Dissolution-precipitation creep of K-feldspar in mid-crustal granite mylonites

Menegon, Luca; Pennacchioni, Giorgio; Spiess, Richard

doi:10.1016/j.jsg.2008.02.001

Cited by 103 publications

(74 citation statements)

References 45 publications

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“…In wet facies, during metamorphism, as the fluid phase contains at least two volatile species, H 2 O and CO 2 (Bucher and Grapes 2011), a similar effect can probably be expected in the case of a CO 2 -rich fluid (Carroll and Knauss 2005). Electron backscatter diffraction (EBSD) is the most commonly used method to ascertain how feldspar is deformed (Schulmann et al 1996;Ishii et al 2007;Menegon et al 2008;Svahnberg and Piazolo 2013), and such studies are enhanced by the correlation of structural deformation with compositional changes in terms of major elements or focuses only on the physical impact on crystal structure.…”

Section: Introductionmentioning

confidence: 99%

“…Alkali feldspar is frequently used to give insight into complex magmatic and metamorphic processes (e.g., Vernon 1986Vernon , 2004Knesel et al 1999;Perini et al 2003;Ginibre et al 2004Ginibre et al , 2007Zellmer and Clavero 2006;Słaby et al 2007aSłaby et al , b, 2008Ishii et al 2007;Menegon et al 2008;Vernon and Paterson 2008). The composition of a megacryst, in recording many local events during magma evolution, can be expected to give detailed information about changes in its environment throughout the duration of its growth.…”

Section: Introductionmentioning

confidence: 99%

“…The transformation of K-feldspar into fine-grained assemblages is interpreted to be due to dissolution-precipitation creep proceeding along some preferred crystallographic axes (Ishii et al 2007;Menegon et al 2008). Dislocation creep or glide is rarely observed (Menegon et al 2008).…”

Section: Introductionmentioning

confidence: 99%

“…Dislocation creep or glide is rarely observed (Menegon et al 2008). Svahnberg and Piazolo (2013) noted the feedback between physical and chemical processes during feldspar deformation and recrystallization.…”

Section: Introductionmentioning

confidence: 99%

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Protomylonite evolution potentially revealed by the 3D depiction and fractal analysis of chemical data from a feldspar

Słaby

Domonik

Śmigielski

et al. 2014

Contrib Mineral Petrol

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An alkali feldspar megacryst from a protomylonite has been studied using laser ablation-ICP-mass spectrometry combined with cathodoluminescence imaging, Raman spectroscopy, and electron probe microanalysis. The aim was to determine the original (magmatic) geochemical pattern of the crystal and the changes introduced by protomylonitization. Digital concentration-distribution models, derivative gradient models, and fractal statistics, e.g., Hurstexponent values are used in a novel way to reveal subtle changes in the trace-element composition of the feldspar. Formation of the crystal is reflected in a slightly chaotic trace-element (Ba, Sr, and Rb) distribution pattern that is more or less characterized by continuous development from a fairly homogeneous environment. Derivative gradient models demonstrate a microdomain pattern. Fractal statistics show that element behavior was changeable, with Ba and Sr always more persistent (continuing) and Rb always less persistent, with the latter showing a tendency to migrate. The variations in the Hurst exponent are, however, too large to be explained by magmatic differentiation alone. The observed element behavior may be explained by structural changes revealed by Raman spectroscopy and CL. In high-strain domains, T-O-T modes become stronger for Si-O-Al than Al-O-Al linkages. Increasing amounts of Al-O--Al defects are demonstrated by cathodoluminescence. Both may result from small-distance diffusion creep, making the crystal geochemical pattern slightly patchy. In turn, the marginal part of the megacryst has a mosaic of randomly orientated, newly crystallized K-feldspars. The re-growth is confirmed by trace-element distribution patterns and fractal statistics which identify an abrupt change in the transformation environment. The novel set of tools used in this study reveals a complicated history of megacryst formation and transformation that otherwise would be difficult to unravel and decipher.Communicated by J. Hoefs. Electronic supplementary materialThe online version of this article

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Protomylonite evolution potentially revealed by the 3D depiction and fractal analysis of chemical data from a feldspar

