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Showing 1 to 20 of 176 for “"plagioclase"”.
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The Elastic Behavior of Plagioclase Feldspar at High Pressure
… the structural behavior of various intermediate plagioclases at pressure has been undertaken with the intent of categorizing the elastic behavior with pressure across the solid solution series and establishing a conceptual model to characterize feldspar compression. Complex behavior has been …
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Water and fluorine contents in Mt. Hood magmas recorded by plagioclase phenocrysts
… study, concentration profiles of H2O and F in plagioclase from Mt. Hood, OR are paired with previously studied MI volatile contents from the same pyroclasts (Koleszar et al. 2012) to assess the fidelity of H2O and F records retained in volcanic plagioclase. The spatial resolution of secondary …
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Plagioclase preferred orientation in layered mylonites : evaluation of flow laws for the lower crust
We evaluate the applicability of plagioclase and gabbro flow laws by comparing predicted and observed deformation mechanisms in gabbroic shear zones. Gabbros and layered gabbro mylonites were collected from the Southwest Indian Ridge (SWIR), ODP Hole 735B. Deformation temperatures are constrained …
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Crustal contamination recorded by zoned plagioclase in primitive Karoo flood basalts, Luenha River, Mozambique
Jurakautinen (182 Ma) Karoon laakiobasalttiprovinssi on geokemialtaan erittäin heterogeeninen. Heterogeenisyyden on ajateltu olevan peräisin kahdesta toisistaan eriävästä vaippalähteestä. Mozambikin koillisosassa sijaitseva Luenha joen paljastuma sisältää primitiivistä pikriittejä, …
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Plagioclase preferred orientation in the layered mylonites : evaluation of flow laws for the lower crust
We evaluate the applicability of plagioclase and gabbro flow laws by comparing predicted and observed deformation mechanisms in gabbroic shear zones. Gabbros and layered gabbro mylonites were collected from the Southwest Indian Ridge (SWIR), ODP Hole 735B. Deformation temperatures are constrained …
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The Role of Cumulate Plagioclase Entrainment in the Steens Basalt, SE Oregon: Insights from the Magma Chamber Simulator
… large (up to 6 cm) and abundant (up to 40%) plagioclase crystals, it is classified as a Giant Plagioclase basalt (GPB). Understanding the origin of these giant plagioclase yields insight into magmatic processes like recharge, crustal assimilation, cumulate entrainment, and fractional …
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Giant Plagioclase in the Steens Basalt, SE Oregon: Cumulate Entrainment Revealed by Textural and In Situ Chemical Analysis
… (up to 5 cm) and abundant (up to 40 modal %) plagioclase crystals. This thesis presents a model for giant plagioclase formation in a complex system that integrates petrographic and <em>in situ</em> plagioclase compositional analyses with whole-rock data and computational modeling to explain …
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Formation conditions of plagioclase-bearing type I chondrules in CO chondrites : a study of natural samples and experimental analogs
… IA, IAB, and IB textures, also contain igneous plagioclase. While dynamic cooling experiments have put constraints on the formation conditions of chondrules based on olivine and pyroxene textures and morphologies, plagioclase has not been produced in previous experimental chondrule analogs. In …
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Documenting Magnatic Processes at Filicudi Island, Aeolian Arc, Italy: Integrating Quantitative Modeling and Plagioclase Textural and in situ Compositional Data
… Integration of MELTS modeling, whole rock, plagioclase textural and in situ elemental and isotopic data from Filicudi Island, Italy allow documentation of the roles and relative chronology that RAFC played in the magmatic evolution and elucidates aspects of the magma plumbing system …
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Raman Spectroscopy and Synchrotron X-ray Diffraction Study of Lunar and Terrestrial Plagioclase Feldspar at High-Pressure and High-Temperature Conditions
Plagioclase feldspar is one of the abundant minerals on the surface of the Earth, the Moon and Mars, and is also commonly found in meteorites. This dissertation seeks to better understand the phase changes in plagioclase when subjected to meteorite impact and fundamental information about impact …
