Changes

'''Strain partitioning''' is commonly referred to as a [[Deformation (engineering)|deformation]] process in which the total [[Deformation (mechanics)|strain]] experienced on a rock, area, or region, is heterogeneously distributed in-terms of the strain intensity and strain type (i.e. [[Shear (geology)|pure shear]], [[simple shear]], [[dilation (geology)|dilatation]]).<ref name=Jones&Tanner>Jones, Richard; Tanner, P.W. Geoff (1995). "Strain partitioning in transpression zones". Journal of Structural Geology 17 (6): 793–802.</ref><ref name=Carreras>Carreras, Jordi; Cosgrove, John; Druguet, Elena (2013). "Strain partitioning in banded and/or anisotropic rocks: Implications for inferring tectonic regimes". Journal of Structural Geology 50: 7–21. doi:10.1016/j.jsg.2012.12.003.</ref><ref name=Fossen>Fossen, Haakon (2012). Structural Geology. New York, USA: Cambridge University Press. ISBN 978-0-521-51664-8.</ref> This process is observed on a range of scales spanning from the grain - [[crystal]] scale to the [[tectonic plate|plate]] - lithospheric scale and occurs in both the brittle and plastic deformation regimes.<ref name=Jones&Tanner /><ref name=Carreras /> The manner and intensity by which strain is distributed is controlled by a number of factors listed below.<ref name=Carreras />

'''Strain partitioning''' is commonly referred to as a [[deformation]] process in which the total [[Wikipedia:Deformation (mechanics)|strain]] experienced on a rock, area, or region, is heterogeneously distributed in-terms of the strain intensity and strain type (i.e. [[Wikipedia:Shear (geology)|pure shear]], [[simple shear]], [[Wikipedia:dilation (geology)|dilatation]]).<ref name=Jones&Tanner>Jones, R., and P. W. G. Tanner, 1995, Strain partitioning in transpression zones: Journal of Structural Geology, vol. 17, no. 6, 793–802.</ref><ref name=Carreras>Carreras, J., J. Cosgrove, and E. Druguet, 2013, Strain partitioning in banded and/or anisotropic rocks: Implications for inferring tectonic regimes: Journal of Structural Geology, vol. 50, 7–21. doi:10.1016/j.jsg.2012.12.003.</ref><ref name=Fossen>Fossen, H., 2012, Structural Geology. Cambridge University Press: New York, USA. ISBN 978-0-521-51664-8.</ref> This process is observed on a range of scales spanning from the grain - [[crystal]] scale to the [[Cambridge University Presstectonic plate|plate]] - lithospheric scale and occurs in both the brittle and plastic deformation regimes.<ref name=Jones&Tanner /><ref name=Carreras /> The manner and intensity by which strain is distributed is controlled by a number of factors listed below.<ref name=Carreras />

==Factors which influence strain partitioning<ref name=Jones&Tanner /><ref name=Carreras /><ref name=Fossen />==

==Factors which influence strain partitioning<ref name=Jones&Tanner /><ref name=Carreras /><ref name=Fossen />==

==Superposition of individual strain components==

==Superposition of individual strain components==

The superposition of individual strain components can be expressed at the tectonic scale involving oblique convergent margins and transpression / transtension tectonic regimes.<ref name=Jones&Tanner />

The superposition of individual strain components can be expressed at the tectonic scale involving oblique convergent margins and transpression / transtension tectonic regimes.<ref name=Jones&Tanner />

===Oblique convergent margins===

===Oblique convergent margins===

[[File:Obconv2.jpeg|500px|thumbnail|right|Block diagram illustrating strain partitioning at an oblique [[Convergent boundary|convergent margin]]. The obliquity of plate convergence (blue arrows) induces stress components that are normal to the margin (yellow arrow) and parallel to the margin (green arrow). Elevated magnitudes of the arc parallel component induces horizontal translation (red arrows) between the wedge and the backstop. Adapted and modified from Platt, 1993.<ref name=Platt93 /> please click on the figure for a better image]]

[[File:Obconv2.jpeg|500px|thumbnail|right|Block diagram illustrating strain partitioning at an oblique [[Convergent boundary|convergent margin]]. The obliquity of plate convergence (blue arrows) induces stress components that are normal to the margin (yellow arrow) and parallel to the margin (green arrow). Elevated magnitudes of the arc parallel component induces horizontal translation (red arrows) between the wedge and the backstop. Adapted and modified from Platt, 1993.<ref name=Platt93 /> please click on the figure for a better image]]

