k feldspar microstructures

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(PDF) Microstructural observation of quartz and K-feldspar ...

Reference: Menegon, L., Pennacchioni G., Spiess R., 2008. Dissolution-precipitation creep of K-feldspar in mid-crustal granite mylonites. Journal of Structural Geology 30(5): 565-579 Keywords: Microstructures, Quartz, K-feldspar, Quartz micro boudins 1/1

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Where is the Hydrogen? | Request PDF

Article. Where is the Hydrogen? June 2021; Elements 17(3):163-168

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Microstructures in Two Alkali Feldspar Megacrysts from the ...

The microstructures of alkali feldspars crystalli-sed at lower temperatures are relatively less known. TEM observations of twinning and exsolution texture in a hydrothermal and two pegmatitic microclines (TIBBALS & OLSEN, 1977) extended the study of K-feldspar microtextures below the temperature of the monoclinic–triclinic transformation.

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(Energy related studies utilizing microline ...

Jan 01, 1991· Progress report, 1990--1991. Technical Report. In our first year of the current funding cycle, we have investigated three interrelated aspects of K-feldspar thermochronology; (1) the Ar diffusion properties and microstructures of K-feldspars, (2) the thermal evolution of the Valles Caldera and (3) the continued development of microanalysis.

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USING MICRO CT IMAGING TO UNDERSTAND K-FELDSPAR …

In this study, detailed analyses of zoning and intracrystalline microstructures in K-feldspar megacrysts are employed. K-feldspar megacrysts are common in felsic plutons (Pitcher, 1997) and can form chemical zones that record physiochemical changes in the system during crystallization (Müller et al., 2005).

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Quartz and Feldspar Microstructures in Metamorphic Rocks

Quartz and Feldspar Microstructures in Metamorphic Rocks. Vernon, R.H. School of Earth Sciences, Macquarie University, Sydney NSW 2109, Australia ... Simple twinning in K-feldspar appears to be indicative of a magmatic orgin, and evidence of magmatic flow is provided by aligned feldspar crystals. Though deformation and recrystallization tend to ...

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Quartz microstructures and deformation conditions in the ...

Microstructures in the Hatagawa shear zone as observed under the optical microscope. (a) Quartz microstructure A. (b) Quartz microstructure B. (c) K‐feldspar porphyroclast (K ) in the samples with quartz microstructure B. Evidence for the replacement of K‐feldspar porphyroclast by myrmekite (my ) is visible.

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Igneous microstructures in migmatites - NASA/ADS

Clear differences between the microstructures of leucosomes and mesosomes occur in some nebulitic migmatites in the Proterozoic Arunta block, central Australia. The leucosomes show crystal faces of K-feldspar (microcline-microperthite), cordierite, andalusite, and plagio clase against quartz, indicating crystallization of a melt. In contrast, the mesosomes show …

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(PDF) Shock melting of K-feldspar and interlacing with ...

Plagioclase (An10–20) was cataclastically deformed and comminuted, whereas K-feldspar and mesoperthite are devoid of cataclastic microstructures. K-feldspar …

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Igneous origin of K-feldspar megacrysts in deformed ...

Many points of evidence, especially igneous microstructures and structures resulting from solid-state deformation, indicate that K-feldspar megacrysts in deformed granites of the Papoose Flat pluton are residual phenocrysts, not porphyroblasts. Evidence of an igneous origin includes features such as crystal shapes, simple twinning, zonally arranged euhedral plagioclase …

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Shock melting of K-feldspar and interlacing with ...

Folded sheets of Mesoarchaean, leucocratic plagioclase-K-feldspar-mesoperthite-bearing granitic rocks in the Toqqusap Nunaa area of the Maniitsoq structure, West Greenland, are characterised by their very fine grain sizes and microstructures without normal igneous or planar/linear tectonic fabrics. Quartz forms equidimensional and branching, ductilely deformed …

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(PDF) Microstructural observation of quartz and K-feldspar ...

