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Academic literature on the topic 'Craton margins'

Author: Grafiati
Published: 10 December 2022
Last updated: 29 January 2023

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Journal articles on the topic "Craton margins"

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Wang, Xu, Peimin Zhu, Timothy M. Kusky, Na Zhao, Xiaoyong Li, and Zhensheng Wang. "Dynamic cause of marginal lithospheric thinning and implications for craton destruction: a comparison of the North China, Superior, and Yilgarn cratons." Canadian Journal of Earth Sciences 53, no. 11 (November 2016): 1121–41. http://dx.doi.org/10.1139/cjes-2015-0110.

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We present a comparative tectonic analysis of the North China Craton (NCC), which has lost parts of its root, with the Yilgarn and Superior cratons, which preserve their roots. We compare the geophysical structure and tectonic histories of these cratons to search for reasons why some cratons lose their roots, while others retain them. Based on the comparison and analysis of geological, geophysical, and geochemical data, it is clear that the lithospheric thinning beneath craton margins is a common phenomenon, which may be caused by convergence between plates. However, craton destruction is not always accompanied by lithospheric thinning, except for cratons that suffered subduction and collision from multiple sides. The Western Block (also known as the Ordos Block) of the NCC, Yilgarn and Superior cratons have not experienced craton destruction; the common ground among them is that they are surrounded by weak zones (e.g., mobile belts or orogens) that sheltered the cratons from deformation, which contributes greatly to the long-term stability of the craton. Subduction polarity controlled the water released by the subducting plate, and if subducting plates dip underneath the craton, they release water that hydroweakens the overlying mantle, and makes it easy for delamination or sub-continental lithospheric mantle erosion to take place in the interior of the craton. Thus, subduction polarity during convergence events is an important element in determing whether a craton retains or loses its root.
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Dalziel, Ian W. D. "Antarctica and supercontinental evolution: clues and puzzles." Earth and Environmental Science Transactions of the Royal Society of Edinburgh 104, no. 1 (March 2013): 3–16. http://dx.doi.org/10.1017/s1755691012000096.

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ABSTRACTAntarctica has been known as the “keypiece” of the Gondwana supercontinent since publication of Du Toit's 1937 classic bookOur Wandering Continents. It is also important to reconstruction of the early Neoproterozoic supercontinent Rodinia. Laurentia, with its circumferential late Precambrian rifted margins, can be regarded as the ‘keypiece’ of Rodinia. TheSouthwest US–EastAntarctica (SWEAT) hypothesis suggested former juxtaposition of the Pacific margins of Laurentia and East Antarctica. Several new lines of evidence support this hypothesis in a revised form, but must be reconciled with opening of the Pacific Ocean basin predating amalgamation, not only of Gondwana, but even of today's East Antarctic craton. The sequence of events is envisaged to have been: (1) formation prior to 1·6 Ga of a craton, including Laurentia and the Mawson craton, that extended from South Australia along the present Transantarctic margin to the Shackleton Range; (2) suturing of southernmost Laurentia to the Kalahari craton along the Grenville, Namaqua–Natal–Maud orogenic belt ca. 1·0 Ga; (3) rifting of the East Antarctic margin (Mawson craton) from western Laurentia ca. 0·7 Ga; (4) pan-African suturing of the Mawson craton to southernmost Laurentia as Gondwana amalgamated, forming the ephemeral Pannotia supercontinent; and (5) end-Precambrian separation of Laurentia as Iapetus opened.
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Pearson, N. J., S. Y. O'Reilly, and W. L. Griffin. "The crust-mantle boundary beneath cratons and craton margins: a transect across the south-west margin of the Kaapvaal craton." Lithos 36, no. 3-4 (December 1995): 257–87. http://dx.doi.org/10.1016/0024-4937(95)00021-6.

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Hoffman, Paul F. "The Origin of Laurentia: Rae Craton as the Backstop for Proto-Laurentian Amalgamation by Slab Suction." Geoscience Canada 41, no. 3 (August 29, 2014): 313. http://dx.doi.org/10.12789/geocanj.2014.41.049.

