Thesis (Ph. D.)--University of Texas at Austin, 2000. / Vita. Includes bibliographical references (leaves 176-179). Available also in a digital version from Dissertation Abstracts.

The Aegean region contains numerous metamorphic core complexes that reflect post-collision extensional tectonics. The largest of these is the Menderes Massif of western Turkey, which covers an area of ~40,000 km². The Selimiye Shear Zone bounds its southern border and is a key location for studying the metamorphic history of the massif. Models of the tectonic evolution of the region requires an understanding of the peak pressure-temperature (P-T) conditions recorded by rocks in the massif, and the time (t) at which they achieved those conditions. However, limited P-T-t data exists in the Southern Menderes Massif. Here, P-T-t data was obtained from garnet-bearing rocks collected perpendicular to strike along seven transects spaced about 35 km across the Selimiye Shear Zone. Garnets in nine samples from four transects were analyzed using high-resolution back-scattered electron (BSE) imagery, X-ray element (Fe, Mg, Mn, Ca and Y) maps, and quantitative compositional analyses. Both zircon and monazite grains were dated in rock thin section using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Secondary Ion Mass Spectrometry (SIMS) to ascertain the timing of events recorded by the rocks. Some garnet X-ray element maps show zoning consistent with multiple stages of growth, diffusion, and retrogression. Distinct zones in each sample are visible on high contrast BSE images and can be related to Y, Fe, and Mn contents. The conventional garnet + biotite geothermometer and garnet + plagioclase + muscovite + biotite geobarometer were used to estimate peak metamorphic P-T conditions. These range from 556±10°C to 671±27°C, and 15.3±0.2 kbar to 22.4±0.5 kbar. The temperatures are similar to previous estimates, but the pressures appear about ~10 kbar higher the previous estimates. U-Pb zircon ages range from 2022±30 Ma (13.4% disc.) to 254±5 Ma (13.4% disc.). Based on Th/U contents, the oldest ages are likely related to inherited grains from magmatic sources. The youngest zircon age is the first reported Triassic grain from the Southern Menderes Massif and may relate to the closure event of the Paleo-Tethyan Ocean. A younger history is recorded by U-Pb and Th-Pb monazite ages, which range Cretaceous to Miocene. Monazite geochronology is hindered by the contamination of high amounts of common Pb, but U-Pb and Th-Pb age calculations show Miocene to Jurassic ages. The textures of monazite (i.e. drusy, filling cracks of garnet and in reaction with allanite) imply that ages could record crystallization and/or fluid dissolution/reprecipitation mediated events in the Oligocene. Data reported here support the observation that polymetamorphic events are recorded in the Southern Menderes Massif rocks in close proximity to the Selimiye Shear Zone. Two options are possible environments of continental exhumation of rocks along the zone: (1) a polymetamorphic history that records relict high-pressures from previous metamorphic events or (2) a single-stage exhumation of high-pressure rocks. / text

