k feldspar microstructures

Preferred orientation distribution of shock‐induced planar

The orientation of planar microstructures, such as PDFs in quartz, PFs, PDFs, and (likely shock‐induced) microtwins in feldspar, as well as the orientation of the c‐axis in quartz grains containing PDFs were determined using the universal‐stage (U‐stage), following the method described in Passchier and Trouw and Langenhorst, …

Microstructures in feldspars from a major crustal thrust …

Brittle microstructures Microfractures in zone 5 and the localized polysynthetic twins in K-feldspar that highlight the fractures are assumed to be a late feature imposed during uplift to higher crustal levels, resulting from either interaction with water (Tullis & Yund 1980, Tuilis 1983) or extension due to unloading.

Trapped K‐feldspar phenocrysts as a signature of …

Here, we use quantitative orientation mapping, scanning electron microscope (SEM)-based imaging and chemical analysis to characterize quartz and K-feldspar …

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 …

Quartz and feldspar microstructures in metamorphic …

Feldspar. Inclusions. Leucosome. Metamorphism. Microstructures. Migmatites. Quar tz. Fingerprint. Dive into the research topics of 'Quartz and feldspar microstructures in …

Argon diffusion domains in K-feldspar I: microstructures in …

Samples of MH-10, a K-feldspar thought to contain discrete diffusion domains for argon, have been examined by light and TEM microsopy to search for domain boudaries. We examined both unheated K-feldspar separates and samples heated in vacuum between 750 and 1150°C in order to characterize the initial microstructure as well as any …

(PDF) Quartz and K-Feldspar Microboudins in Felsic

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 ...

How late are K-feldspar megacrysts in granites? Lithos

K-feldspar crystals commonly occur as anhedral to subhedral phenocrysts, with euhedral inclusions of zoned plagioclase grains (Fig. 4a) and euhedral inclusions of biotite (Fig. 4b); in places, the ...

[PDF] Understanding K-feldspar 40Ar/39Ar data: reconciling …

Several descriptions of argon diffusion in K-feldspar have been developed, including the quantitative multiple-diffusion-domain (MDD) and multipath models and the qualitative 'recrystallization' model. These models remain contentious and the natural range in behaviour remains poorly understood. Feldspars from the Klokken syenite intrusion …

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 …

Argon diffusion domains in K-feldspar I: …

Three classes of substructure are present in the K-feldspar, but only the third appears to have been affected by laboratory heating: (1) Cross-hatched extinction in light …

Exsolution and alteration microtextures in alkali feldspar …

Alkali feldspar phenocrysts (bulk composition Or 75.0 Ab 24.6 An 0.4) in the subsolvus Shap granite comprise a fine-scale mixture of subregular pristine crypto- and micro-perthites with altered, micropore-rich feldspar with irregular microstructures.The regular perthites are strain-controlled intergrowths of Albite and/or Periclinetwinned albite exsolution …

Biochemical evolution II: Origin of life in tubular microstructures …

We have described periodic, self-organized tubular microstructures, in exactly the size range of modern soil bacteria, on the surfaces of weathered alkali feldspar crystals (6, 7). ... 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 ...

How deceptive are microstructures in granitic rocks?

Although the growth rates of K-feldspar have only been experimentally determined for hydrous silicic melts at much greater undercoolings than may be achieved in the large plutons in which K-feldspar megacrysts occur (see, e.g., Fenn 1977; Naney and Swanson 1980), it is entirely plausible that alkali-feldspar crystals can grow to …

Deformation-induced Pb isotope exchange between K-feldspar …

All deformed K-feldspar porphyroclasts show core-and-mantle microstructures, which indicate GBM (grain boundary migration) recrystallization at the temperature of 400–500 °C. The shapes and microstructures of K-feldspar porphyroclasts suggest that the Koitere and Nilsiä granodiorites were deformed to diverse extent in low- …

Fluid-enhanced grain-size reduction of K-feldspar from a

Deformation temperatures are constrained from 400 °C to 550 °C, estimated using the feldspar and quartz microstructures, crystal-preferred orientation patterns of recrystallized quartz, and a ...