Słaby

Domonik

Śmigielski

et al. 2014

Contrib Mineral Petrol

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“…Knipe et al 1993;Nelson et al 1999), mylonite to ultramylonite development (e.g. Mancktelow et al 1998;Menegon et al 2008;Billia et al 2013) and high pressure rocks (e.g Wassmann and Stöckhert 2012; however, the link to the pressure solution on grain boundary scale is lacking.…”

Section: Introductionmentioning

confidence: 99%

Pressure solution in rocks: focused ion beam/transmission electron microscopy study on orthogneiss from South Armorican Shear Zone, France

Bukovská

Wirth

Morales

2015

Contrib Mineral Petrol

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In order to characterize the µm-to-nm structures related to operation of pressure solution on phase boundaries in naturally deformed rocks, we have performed a detailed focused ion beam/transmission electron microscopy study in ultramylonite samples from South Armorican Shear Zone (France) that focused on grain boundary scale. We have studied phase boundaries between quartz, K-feldspar and white mica both in 2 and 3D and compare our evidences with theoretical dissolution-precipitation models in the current literature. The dissolution (re)precipitation processes lead to the development of different features at different phase boundaries. In both quartz-white mica and quartz-K-feldspar phase boundaries, voids were ubiquitously observed. These voids have different shapes and the development of some of them is crystallographically controlled. In addition, part of these voids might be filled with vermiculite.Amorphous leached layers with kaolinite composition were observed at the boundaries of Kfeldspar-quartz and K-feldspar-white mica. The development of different features along the phase boundaries is mainly controlled by the crystallography of the phases sharing a common interface, together with the presence of fluids that either leaches or directly dissolve the mineral phases. In addition, the local dislocation density in quartz may play an important role during pressure solution.We suggest that the nano-scale observations of the quartz -white mica phase boundaries show direct evidence for operation of island-and-channel model as described in Wassmann and Stöckhert (2013), while K-feldspar -quartz phase boundaries represents amorphous layers formed via interface-coupled dissolution-reprecipitation as described by Hellmann et al. (2012).

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Semibrittle deformation and partial melting of perthitic K‐feldspar: An experimental study

et al. 2014

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To investigate the relationships between deformation, cracking, and partial melting in the lower continental crust, axial compression and hydrostatic experiments were performed on K-feldspar single crystals at temperatures of 700°and 900°C and confining pressures between 0.75 and 1.5 GPa. Sample deformation was carried out at a constant strain rate of~10 À6 s À1 . The samples deformed at 700°C show typical brittle behavior with formation of conjugate fractures and peak stresses that increase with confining pressure. Samples deformed at 900°C show formation of shear fractures, peak stresses below the Goetze criterion, and inverse confining pressure dependence of peak stress, indicating that along the fractures deformation was not dominantly friction controlled. Microstructural and chemical analyses reveal the presence of melt (<6 vol %) of inhomogeneous composition along the shear zones and chemical compositional changes of gouge fragments. In a hydrostatic experiment performed at 900°C, no melt and no compositional changes were observed. These observations indicate that deformation of K-feldspars at high pressures and temperatures is controlled by the simultaneous formation of brittle fractures and melt. The formation of melt is strongly accelerated and kinetically favored by cracking, as demonstrated by the absence of melting in the hydrostatic experiments. However, the melt along fractures does not dramatically weaken the samples, as the melt domains remain isolated during deformation. The fine-grained gouge fragments formed along the fracture systems undergo chemical homogenization. The dominant deformation mechanism in the gouge is likely to be melt-enhanced diffusion creep, which may also assist the chemical homogenization process.

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Dissolution-precipitation creep of K-feldspar in mid-crustal granite mylonites

Cited by 103 publications

References 45 publications

Protomylonite evolution potentially revealed by the 3D depiction and fractal analysis of chemical data from a feldspar

Protomylonite evolution potentially revealed by the 3D depiction and fractal analysis of chemical data from a feldspar

Pressure solution in rocks: focused ion beam/transmission electron microscopy study on orthogneiss from South Armorican Shear Zone, France

Semibrittle deformation and partial melting of perthitic K‐feldspar: An experimental study

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