High-temperature microstructures and rheology of deformed granite, Erzgebirge, Bohemian Massif

Schulmann, Karel; Mlčoch, Bedřich; Melka, Radek

doi:10.1016/s0191-8141(96)80007-1

Cited by 71 publications

(39 citation statements)

References 40 publications

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“…4g) showing kink bands, subgrains, or development of core and mantle structures containing polygonal new grains of the same size as the adjacent subgrains, indicate that climb was even more active in this mineral than in k-feldspar. This behavior is consistent with the fact that the activation energy of dynamic recrystallization and dislocation glide is lower for plagioclase than for K-feldspar in middle to high homologous temperatures (e.g., Fitz Gerald and Stunitz, 1993;Schulmann et al, 1996). Plagioclase new grains (up to 225 lm) formed by either GBMR or SGRR are greater than recrystallized matrix k-feldspar grains (50 lm), consistent with the preceding statement.…”

Section: Feldsparssupporting

confidence: 81%

Counterclockwise tectonometamorphic evolution of the Pringles Metamorphic Complex, Sierras Pampeanas of San Luis (Argentina)

Delpino

Bjerg

Ferracutti

et al. 2007

Journal of South American Earth Sciences

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Section: Feldsparssupporting

confidence: 81%

Counterclockwise tectonometamorphic evolution of the Pringles Metamorphic Complex, Sierras Pampeanas of San Luis (Argentina)

Delpino

Bjerg

Ferracutti

et al. 2007

Journal of South American Earth Sciences

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“…On the basis of major traditionally mapped "lithostratigraphical" units (e.g., Hoth et al, 1983), recent petrological studies in combination with tec tonic investigations (e.g., Sebastian, 1995;Krohe, 1996;Schulmann et al, 1996) and geochemical cor relation (Mingram, 1996), a new subdivision of the dome has been introduced for a better overview (e.g., Kröner et al, 1995;Rötzler, 1995;Willner et al, 1994Willner et al, , 1997. These tectonometamorphic units are defined by their dominant rock associations, and, in particular, by their overall trends in metamorphic evolution.…”

Section: Characterization Of the P-t-t-d Evolution Of The Tectono-metmentioning

confidence: 99%

Interrelated P-T-t-d Paths in the Variscan Erzgebirge Dome (Saxony, Germany): Constraints on the Rapid Exhumation of High-Pressure Rocks from the Root Zone of a Collisional Orogen

WlLLNER

Krohe

Maresch

2000

International Geology Review

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The Erzgebirge dome consists of several superimposed composite tectonometamorphic units of medium-to high-grade metamorphic rocks from different crustal depths. These exhibit high pres sure-high temperature and even ultrahigh-pressure imprints inherited from the root zone of a Variscan orogen and were exhumed almost immediately after attainment of maximum pressures at ~341 Ma. At present, the entire stack of tectonometamorphic units lies underneath an upper-crustal sequence of Paleozoic metasediments and tectonic slivers of pre-Carboniferous metamorphic rocks.Shear zones active at different times and at different depths are preserved, mainly recording two successive stages of the exhumation history between 340 and 330 Ma. Tectonic transport during exhumation was remarkably constant in an E-W direction, swinging to NW-SE in the eastern part of the Erzgebirge parallel to a ductile transtensional zone (Elbe zone) that was concomitantly active. The various tectonometamorphic units have characteristically correlated, convergent P-T-t-d paths (both "cooling during decompression" and "heating during decompression") that can be deduced from the dominant quartzofeldspathic rocks. These paths indicate successive exhumation of hotter rocks from increasingly deeper structural positions and juxtaposition against cooler rocks in higher positions, concomitant with the excision of intermediate crustal levels. We interpret this type of successive vertical telescoping of the metamorphic profile to be the result of extension of the thick ened tectonometamorphic stack.Extensional unroofing in the middle and upper crust was contemporaneous with and outlasted underthrusting and hence prograde metamorphism and deformation at deeper levels of the tectono metamorphic pile. Underthrusting is documented by a major inversion of the maximum pressure conditions in the lowermost units. However, structures related to compressional stacking now gener ally occur only as relics transposed by extensional deformation at lower pressure, or are restricted to rare small slivers with preserved prograde structures. Sedimentation of Lower Dinantian turbidites occurred along the flanks of the Erzgebirge dome during the exhumation process.The extrusion of high-pressure rocks is interpreted to have been driven mainly by a major regional buoyancy instability caused by the delamination of the lithospheric mantle underneath the neighbor ing Bohemian Massif, which represented overthickened crust at least from the Devonian to the early Visean. Major controlling factors were boundary forces exerted by the thickened crustal bulge on the neighboring thin crustal segments in the north and east, effecting lateral extension of this orogenic wedge and extrusion-i.e., convective upward flow of gravitationally unstable crustal material.

