Deformed lineation in ductile shear zones: a case study from the Proterozoic fold belt of Singhbhum, eastern India

1997 ◽  
pp. 219-236
Author(s):  
Dhruba Mukhopadhyay ◽  
Durga Pada Pati
Keyword(s):  
Shear Zones ◽  
Eastern India ◽  
Fold Belt ◽  
Ductile Shear Zones ◽  
Ductile Shear ◽  
Deformed Lineation

scholarly journals The key role of µH2O gradients in deciphering microstructures and mineral assemblages of mylonites: examples from the Calabria polymetamorphic terrane

2021 ◽  
Author(s):  
Fabrizio Tursi
Keyword(s):  
Chemical Potential ◽  
Shear Zones ◽  
Chemical Potentials ◽  
Ductile Shear Zones ◽  
Mineral Assemblages ◽  
Potential Gradients ◽  
Ductile Shear ◽  
Chemical Potential Gradients

AbstractA careful petrologic analysis of mylonites’ mineral assemblages is crucial for a thorough comprehension of the rheologic behaviour of ductile shear zones active during an orogenesis. In this view, understanding the way new minerals form in rocks sheared in a ductile manner and why relict porphyroblasts are preserved in zones where mineral reactions are generally supposed to be deformation-assisted, is essential. To this goal, the role of chemical potential gradients, particularly that of H2O (µH2O), was examined here through phase equilibrium modelling of syn-kinematic mineral assemblages developed in three distinct mylonites from the Calabria polymetamorphic terrane. Results revealed that gradients in chemical potentials have effects on the mineral assemblages of the studied mylonites, and that new syn-kinematic minerals formed in higher-µH2O conditions than the surroundings. In each case study, the banded fabric of the mylonites is related to the fluid availability in the system, with the fluid that was internally generated by the breakdown of OH-bearing minerals. The gradients in µH2O favoured the origin of bands enriched in hydrated minerals alternated with bands where anhydrous minerals were preserved even during exhumation. Thermodynamic modelling highlights that during the prograde stage of metamorphism, high-µH2O was necessary to form new minerals while relict, anhydrous porphyroblasts remained stable in condition of low-µH2O even during exhumation. Hence, the approach used in this contribution is an in-depth investigation of the fluid-present/-deficient conditions that affected mylonites during their activity, and provides a more robust interpretation of their microstructures, finally helping to explain the rheologic behaviour of ductile shear zones.

Applying a general triclinic transpression model to highly partitioned brittle-ductile shear zones: A case study from the Torcal de Antequera massif, external Betics, southern Spain

2014 ◽  
Vol 68 ◽  
pp. 316-336 ◽  
Author(s):  
M. Díaz-Azpiroz ◽  
L. Barcos ◽  
J.C. Balanyá ◽  
C. Fernández ◽  
I. Expósito ◽  
...  
Keyword(s):  
Shear Zones ◽  
Southern Spain ◽  
Ductile Shear Zones ◽  
Ductile Shear

LONGEVITY OF DUCTILE SHEAR ZONES FROM DIFFUSION GEOSPEEDOMETRY OF KINEMATICALLY-SENSITIVE MINERAL INCLUSIONS

2019 ◽  
Author(s):  
William O. Nachlas ◽  
◽  
Christian Teyssier ◽  
Donna L. Whitney ◽  
Greg Hirth
Keyword(s):  
Shear Zones ◽  
Mineral Inclusions ◽  
Ductile Shear Zones ◽  
Ductile Shear

What controls the width of ductile shear zones?

2021 ◽  
pp. 229033
Author(s):  
T.K. Cawood ◽  
J.P. Platt
Keyword(s):  
Shear Zones ◽  
Ductile Shear Zones ◽  
Ductile Shear
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