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Proto-Laurentia (i.e. pre-Grenvillian Laurentia) is an aggregate of six or more formerly independent Archean cratons that amalgamated convulsively in geons 19 and 18 (Orosirian Period), along with non-uniformly distributed areas of juvenile Paleoproterozoic crust. Subduction polarities and collision ages have been provisionally inferred between the major cratons (and some minor ones), most recently between the Rae and Hearne cratons. The oldest Orosirian collisions bound the Rae craton: 1.97 Ga (Taltson-Thelon orogen) in the west, and 1.92 Ga (Snowbird orogen) in the southeast. All other Orosirian collision ages in proto-Laurentia are < 1.88 Ga. The Rae craton was the upper plate during (asynchronous) plate convergence at its western and, tentatively, southeastern margins. Subsequent plate convergence in the Wopmay and Trans-Hudson orogens was complex, with the Rae craton embedded in the lower plate prior to the first accretion events (Calderian, Reindeer and Foxe orogenies), but in the upper plate during major subsequent convergence and terminal collisions, giving rise to the Great Bear and Cumberland magmatic arcs, respectively. The ‘orthoversion’ theory of supercontinental succession postulates that supercontinents amalgamate over geoidal lows within a meridional girdle of mantle downwellings, orthogonal to the lingering superswell at the site of the former supercontinent. If the downwelling nodes develop through positive feedback from the descent of cold oceanic slabs, then viscous traction should contribute to drawing the cratons together over the downwelling node. Viewed in this way, the Rae craton was the first to settle over the downwelling node and became the backstop for the other cratons that were drawn towards it by subduction. It was, literally, the origin of Laurentia. Whether the Rae craton was also the origin of Nuna, the hypothetical cogenetic supercontinent, depends on ages and subduction polarities of Orosirian sutures beyond proto-Laurentia.SOMMAIRELa proto-Laurentie (c.-à-d. la Laurentie pré-grenvillienne) est un agrégat d’au moins six cratons archéens indépendants qui se sont amalgamés convulsivement durant les géons 19 et 18 (Orosirien), le long de zones de croûtes juvéniles paléoprotérozoïques réparties de manière hétérogène. Les polarités de subduction et les âges de collision entre les grands cratons (et d’autres moins grands) ont été provisoirement déduits, le plus récemment entre le craton de Rae et le craton de Hearne. Les plus anciennes collisions orosiriennes ont soudé le craton de Rae : 1,97 Ga (orogène de Taltson-Thelon) dans l’ouest, et 1,92 Ga (orogène de Snowbird) dans le sud-est. Tous les autres âges de collision en proto-Laurentie sont inférieurs à 1,88 Ga. Le craton de Rae constituait la plaque supérieure durant la convergence de plaque (asynchrone) à sa marge ouest, et peut-être aussi à ses marges sud-est. La convergence de plaque subséquente dans les orogènes de Wopmay et Trans-Hudson a été complexe, le craton de Rae étant encastré dans la plaque inférieure avant les premiers événements d’accrétion (orogènes caldérienne, de Reindeer et de Fox), puis dans la plaque supérieure durant la grande convergence subséquente et les collisions terminales, ce qui a créé les arcs magmatiques de Great Bear et de Cumberland respectivement. La théorie de « l’orthoversion » de la succession des supercontinents présuppose que les supercontinents s’amalgament au-dessus de creux géoïdaux en deça d’une gaine méridienne de convections mantéliques descendantes, à angle droit d’un super-renflement persistant au site d’un ancien supercontinent. Si le nœud de convection descendante s’établit par rétroaction positive de la descente de plaques océaniques froides, la traction visqueuse devrait contribuer à entraîner les cratons ensembles au-dessus du nœud de convection descendante. Vu de cette façon, le craton de Rae a été le premier à s’établir au-dessus du nœud de convection descendante, ce qui en a fait la butée des autres cratons entraînés par la subduction. Littéralement, telle a été l’origine de la Laurentie. Quant à savoir si c’est le craton de Rae qui a été à l’origine de Nuna, cet hypothétique surpercontinent cogénétique, cela dépend des âges et des polarités de subduction des sutures orosiriennes au-delà de la proto-Laurentie.
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Likhanov, Igor I. "Provenance, Age, and Tectonic Settings of Rock Complexes (Transangarian Yenisey Ridge, East Siberia): Geochemical and Geochronological Evidence." Geosciences 12, no. 11 (October 29, 2022): 402. http://dx.doi.org/10.3390/geosciences12110402.

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The tectonic evolution of the Siberian Cratonic margins offers important clues for global paleogeographic reconstructions, particularly with regard to the complex geological history of Central Asia and Precambrian supercontinents Columbia/Nuna and Rodinia and its subsequent breakup with the opening of the Paleo-Asian Ocean. Here, we present an overview of geochemical, petrological, and geochronological data from a suite of various rocks to clarify the age, tectonic settings, and nature of their protolith, with an emphasis on understanding the tectonic history of the Yenisey Ridge fold-and-thrust belt at the western margin of the Siberian Craton. These pre-Grenville, Grenville, and post-Grenville episodes of regional crustal evolution are correlated with the synchronous successions and similar style of rocks along the Arctic margin of Nuna-Columbia and Rodinia and support the possible spatial proximity of Siberia and North Atlantic cratons (Laurentia and Baltica) over a long period ~1.4-0.55 Ga.
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Ernst, Richard, and Wouter Bleeker. "Large igneous provinces (LIPs), giant dyke swarms, and mantle plumes: significance for breakup events within Canada and adjacent regions from 2.5 Ga to the PresentThis article is one of a selection of papers published in this Special Issue on the the theme Lithoprobe—parameters, processes, and the evolution of a continent.Lithoprobe Contribution 1482. Geological Survey of Canada Contribution 20100072." Canadian Journal of Earth Sciences 47, no. 5 (May 2010): 695–739. http://dx.doi.org/10.1139/e10-025.

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Large igneous provinces (LIPs) are high volume, short duration pulses of intraplate magmatism consisting mainly of flood basalts and their associated plumbing system, but also may include silicic components and carbonatites. Many LIPs have an associated radiating diabase dyke swarm, which typically converges on a cratonic margin, identifies a mantle plume centre, and is linked to breakup or attempted breakup to form that cratonic margin. We hypothesize that every major breakup margin in Canada can be associated with a LIP, and we attempt to identify this LIP. To this end, we focus mainly on high-precision age determinations and the distribution of diabase dyke swarms, which are uniquely valued for preserving the record of magmatic events. The analysis extends from the Phanerozoic to the Neoarchean, but our most complete information is for the Superior craton. There, events at 2.50–2.45, 2.22–2.17, and 2.12–2.08 Ga (LIP and plume) are linked with rifting and breakup or attempted breakup of the south-southeastern, northeastern, and southern margins, respectively. Events at 2.00–1.97 Ga are probably linked with the northern margin (Ungava promontory), while the Circum-Superior event at ca. 1.88 Ga is linked to the north to northwestern margins during a time of Manikewan Ocean closure. Similar linkages for other cratons of North America improve understanding of the breakup history to help identify which blocks were nearest neighbours to Canadian crustal blocks in Precambrian supercontinents. Such interpretations provide a framework for interpreting other geological features of these margins to further test models for the timing and location of breakup.
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Manighetti, Isabelle, André Michard, and Omar Saddiqi. "The West African Craton and its margins. Foreword." Comptes Rendus Geoscience 350, no. 6 (September 2018): 233–35. http://dx.doi.org/10.1016/j.crte.2018.07.001.