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“…This assumption is essential in assessing rheology of polyphase rocks with different proportion of weak quartz and ''strong skeleton'' formed by feldspars in both loadbearing framework and interconnected weak layer microstructures [Handy, 1990[Handy, , 1994Schulmann et al, 1996;Ji et al, 2004;Rybacki and Dresen, 2004]. However, change of deformation mechanism in feldspars from dislocation to diffusion creep has never been considered in term of mineral strength contrast between quartz and feldspars.…”

Section: Comparative Rheology Between Feldspars and Quartzmentioning

confidence: 99%

Extreme ductility of feldspar aggregates—Melt‐enhanced grain boundary sliding and creep failure: Rheological implications for felsic lower crust

Závada

Schulmann²,

Konopásek

et al. 2007

J. Geophys. Res.

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[1] High-grade orthogneisses from granulite-bearing lower crustal unit show extreme finite strains of both K-feldspar and plagioclase with respect to weakly deformed quartz aggregates. K-feldspar aggregate in the most intensely deformed sample shows interstitial grains of quartz and albite, which also mark some intragranular fractures within K-feldspar grains. Both interstitial grains and fractures are oriented mostly perpendicular to the sample stretching lineation. Quartz and albite grains within K-feldspar bands are interpreted as crystallized from interstitial melt and the petrology study shows that the melt was produced by a metamorphic reaction in plagioclase-mica bands. Thermodynamic Perple_X modeling shows that melt volume increase was negligible and melt amount was too small to generate considerable melt overpressure for calculated PT conditions. It is therefore suggested that dilation of K-feldspar aggregates and fracturing of its grains represent a final creep failure state, which resulted from the cavitation process accompanying grain boundary sliding controlled diffusion creep. The consequence of cavitation-driven dilation of K-feldspar aggregates is the local underpressure resulting in infiltration of melt from plagioclase bands. Analogy with metallurgy experiments shows that the cavitation process, exclusively developed in cryptoperthitic K-feldspar, can be attributed to its lower purity compared to more pure plagioclase. Contrasting rheological behavior of feldspars with respect to quartz prior to fracturing is attributed to different deformation mechanisms. Feldspars appear weaker due to grain boundary sliding accommodated by coupled melt-enhanced diffusion creep along grain boundaries and dislocation creep within grains, in contrast to quartz deforming via grain boundary migration accommodated dislocation creep.Citation: Závada, P., K. Schulmann, J. Konopásek, S. Ulrich, and O. Lexa (2007), Extreme ductility of feldspar aggregates-Meltenhanced grain boundary sliding and creep failure: Rheological implications for felsic lower crust,

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High-temperature microstructures and rheology of deformed granite, Erzgebirge, Bohemian Massif

Cited by 71 publications

References 40 publications

Counterclockwise tectonometamorphic evolution of the Pringles Metamorphic Complex, Sierras Pampeanas of San Luis (Argentina)

Counterclockwise tectonometamorphic evolution of the Pringles Metamorphic Complex, Sierras Pampeanas of San Luis (Argentina)

Interrelated P-T-t-d Paths in the Variscan Erzgebirge Dome (Saxony, Germany): Constraints on the Rapid Exhumation of High-Pressure Rocks from the Root Zone of a Collisional Orogen

Extreme ductility of feldspar aggregates—Melt‐enhanced grain boundary sliding and creep failure: Rheological implications for felsic lower crust

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