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Documenting the Origin of Compositional Diversity of Subduction Zone Magmatism, Alicudi, Aeolian Arc (Southern Tyrrhenian Sea, Italy) Using in situ Plagioclase Data
… elements and strontium/neodymium isotopes, and plagioclase textural types, major and trace elements, and strontium isotopes; numerical modeling was also conducted. Integration of these data suggests that recharge, assimilation, storage at different levels below the volcano, and homogenization …
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Documenting Magma Evolution of the Fossa delle Felci (Salina Island, South Tyrrhenian Sea) by Integrating In Situ Plagioclase Data with Quantitative Modeling
… of petrographic, whole rock, and in situ plagioclase data with quantitative magma chamber models suggests differentiation dominated by fractional crystallization and magma recharge/mixing in reservoirs located at different crustal levels. At ~12 km depth, magma evolved through …
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Garnet-biotite thermometry, garnet-aluminum silicate-silica-plagioclase barometry, and Emp monazite geochronology of the early Proterozoic Ivanpah Mountains, eastern Mojave Desert, Se California
… Peak P-T conditions, using garnet-Al2SiO5-silica-plagioclase barometry and garnet-biotite thermometry, were ∼4.0kb and >700°C, respectively. Peak metamorphic-T's were recorded by the largest garnet studied; Electron Microprobe Analysis on monazite, using U-Th-Pb radioactive decay, suggest …
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Mineral-Scale Sr Isotopic Study of Plagioclase in the Mafic Dikes of the North American Wall and the Diorite of the Rockslides, Yosemite Valley, California.
… presence of a crustal component in the system. Plagioclase phenocrysts within each unit display bimodal compositional populations. Subhedral to euhedral partially resorbed calcic cores (mode = An84-88) are reminiscent of a mafic magma, while sodic rims (mode = An48-50) are the product of a more …
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Petrology of the Numabin Bay intrusions, Reindeer Lake, Saskatchewan
… Petrographic modal analyses and accurate plagioclase determinations by the Rittman Zone Method and X-ray diffraction revealed: (1) a general decrease in anorthite content of the plagioclase and in the amounts of plagioclase, hornblende,and biotite; (2) an increase in the percentage of K …
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The geochemistry, mineralogy and igneous petrology of some fracture zone basalts from the southern Mid-Atlantic Ridge
… into four distinct groups; an evolved sparsely plagioclase phyric suite (Group A), a less evolved sparsely plagioclase phyric suite (Group B), an olivine phyric suite (Group C) and a highly plagioclase phyric suite (Group D). The Group A basalts are characterised by their evolved nature (Mg# = …
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Petrology of the Roxboro metagranite, North Carolina
… granite, now metamorphosed. Phenocrysts of plagioclase, quartz, and perthite are accompanied by porphyroblasts of epidote. Relict igneous textural relationships suggest two possible fractional crystallization models, in which the order of crystallization was plagioclase, quartz, and then …
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Geochemistry and mineralogy of selected Atlantic Ocean basalts
… phenocrysts distinguishes the picritic basalts, plagioclase phyric basalts and plagioclase-pyroxene basalts from the olivine basalts. The NiO content of these phenocrysts in the former three basalt types is low, or a given Mg Mg+Fe²⁺ atomic ratio of the mineral, relative to the phenocrysts in the …
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Petrology of the Ashe Formation, Shortt's Knob area, Floyd County, Virginia
… are hornblende + clinozoisite and/or epidote + plagioclase + sphene ± quartz ± garnet. Amphibolites may be divided into four types on the basis of texture, sphene-content, and epidote-composition. Chlorite schists are ultrabasic rocks containing the assemblage Mg-chlorite + actinolite and/or …
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The interaction between chemical and mechanical processes during metamorphism: a microstructural and petrologic study of amphibolite shear zones, Cheyenne Belt, Southeastern Wyoming
… is marked by the rotation of amphibole and plagioclase aggregates into parallelism with the shear zone boundary and progressive grain size reduction. These observations indicate that strain magnitude increases across the shear zone. Detailed petrologic and microstructural analysis of a …
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