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Hoffman, Paul F., Samuel A. Bowring, Robert Buchwaldt, and Robert S. Hildebrand. "Birthdate for the Coronation paleocean: age of initial rifting in Wopmay orogen, CanadaThis article is one of a series of papers published in this Special Issue on the theme of Geochronology in honour of Tom Krogh." Canadian Journal of Earth Sciences 48, no. 2 (February 2011): 281–93. http://dx.doi.org/10.1139/e10-038.

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The 1.9 Ga Coronation “geosyncline” to the west of Slave craton was among the first Precambrian continental margins to be identified, but its duration as a passive margin has long been uncertain. We report a new U–Pb (isotope dilution – thermal ionization mass spectrometry (ID–TIMS)) 207Pb/206Pb date of 2014.32 ± 0.89 Ma for zircons from a felsic pyroclastic rock at the top of the Vaillant basalt, which underlies the passive margin sequence (Epworth Group) at the allochthonous continental slope. A sandstone tongue within the basalt yields Paleoproterozoic (mostly synvolcanic) and Mesoarchean detrital zircon dates, of which the latter are compatible with derivation from the Slave craton. In contrast, detrital zircon grains from the Zephyr arkose in the accreted Hottah terrane have Paleoproterozoic and Neoarchean dates. The latter cluster tightly at 2576 Ma, indistinguishable from igneous zircon dates reported here from the Badlands granite, which is faulted against the Vaillant basalt and underlying Drill arkose. We interpret these data to indicate that Badlands granite belongs to the hanging wall of the collisional geosuture between Hottah terrane and the Slave margin, represented by the Drill–Vaillant rift assemblage. If 2014.32 ± 0.89 Ma dates the rift-to-drift transition and 1882.50 ± 0.95 Ma (revised from 1882 ± 4 Ma) the arrival of the passive margin at the trench bordering the Hottah terrane, the duration of the Coronation passive margin was ∼132 million years, close to the mean age of extinct Phanerozoic passive margins of ∼134 million years (see Bradley 2008).
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Currie, Claire A., and Jolante van Wijk. "How craton margins are preserved: Insights from geodynamic models." Journal of Geodynamics 100 (October 2016): 144–58. http://dx.doi.org/10.1016/j.jog.2016.03.015.

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Gorczyk, W., D. R. Mole, and S. J. Barnes. "Plume-lithosphere interaction at craton margins throughout Earth history." Tectonophysics 746 (October 2018): 678–94. http://dx.doi.org/10.1016/j.tecto.2017.04.002.

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Dissertations / Theses on the topic "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.

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The Abrahamskraal kimberlite pipe (group I) occurs approximately 5 km to the south-west of the geophysically defined margin of the Kaapvaal craton in the central Cape Province, and contains a variety of crustal and mantle xenoliths. This study focusses on xenoliths of deep-seated origin (mantle and lower-crustal), and in particular on garnet-orthopyroxene bearing assemblages which are amenable to thermobarometric techniques. Four major types of deep-seated xenolith have been identified, i.e. peridotites, dunites , eclogites, and garnet pyroxenites. The petrographic features and mineral compositions of these xenoliths are described . Pressures and temperatures of equilibration have been calculated primarily using the garnet-orthopyroxene thermometer of Harley (1984), and the Al-in-enstatite barometer of Nickel and Green (1985). The peridotites are coarse-textured (Harte, 1977), magnesium -rich rocks, and are typical examples of the common type I peridotites which generally dominate mantle xenolith suites in kimberlites. Garnet peridotite xenoliths define a geotherm which lies along a typical theoretical conductive geothermal gradient for shield areas (Pollack and Chapman, 1977), and which extends to a maximum pressure of 41 kb (~130 km). Comparison of the Abrahamskraal geotherm with that constructed for the northern Lesotho xenolith suite (calculated using the same thermobarometer couple), suggests that the lithosphere at the Namaqua /Kaapvaal boundary is not significantly thinner or hotter than that underlying the craton. Modelling of the craton boundary under the constraints provided by the Abrahamskraal geotherm, and by the distribution of diamond-bearing kimberlites in southern Africa, indicates that the Abrahamskraal kimberlite has sampled relatively thick, cool , Namaqua lithosphere. It is suggested that, in terms of diamond distribution, the age and magmatic history of the Namaqua lithosphere is of greater significance than its thickness. Two varieties of dunite occur at Abrahamskraal. Coarse-textured dunites with Mg-rich olivine compositions similar to those of the peridotitic olivines, probably originated by similar (but perhaps more extreme) processes to those which formed the peridotites. A finer-grained and relatively Fe-rich variety of dunite may represent ultramafic cumulates formed by fractionation of basic or ultrabasic magmas within the mantle. Two varieties of eclogite have been distinguished. Coarse-grained eclogites which yield relatively high temperature estimates, are believed to have originated from depths similar to those determined for the garnet peridotites, i.e. from the lower lithosphere. A distinctly finer grained variety of eclogite, yields significantly lower temperatures which may be based on frozen-in equilibria. A maximum depth of approximately 87 km (~ 27 kb) has been estimated for these xenoliths, but they may have originated from significantly shallower (possibly lower-crustal) levels. The garnet pyroxenite xenoliths are generally orthopyroxene-rich rocks which contain varying amounts of garnet (8 to 33 %) and clinopyroxene (0 to 64 %). Textural features indicate that the garnet and possibly some of the clinopyroxene has exsolved from an originally A l -rich orthopyroxene. The rocks are significantly more Fe-rich than the peridotite xenoliths, and their constituent minerals show a wide range of Mg/Mg+Fe ratios. The pressure-temperature array defined by the garnet pyroxenites is approximately isothermal, and spans a depth range from approximately 30 to 95 km. It deviates strongly (to higher temperatures) from the ambient geothermal gradient at the time of kimberlite emplacement, as inferred from the garnet peridotite xenoliths. The pressures and temperatures calculated for the garnet pyroxenites are based on mineral equilibria which are believed to have been frozen-in during cooling from an intial high­temperature (probably molten) state. Qualitative modelling of possible cooling paths in pressure-temperature-composition space, indicates that the apparent depth range displayed by the garnet pyroxenites, approximates the true depth range over which these rocks were emplaced. However, the apparent pressures calculated from core compositions are significantly lower than the true pressures at which the original rocks formed . The garnet pyroxenite xenoliths appear to represent a major, possibly Namaqua ­ age (~1000-1400 Ma), magmatic event involving the emplacement of large amounts of mafic magma over a significant depth range in the shallow upper mantle
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Downey, 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.

