Late Palaeozoic deformation of post-Variscan lower crust: shear zone widening due to strain localization during retrograde shearing

Zibra, I.; Kruhl, Jörn H.; Braga, Roberto

doi:10.1007/s00531-009-0441-5

Cited by 17 publications

(29 citation statements)

References 94 publications

Supporting

Mentioning

Contrasting

Order By: Relevance

“…9d). However, activity of c slip in quartz typically requires temperature in excess of 600 • C (Kruhl, 1996;Zibra et al, 2010) and, therefore, appears unlikely in our samples. Moreover, misorientation profiles across low-angle boundaries with a subset 2 orientation show abrupt misorientation jumps of up to 6 • (profiles c-d in Figs.…”

Section: Quartz In the Host Rockmentioning

confidence: 90%

Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

Molli

Menegon

Malasoma³

2017

Solid Earth

View full text Add to dashboard Cite

Abstract. The switching in deformation mode (from distributed to localized) and mechanisms (viscous versus frictional) represent a relevant issue in the frame of crustal deformation, being also connected with the concept of the brittle-"ductile" transition and seismogenesis. In a subduction environment, switching in deformation mode and mechanisms and scale of localization may be inferred along the subduction interface, in a transition zone between the highly coupled (seismogenic zone) and decoupled deeper aseismic domain (stable slip). However, the role of brittle precursors in nucleating crystal-plastic shear zones has received more and more consideration being now recognized as fundamental in some cases for the localization of deformation and shear zone development, thus representing a case in which switching deformation mechanisms and scale and style of localization (deformation mode) interact and relate to each other. This contribution analyses an example of a millimetrescale shear zone localized by brittle precursor formed within a host granitic protomylonite. The studied structures, developed in ambient pressure-temperature (P -T ) conditions of low-grade blueschist facies (temperature T of ca. 300 • C and pressure P ≥ 0.70 GPa) during involvement of Corsican continental crust in the Alpine subduction. We used a multidisciplinary approach by combining detailed microstructural and petrographic analyses, crystallographic preferred orientation by electron backscatter diffraction (EBSD), and palaeopiezometric studies on a selected sample to support an evolutionary model and deformation path for subducted continental crust. We infer that the studied structures, possibly formed by transient instability associated with fluctuations of pore fluid pressure and episodic strain rate variations, may be considered as a small-scale example of fault behaviour associated with a cycle of interseismic creep and coseismic rupture or a new analogue for episodic tremors and slow-slip structures. Our case study represents, therefore, a fossil example of association of fault structures related to stick-slip strain accommodation during subduction of continental crust.

show abstract

Section: Quartz In the Host Rockmentioning

confidence: 90%

Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

Molli

Menegon

Malasoma³

2017

Solid Earth

View full text Add to dashboard Cite

show abstract

“…On the contrary, in typified blastomylonitic D 3 shear zones and from outer to inner zones, dynamic recrystallizations features range from quartz GBM to SGAR, feldspars SGR to GBM and amphibole SGR (Kurse et al, 2001;Passchier & Trouw, 2005;Stipp et al, 2002;Zibra, 2010Zibra, , 2012Zibra et al, 2012). D 3 folded S 0/1/2 and S 2 foliations in F 3 meso-and large-scale folds and emplaced shear zones in Central Africa from Ma (U/Pb-Zr, Toteu et al, 1994; Pb/Pb-Zr, Morin et al, 1991) to 1742 Ma in Cameroon (Ar/Ar-Bt, Owona, 2008).…”

Section: Discussionmentioning

confidence: 99%

“…Dynamic recrystallizations features define S 2 -C 3 structures and S 3 schistosities. The coexistence of quartz GBM to SGAR and feldspars kinked, SGR to GBM and amphibole SGR dynamic recrystallizations attest that shear zone emplaced under amphibolite to granulite conditions, ranging from 500 to 850 °C (Kurse et al, 2001;Passchier & Trouw, 2005;Stipp et al, 2002;Zibra, 2010Zibra, , 2012Zibra et al, 2012). P-T paths from the WCAFB define amphibolite to granulite conditions.…”

Section: Discussionmentioning

confidence: 99%

“…New and small grains with undulated boundaries disappeared for idiomorphic blasts with triple points replacing the old core minerals. Details of dynamic recrystallization stages and mechanisms can be consulted in Kurse et al (2001), Stipp et al (2002), Passchier and Trouw (2005), Zibra (2010Zibra ( , 2012, Zibra et al (2012). If these assertions are accepted, plastic recrystallizations define a reworked deformation affecting primary minerals such as porphyroclasts and porphyroblasts.…”