Apr 29, 2014· Exsolution microstructures indicate a ductility enhancement of K-feldspar due to the cryptoperthite formation (coherent spinodal decomposition) on the retrograde cooling path (Athurupana et al ...

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The effects of deformation-induced microstructures on ...

Automated mapping of K-feldspar by electron backscatter diffraction (EBSD) and application to 40Ar/39Ar dating McLaren, S. ; Reddy, Steven ( 2008 ) The ability to quantify feldspar microstructure using the electron backscatter diffraction (EBSD) method has direct application in the study of rock deformation and strain kinematics.

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Na-K interdiffusion and coherent exsolution in alkali feldspar

Sanidine is a widespread liquidus phase in K-rich volcanic rocks. At temperatures above about 600˚ C it forms a continuous solid-solution between KAlSi3O8 (Ksp) and NaAlSi3O8 (Ab) with minor admixtures of CaAl2Si2O8(An) and BaAl2Si2O8 (Cn). Towards lower temperatures a solvus opens leading to lamellar unmixing of alkali-feldspar with intermediary composition …

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PLANAR MICROSTRUCTURES (LAMELLAR SUBGRAINS) IN …

microstructures (such as PDFs) from those formed prior to impact such as exsolution lamellae, veins, cleavages, and twin planes [e.g. 2]. We investigated the microstructures of Or-rich alkali feldspar phenocrysts from granitoid rocks recovered from the peak ring of the Chicxulub impact structure during the recent IODP-ICDP Expedition 364 [3].

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Biochemical evolution II: Origin of life in tubular ...

Dec 22, 1998· Potassium-rich alkali feldspar (K-feldspar) makes up 20–40% by vol of granites and is a major constituent of the Earth's crust. Metamorphism has obscured the early geological record, but radioactive dating coupled with field geology and petrography is yielding valuable information on the earliest rocks.

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Muscovite dehydration melting: Reaction mechanisms ...

Sep 30, 2019· (b) In quartzofeldspathic domains, K‐feldspar replaces plagioclase by K + –Na + cation exchange, while melt and intergrowths of sillimanite+quartz form in the aluminous domains. (c) At 7–8 vol.% melt generation, the system evolves from a closed to open system and all phases coarsen by up to two orders of magnitude, resulting in large K ...

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Microstructures and quartz lattice‐preferred orientations ...

K-feldspar microstructures include fractures, undulose extinction, subgrains and myrmekite. Undeformed recrystallized feldspar grains, similar in size to subgrains, are occasionally recognizable adjacent to porphyroclasts, and we infer that these probably formed as a result of subgrain-rotation recrystallization (Figure 5d). Obvious core-and ...

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Correlations between microstructures, K-feldspar ...

Correlations between microstructures, K-feldspar triclinicity and trace element geochemistry in stanniferous and barren granites, northern Nigeria Badejoko, T. A. Abstract. The biotite granites in the Nigerian Younger Granites are a major source of the economic metals Sn, Nb, Zn and W. The textural variations in these rocks are considered ...

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(PDF) Dissolution-precipitation creep of K-feldspar in mid ...

Analytical techniques K-feldspar porphyroclasts (Kfs1) show pervasive cross- The microstructures of the Piantonetto protomylonites and hatched twinning typical of microcline and, within the coarser mylonites were analysed by optical and scanning electron mi- porphyroclasts, exsolution lamellae of perthitic albite.

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Deformation-induced Pb isotope exchange between K-feldspar ...

Deformation-induced Pb isotope exchange between K-feldspar and whole rock in Neoarchean granitoids: Implications for assessing Proterozoic imprints. Esa Heilimo. Related Papers. Eurogranites 2005: Proterozoic and Archean Granites and Related Rocks of the Finnish Precambrian. By M. Nironen.

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Microstructures of melt-bearing regional metamorphic rocks ...

Feb 01, 2011· Microstructures of melt-bearing regional metamorphic rocks Author(s) ... or peritectic minerals (e.g., garnet, cordierite, orthopyroxene, K-feldspar) lining felsic "protoleucosomes"; (2) inclusion-free euhedral overgrowths of feldspar (precipitated from liquid) or peritectic minerals (e.g., garnet, cordierite, orthopyroxene, K-feldspar) on ...