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The Gull Rapids area, Manitoba, lies on the Superior craton margin and forms part of the Superior Boundary Zone (SBZ), a major collisional zone between the Archean Superior craton and the adjacent Paleoproterozoic Trans-Hudson Orogen. There are two main rock assemblages at Gull Rapids: orthogneisses (of possible Split Lake Block origin) and supracrustal rocks (metavolcanic and metasedimentary). Late, crosscutting felsic and mafic intrusive bodies (mostly dykes and sills) are used to constrain the relative and absolute timing of deformation and metamorphism.

The 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.
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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.

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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
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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/.

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As condições de pressão e temperatura existentes no evento tectônico que atuou na zona de fold-and-thrust da margem oeste do Cráton do São Francisco foram estimadas com base em estudos estruturais, microestruturais, petrográficos e de inclusões fluidas de veios sintectônicos. A presença de veios de diferentes gerações na zona de fold-and-thrust é evidenciada por fluidos atuando em diferentes cenários de paleoestresse ao longo da história deformacional da área. A área é composta por rochas do Grupo Bambuí fracamente deformadas que registram condições de metamorfismo que variam de diagênese a fácies subxisto verde. Dois eventos tectônicos foram identificados através da disposição geométrica dos veios e da superfície dobrada: (i) uma compressão principal NE-SW (D1) com \'sigma\'1 subhorizontal de orientação SW e \'sigma\'3 sub-vertical, relacionado à formação de veios sintectônicos sub-horizontais de orientação NW formados em condições que atingiram pelo menos 140- 160°C e pressões em torno de 200-363 MPa; (ii) uma compressão posterior NW-SE (D2) com \'sigma\'1 sub-horizontal de orientação NW e \'sigma\'3 também sub-horizontal de orientação NE. Estão relacionados à D2 a formação de veios sintectônicos sub-verticais paralelos à clivagem, formados nas mesmas condições mínimas de temperatura de 140-160°C e pressões entre 181- 295 MPa. A indicação de flutuações na pressão durante esses eventos desempenhou um papel crucial, pois os fluidos influenciam significativamente os processos mecânicos, os mecanismos de deformação e as reações químicas que operam em cinturões de fold-andthrust. Os fluidos apresentam composição formada por H2O-NaCl-CaCl2, onde o processo de mistura de diferentes fontes de fluidos (metamórficas e meteóricas) é evidenciado pela tendência evolutiva de temperaturas de homogeneização e salinidades, resultando em alguma variação na salinidade (12 contra 4% em peso equivalente de NaCl para os veios subhorizontais e para os paralelos à clivagem, respectivamente). Este trabalho confirma que a combinação entre a reconstrução do paleoestresse e o estudo de inclusões fluidas podem fornecer informações fundamentais sobre a relação entre o fluxo de fluidos e a tectônica de terrenos orogênicos, contribuindo para o conhecimento científico sobre a evolução deformacional/metamórfica do Grupo Bambuí e, consequentemente, da zona de fold-andthrust da margem ocidental do Cráton do São Francisco.
P-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.
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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.

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>Magister Scientiae - MSc
The 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
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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.

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Cette thèse s'inscrit dans le cadre du projet "Source to Sink Guyane" de TOTAL et BRGM. Son objectif était de poser les bases d'une étude Source to Sink du Craton Guyanais, en étudiant l'évolution géo-dynamique de sa marge passive depuis 200 Ma. Pour ce faire, nous avons interprété des données sismiques, construit des coupes crustales, des cartes paléo-géographiques et quantifié l'histoire de l'accumulation terrigène de la marge. La marge passive du bouclier des Guyanes est composée de deux bassins : Guiana/Suriname (GS) et Foz d'Amazonas (FOZ), issus d'un rifting diachrone jurassique, puis crétacé inférieur respectivement. L'étude des données de sub-surface nous a permis de montrer que la superposition des deux rifts a façonné le plateau de Demerara en un bloc continental aminci deux fois et entouré de croûte océanique sur trois côtés. Le rifting plus oblique du bassin de FOZ forme des segments systématiquement plus étroits et des dépôts syn-rift plus fins que dans le bassin de GS. L'évolution paléo-géographique de la marge et l'accumulation terrigène, sur huit intervalles de temps (à partir de 200 Ma), montrent une évolution différente des deux bassins. La distribution lithologique des systèmes sédimentaires s'homogénéise à partir du Campanien, lorsque les deux bassins atteignent le stade tardi-post-rift, durant lequel la distribution est principalement contrôlée par la dynamique fluviatile continentale. Les volumes terrigènes accumulés montrent cependant une évolution opposée au Crétacé dans les deux bassins, en lien avec la diminution et l'augmentation des aires drainées des fleuves majeurs de cette époque, de paléo-Berbice et de paléo-Tocantins respectivement. Les apports siliciclastiques vers la marge sont faibles de façon générale (entre 2 et 11 m/Ma), mais alternés par des périodes de forts apports correspondant à la recréation du relief sur le continent
This 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
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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.