The Aegean region contains numerous metamorphic core complexes that reflect post-collision extensional tectonics. The largest of these is the Menderes Massif of western Turkey, which covers an area of ~40,000 km². The Selimiye Shear Zone bounds its southern border and is a key location for studying the metamorphic history of the massif. Models of the tectonic evolution of the region requires an understanding of the peak pressure-temperature (P-T) conditions recorded by rocks in the massif, and the time (t) at which they achieved those conditions. However, limited P-T-t data exists in the Southern Menderes Massif. Here, P-T-t data was obtained from garnet-bearing rocks collected perpendicular to strike along seven transects spaced about 35 km across the Selimiye Shear Zone. Garnets in nine samples from four transects were analyzed using high-resolution back-scattered electron (BSE) imagery, X-ray element (Fe, Mg, Mn, Ca and Y) maps, and quantitative compositional analyses. Both zircon and monazite grains were dated in rock thin section using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Secondary Ion Mass Spectrometry (SIMS) to ascertain the timing of events recorded by the rocks. Some garnet X-ray element maps show zoning consistent with multiple stages of growth, diffusion, and retrogression. Distinct zones in each sample are visible on high contrast BSE images and can be related to Y, Fe, and Mn contents. The conventional garnet + biotite geothermometer and garnet + plagioclase + muscovite + biotite geobarometer were used to estimate peak metamorphic P-T conditions. These range from 556±10°C to 671±27°C, and 15.3±0.2 kbar to 22.4±0.5 kbar. The temperatures are similar to previous estimates, but the pressures appear about ~10 kbar higher the previous estimates. U-Pb zircon ages range from 2022±30 Ma (13.4% disc.) to 254±5 Ma (13.4% disc.). Based on Th/U contents, the oldest ages are likely related to inherited grains from magmatic sources. The youngest zircon age is the first reported Triassic grain from the Southern Menderes Massif and may relate to the closure event of the Paleo-Tethyan Ocean. A younger history is recorded by U-Pb and Th-Pb monazite ages, which range Cretaceous to Miocene. Monazite geochronology is hindered by the contamination of high amounts of common Pb, but U-Pb and Th-Pb age calculations show Miocene to Jurassic ages. The textures of monazite (i.e. drusy, filling cracks of garnet and in reaction with allanite) imply that ages could record crystallization and/or fluid dissolution/reprecipitation mediated events in the Oligocene. Data reported here support the observation that polymetamorphic events are recorded in the Southern Menderes Massif rocks in close proximity to the Selimiye Shear Zone. Two options are possible environments of continental exhumation of rocks along the zone: (1) a polymetamorphic history that records relict high-pressures from previous metamorphic events or (2) a single-stage exhumation of high-pressure rocks. / text

The Aegean region contains numerous metamorphic core complexes that reflect post-collision extensional tectonics. The largest of these is the Menderes Massif of western Turkey, which covers an area of ~40,000 km². The Selimiye Shear Zone bounds its southern border and is a key location for studying the metamorphic history of the massif. Models of the tectonic evolution of the region requires an understanding of the peak pressure-temperature (P-T) conditions recorded by rocks in the massif, and the time (t) at which they achieved those conditions. However, limited P-T-t data exists in the Southern Menderes Massif. Here, P-T-t data was obtained from garnet-bearing rocks collected perpendicular to strike along seven transects spaced about 35 km across the Selimiye Shear Zone. Garnets in nine samples from four transects were analyzed using high-resolution back-scattered electron (BSE) imagery, X-ray element (Fe, Mg, Mn, Ca and Y) maps, and quantitative compositional analyses. Both zircon and monazite grains were dated in rock thin section using Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS) and Secondary Ion Mass Spectrometry (SIMS) to ascertain the timing of events recorded by the rocks. Some garnet X-ray element maps show zoning consistent with multiple stages of growth, diffusion, and retrogression. Distinct zones in each sample are visible on high contrast BSE images and can be related to Y, Fe, and Mn contents. The conventional garnet + biotite geothermometer and garnet + plagioclase + muscovite + biotite geobarometer were used to estimate peak metamorphic P-T conditions. These range from 556±10°C to 671±27°C, and 15.3±0.2 kbar to 22.4±0.5 kbar. The temperatures are similar to previous estimates, but the pressures appear about ~10 kbar higher the previous estimates. U-Pb zircon ages range from 2022±30 Ma (13.4% disc.) to 254±5 Ma (13.4% disc.). Based on Th/U contents, the oldest ages are likely related to inherited grains from magmatic sources. The youngest zircon age is the first reported Triassic grain from the Southern Menderes Massif and may relate to the closure event of the Paleo-Tethyan Ocean. A younger history is recorded by U-Pb and Th-Pb monazite ages, which range Cretaceous to Miocene. Monazite geochronology is hindered by the contamination of high amounts of common Pb, but U-Pb and Th-Pb age calculations show Miocene to Jurassic ages. The textures of monazite (i.e. drusy, filling cracks of garnet and in reaction with allanite) imply that ages could record crystallization and/or fluid dissolution/reprecipitation mediated events in the Oligocene. Data reported here support the observation that polymetamorphic events are recorded in the Southern Menderes Massif rocks in close proximity to the Selimiye Shear Zone. Two options are possible environments of continental exhumation of rocks along the zone: (1) a polymetamorphic history that records relict high-pressures from previous metamorphic events or (2) a single-stage exhumation of high-pressure rocks. / text

