and Stratigraphic Analysis of Units Defining the Basal Sauk Supersequence Across the Craton Margin Hinge Zone, Southeastern California." 2011. http://trace.tennessee.edu/utk_gradthes/880.
Повний текст джерелаHilliard, Paul. "Structural evolution and tectonostratigraphy of the Kheis Orogen and its relationship to the south western margin of the Kaapvaal Craton." Thesis, 1999. http://hdl.handle.net/10413/10830.
Повний текст джерелаPriyatkina, Nadezhda. "The Proterozoic history of the northern and western Siberian cratonic margins based on results of U-Pb-Hf detrital zircon analysis." Thesis, 2017. http://hdl.handle.net/1959.13/1383756.
Повний текст джерелаAlong the western and northern margins of the Siberian Craton the Proterozoic sedimentary formations form pre-orogenic and post-orogenic sedimentary cycles, separated by a major unconformity. In various uplifts of Meso-to Neoproterozoic sedimentary rocks of Siberian cratonic margin, such as the Taimyr, the Yenisey Ridge and the Prisayan, detrital zircon signatures below the unconformity are compared with those of immature post-accretionary sedimentary rocks occurring above the unconformity. The data are further used to characterize the age of Early Precambrian basement and Neoproterozoic crust along the northern and western Siberian cratonic margins and to assist with identifying the tectonic setting of Neoproterozoic magmatic belts, their cratonic affinity and the overall geological evolution of these margins. It has been confirmed that Siberian cratonic basement is heterogenous in its age. Along the southwestern cratonic margin (Prisayan Uplift) the basins accumulated predominantly 3.4-2.7 Ga and 1.9-1.85 Ga detritus; along the western cratonic margin (Turukhansk Uplift, northern Yenisey Ridge), the basins accumulated predominantly 2.6–2.5 Ga and 1.9–1.85 Ga erosional products, while the main sources for the fill of intracratonic basin to the northeast near the Anabar Shield (East Anabar basin) were 2.9–2.7 Ga and 2.1–1.95 Ga old igneous rocks. The studied pre-orogenic rocks were mostly deposited during the Meso – to Early Neproterozoic rift-related or passive margin settings. Along with magmatic components of the Neoproterozoic crustal fringe, these rocks underwent major craton-wide recycling to produce late Ediacaran post-orogenic siliciclastic successions. Results of Hf in zircon study allow to identification of four distinct magmatic systems belt, associated with development of continental arcs at ca. 970-800 Ma and 720-600 Ma, and an oceanic arc at ca. 800-720 Ma in the Taimyr orogenic belt, and development of a long term continental arc during 950-600 Ma in the Yenisey Ridge and the north-western East Sayan. In addition to isotopic data, a geological evidence is discussed to support that Neoproterozoic crustal growth occurred near the northern and western Siberian margins and resulted in forming siginifcant portion of Arctic crust.