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He, 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.

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Davenport, 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.

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Dense array seismic techniques can be applied to multiple types of seismic data to understand regional tectonic processes via analysis of crustal velocity structure, imaging reflection surfaces, and calculating high-resolution hypocenter locations. The two regions presented here include an intraplate seismogenic fault zone in Virginia and a steep cratonic margin in eastern Oregon and Idaho. The intraplate seismicity study in Virginia consisted of using 201 short-period vertical-component seismographs, which recorded events as low as magnitude -2 during a period of 12 days. Dense array analysis revealed almost no variation in the seismic velocity within the hypocentral zone, indicating that the aftershock zone is confined to a single crystalline-rock terrane. The 1-2 km wide cloud of hypocenters is characterized by a 29° strike and 53° dip consistent with the focal mechanism of the main shock. A 5° bend along strike and a shallower dip angle below 6 km points toward a more complex concave shaped fault zone. The seismic study in Idaho and Oregon was centered on the inversion of controlled-source wide-angle reflection and refraction seismic P- and S-wave traveltimes to determine a seismic velocity model of the crust beneath this part of the U.S. Cordillera. We imaged a narrow, steep velocity boundary within the crust that juxtaposes the Blue Mountains accreted terranes and the North American craton at the western Idaho shear zone. We found a 7 km offset in Moho depth, separating crust with different seismic velocities and Poisson's ratios. The crust beneath the Blue Mountains terranes is consistent with an intermediate lithology dominated by diorite. In the lower crust there is evidence of magmatic underplating which is consistent with the location of the feeder system of the Columbia River Basalts. The cratonic crust east of the WISZ is thicker and characterized by a felsic composition dominated by granite through most of the crust, with an intermediate composition layer in the lower crust. This sharp lithologic and rheologic boundary strongly influenced subsequent deformation and magmatic events in the region.
Ph. D.
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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.

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A zone of high magnetization along the SE margin of Paleoproterozoic Laurentia in the United States is indicated by magnetic anomaly data. The SE edge corresponds to the geochemical Neodymium mantle derivation model age (TDM) boundary and the entire anomaly overlies the Paleoproterozoic Mazatzal Province. Two-dimensional gravity and magnetic models across the Nd boundary are created with Moho constrained from receiver functions with gravity, sedimentary thickness and the base of the crustal magnetization. Upper crustal magnetization does not show strong variation across this boundary and much of the strong magnetization appears to lie in the middle crust. Using magnetic modeling of several potential geologic scenarios, we estimate magnetization, depth extent, and width of this zone of high magnetization. The anomaly has variable width (~ 300 km) with amplitude of approximately 200 nT. Pre-1.55Ga Paleoproterozoic mid crustal blocks have significantly higher average effective susceptibility (0.06 SI) than those of the post-1.55Ga Mesoproterozoic (0.01 SI). In two of the three profiles, the Paleoproterozoic zone of high magnetization has the highest average susceptibility indicating the Mazatzal province is innately highly magnetic. The zone may have formed either by magmatism associated with westward subduction or from highly magnetic terranes wedging between accreting island arcs.
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Books on the topic "Craton margins"

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Brommer, 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 nothern crystalline belt of the Shackleton Range, Antarctica : Proterozoic and Ross-orogenic crustal dynamics along the margin of the East Antarctic Craton. Bremerhaven: Alfred-Wegener-Institut für Polar- und Meeresforschung, 1998.

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Bott, M. H. P. Sedimentary Basins of Continental Margins and Cratons. Elsevier, 2013.

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Booth, Adam M., and Anita L. Grunder, eds. From Terranes to Terrains: Geologic Field Guides on the Construction and Destruction of the Pacific Northwest. Geological Society of America, 2021. http://dx.doi.org/10.1130/fld062.

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The eight field trips in this volume, associated with GSA Connects 2021 held in Portland, Oregon, USA, reflect the rich and varied geological legacy of the Pacific Northwest. The western margin of North America has had a complex subduction and transform history throughout the Phanerozoic, building a collage of terranes. The terrain has been modified by Cenozoic sedimentation, magmatism, and faulting related to Cascadia subduction, passage of the Yellowstone hot spot, and north and westward propagation of the Basin and Range province. The youngest flood basalt province on Earth also inundated the landscape, while the mighty Columbia watershed kept pace with arc construction and funneled epic ice-age floods from the craton to the coast. Additional erosive processes such as landslides continue to shape this dynamic geological wonderland.
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Book chapters on the topic "Craton margins"

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Heilbron, Monica, Umberto G. Cordani, and Fernando F. Alkmim. "The São Francisco Craton and Its Margins." In São Francisco Craton, Eastern Brazil, 3–13. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-01715-0_1.

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Adams, John, and Peter W. Basham. "Seismicity and Seismotectonics of Canada’s Eastern Margin and Craton." In Earthquakes at North-Atlantic Passive Margins: Neotectonics and Postglacial Rebound, 355–70. Dordrecht: Springer Netherlands, 1989. http://dx.doi.org/10.1007/978-94-009-2311-9_21.

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Müller, Daniel, and David I. Groves. "Direct Associations Between Potassic Igneous Rocks and Copper-Gold Deposits on Craton Margins." In Potassic Igneous Rocks and Associated Gold-Copper Mineralization, 191–201. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-23051-1_7.

