Ductile deformation of tonalite in the Suomusjärvi shear zone,south-western Finland

Lonka, Harriet; Schulmann, Karel; Venera, Zdeněk

doi:10.1016/s0191-8141(98)00003-0

Cited by 31 publications

(20 citation statements)

References 38 publications

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“…The sum of modal contents for opaque and other minerals is less than 10% in all the samples. A decrease in quartz and an increase in sheet silicate contents in mylonite are also reported by Hippertt (1998) and Lonka et al (1998).…”

Section: Shear Zone Development In the Shimono-sawa Routesupporting

confidence: 64%

“…Mylonitic shear zones in the Shimono-sawa route probably serve some water pathway or absorber in the lower crust. If so, it is possible that the decrease of quartz content in mylonite is partly due to the predominant dissolution of quartz during mylonitization (e.g., Hippertt, 1998;Lonka et al, 1998). Decreased quartz content certainly established more sheet silicate rich modal composition, and probably contributed to subsequent preferential mylonitization in the sheet silicate rich zone.…”

Section: Discussionmentioning

confidence: 99%

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Occurrence of mylonite zones and pseudotachylyte veins around the base of the upper crust: An example from the southern Hidaka metamorphic belt, Samani area, Hokkaido, Japan

et al. 2014

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Geological studies on exhumed pseudotachylyte-bearing mylonite zones in S-type tonalite were carried out in the southern Hidaka metamorphic belt, Hokkaido, Japan. Mylonitization is characterized by (1) development of composite planar fabrics, (2) grain size reduction, and (3) change in modal composition an increase in mica content and a decrease in quartz content from protolith to mylonite. Mylonite zones are heterogeneously concentrated in the host rocks. At microscopic scales, shear deformation is concentrated heterogeneously in finegrained layers along C-surfaces. Most of the pseudotachylyte layers are subparallel to the C-surface, and tend to overprint thick mylonite zones. The heterogeneous development of mylonite zones, which may be activated as layers of co-seismic slip, should be incorporated into numerical modeling of seismogenic zones.

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Section: Shear Zone Development In the Shimono-sawa Routesupporting

confidence: 64%

Section: Discussionmentioning

confidence: 99%

Occurrence of mylonite zones and pseudotachylyte veins around the base of the upper crust: An example from the southern Hidaka metamorphic belt, Samani area, Hokkaido, Japan

et al. 2014

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“…Previous studies showed that the deformation gradient in metagranitoids at high temperatures is characterized by the development of augen-gneisses and banded gneisses at higher strains (Handy, 1990;Schulmann and Mlčoch, 1996). Further increase of deformation intensity results in complete disintegration of the layers associated with resorption of older grains and precipitation of new grains from the percolating fluids and/or melts in the core of the shear zones (Lonka et al, 1998;Hasalová et al, 2008aHasalová et al, , 2008bOliot et al, 2014). Typical microstructural features of this sequence are the decrease of grain size and progressive disintegration of the compositional layering by crystallization of interstitial unlike phases in host banded aggregates.…”

Section: Are Granofelses Cores Of High Strain Zones?mentioning

confidence: 99%

“…To test the relative mobility of melt and/or fluids between the different rock types, we have compared their element budgets using bulkrock geochemistry (Lonka et al, 1998;Hasalová et al, 2008c;Oliot et al, 2014) (Fig. 11; Fig.…”

Section: Whole-rock Geochemistrymentioning

confidence: 99%

Role of strain localization and melt flow on exhumation of deeply subducted continental crust

