Granular flow in polymineralic rocks bearing sheet silicates: new evidence from natural examples

Herwegh, Marco; Jenni, Andreas

doi:10.1016/s0040-1951(00)00288-2

Cited by 46 publications

(29 citation statements)

References 28 publications

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“…In contrast, high strain experiments on olivine-opx aggregates show extensive mixing of the two phases due to grain boundary sliding (Farla et al, 2013). In addition, as shown by rock analogue experiments (Ree, 1991) and suggested for the generation of new mica grains as second phases in calcite mylonites (Herwegh and Jenni, 2001), grain boundary sliding generates voids particularly at grain triple junctions. Under the presence of fluids, pore fluid pressure in the new voids drops and new phases can be precipitated/ nucleated.…”

Section: Dynamic Recrystallization Grain Nucleation and Grain Boundamentioning

confidence: 90%

“…12, de Ronde et al, 2004;Kruse and Stünitz, 1999). Although at the time this nucleation occurs, grain boundary sliding is not necessarily required to mix the phases, it will enhance it by providing the nucleation sites in voids between the sliding grains (Herwegh and Jenni, 2001) In this way, retrograde grain size reduction in olivine by subgrain rotation with an increasing grain boundary sliding component will (i) result in smaller olivine grain sizes, providing smaller interparticle distances with grain boundary voids as preferential nucleation site for second phases. (ii) Consequently, the interparticle distances of newly nucleated second phases decrease with decreasing temperature.…”

Section: Metamorphic Reactionsmentioning

confidence: 99%

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Small quantity but large effect — How minor phases control strain localization in upper mantle shear zones

2015

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Section: Dynamic Recrystallization Grain Nucleation and Grain Boundamentioning

confidence: 90%

Section: Metamorphic Reactionsmentioning

confidence: 99%

Small quantity but large effect — How minor phases control strain localization in upper mantle shear zones

2015

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“…Neither of the two complexities is currently included in the mechanical description and would complicate extrapolation to natural conditions. Apart from the direct effect on strength, open void space has important consequences for the activity of fluid phases and precipitation of secondary phases that in turn may affect the structure development [e.g., Herwegh and Jenni , 2001; Mas and Crowley , 1996].…”

Section: Discussionmentioning

confidence: 99%

Dislocation creep of calcite

2002

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[1] When the power law equation, _ e / s n exp(ÀQ/RT ), which relates strain rate (_ e), stress (s), gas constant (R), and temperature (T ), is used to describe thermally activated dislocation creep of calcite rocks, the stress sensitivity (n) and temperature sensitivity or apparent activation energy (Q) differ greatly from rock to rock. To better constrain parameters of a mechanical equation of state, we performed triaxial deformation experiments on dense synthetic aggregates of polycrystalline calcite at temperatures of 873-1073 K and strain rates between 5 Â 10 À7 and 3 Â 10 À3 s À1 to strains <0.20. The strength of the marbles decreases with increasing temperature or decreasing strain rate. Combining microstructure analysis with mechanical data indicates that strength decreases with increasing grain size (d) following a Hall-Petch relation. A detailed analysis of the data revealed systematic dependence of n and Q on stress, grain size, and temperature. The variations in n and Q can be accommodated by using a Peierls law, _ e P = A P s 2 exp(s/ s P )exp(ÀQ P /RT). The resistance to glide, s P , is composed of an intrinsic Peierls stress and a grain size dependent back stress and is given by s P = (AE P,0 + Kd À0.5 )(T m À T ), where T m denotes the melting temperature. The following parameters seem to apply to all calcite rocks: A P % 10 ±0.5 MPa À2 s À1 , Q P % 200 kJ/mol, AE P,0 % 7.8 MPa kK À1 , and K % 115 MPa kK À1 mm 0.5 . Under some laboratory conditions, dislocation creep may operate simultaneously with grain size sensitive diffusion creep, complicating the quantification of the individual flow laws. More accurate flow laws will need to include the evolution of microstructure in composite flow laws, perhaps requiring a statistical description of a microstructure variable yet to be specified exactly.

