<p> Precambrian iron formations from N.W. Ontario and Melville Peninsula, District of Franklin, were analyzed for Li and major elements. The N.W. Ontario samples contain little Li (0.46 to 5.88 ppm) but high percentages of mafic silicates (20 to 50%). The Melville Peninsula samples show the opposite, having higher Li (1.65 to 58.2 ppm) and lower silicate material (0.6 to 25.0%).</p> <p> Results from acetic acid leaching experiments show that part of the Li in the Melville irons may be removed, indicating Li to be present both by absorption and substitution.</p> <p> The higher Li abundances in the Melville Peninsula rocks may be attributed to the effect of later intrusive granites.</p> / Thesis / Bachelor of Science (BSc)

1 v. / Title page, contents and abstract only. The complete thesis in print form is available from the University Library. / Thesis (Ph.D.)--University of Adelaide, Dept. of Geology and Geophysics, 1986

The Great Glen Fault (GGF) is a major northeast to southwest trending structure and has been interpreted as a terrane boundary separating the Precambrian Moine terrane to the northwest from the Precambrian Dalradian terrane to the southeast (e. g. Bluck & Dempster 1991). If the GGF is a terrane boundary no `Moine' rocks could be found southeast of the GGF and no `Dalradian' rocks could be found to the northwest of the GGF and each crustal block would have distinct tectonometamorphic, provenance and igneous intrusive characteristics. To assess this, carefully selected orthoamphibolite and metasediment samples were collected from both the Northern and Central Highlands, and were analysed by a combination of petrography, geochemistry and geochronology. Geochemical analysis suggests that a Neoproterozoic metagabbro and metadolerite suite was emplaced during crustal extension across the Northern and Central Highlands at approximately the same time, and that this suite represents an earlier intrusive event to that represented by amphibolites in the Dalradian Appin Group. Geochemistry also suggests that the Upper Morar Psammite Formation of the Moine Supergroup in the Northern Highlands is unlikely to correlate with the pebbly psammite formations in the Central Highlands and shows that the Upper Shiaba Psammite Formation metasediments on the Isle of Mull are geochemically distinct from the Upper Morar Psammite Formation metasediments on the mainland. The Glen Urquhart Complex in the Northern Highlands cannot be correlated with the Ord Ban Subgroup or Grantown Formation in the Central Highlands. However, despite these differences U-Pb detrital geochronology shows that the Upper Morar Psammite and Central Highland pebbly psammite formations are dominantly derived from similar Mesoproterozoic and Palaeoproterozoic sources, with a small amount of material of Archaean derivation. This, together with the matching amphibolite suites, means that the Great Glen Fault is very unlikely to be a terrane boundary.

No description available.

<p> An attempt has been made to estimate the abundance of trace and major constituents in the Precambrian surficial rocks in a large part (43,000 square miles) of the Red Lake - Lansdowne House area in northwestern Ontario. The area has an average composition which is close to that of granodiorite, more silicic than most estimates of crustal abundance, close to other estimates for continental shield areas, but possibly deficient in K2O relative to Poldervaart's (1955) estimate. The rocks of this area appear to be low in Be, Ti, V, Cu, Y, Sc and Zr, and high in Sr, relative to crustal abundances based on the proportion of exposed rocks on the surface of the continents (Turekian and Wedepohl, 1961). Analysis of variance techniques have detected significant regional variations of Cr, Mn, Sr and Ba. Significant variation exists between rock types for all trace elements analyzed except Cu.</p> / Thesis / Master of Science (MSc)