et al. 2018

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A section of anatectic felsic rocks from a high-pressure (>13 kbar) continental crust (Variscan Bohemian Massif) preserves unique evidence for coupled melt flow and heterogeneous deformation during continental subduction. The section reveals layers of migmatitic granofels interlayered with anatectic banded orthogneiss and other rock types within a single deformation fabric related to the prograde metamorphism. Granofels layers represent high strain zones and have traces of localized porous melt flow that infiltrated the host banded orthogneiss and crystallized granitic melt in the grain interstices. This process is inferred from: (1) gradational contacts between orthogneiss and granofels layers; (2) grain size decrease and crystallographic preferred orientation of major phases, compatible with oriented growth of crystals from interstitial melt during granular flow, accommodated by melt-assisted grain boundary diffusion creep mechanisms; and (3) pressuretemperature equilibria modeling showing that the melts were not generated in situ. We further argue that this porous melt flow, focused along the deformation layering, significantly decreases the strength of the crustal section of the subducting continental lithosphere. As a result, detachment folds develop that decouple the shallower parts of the layered anatectic sequence from the underlying and continuously subducting continental plate, which triggers exhumation of this anatectic sequence.

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“…In the case of fault zones, changes between fault zones and less deformed wall rocks were interpreted either as (1) volume loss within the fault zone: as outlined by numerous authors (e.g. Demény et al, 1997;Dickin, 1988;Lonka et al, 1998;O'Hara, 1988), fault zones commonly show increasing contents of relatively immobile elements suggesting a volume loss that can be explained as the result of depletion of other more soluble elements during deformation, (2) volume gain during deformation: this case corresponds to a high activity of metamorphic fluids which change the rates of chemical and mechanical processes (e.g. Hippertt, 1998;Selverstone et al, 1991), (3) isochoric (constant volume) deformation: in this case, the activity of internal fluids may cause mineral reactions but no change in bulk volume nor chemistry (e.g.…”

Section: Transfers In the Millaris Fault Zonementioning

confidence: 99%

Quantification of mass transfers and mineralogical transformations in a thrust fault (Monte Perdido thrust unit, southern Pyrenees, Spain)

Trincal

Charpentier

Buatier

et al. 2014

Marine and Petroleum Geology

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In fold-and-thrust belts, shortening is mainly accommodated by thrust faults which are preferential zones for recrystallisation and mass transfer. This study focuses on a detachment fault related to the emplacement of the Monte Perdido thrust unit in the southern Pyrenees. The studied fault zone consists of a 10 m thick intensively foliated phyllonite developed within the Millaris marls, of Eocene age. The lithological homogeneity of the hanging wall and footwall allows us to compare the Millaris marls outside the fault zone with the highly deformed marls located in the fault zone and to quantify the chemical, mineralogical and volumetric changes related to deformation processes along the fault.The Millaris marls are composed of detrital quartz, illite, chlorite, minor albite and pyrite, in a micritic calcite matrix. In the fault zone, the cleavage planes are marked by clay minerals and calcite AE chlorite veins attest to fluidemineral interactions during deformation.The mineral proportions in all samples from both the fault zone and Millaris marls have been quantified by two methods: (1) X-ray diffraction and Rietveld refinement, and (2) bulk chemical analyses as well as microprobe analyses to calculate modal composition. The excellent agreement between the results of these two methods allows us to estimate mineralogical variations using a modification of the Gresens' equation. During fault activation, up to 45 wt% of calcite was lost while the amounts of quartz and chlorite remained unchanged. Illite content remained constant to slightly enriched. The mineralogical variations were coupled with a significant volume loss (up to 45%) mostly due to the dissolution of micritic calcite grains. Deformation was accompanied by pressure solution and phyllosilicates recrystallisation. These processes accommodated slip along the fault. They required fluids as catalyst, but they did not necessitate major chemical transfers.

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Ductile deformation of tonalite in the Suomusjärvi shear zone,south-western Finland

Cited by 31 publications

References 38 publications

Occurrence of mylonite zones and pseudotachylyte veins around the base of the upper crust: An example from the southern Hidaka metamorphic belt, Samani area, Hokkaido, Japan

Occurrence of mylonite zones and pseudotachylyte veins around the base of the upper crust: An example from the southern Hidaka metamorphic belt, Samani area, Hokkaido, Japan

Role of strain localization and melt flow on exhumation of deeply subducted continental crust

Quantification of mass transfers and mineralogical transformations in a thrust fault (Monte Perdido thrust unit, southern Pyrenees, Spain)

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