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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 24 for “"eclogites"”.
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Petrology and tectonic setting of relatively low temperature eclogites and related rocks in the Dalsfjord area, Sunnfjord, West Norway.
… the overlying unit by a zone of protomylonites. Eclogites are found in all the units. Gradational or intrusive relationships show that all the units are mutually autochthonous. Many eclogites had demonstrable low-pressure igneous protoliths and/or intrusive relationships with the gneisses, …
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Petrological and geochronological constraints on the metamorphic evolution of high-pressure granulites and eclogites of the Snowbird tectonic zone, Canada
… geochronology of high-pressure granulites and eclogites within the Snowbird tectonic zone of the western Canadian Shield. The focus of this study is the East Athabasca mylonite triangle (EAmt), a well-exposed terrane of granulite facies mylonitic rocks along the trace of the Snowbird tectonic …
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A detailed geochemical investigation of diamond-bearing eclogite xenoliths from the Kaalvallei kimberlite, South Africa
The eclogites are essentially bimeneralic assemblages of garnet and clinopyroxene. Thirteen xenoliths contain accessory diamond with graphite on diamond surfaces. One has accessory ilmenite. The rocks are well equilibrated and are classified as Group 1 eclogites, based on their mineral textures and …
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The geochemistry and origin of xenoliths from the Roberts Victor Mine
… samples were carried out. Orthopyroxene bearing eclogites (garnet websterites) constitute a significant portion of the eclogite suite, and orthopyroxene plays an important role in the evolution of the Roberts Victor eclogites. Three categories of inhomogeneous eclogites, …
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A detailed investigation into diamond-bearing xenoliths from Newlands Kimberlite, South Africa
… mid-Archrean (maximum TMA 3.52 Ga). Seventeen eclogites (2 to 6 cm in size) containing diamond are dominated by coarse-grained garnet and clinopyroxene, with primary trace phases including sulphides and rutile. Alteration is pervasive and ranges from minor grain boundary effects to massive …
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Cratonic eclogite xenoliths - formation and evolution of the subcontinental lithospheric mantle
… (cpx)), coesite-, kyaniteand corundum-bearing eclogites. Metasomatized eclogites (Type I) have a higher alkali- (Na2O in garnet and K2O in omphacite) and LREE, LILE-content. Non-metasomatized (Type II) eclogites include two main compositional groups, derived from different protoliths. The first …
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Applying Garnet and Zircon REE Linkages to Determine Timing of P-T Conditions and Tectonic Implications for UHP Eclogites and HP Granulites, Dulan UHP Terrane, China
… the timing of peak P-T conditions in UHP eclogites and HP granulites, and the tectonic significance of their spatial relationship within the Dulan UHP terrane are not well understood. This study, (1) evaluates rare earth element (REE) equilibrium between garnet and zircon, to assess coeval …
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Estimating the thickness of an ultrahigh-pressure (UHP) terrane: insights from phase equilibria modelling and Zr-in-rutile thermometry, Dulan area, North Qaidam terrane, China
… UHP terrane, in western China, exposes minor UHP eclogites hosted by ortho- and paragneisses. In the southeastern part of the terrane, the Dulan area exposes eclogite with the mineral assemblage Grt + Omp ± Ky ± Ph ± Zo ± Qz/Coe. LASS U-Pb analyses of zircons yield weighted mean ages of 463-425 …
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Geochemistry, Geothermobarometry and Geochronology of High-Pressure Granulites and Implications for the Exhumation History of Ultrahigh-Pressure Terranes: Dulan, Western China
… burial to ~50 km could either be overprinted eclogites or a separate high-pressure-high-temperature (HP-HT) granulite unit. Overprinted eclogites and HP-HT granulites imply different P-T-t paths for UHP rocks. Metamorphic conditions for the granulites are 750–880 °C and 14–17 kbar. Zircon U-Pb …
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Blueschists and associated rocks in the south Sepik region, Papua New Guinea; field relations, petrology, mineralogy, metamorphism and tectonic setting