Section: Methodsmentioning

confidence: 99%

“…Since last decades, significant progress has been made in understanding the microstructural evolution of crystallizing or melting rocks in natural and numerical experiments and tectonic models (e.g. While, 1973While, , 1977Urai et al, 1986;Vernon, 2000;Hirth et al, 2001;Stipp et al, 2002;Passchier & Trouw, 2005;Zibra et al, 2010Zibra et al, , 2012Zibra, 2012). A close spatial and temporal relationship between pluton emplacement and shear zones has been documented in various geological settings (see Rosenberg, 2004 for a review; Weinberg et al, 2004).…”

Section: Introductionmentioning

confidence: 99%

See 2 more Smart Citations

Evidence of Quartz, Feldspar and Amphibole Crystal Plastic Deformations in the Paleoproterozoic Nyong Complex Shear Zones Under Amphibolite to Granulite Conditions (West Central African Fold Belt, SW Cameroon)

Owona¹,

Ondoa²,

Ekodeck³

2013

JGG

View full text Add to dashboard Cite

The Paleoproterozoic is characterised by a global-scale period of crust formation, extensive mafic to granitic magmatism, crustal reworking and intracrustal partial melting. Since a dramatic strength drop is associated with the presence of melt in crystallising or melting rocks, Paleoproterozoic continental deformation is thought to have been largely accommodated by shearing of high-grade gneisses and syntectonic granitoids. The Paleoproterozoic Nyong complex, which is made up of volumetrically dominant granitoids, metapelites and granitic gneisses, quartzites and banded iron formations; has been affected by the Eburnean/Transamazonian polyphase ductile and brittle deformation responsible of S 1/2 foliation and S 2 schistosity, L 2 stretching and mineral lineations, F 3 meso-and large-scale folds, S 2 /C 3 structures and faults. Its shear zone strain anisotropies represent a natural laboratory to study the effect of crystal plastic deformation of felsic minerals and amphibole as predicted by numerical experiments and tectonic models. This paper describes the geometry of the deformation and focus on microstructural evidence of dynamic recrystallization features that were active under granulite conditions (>800 °C, >8.5 Kbar). These thermal conditions can be extended in similar Proterozoic worldwide shear zones.

show abstract

Tracing the thermal evolution of the Corsican lower crust during Tethyan rifting

et al. 2016

View full text Add to dashboard Cite

Continental rifting requires thinning the continental lithosphere from ~120 km to <20 km by a series of processes which each impart a characteristic thermal signature to the extending lithosphere. Here high‐resolution thermochronology is used to trace the synrift thermal evolution within a lower crustal section of an upper plate hyperextended margin sampled in Corsica. Novel zircon, rutile, and apatite 206Pb/238U depth profiling coupled with garnet trace element diffusion modeling provide compelling evidence for rift‐related crustal reheating. A Jurassic thermal pulse is recorded in the footwall of the Belli Piani Shear Zone (BPSZ), where 200–180 Ma zircon 206Pb/238U overgrowth ages on Permian core populations and the preservation of stranded diffusion profiles in resorbed garnets implies the dominant footwall fabric formed as a result of high‐temperature (T ~ 800°C) ductile thinning of the lower crust. Conductive reheating of middle crustal rocks in the immediate BPSZ hanging wall, demonstrated by Jurassic apatite 206Pb/238U ages, was likely achieved by synkinematic juxtaposition against the hot footwall and wholesale conductive steepening of geothermal gradients. Subsequent rapid cooling from 180 to 160 Ma, coeval with extensional unroofing of the footwall, underscores the importance of extreme ductile thinning during crustal hyperextension. The results of this study suggest that early lithospheric‐scale depth‐dependent thinning follows an early phase of diffuse rifting and tectonic subsidence and triggers crustal reheating during early hyperextension. Continued extension results in rapid exhumation and cooling of the lower crust, extreme crustal attenuation, and mantle exhumation followed by relaxation to a steady state thermal field coeval with the start of seafloor spreading.

show abstract

Late Palaeozoic deformation of post-Variscan lower crust: shear zone widening due to strain localization during retrograde shearing

Cited by 17 publications

References 94 publications

Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

Switching deformation mode and mechanisms during subduction of continental crust: a case study from Alpine Corsica

Evidence of Quartz, Feldspar and Amphibole Crystal Plastic Deformations in the Paleoproterozoic Nyong Complex Shear Zones Under Amphibolite to Granulite Conditions (West Central African Fold Belt, SW Cameroon)

Tracing the thermal evolution of the Corsican lower crust during Tethyan rifting

Contact Info

Product

Resources

About