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Müller, Daniel, and David I. Groves. "Direct Associations Between Potassic Igneous Rocks and Copper–Gold Deposits on Craton Margins." In Potassic Igneous Rocks and Associated Gold-Copper Mineralization, 255–77. Cham: Springer International Publishing, 2018. http://dx.doi.org/10.1007/978-3-319-92979-8_7.

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Gordon, Andres, Nivaldo Destro, and Monica Heilbron. "The Recôncavo-Tucano-Jatobá Rift and Associated Atlantic Continental Margin Basins." In São Francisco Craton, Eastern Brazil, 171–85. Cham: Springer International Publishing, 2016. http://dx.doi.org/10.1007/978-3-319-01715-0_9.

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Veevers, J. J. "Basins of the Australian Craton and Margin." In Dynamics of Plate Interiors, 73–80. Washington, D. C.: American Geophysical Union, 2013. http://dx.doi.org/10.1029/gd001p0073.

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Jiang, Yuhang, Yan Zhao, and Hecai Niu. "Paleoproterozoic Copper System in the Zhongtiaoshan Region, Southern Margin of the North China Craton: Ore Geology, Fluid Inclusion, and Isotopic Investigation." In Main Tectonic Events and Metallogeny of the North China Craton, 229–50. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-1064-4_9.

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Bartholomew, Mervin J. "Structural characteristics of the Late Proterozoic (post-Grenville) continental margin of the Laurentian craton." In Proceedings of the International Conferences on Basement Tectonics, 443–67. Dordrecht: Springer Netherlands, 1992. http://dx.doi.org/10.1007/978-94-011-1614-5_30.

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Zhao, Taiping, and Xiaoqin Deng. "Petrogenesis and Tectonic Significance of the Late Paleoproterozoic to Early Mesoproterozoic (~1.80–1.53 Ga) A-Type Granites in the Southern Margin of the North China Craton." In Main Tectonic Events and Metallogeny of the North China Craton, 423–34. Singapore: Springer Singapore, 2016. http://dx.doi.org/10.1007/978-981-10-1064-4_16.

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Suryanarayana Rao, K. V., C. Kumar, A. Kumar, V. Nandish, and R. T. Swamy. "Lamproites from the Eastern Margin of the Bhandara Craton, Orissa, India: An Exploration Case Study." In Proceedings of 10th International Kimberlite Conference, 129–41. New Delhi: Springer India, 2013. http://dx.doi.org/10.1007/978-81-322-1173-0_9.

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Conference papers on the topic "Craton margins"

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Attoh, K., and L. Brown. "Deep structure of the southeastern margin of the West African craton." In 10th SAGA Biennial Technical Meeting and Exhibition. European Association of Geoscientists & Engineers, 2007. http://dx.doi.org/10.3997/2214-4609-pdb.146.5.1.

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Ding, Jikai, Shihong Zhang, Shihong Zhang, David A. D. Evans, David A. D. Evans, Tianshui Yang, Tianshui Yang, et al. "NORTH CHINA CRATON: THE CONJUGATE MARGIN FOR NORTHWESTERN LAURENTIA IN RODINIA." In GSA 2020 Connects Online. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020am-359523.

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Cassola Molina, Eder, Naomi Ussami, and Yára Regina Marangoni. "Digital 5' x5' Gravity Maps of the Săo Francisco Craton, the Marginal Fold/Thrust Belts and Contiguous Continental Margin/Oceanic Basins." In 5th International Congress of the Brazilian Geophysical Society. European Association of Geoscientists & Engineers, 1997. http://dx.doi.org/10.3997/2214-4609-pdb.299.225.

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Takenaka, Lynthener B., William Griffin, Suzanne Yvette O'Reilly, Miguel Basei, Carlos Eduardo Ganade, and Dorrit E. Jacob. "Lithosphere Mapping in the South-Western Margin of the São Francisco Craton." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.2535.

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Karpenko, Ivan, and Oleksii Karpenko. "Preservation and Destruction of Accumulations in Petroleum Systems of Western Margin of East European Craton." In SPE Eastern Europe Subsurface Conference. SPE, 2021. http://dx.doi.org/10.2118/208542-ms.

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Abstract The offshore segments of the Pre-Dobrogea foredeep is absolutely unexplored, there is no a single well penetrated Paleozoic units within offshore areas. This study, a deep dive into petroleum system evolution of similar foredeep basin based on a 3D basin modeling was performed in order to get understanding of petroleum systems and geology of offshore segment of Pre-Dobrogea. Western edge of East European craton is about 1450 km takes from Western Black sea shore to Southern shore of Baltic sea. This area within Ukraine includes Pre-Dobrogea foredeep basin, Pre-Carpathian foredeep basin (Bylche-Volytsa foredeep), Lviv Paleozoic basin and extensive Paleozoic margin called Volyno-Podillia area (Figure 1). All mentioned basins have similar sedimentary history, similar dynamics of tectonic evolution, proven petroleum systems of almost the same age, discovered commercial and sub-commercial accumulations and are heavily underexplored and undervalued. 3D basin modeling as a primary exploration technique was applied to mentioned basins in order to identify common features in tectonic development, in sedimentation and evolution of petroleum systems. Identified basins’ similar features now could be extrapolated to underexplored formations and areas within the study area. Figure 1 Western margin of East European Craton with marked areas of study (edited after Mikołajczak, 2016)
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He, Yu, Yuan-Bao Wu, Yujie Zhao, and Guang-Yan Zhou. "Neoproterozoic Amphibolite-Facies Metamorphism of Douling Complex at the Northern Margin of the Yangtze Craton." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.1003.

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Tang, Qing, Shuhai Xiao, Ke Pang, Lei Chen, and Xunlai Yuan. "ROCKS FROM THE EAST: THE TONIAN SYSTEM ON EASTERN MARGIN OF THE NORTH CHINA CRATON." In GSA 2020 Connects Online. Geological Society of America, 2020. http://dx.doi.org/10.1130/abs/2020am-355201.