Thermobarometry, detailed petrography, electron microprobe analysis, and fluid inclusion microthermometry were used to quantify the history of a high grade Proterozoic terrane exposed within the northeastern Colorado Front Range. Pressure-temperature calculations identified two blocks from different crustal levels exposed adjacent to one another within the Poudre Canyon west of Fort Collins. They are the eastern, higher pressure, block (HPB; 734 degree C, 7.1 kbar) and the western, lower pressure, block (LPB; 655 degree C, 5.2 kbar). The blocks followed a clockwise uplift path and were juxtaposed by ductile shear near the end of the decompressive stage of uplift. Final assembly of the separate blocks to the same crustal level was constrained by mineralogic and textural considerations and by the isochores of identical low density carbon dioxide inclusions trapped by both blocks. Both blocks experienced peak metamorphism within the sillimanite-K-feldspar zone accompanied by partial melting, are characterized by stromatic migmatites, and show textural evidence for localized reactions related to decompression and cooling. Differences between the blocks include the type of melt-generating reactions and the pronounced late muscovite in the LPB. Gibbs' Method calculations indicate that local (outcrop scale) textural and mineralogical differences between HPB Mg-enriched pelites are caused by small differences in bulk composition and locally variable H2O content. The quartzo-feldspathic biotite gneisses in the LPB generated migmatites by wet melting, whereas the pelitic schists and gneisses in the HPB generated migmatites by dehydration melting of muscovite and biotite. Biotite dehydration melting enriched the leucosomes in HPB pelitic migmatites in K-feldspar and garnet. The minor presence of late muscovite in the HPB relative to the LPB was controlled by the different positions of their uplift paths relative to the muscovite breakdown reaction. / Ph. D.

The aim of this studv is to investigate interrelationships betweenbedrock relief and geological material. The area of investigation covers ca 350 km and is located in the Precambrian bedrock in the central part of Umeå commune, in northern Norrland. The boundary between two morphologically different types of landscape, the coastal plain (kustslätten) and the Norrland terrain (Norrlandsterrängen), crosses this area in a north-westerly direction.The study area's Precambrian bedrock has been mapped in detail by the author and the results are presented in a map at the scale of 1:50,000 together with a description. The occurring rock types have been studied with regard to their resistance against physical and chemical weathering. By relating recent research experience concerning Fennoscandia's palaeogeography, palaeoclimatology and isostasy, an appreciation is given of the character and strength of the forces of disintegration. Accordingly, it seems probable that chemical weathering was the dominant phenomenon during Silurian, Devonian, and even Carboniferous and Permian, whereas when the climate worsened significantly after the Tertiary period Fennoscandia's landscape was resculptured by glacial forces.During Tertiary and Quarternary times, Pennoscandia was twice uplifted and once loweredStatistical correlations between landscape relief, bedrock structure and rock variations, show that the highest sections of the landscape are dominated by resistant older granitoids, granitic mobilizate and veined gneisses, whereas the low-lying valleys and plains are characterized by the easily weathered biotite-plagioclase schists. Much suggests that the distinctive morphology of the coastal plain and Norrland terrain was initiated by bedrock structure and rock variations. As in some earlier works on Fennoscandia, this study attributes great importance to selective weathering in shaping the landscape. / digitalisering@umu

No description available.

No description available.