The Åreskutan nappe complex consists of the partly molten rock migmatite, which originates from the subduction formed by the collision of continents Baltica and Laurentia. It is a so-called hot nappe, which has been deeply buried in the subduction zone, based on findings of high-pressure minerals in the migmatitic gneiss. As the nappe returned to shallower depths the rock was partially molten during the subsequent exhumation as the lithostatic pressure decreased. Tectonic forces led to thrusting of the nappe towards the east and the building of mount Åreskutan. It is generally accepted that the shear zone between the migmatite of the Åreskutan Nappe and the underlying Lower Seve Nappe is a mylonitic shear zone, but the question of whether similar shear zones can be found at other sites in the migmatite complex has now been raised. In this project two major shear zones have been identified and shear direction has been determined after detailed geological mapping. Many small shear zones have also been identified, but their sense of shear direction was more difficult to determine. The two major shear zones identified have been labelled the Eastern Major Shear Zone and Western Major Shear Zone. In these shear zones the original migmatite appearing on Åreskutan is deformed and sheared with a top to the east sense of shear. The strongest evidence for determining the shear sense are garnets found mantled by micas in a sigma-type shear microstructures, found during microscope analysis. A grade of mylonitization can be seen in the mineral microstructures, with the most fine-grained matrix in the centre of the shear zones. It indicates that ductile deformation dominates, even though some minerals tend to break in a brittle manner.

A general algorithm for the computation of chemical equilibria in complex systems containing non-ideal solutions has been developed. The method is a G-minimization based on repeated linear and nonlinear programming steps. A computer program (THERIAK) based on this algorithm has been written and was used to solve a great variety of problems, ranging from a simple blast furnace calculation to liquid-liquid unmixing in a four component silicate melt. The computing times are in the magnitude of 1/2 to 2 seconds for each calculation. The method can also be used to test the consequences of thermodynamic models and data in systems of interest to many fields, including chemistry, geochemistry and metallurgy. Integrated powder diffraction intensities can be used to measure Mn-Mg and Fe-Mg site occupancies in olivines because of the difference in scattering factors between Mg and Mn or Fe. Theoretically calculated intensity ratios are subject to uncertainties from positional parameters (less than 3.5 % for peaks with a relative intensity greater than 25 %) and unknown charge distribution (up to 30 %). Several peak ratios are less subject to this last uncertainty and may be used to measure the site occupancies in olivines. 27 synthetic Fe-Mn-Mg olivines (800 °C, vacuum, with graphite) were investigated with Mossbauer spectroscopy and XRD intensity evaluation, producing occupancies accurate to approximately 0.03 per site. A thermodynamic speciation model represents the data very well. Preliminary Fe-Mn-Mg exchange experiments involving olivine and garnet place some limits on element distributions between these two minerals. / Science, Faculty of / Earth, Ocean and Atmospheric Sciences, Department of / Graduate

京都大学 / 0048 / 新制・課程博士 / 博士(人間・環境学) / 甲第21849号 / 人博第878号 / 新制||人||210(附属図書館) / 2018||人博||878(吉田南総合図書館) / 京都大学大学院人間・環境学研究科相関環境学専攻 / (主査)教授 田部 勢津久, 教授 内本 喜晴, 教授 加藤 立久, 教授 吉田 寿雄 / 学位規則第4条第1項該当 / Doctor of Human and Environmental Studies / Kyoto University / DGAM

High precision 147Sm-143Nd geochronology of garnet is performed in two localities to solve problems in tectonics. In Chapter 1, the age of the basal amphibolite unit of the Ballantrae Ophiolite complex in Scotland is dated at 477.6 ± 1.9 million years old. This age constrains the duration of Grampian orogenesis to 12.6 ± 3.1 million years and allows us to conclude that classic metamorphism by overthickening of continental crust cannot account for the very short-lived event in this region. In Chapter 2, we report ages from a Variscan relict (318 ± 130 Ma) to a range of Cenozoic ages from 35.5 ± 2.1 Ma to 9 ± 10 Ma in the Betic Cordillera of southern Spain. This alone indicates prolonged orogenesis in the region. These ages are linked directly to a microstructure known as a Foliation Intersection Axis (FIA). Results are inconclusive, but they generally indicate that there may be a relationship between broad scale plate motion and FIA orientations at a regional scale.

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