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“…A kőzet mikrokristályos alapanya gának irányítatlan szöve -te, továbbá a szigmoidális klasztokon azonosítható kép -lé keny nyírásos alakváltozás arra utal, hogy ezekben a mintákban a deformáció fő mec hanizmusa a szemcsehatár menti csúszás (grain boundary sliding) lehetett (PASSCHIER & TROUW 2005). Ez a deformációs mechanizmus mikrokristályos szemcseaggre gá -tumok esetén nagyon hatékony és domináns folyamat, mely fluidum jelenlétében jellemzően diffúziós tömeg áramlással társul (KURZ et al 2000, HERWEGH & JENNI 2001, PASSCHIER & TROUW 2005. Feltételezhető tehát, hogy a nagyobb méretű karbonátszemcsék kezdeti dinamikus át kristályo sodásának a kőzet-fluidum kölcsönhatás kedvez hetett (RUTTER 1971, NEWMAN & MITRA 1994, KENNEDY & LOGAN 1998.…”

Section: Táblázat a Vizsgált Minták Petrográfiai Jellemzőiunclassified

“…Az M. TÓTH (2008) által megálla pított kis hőmérsékletű töréses deformáció jelei főként mak roszkópos léptékben jellem zők, a mikroszkópos vizsgála tok során a mintákban képlé keny deformációra utaló bélye gek azonosíthatók. A kristály plasztikus deformációs szerke ze tek jellegei alapján feltéte lez hető, hogy a képlékeny a lak változás kis hőmér sék -le ten, vélhetően erőteljes flui dum ha tás eredményeként ment végbe (NEWMAN & MITRA 1994, KENNEDY & LOGAN 1998, KURZ et al 2000, HERWEGH & JENNI 2001, LIU et al 2002, PASSCHIER & TROUW 2005.…”

Section: Táblázat a Vizsgált Minták Petrográfiai Jellemzőiunclassified

A dorozsmai márvány (Tiszai-főegység) kőzettani újravizsgálata: deformáció és fluidum hatása a mikroszerkezet fejlődésére

Papp¹,

Varga²,

Mészáros³

et al. 2017

Földt. Közl.

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Detailed petrographic studies on marbles are rare in the Hungarian geological literature. Determination of the mineral phases and their grain size, examination of the grain boundaries as well as deformation microstructures, however, can provide a comprehensive information about the metamorphic evolution and the deformation history of a marble unit.The metamorphic basement block near the village of Dorozsma contains a few-meter-thick marble zone within the Békés-Codru Zone. A petrographic study of archive thin sections representing this marble zone was carried out from the boreholes Dorozsma-4, Dorozsma-7 and Dorozsma-54.The fine-grained marble samples show heteroblastic texture with a composition of carbonate + quartz + muscovite + Mg-chlorite ± talc. The carbonate crystal boundaries are dominantly sutured, embayed and rarely curved. All the morpho logical types of deformation twins appear in the samples, but dominantly twin types II and IV are present. The characteristic features of the samples are small dissolution cavities filled with fine crystalline carbonate, blocky quartz and, in some cases, with saddle dolomite. In the samples from the borehole Dorozsma-4 small inclusion free carbonate grains substitute the deformation twins of the large carbonate crystals. In addition, small carbonate neoblasts and Mgchlorite flakes can be found among the large carbonate crystals. Characteristic microstructures of the samples from the well Dorozsma-7 are large sigmoid carbonate clasts in a very fine-grained matrix. The deformation twins of the carbonate clasts can be easily identified and show the signs of recrystallization. These samples beside the carbonate clasts also contain irregularly shaped polycrystalline quartz grains with dissolved edges, undulose extinction and signs of incipient dynamic recrystallization.The microstructures presented above suggest a polyphase deformation. The D 1 deformation event took place above 250 °C based on the relict microstructures. The subsequent D 2 ductile deformation event was a low-temperature dynamic recrystallization with a simple shear component, which could be the result of a hydrolitic weakening effect of hydrothermal fluids during deformation of the Dorozsma marble.Keywords: Dorozsma, marble, petrography, ductile deformation, metasomatism Összefoglalás A márványok petrográfiai vizsgálata napjainkig alárendelt szerepet kapott a hazai földtani szakirodalomban. A már -ványt felépítő ásványfázisok, valamint azok szemcsemérete és a szemcsehatár jellegének meghatározása (kőzetszövet), illetve a deformációs bélyegek feltárása és értelmezése révén azonban átfogó képet kaphatunk a kőzet metamorf fejlő dé -séről és deformációtörténetéről, ami független bizonyítékokkal szolgálhat a befoglaló metamorf kőzettest korreláció -jához.A Békés-Codrui-egységen belül elhelyezkedő, Dorozsma környéki kristályos aljzatban egy maximum néhányszor tíz mé ter vastagságú, markáns töréses deformációt szenvedett márványzóna található. Tanulmányunkban az e zónát mintázó Dorozsma-4, -7 és -54 fúrá...

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Granular flow in polymineralic rocks bearing sheet silicates: new evidence from natural examples

Cited by 46 publications

References 28 publications

Small quantity but large effect — How minor phases control strain localization in upper mantle shear zones

Small quantity but large effect — How minor phases control strain localization in upper mantle shear zones

Dislocation creep of calcite

A dorozsmai márvány (Tiszai-főegység) kőzettani újravizsgálata: deformáció és fluidum hatása a mikroszerkezet fejlődésére

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