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior / O presente trabalho teve por objetivo a caracterização petrográfica e geoquímica das rochas graníticas formadas durante o evento Sunsás e de seu embasamento no SW do Craton Amazônico na Bolívia. As unidades estudadas compreendem, além dos granitóides da Orogenia Sunsás (1,30 Ga-950 Ma), o embasamento (> 1400 Ma) representado por gnaisses La Chiquitania, enderbitos e gnaisses Lomas Maneches e granitóides San Ignácio (1400-1300 Ma). A área de estudo encontra-se no extremo leste da Bolívia envolvendo os estados de Santa Cruz de La Sierra e Beni. A justificativa para este estudo é a ausência de trabalhos desde a década dos oitenta, quando foi mapeado o pré- Cambriano boliviano pelo Serviço Geológico da Bolívia com o Serviço Geológico Britânico. Para o embasamento, a unidade La Chiquitania apresenta rochas como ortognaisses de composição granítica além de litotipos granadíferos. A unidade Lomas Maneches apresenta enderbitos e rochas graníticas metaluminosas a debilmente peraluminosas. O ambiente tectônico no qual foi formada varia desde pré-colisional a tardi-orogênico com rochas preferencialmente graníticas e os ETR sugerem um processo de fracionamento magmático para a geração das rochas. Os granitóides San Ignácio incluem as intrusões graníticas San Andrés, El Refugio e San Ramón. Segundo a química, estas rochas variam de metaluminosa a debilmente peraluminosa. Os diagramas tectônicos indicam ambientes que variam de pré-colisionais a post-orogênicos e os padrões de ETR sugerem a existência de dois grupos provavelmente originados de fontes diferentes ou a partir de processos de fracionamento diferentes. Os granitóides Sunsas incluem as intrusões Talcoso, Cachuela, Naranjito, Taperas e Primavera. Os estudos petrográficos dos primeiros 3 granitóides permitem classificá-los como granitos, sendo que os últimos dois foram classificados como granodioritos. Os resultados geoquímicos dos ETR permitem sugerir que estes granitóides apresentam um comportamento metaluminoso, com afinidade pós-orogênica. Neste sentido, os granitos Naranjito, Primavera e Talcoso são produto de uma cristalização fracionada. O granito Cachuela é o representante mais primitivo e o granito Taperas tem posição intermédia no processo de fracionamento magmático. A partir dos resultados apresentados e com os dados da literatura pode-se sugerir que os gnaisses La Chiquitania e do Lomas Maneches foram resultado de um importante evento acrecionário na região (Orogênese Lomas Maneches). Ocorrido por volta de 1680-1660 Ma. Seguindo o tempo geológico foi registrado o evento San Ignácio, de idade entre 1,34 Ga e 1,33 Ga, cujo ambiente tectônico mais provável foi um arco magmático continental. Para o evento Sunsas, os corpos graníticos são classificados como granitos tipo I, resultando do estabelecimento de um arco magmático continental por volta de 1,07 Ga. Os elementos terras-raras permitem sugerir que estes granitóides foram gerados em um processo de fracionamento magmático, provavelmente de origem mantélica, durante o processo de subducção que terminou na colisão Greenviliana que, conforme a literatura, resultou na aglomeração do supercontinente Rodínia. Palavras-chave: Pré-cambriano; Bolívia / The main objectives of this work were the petrographic characterization and geochemistry studies of the Sunsas granitic intrusions and their country rocks in the Bolivian sector of the SW Amazonian craton. The studied units comprise the Sunsas Orogeny granitoids (1,30 Ga-950 Ma), the basement (>1400 Ma) including La Chiquitania gneiss, enderbitic and granitic gneiss of the Lomas Maneches unit and San Ignacio granitoids (1400-1300 Ma). The studied area is located in the west sector of Bolivia and involves the Santa Cruz de La Sierra and Beni states. The justificative for this study is the absence of investigation focusing the area since the 1980 decade, when the Bolivian Geological Survey with the Geological British Survey mapped the Bolivian pre-Cambrian. The Lomas Maneches unit comprises enderbitic and granitic gneiss from metaluminous to peraluminous composition. The tectonic setting indicated by the tectonic diagrams suggest late-orogenic to post-tectonic origin and the REE patterns suggest fractional crystallization processes for the rocks formation. The La Chiquitania unit presents two types of rocks (granitic gneiss and the garnet gneiss) here interpreted as similar to the Lomas Maneches rocks. The San Ignácio granitoids include San Andrés, El Refugio and San Ramon granites. According to the geochemistry results the rocks are characterized as metaluminous and peraluminous and the tectonic setting where the rocks were formed vary from pre-collision to post-orogenic and the REE patterns suggest the existence of two groups of rocks originated in different sources or as result of different processes of magma fractionation.The Sunsas granitoids here studied included the Talcoso, Cachuela, Naranjito, Taperas and Primavera intrusions. The petrography study allowed to classificate the first three granitoids as granites and the other two as granodiorite. The geochemical study of all the granites indicates metaluminous trend and according to the REE patterns, the Naranjito, Primavera and Talcoso granites are product of the fractional crystallization processes; the Cachuela granite represents the more primitive, and the Taperas granite with intermediate position in the magmatic fractional processes.The present study and previously works suggest that the La Chiquitania paragneiss were formed as result of erosion and sedimentation from sources dating at 1,76 Ga. At about 1680-1660 occurred an important accretionary event in this region (here defined as Lomas Maneches Orogeny). Following the geological time, the San Ignácio event was recorded by granitogenesis ca. 1,34 Ga and 1,33 Ga, whose tectonic environment probably is related to a continental magmatic arc. The Sunsas event granitoids may be classificated as I-type granites, resulted of the continental magmatic arc setting at 1,07 Ga. The REE patterns allow to suggest these granites were generate from a magmatic fractionating processes, with mantelic source during which subduction finished with the Grenvillian collision, according to the literature, responsible for the Rodinia supercontinent assembly.