Global ETD Search
Search theses and dissertations gathered from participating repositories worldwide. Every result links back to the library that holds it. No account is needed.
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Showing 1 to 20 of 30 for “"Archaean"”.
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Geochemical characterisation of Archaean granitoids in eastern Finland
The oldest rocks in Finland are the Archaean grey gneisses of eastern and northern Finland. The Archaean of the Karelian craton spans about 1000 Ma of crustal growth and evolution and forms the core of the Fennoscandian shield. The Karelian province is a complex patchwork of different rock types. …
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The evolution of the Archaean continental crust of Northern Zimbabwe
Granitoid clasts preserved in Late Archaean conglomerates indicate the presence of continental crust in Northern Zimbabwe prior to the"" 2.7 to "" 2.6Ga "event" which terminated with the stabilisation of the Zimbabwe Craton. The "Kober Technique" (Kober, 1986, 1987) of direct thermal ionisation of …
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Petrology and geochemistry of the granitoids of the Halfway House Dome
… and geotectonic processes active during Archaean times has led to re-evaluations of important Archaean terrains world-wide in the light of growing support for the notion that plate tectonic processes were active in the Archaean. Archaean cratons are considered to consist typically of …
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A comparative study of the geohydrology of archaean formations and associated rocks in the North-Western Transvaal and the North-Western Cape Province
… and hydrology. In the Transvaal the Archaean Formations range from the Swaziland System to the Dominion Reef System, with younger intrusives and a cover of Tertiary to Recent ferricrete, calcrete and soil. In the Cape Province the comparable formations are the Kheis System to the …
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Geodynamic evolution and petrogenesis of the neoarchaean Francistown granite-greenstone complex in NE Botswana, SW margin of the Zimbabwe craton
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 …
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Geochemistry of the Sabie River Basalt Formation in the central Lebombo, Karoo Igneous Province
… association of LFE-type basalts with Archaean crust (or Archaean crust re-worked in low temperature - high pressure events) and N-type basalts with post-Archaean crust (or Archaean crust re-worked in high temperature - low pressure events). This model suggests the derivation of the LFE …
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An investigation of a polymetamorphic terrain using <sup>40</sup>Ar-<sup>39</sup>Ar geochronology
… of metamorphism: M1- granulite facies in the Archaean, M2 - amphibolite facies in the Early Proterozoic, and M3 - greenschist to epidote-amphibolite facies in the Mid-Proterozoic. Because of the relatively low blocking temperature of the 40Ar- 39Ar geochronological system in mica (c.300-350 …
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Structural geology and stratigraphy at the junction of the curral anticline and the moeda syncline, Quadrilatero Ferrifero, Minas Gerais, Brazil
… are divided into two large subdivisions: the Archaean Nova Lima greenstone and the Bonfim granitoid gneisses, and the overlying Proterozoic Minas metasedimentary and metavolcanic rocks, including abundant iron formation. These groups are separated by a major unconformity. These new studies in …
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Tektonometamorphe Entwicklung von Scherzonen im präkambrischen Basement Südindiens
… predominantly dip-slip transport separating the Archaean Dharwar Craton in the north from the late Archaean Nilgiri Block in the south. The NE-SW-trending, dextral-transpressive Bhavani Shear Zone (BSZ) constitutes the southern boundary of the Nilgiri Block in its western part and bounds the …
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U-Th-Pb fractionation in selected carbonate and silicate systems
… xenoliths appear to have been fonned in the Archaean and to have had their Nd isotopes reset in the Proterozoic. Most Pb isotope ratios from the granulites xenoliths are unradiogenic relative to the Geochron, which indicates relatively low V /Pb ratios in the later parts of their histories. …
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The structural setting of the Canaã dos Carajás region and Sossego-Sequeirinho deposits, Carajás – Brazil
… Sossego and Sequeirinho deposits, located in the Archaean granite-gneiss basement of the Canaã dos Carajás region, the boundary between the Carajás and Rio Maria Granite Greenstone Terranes. The study focuses on the understanding of the processes, controls and styles of two regionally …
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The tectonic evolution of the Southern Granulite Terrane of India and its role in the amalgamation of Gondwana.
… in the northern part of Madurai Block yielded Neoarchaean and Cryogenian (ca.2.7 - 2.5 Ga and 795 ± 17 Ma) crystallization ages with metamorphic overprinting at ca. 535 Ma. Their Nd and Sr isotopic ratios (εNd₍τ₎ = -16.9 and +4.55, ⁸⁷Sr/⁸⁶Sr = 0.7017 - 0.7567) suggest they were generated by …
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Exploring the distribution and physiological roles of bacterial membrane lipids in the marine environment
… in the geologic record extending back to the Archaean. Since the phylogenetic diversity of life is reflected in the structural diversity of biomolecules, lipid biomarkers that are shown to be diagnostic of certain organisms that carry out specific biochemical processes or that are demonstrated …
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Exploring the distribution and physiological roles of bacterial membrane lipids in the marine environment
… in the geologic record extending back to the Archaean. Since the phylogenetic diversity of life is reflected in the structural diversity of biomolecules, lipid biomarkers that are shown to be diagnostic of certain organisms that carry out specific biochemical processes or that are demonstrated …
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Evolution of continental crust in the Proterozoic : growth and reworking in orogenic systems
… between a 2.1–1.9 Ga juvenile component and Archaean crust. Between 1.7 and 1.4 Ga the continental crust of the Eastern Segment was reworked with little or no generation of new crust. Further to the west, in the Idefjorden terrane of the Sveconorwegian Province, 1.65 to 1.33 Ga rocks have …
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Application of HPGR and X-Ray CT to investigate the potential of Witwatersrand gold ore for heap leaching : a process mineralogy approach
Auriferous conglomerates of the Archaean Witwatersrand Basin in South Africa host one of the largest known gold resources and rate as the world’s most outstanding example of a fossil megaplacer deposit. For the past 40 years, Witwatersrand gold production in South Africa has been progressively …
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A metamorphic and geochemical study of mafic rocks across the Pencksökket-Jutulstraumen Discontinuity, western Dronning Maud Land, East Antarctica
… metabasic rocks on the easern margin of the Archaean Grunehogna Craton and the adjacent Maud Belt in western Dronning Maud Land, East Antarctica, revealed a difference in peak metamorphic conditions from T = ~275° to 730°C and P=2 to 10.7 kbar over a distance of only 30 km across a major …
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