Dissertations / Theses on the topic 'Craton margins'

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

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.

Includes abstract.
Includes 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

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.

>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

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

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.

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.

Joshua Spence studied a 1.75 to 1.71 billion year tectonic event within the Mount Isa Inlier. He found that this event can be distinguished from a younger mountain building event, the Isan Orogeny, which aids regional mineral exploration models and understanding of the evolution of the North Australian Craton.

D.Phil.
The 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.

The tectonic evolution of the cratonic elements of Proterozoic Australia has been debated for over 20 years. There is a growing view that plate margin processes were involved in the tectonic evolution and growth of the pre-Cryogenian elements of Australia, however the timing, nature and configuration of cratonic amalgamation remains contentious. This study investigates the metamorphic, geochronological and isotopic evolution of key or debated areas of Proterozoic Australia, focusing on the proposed southern margin of the Archean to Paleoproterozoic North Australian Craton (NAC) in the Arunta Region, and eastern margin of the Archean to Paleoproterozoic West Australian Craton (WAC) in the Rudall Province. The overall aim of this study is to provide new constraints on Proterozoic tectonism in the Arunta Region and Rudall Province in order to better understand the timing and nature of Proterozoic Australia assembly. In the southern Aileron Province (Arunta Region), the Mount Hay area and Adla Domain occur close to the proposed Paleoproterozoic southern margin of the NAC. Pressure– temperature (P–T) constraints indicate the attainment of peak metamorphic conditions of ~8–10 kbar, ~850−900 °C for Mount Hay and the adjacent Capricorn Ridge, and ~7–10 kbar, ~850−900 °C for the Adla Domain fabrics. The granulite facies metamorphism postdates a period of extensive basin development in the Arunta Region between c. 1805−1780 Ma. This basin development was associated with magmatism and localised high temperature–low pressure (HTLP) metamorphism. Hf isotopic data on late Paleoproterozoic granitoids (c. 1650–1625 Ma) from the Aileron Province have isotopic compositions close to CHUR (ɛHf -6.2 to +1.5) and crustal model ages between 2200–2700 Ma. The granitoids are broadly contemporaneous with the c. 1640–1635 Ma Liebig Orogeny in the Warumpi Province, which involved coeval mafic magmatism, suggesting at least some component of extension. The Paleoproterozoic tectonic evolution of the Arunta Region (southern NAC) is considered to have involved a long-lived (>150 Ma) margin with an overall extensional character punctuated by comparatively localised and short lived periods of thickening. In the central Aileron Province, the tectonothermal evolution of the Anmatjira Range Province has been debated considerably over the last 20 years. The timing and metamorphic evolution of the Anmatjira Range was investigated using monazite U–Pb geochronology and P–T pseudosections calculated for high temperature granulite facies metapelites in the southeastern Anmatjira Range. Estimated peak conditions of ~870–920 °C and ~6.5–7.2 kbar were attained at c. 1580–1555 Ma, followed by a clockwise retrograde evolution. In the absence of concurrent magmatism, and lack of evidence of decompression from high-P conditions, the most probable driver for this metamorphism is heating largely driven by high-heat production from older granites (c. 1820–1760 Ma) in the region. To the west, the Rudall Province (eastern WAC) is one of the few localities of Proterozoic, Barrovian-style metamorphism in Australia. In several previous studies, the Rudall Province has been considered to record the collision of the WAC and NAC during the Yapungku Orogeny at c. 1780 Ma. However, prior to this study, medium-P assemblages interpreted to have grown during the Yapunkgu Orogeny (inferred thermal gradients of minimum ~60–80 °C/kbar) had not been directly age-constrained. Monazite age data on metasedimentary rocks from both medium-P and high temperature–low pressure (HTLP) assemblages, and zircon U–Pb age data from a medium-P, garnet-diopside bearing mafic amphibolite yield age populations between c. 1380 and 1275 Ma, with one monazite age population of c. 1665 Ma. No evidence for older c. 1780 Ma metamorphism was found in this study. The large age population range of c. 1380– 1275 Ma yielded in this study may be a response of a stage-wise tectonic evolution, involving the accretion of ribbons. If the Yapunkgu Orogeny does reflect the collision between the WAC and NAC, it most likely did not occur until the Mesoproterozoic, contemporaneous with initial breakup stages of supercontinent Nuna. The overall results of this work support a long-lived, retreating margin on the southern NAC during the late Paleoproterozoic, prior to the assembly of cratonic Australia in the Mesoproterozoic. The proposed Mesoproterozoic assembly negates the need for Australian cratons to be in close proximity in supercontinent Nuna reconstructions.
Thesis (Ph.D.) (Research by Publication) -- University of Adelaide, School of Physical Sciences, 2015.

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Multi-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

In the Death Valley and Mojave Desert regions of southeastern California, the contact separating the lower and middle members of the Wood Canyon Formation (WCF) is currently interpreted as a regional scale unconformity coincident with the base of the Sauk Sequence. Regional mapping of this surface, however, reveals a nonconformable contact with underlying crystalline basement in cratonic settings, and a relatively conformable contact atop a northwest thickening wedge of miogeoclinal strata that is capped by the lower member of the WCF. Consistent with an unconformity, the progressive loss of three carbonate units within the lower member of the WCF has been attributed to incision by the base of the middle member WCF. However, fossil evidence and correlation based on carbon isotope compositions of each lower member WCF dolostone units rejects top-down erosion to describe their loss and overall cratonward thinning. Results from multiple detailed, measured, stratigraphic sections of a conglomerate found at the base or low in the middle member WCF also do not support a top-down erosion model because the conglomerate has variable stratigraphic position and absence in some locations. Middle member WCF conglomerate clasts also reveal variation in composition and grain size across the regions. Sequence stratigraphic architecture indicates that filling of available accommodation space and short period normal regression, as opposed to a forced regression, are the causal mechanisms for formation of the basal middle member WCF unconformity, and that the base of the Sauk Sequence rests lower in the stratigraphic section.

Research Doctorate - Doctor of Philosophy (PhD)
Along 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.