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ALEX STREKEISEN-Feldspar structure-

Adularia is a K-feldspar produced by low-temperature hydrothermal (veins) or authigenic processes. It is structurally similar to microcline but without the cross-hatched twinning. Anorthoclase is the only alkali feldspar that is not K-feldspar. It is sodic in composition, optically triclinic and characterized by a twinning similar to microcline ...

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ALEX STREKEISEN

One of the best known is the arrangement of plagioclase and mica enclosed in K-feldspar. Most commonly the (010) faces of plagioclase and the (001) faces of mica are aligned parallel to the principal faces of K-feldspar. Bibliography • Cox et al. (1979): The Interpretation of Igneous Rocks, George Allen and Unwin, London.

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(PDF) Biochemical Evolution II: Origin of Life in Tubular ...

Biochemical Evolution II: Origin of Life in Tubular Microstructures on Weathered Feldspar Surfaces January 1999 Proceedings of the National Academy of Sciences 95(26):15173-6

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Shock melting of K-feldspar and interlacing with ...

The feldspar microstructures with direct K-feldspar melts in the leucocratic orthogneisses of the Toqqusap Nunaa area thus confirm that the recently discovered Maniitsoq structure represents the deep-crustal remnants of a giant Mesoarchaean meteorite impact.

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Igneous microstructures in migmatites — Macquarie University

Therefore, igneous microstructures can be preserved in leucosomes that have not undergone penetrative subsolidus deformation and recrystallization. The cores of many of the crystals of cordierite and K-feldspar have small, locally oriented inclusions similar to those in the same minerals in the mesosomes.

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Metamorphic microstructures - Union College

Mylonite (50-90% grain size reduced) apparently derived from a granodioritic protolith. Large feldspar porphyroclasts still remain, though less abundant than in the protomylonite immediately above. Ihe matrix contains quartz and feldspars, plus epidote, muscovite, biotite, and titanite. Thrust fault at the base of the Jotun Nappe, Norway.

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(PDF) ZAGREB 2004 Microstructures in Two Alkali Feldspar ...

Geologia Croatica 57/2 149–158 7 Figs. 2 Tabs. ZAGREB 2004 Microstructures in Two Alkali Feldspar Megacrysts from the Papuk Mt., Croatia Viktória KOVÁCS KIS1, Marija HORVAT2 and István DÓDONY1 Key words: Microstructure, Modulation, Alkali feld- in the host as porphyric (in adamellite and granodio- spar, Low microcline, Thermal history, Papuk Mt., rite), vein filling …

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Phase Transformations: Spinodal Decomposition

Spinodal microstructures 3.205 L10 11/30/06 2. A phase diagram with a spinodal region ... K is a positive materials constant called the gradient-energy coefficient and f(c) is the free energy for a homogeneous system. 3.205 L10 11/30/06 5. Interdiffusion in the spinodal region

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K Feldspar: Mineral information, data and localities.

Keefer K D, Brown G E (1978) Crystal structure and composition of sanidine and high albite in cryptoperthitic intergrowth Note this sample of feldspar is from the Rabb Canyon pegmatite, Grant County, New Mexico, USA American Mineralogist 63 1264-1273. 1978.

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Quartz and feldspar microstructures in metamorphic rocks ...

TY - JOUR. T1 - Quartz and feldspar microstructures in metamorphic rocks. AU - Vernon, Ron H. PY - 1999/4. Y1 - 1999/4. N2 - The shapes of quartz and feldspar grains in metamorphic rocks are among the most reliable criteria for determining parental rock-types.

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The microstructures of perthitic alkali feldspars revealed ...

The microstructures of perthitic alkali feldspars revealed by hydrofluoric acid etching. K. Waldron 1, M. R. Lee 2 & I. Parsons 2 Contributions to Mineralogy and Petrology volume 116, pages 360–364 (1994)Cite this article

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