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Shatsky, Vladislav, Alexey Ragozin, Alla Logvinova, Richard Wirth, and Vadim Reutsky. "Evidence of Low Oxygen Fugacity in the Upper Mantle Domains beneath Northeastern Margin of Siberian Craton." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.2351.

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Renju, M. "Review of Magmatic Systems at Cratonic Margins, Case Study of Homa Hills, Kenya." In EAGE GET 2022. European Association of Geoscientists & Engineers, 2022. http://dx.doi.org/10.3997/2214-4609.202221100.

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Su, Haiyan, Yican Liu, and Yang Yang. "Petrogenesis and Element Mobility of Neoarchean Alkaline Granitic Gneisses in the Southeastern Margin of the North China Craton." In Goldschmidt2020. Geochemical Society, 2020. http://dx.doi.org/10.46427/gold2020.2477.

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Reports on the topic "Craton margins"

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Thomas, M. D. Magnetic and gravity characteristics of the Thelon and Taltson orogens, northern Canada: tectonic implications. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/329250.

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Differences of opinion concerning the relationship between the Thelon tectonic zone and the Taltson magmatic zone, as to whether they are individual tectonic elements or two independent elements, have generated various plate tectonic models explaining their creation. Magnetic and gravity signatures indicate that they are separate entities and that the Thelon tectonic zone and the Great Slave Lake shear zone form a single element. Adopting the single-element concept and available age dates, a temporally evolving plate tectonic model of Slave-Rae interaction is presented. At 2350 Ma, an Archean supercontinent rifted along the eastern and southern margins of the Slave Craton. Subsequent ocean closure, apparently diachronous, began with subduction at 2070 Ma in the northern Thelon tectonic zone, followed by subduction under the Great Slave Lake shear zone at 2051 Ma. Subduction related to closure of an ocean between the Buffalo Head terrane and the Rae Craton initiated under the Taltson magmatic zone at 1986 Ma, at which time subduction continued along the Thelon tectonic zone. At 1970 Ma, collision in the northern Thelon tectonic zone is evidenced in the Kilohigok Basin. From 1957 to 1920 Ma, plutonism was active in the Taltson magmatic zone, Great Slave Lake shear zone, and southern Thelon tectonic zone. The plutonism terminated in the northern Thelon tectonic zone at 1950 Ma, but it resumed at 1910 Ma and continued until 1880 Ma. The East Arm Basin witnessed igneous activity as early as 2046 Ma, though this took place more continuously from 1928 to 1861 Ma; some igneous rocks bear subduction-related trace element signatures. These signatures, and the presence of northwest-verging nappes, may signify collision with the Great Slave Lake shear zone as a result of southeastward subduction, completing closure between the Slave and Rae cratons.
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Hayward, N., and S. Paradis. Geophysical reassessment of the role of ancient lineaments on the development of the western margin of Laurentia and its sediment-hosted Zn-Pb deposits, Yukon and Northwest Territories. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/330038.

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The role of crustal lineaments in the development of the western margin of Laurentia, Selwyn basin and associated sediment-hosted Zn-Pb deposits (clastic-dominated, Mississippi-Valley-type) in Yukon and NWT, are reassessed through a new 3-D inversion strategy applied to new compilations of gravity and magnetic data. Regionally continuous, broadly NE-trending crustal lineaments including the Liard line, Fort Norman structure, and Leith Ridge fault, were interpreted as having had long-standing influence on craton, margin, and sedimentary basin development. However, multiple tectonic overprints including terrane accretion, thrust faulting, and plutonism obscure the region's history. The Liard line, related to a transfer fault that bounds the Macdonald Platform promontory, is refined from the integration of the new geophysical models with published geological data. The geophysical models support the continuity of the Fort Norman structure below the Selwyn basin, but the presence of Leith Ridge fault is not supported in this area. The ENE-trending Mackenzie River lineament, traced from the Misty Creek Embayment to Great Bear Lake, is interpreted to mark the southern edge of a cratonic promontory. The North American craton is bounded by a NW-trending lineament interpreted as a crustal manifestation of lithospheric thinning of the Laurentian margin, as echoed by a change in the depth of the lithosphere-asthenosphere boundary. The structure is straddled by Mississippi Valley-type Zn-Pb occurrences, following their palinspastic restoration, and also defines the eastern limit of mid-Late Cretaceous granitic intrusions. Another NW-trending lineament, interpreted to be associated with a shallowing of lower crustal rocks, is coincident with clastic-dominated Zn-Pb occurrences.
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Harris, L. B., P. Adiban, and E. Gloaguen. The role of enigmatic deep crustal and upper mantle structures on Au and magmatic Ni-Cu-PGE-Cr mineralization in the Superior Province. Natural Resources Canada/CMSS/Information Management, 2021. http://dx.doi.org/10.4095/328984.