Fluid-enhanced grain-size reduction of K-feldspar from a …

The mylonites are characterized by a typical microstructure of coarse-grained K-feldspar porphyroclasts surrounded by fine-grained matrix of oligoclase, K-feldspar, and quartz. Deformation temperatures are constrained from 400 °C to 550 °C, estimated using the feldspar and quartz microstructures, crystal-preferred orientation patterns of ...

Transition from cataclastic flow to dislocation creep of feldspar

Feldspar aggregates exhibit cataclastic flow over a wide range of conditions between low-temperature faulting and high-temperature dislocation creep; this is due to the ease of cracking on the two good cleavages and the difficulty of dislocation motion.

Microstructures of melt-bearing regional metamorphic rocks

The contact of the minerals quartz, K-feldspar and plagioclase grains ( Figure 5e) is indicative of simultaneous crystallization from melt (Clemens and Holness, 2000;Vernon et al., 2004 ...

The microstructures of microcline from some granitic …

The Microstructures of Microcline from Some Granitic Rocks and Pegmatites J.D. Fitz Gerald* and A.C. McLaren Department of Earth Sciences and Department of Physics, Monash University, Clayton, Victoria 3168, Australia ... K-feldspar show undulatory extinction varying from 0 ~ to 15 ~ with fine, diffuse cross-hatching or a fine, blocky struc ...

Quartz and feldspar microstructures in metamorphic rocks

Abstract. The shapes of quartz and feldspar grains in metamorphic rocks are among the most reliable criteria for determining parental rock-types. Rational faces and elongate crystals of feldspar, especially with oscillatory zoning, indicate an igneous precursor, and residual faces and embayments in quartz indicate a volcanic precursor.

Fluid-enhanced grain-size reduction of K-feldspar …

The mylonites are characterized by a typical microstructure of coarse-grained K-feldspar porphyroclasts surrounded by fine-grained matrix of oligoclase, K …

Effects of fluorine on dynamic reaction interfaces in …

In previous work, we discovered that K-feldspar-albite-sanidine zonation textures developed dynamically when sanidine ((K,Na)AlSi 3 O 8) was reacted with NaCl or NaF in H 2 16 O- and H 2 18 O-enriched solutions at 600 °C and 2 kbar in a closed system. Based on a detailed SEM and TEM characterisation, the present study aims to constrain …

Crystallographic Controls on the Alteration of Microcline

Fitz Gerald JD, Harrison TM. 1993. Argon diffusion domains in K-feldspar I: Microstructures in MH-10. Contrib Mineral Petrol 113:113–380. Article Google Scholar Fitz Gerald JD, McLaren AC. 1982. The microstructures of microcline from some granitic rocks and pegmatites. Contrib Mineral Petrol 80:80–229.

QUARTZ AND FELDSPAR MICROSTRUCTURES IN …

on minerals with inclusion trails (a.g., K-feldspar, cordierite). (4) Simple twinning may occur in K-feldspar, which appears to be diagnostic of crystallization of K-feldspar in a melt, rather than in the solid state. Keywords: crystal faces, feldspar, inclusions, leucosome, metamorphism, microstructures, migmatites, quartz. Sowenn

Microstructures of melt-bearing regional metamorphic rocks

Several other criteria are potentially reliable, namely: (1) euhedral crystals of feldspar (precipitated from liquid) 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 ...

High-temperature microstructures and rheology of …

The microstructures and deformation mechanisms of constitutive minerals are temperature dependent and progressively change either with changing temperature (Knipe 1989) or with increasing deformation intensity (Gapais 1989b). ... (010) crystal face subparallel to the foliation plane (Debat et al. 1978). K-feldspar is strongly recrystallized ...

Lightning-induced high temperature and pressure …

In comparison to a granite reference sample collected from a borehole at a depth of 138 m, microstructures in both the surface and fracture fulgurite are …

(PDF) Pristine microstructures in pseudotachylytes formed …

deformation, pristine pseudotachylyte microstructures can be preserved. This has been the case. for pseudotachylytes in feldspar-rich rocks on Moskenesøya in Lofoten, Northern Norway. The ...

Microstructures of the type-I banded granitic …

The low stress exponent (n = 1.9–5.8), high activation energy (Q = 325–802 kJ/mol), and macrostructures (distributed for most samples) and microstructures (such as kinked, folded and elongated ...