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Showing 1 to 15 of 15 for “"Porphyroblast"”.
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Pyrite porphyroblast paragenesis at the Cherokee Mine, Ducktown, Tennessee
Pyrite porphyroblasts up to 300 mm in size are common in the polymetamorphosed, iron-rich, stratabound, massive sulfide ore at the Cherokee Mine, Ducktown, Tennessee. These porphyroblasts contain abundant inclusions of sphalerite, calcite, and micas that are used to determine the paragenesis of the …
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Relative Timing of Porphyroblast Growth and Peak Metamorphism in the Lower Granite Gorge, Grand Canyon, Arizona.
… and similar in morphology to, S2 indicating that porphyroblasts grew late or after S2 fabric development. Post-porphyroblast movements on S2 fabric involved rotation of porphyroblasts relative to matrix, shearing, and bending of S2 around porphyroblasts. Post-porphyroblast matrix coarsening …
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Microprobe dating of monazite in relation to porphyroblast growth and thermodynamic modelling P-T paths for rocks affected by prolonged orogenesis
… axes (FIAs) of inclusion trails in garnet porphyroblast. Compositional mapping and in-situ microprobe analyses of monazite grains reveal that monazite growth was the result a series of reactions or growth events. Numerous monazite grains preserve complex compositional zoning patterns that …
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Combining microstructural analysis with EPMA monazite geochronology to constrain progressive stages of orogenesis in the Appalachians
Microstructural relationships between porphyroblasts and the matrix have been frequently used to infer the relative timing of porphyroblast growth in deformed and metamorphosed terrains (Bell and Rubenach, 1983; Bell et al., 1986; Schulz, 1990; Barker, 1994; Williams, 1994). Although the …
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Strain path partitioning during forceful emplacement of the Papoose Flat pluton, Inyo Mountains, CA
… dominantly pure shear deformation produced the porphyroblast-matrix relationships within the aureole schists and, 4) pure shear plane strain (symmetrical boudinage) occurred locally within the aureole marbles. The direction of maximum extension within the boudinaged marbles is parallel to a …
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Reconciling the structural and metamorphic record of orogeny in central western New Hampshire through microstructure and garnet isopleth thermobarometry
… a previously defined relative timing scheme for porphyroblast growth that was based on Foliation Intersection Axes preserved within porphyroblast (FIA). Additionally, a tectonic model for central western New Hampshire is presented that explains several key geological features of the region that …
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Petrology of the Taconian-Acadian Overlap Zone, Hartland Belt, Western Connecticut
… and Rowe Formations indicate that garnet porphyroblast rims equilibrated with matrix minerals at P-T conditions that are consistent with an Acadian (Devonian) metamorphic field gradient for this area. P-T conditions were calculated by simultaneously solving for a geothermometer and a …
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The essence of FIA: a study of the distribution of foliation intersection axes data and its significance from hand sample to regional scales
… geometry of curved inclusion trails in garnet porphyroblasts. For the first time, the three-dimensional geometry of these features is shown as an animation, a stereo pair, a VRML model and two-dimensional sections. The spatial resolution of the data in this study, approximately 10 μm, is high …
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Pluton emplacement, aureole deformation and metamorphism, and regional deformation within the central White-Inyo Range, Eastern California
… as a single unit during emplacement. Detailed porphyroblast-matrix analysis within the concordant metasedimentary aureole rocks surrounding the Papoose Flat pluton indicates that inclusion trails within porphyroblasts can be used as strain markers to restore the aureole rocks to their prepluton …
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Using Metamorphic Textures to Infer Deformation and Thermodynamic Histories
Garnet porphyroblasts are commonly used to determine P-T conditions in metamorphic rock assemblages. However, the actual process of porphyroblast nucleation is still poorly understood and garnet growth may occur at different conditions than those predicted by equilibrium thermodynamics. It is …
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Proterozoic thermal and deformational history and geochemical evolution of the 1.4 Ga Priest pluton and its aureole
… inclusions inside contact metamorphic porphyroblasts. Included minerals are interpreted to be part of a regional metamorphic assemblage because similar minerals are found outside the aureole. P-T estimates outside the aureole suggest pre-pluton regional conditions near 525 degrees …
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Structural and metamorphic evolution of the Robertson River metamorphics with pressure-temperature-deformation-time (P-T-D-t) path
… relationships of inclusion trail geometries in porphyroblasts relative to matrix foliations is vital for unravelling complex deformation and metamorphic histories in highly tectonized terranes and the approach used to thin sectioning rocks is critically important for this. Two approaches have …
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Geology of the Ashe Formation between Fries and Galax, Virginia
… which strikes N 50° E and dips SE. Metamorphic porphyroblast growth of biotite, garnet, staurolite, and kyanite followed penetrative foliation development, with metamorphic grade increasing stratigraphically upward to form inverted isograds. Thrust faulting along the Fries Fault caused extensive …
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Multidisciplinary analysis of a polymetamorphic terrane, western New England
… maxima. Rim compositions of the highest-grade porphyroblasts in the Taconian zone generally yield P-T estimates that are inconsistent for subareas within a given thin section. With the onset of Acadian metamorphic overprinting conditions of approximately 500°C, the rim compositions of …
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Kinematic evolution, metamorphism, and exhumation of the Greater Himalayan Series, Sutlej River and Zanskar regions of NW India
… evolution of rocks from this zone. Classic porphyroblast--matrix relationships coupled with the above models provide a structural framework within which to interpret the microstructures and provide additional constraints on the relative timing of metamorphic and deformation events. A …