… an acmitic variety, although omphacite occurs in eclogites. Paragonite is common in the epidote zone, often associated with phengite, while chlorite and albite are present at all grades, generally in small amounts. Calcite, dolomite and chloritoid occur in metasediments of the epidote zone. The …
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Temporal and petrological constraints of ultrahigh-pressure metamorphism and exhumation of crustal material from mantle depths to Earth's surface: Insights from a large and small ultrahigh-pressure terrane
… of: 1) peak UHP metamorphism recorded in the eclogites; 2) the subsequent eclogite retrograde metamorphism; and 3) the host-rock migmatization which likely occurs during exhumation from the mantle to the upper crust.This study investigates the Western Gneiss Region (WGR) of Norway, a giant UHP …
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Metamorphic P-T Path and Multiple Fluid Events During Burial and Exhumation of the Tso Morari UHP Terrane, NW Himalaya
… petrographic observations from the Tso Morari eclogites. Secondly, thermodynamic modelling using P-M(H2O) pseudosections on Tso Morari UHP rocks indicates three distinct fluid events during the prograde and retrograde metamorphism. Fluid Event 1 caused the fluid-assisted homogenization of …
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The geochemistry of a suite of eclogite xenoliths from the Rietfontein Kimberlite, South Africa
… at their characterisation and comparison to eclogites from on-craton and other off-craton localities. Garnet, clinopyroxene, accessory and secondary minerals were analysed for major element compositions using electron microprobe techniques and garnet and clinopyroxene trace element …
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THE INTERPLAY BETWEEN CATION ORDERING AND ELASTICITY OF OMPHACITES TO UNRAVEL PTT PATHS OF METAMORPHIC ROCKS
… is one of the main rock-forming minerals of eclogites and is also found in blueschist facies and ultra-high-pressure rocks. Its widespread occurrence makes it a valuable candidate for Raman elastic geothermobarometry, a method that uses the deformation recorded by mineral inclusions to …
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Surface textures on pyrope, picroilmenite and chrome diopside from Kimberlite
… least commonly found on orange varieties from eclogites.
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EVOLUTION OF THE EASTERN ALPS FROM THE PALEOZOIC ONWARD: CONSTRAINTS AND INSIGHTS FROM THE (ULTRA)BASIC ECLOGITIC COMPLEX OF MILCHENKAR ÖTZTAL-STUBAI COMPLEX (EASTERN ALPS, TYROL, AUSTRIA)
… amphibolites hosting variably retrogressed eclogites and subordinate occurrences of their gabbroic protoliths, often showing igneous cumulitic textures, with crystallization ages around 530 Ma (Miller & Thöni, 1995). In the Milchenkar area, petrological and geochemical analyses on preserved …
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Quantifying crystalline exhumation in the Himalaya
… to mantle depths. Today, these rocks crop out as eclogites, amphibolites and gneisses within the Higher Himalayan Crystalline between low-grade metamorphosed rocks (600-640°C/ ca. 5 kbar) of the Lesser Himalaya and Tethyan sediments. Beside tectonically driven exhumation mechanisms the channel …
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The heterogeneity and volatile content of Earth’s mantle, magmas and crust
… 3, I investigate the volatile content of Raspas eclogites (SW Ecuador), a proxy for deeply subducted oceanic crust, to evaluate volatile transfer from crustal generation at divergent plate boundaries (e.g., mid-ocean ridges) to recycling of ocean crust at subduction zones. In Chapter 4, I use the …
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A study of mantle inclusions in the Koffiefontein Kimberlite Pipe, South Africa
… are pyroxenites. Peridotites are rare and eclogites are very rare. The pyroxenites have been assigned to five categories. In general they show a clear metamorphic textural history with widespread evidence of exsolution, polygonisation and deformation. Some of these pyroxenites are …
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A study of mantle inclusions in the Koffiefontein Kimberlite pipe, South Africa
… are pyroxenites. Peridotites are rare and eclogites are very rare. The pyroxenites have been assigned to five categories. In general, they show a clear metamorphic textural history with widespread evidence of exsolution, polygonisation and deformation. Some of these pyroxenites are …
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