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Aeromagnetic and ground gravity data for the Canadian Superior Province, filtered to extract long wavelength components and converted to pseudo-gravity, highlight deep, N-S trending regional-scale, rectilinear faults and margins to discrete, competent mafic or felsic granulite blocks (i.e. at high angles to most regional mapped structures and sub-province boundaries) with little to no surface expression that are spatially associated with lode ('orogenic') Au and Ni-Cu-PGE-Cr occurrences. Statistical and machine learning analysis of the Red Lake-Stormy Lake region in the W Superior Province confirms visual inspection for a greater correlation between Au deposits and these deep N-S structures than with mapped surface to upper crustal, generally E-W trending, faults and shear zones. Porphyry Au, Ni, Mo and U-Th showings are also located above these deep transverse faults. Several well defined concentric circular to elliptical structures identified in the Oxford Stull and Island Lake domains along the S boundary of the N Superior proto-craton, intersected by N- to NNW striking extensional fractures and/or faults that transect the W Superior Province, again with little to no direct surface or upper crustal expression, are spatially associated with magmatic Ni-Cu-PGE-Cr and related mineralization and Au occurrences. The McFaulds Lake greenstone belt, aka. 'Ring of Fire', constitutes only a small, crescent-shaped belt within one of these concentric features above which 2736-2733 Ma mafic-ultramafic intrusions bodies were intruded. The Big Trout Lake igneous complex that hosts Cr-Pt-Pd-Rh mineralization west of the Ring of Fire lies within a smaller concentrically ringed feature at depth and, near the Ontario-Manitoba border, the Lingman Lake Au deposit, numerous Au occurrences and minor Ni showings, are similarly located on concentric structures. Preliminary magnetotelluric (MT) interpretations suggest that these concentric structures appear to also have an expression in the subcontinental lithospheric mantle (SCLM) and that lithospheric mantle resistivity features trend N-S as well as E-W. With diameters between ca. 90 km to 185 km, elliptical structures are similar in size and internal geometry to coronae on Venus which geomorphological, radar, and gravity interpretations suggest formed above mantle upwellings. Emplacement of mafic-ultramafic bodies hosting Ni-Cr-PGE mineralization along these ringlike structures at their intersection with coeval deep transverse, ca. N-S faults (viz. phi structures), along with their location along the margin to the N Superior proto-craton, are consistent with secondary mantle upwellings portrayed in numerical models of a mantle plume beneath a craton with a deep lithospheric keel within a regional N-S compressional regime. Early, regional ca. N-S faults in the W Superior were reactivated as dilatational antithetic (secondary Riedel/R') sinistral shears during dextral transpression and as extensional fractures and/or normal faults during N-S shortening. The Kapuskasing structural zone or uplift likely represents Proterozoic reactivation of a similar deep transverse structure. Preservation of discrete faults in the deep crust beneath zones of distributed Neoarchean dextral transcurrent to transpressional shear zones in the present-day upper crust suggests a 'millefeuille' lithospheric strength profile, with competent SCLM, mid- to deep, and upper crustal layers. Mechanically strong deep crustal felsic and mafic granulite layers are attributed to dehydration and melt extraction. Intra-crustal decoupling along a ductile décollement in the W Superior led to the preservation of early-formed deep structures that acted as conduits for magma transport into the overlying crust and focussed hydrothermal fluid flow during regional deformation. Increase in the thickness of semi-brittle layers in the lower crust during regional metamorphism would result in an increase in fracturing and faulting in the lower crust, facilitating hydrothermal and carbonic fluid flow in pathways linking SCLM to the upper crust, a factor explaining the late timing for most orogenic Au. Results provide an important new dataset for regional prospectively mapping, especially with machine learning, and exploration targeting for Au and Ni-Cr-Cu-PGE mineralization. Results also furnish evidence for parautochthonous development of the S Superior Province during plume-related rifting and cannot be explained by conventional subduction and arc-accretion models.
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Percival, J. A., A. H. Bailes, and V. McNicoll. Mesoarchean western margin of the Superior Craton in the Lake Winnipeg area, Manitoba. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2001. http://dx.doi.org/10.4095/212096.

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Bleeker, W., and D. E. Ames. System scale and deposit scale controls on Ni-Cu-PGE mineralisation in cratonic areas and their margins. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 2017. http://dx.doi.org/10.4095/299588.

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Bostock, H. H., and W. D. Loveridge. Geochronology of the Taltson Magmatic Zone and its eastern cratonic margin, District of Mackenzie. Natural Resources Canada/ESS/Scientific and Technical Publishing Services, 1988. http://dx.doi.org/10.4095/126603.

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Thomas, M. D. Magnetic and gravity models, northern half of the Taltson Magmatic Zone, Rae Craton, Northwest Territories: insights into upper crustal structure. Natural Resources Canada/CMSS/Information Management, 2022. http://dx.doi.org/10.4095/328244.

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A prominent magnetic low along an eastern portion of the Paleoproterozoic Taltson magmatic zone (TMZ) correlates mainly with the youngest granitoid in the zone, the peraluminous ca. 1936 Ma Konth granite. Flanking belts of higher magnetic intensity coincide mainly with slightly older Taltson plutonic rocks (e.g. ca. 1986 Ma Deskenatlata granodiorite, ca. 1955 Ma Slave granite) to the west and Neoarchean and/or Paleoproterozic gneisses of the Rae Craton to the east. A prominent gravity low along a portion of the northeastern margin of the TMZ correlates mainly with the Konth granite. Modelling of east-west magnetic and gravity profiles crossing the TMZ is used to investigate the geometrical and geological significance of these signatures. Modelling of the gravity low revealed a basin-like shape, with a maximum thickness of 14.9 km, for a composite unit of Konth-Slave magmatic suites. Magnetic modelling, the preferred technique north and south of the gravity minimum, yielded basin-like shapes for an essentially nonmagnetic Konth-Slave unit, but with much smaller maximum thicknesses of 5.0 and 6.5 km, respectively. Farther south in the TMZ, strongly magnetic units within mapped Konth and Slave granites preclude definition of a nonmagnetic Konth-Slave unit. Aside from the Slave unit, most other modelled magnetic units are generally steep and narrow and have fairly large magnetic susceptibilities. They are modelled to a depth of 6.2 km below sea level and have a steeply dipping, near-surface structural fabric extending to significant depth. Granitoids in the TMZ have previously been designated as ilmenite series or magnetite series, but modelled susceptibilities indicate that revisions to some designations may be required.
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