Convergent margins where the angle of subduction is oblique will often result in the partitioning of strain into an arc parallel component (accommodated by strike slip faults or shear zones) and an arc normal component (accommodated through [[thrust fault]]s).<ref name=Platt93>Platt, J.P. (1993). "Mechanics of Oblique Convergence". Journal of Geophysical Research 98 (B9): 16,239–16,256.</ref><ref name=McCaffery92>McCaffrey, Robert (1992). "Oblique Plate Convergence, Slip Vectors, and Forearc Deformation". Journal of Geophysical Research 97 (B6): 8905–8915.</ref> This occurs as a response to shear stress exerted at the base of the overriding plate that is not perpendicular to the plate margin.<ref name=Platt93 /><ref name=Platt93 /><ref name=McCaffery92 /><ref name=Styron>Syron, Richard; Taylor, Michaeal; Murphy, Michael (2011). "Oblique convergence, arc-parallel extension, and the role of strike-slip faulting in the High Himalaya". Geosphere 7 (2): 582–596. doi:10.1130/GES00606.1.</ref>

Convergent margins where the angle of subduction is oblique will often result in the partitioning of strain into an arc parallel component (accommodated by strike slip faults or shear zones) and an arc normal component (accommodated through [[thrust fault]]s).<ref name=Platt93>Platt, J.P. (1993). "Mechanics of Oblique Convergence". Journal of Geophysical Research 98 (B9): 16,239–16,256.</ref><ref name=McCaffery92>McCaffrey, Robert (1992). "Oblique Plate Convergence, Slip Vectors, and Forearc Deformation". Journal of Geophysical Research 97 (B6): 8905–8915.</ref> This occurs as a response to shear stress exerted at the base of the overriding plate that is not perpendicular to the plate margin.<ref name=Platt93 /><ref name=Platt93 /><ref name=McCaffery92 /><ref name=Styron>Syron, Richard; Taylor, Michaeal; Murphy, Michael (2011). "Oblique convergence, arc-parallel extension, and the role of strike-slip faulting in the High Himalaya". Geosphere 7 (2): 582–596. doi:10.1130/GES00606.1.</ref>

====Fundamental factors which control strain partitioning within oblique orogens<ref name=Platt93 /><ref name=McCaffery92 />====  

====Fundamental factors which control strain partitioning within oblique orogens<ref name=Platt93 /><ref name=McCaffery92 />====  

*'''Stress Orientation''':[[Subduction]] angle - Increased subduction angle increases arc parallel component<ref name=Platt93 /><ref name=McCaffery92 />

*'''Stress Orientation''': [[Subduction]] angle - Increased subduction angle increases arc parallel component<ref name=Platt93 /><ref name=McCaffery92 />

*'''Rheology and Anisotropy''':Mechanical properties of the wedge: (Coulomb vs plastic) influences wedge geometry<ref name=Platt93 /><ref name=McCaffery92 />

*'''Rheology and Anisotropy''': Mechanical properties of the wedge: (Coulomb vs plastic) influences wedge geometry<ref name=Platt93 /><ref name=McCaffery92 />

*'''Boundary Conditions''': Friction and geometry between the backstop and wedge<ref name=McCaffery92 /><ref name=Platt93 />

*'''Boundary Conditions''': Friction and geometry between the backstop and wedge<ref name=McCaffery92 /><ref name=Platt93 />

The [[Himalaya]] is a strain partitioned orogen which resulted from the oblique convergence between India and Asia.<ref name=Murphy2014>Murphy, M.A.; Taylor, M.H.; Gosse, J.; Silver, R.P.; Whipp, D.M.; Beaumont, C. (2014). "Limit of strain partitioning in the Himalaya marked by large earthquakes in western Nepal". Nature Geoscience 7 (1): 38–42. doi:10.1038/NGEO2017.</ref> Convergence between the two landmasses persists today at a rate of 2&nbsp;cm/yr.<ref name=Murphy2014 /> The obliquity of plate convergence increases toward the western portion of the orogen, thus inducing a greater magnitude of strain partitioning within the western Himalaya than in the central.<ref name=Murphy2014 />

The [[Himalaya]] is a strain partitioned orogen which resulted from the oblique convergence between India and Asia.<ref name=Murphy2014>Murphy, M.A.; Taylor, M.H.; Gosse, J.; Silver, R.P.; Whipp, D.M.; Beaumont, C. (2014). "Limit of strain partitioning in the Himalaya marked by large earthquakes in western Nepal". Nature Geoscience 7 (1): 38–42. doi:10.1038/NGEO2017.</ref> Convergence between the two landmasses persists today at a rate of 2&nbsp;cm/yr.<ref name=Murphy2014 /> The obliquity of plate convergence increases toward the western portion of the orogen, thus inducing a greater magnitude of strain partitioning within the western Himalaya than in the central.<ref name=Murphy2014 />

Table below shows relative velocities of India's convergence with Asia. The lateral variability in velocity between the central and marginal regions of the orogen sugest strain is partitioned due to oblique convergence.<ref name=Styron /><ref name=Murphy2014 />  

Table below shows relative velocities of India's convergence with Asia. The [[lateral]] variability in velocity between the central and marginal regions of the orogen sugest strain is partitioned due to oblique convergence.<ref name=Styron /><ref name=Murphy2014 />  

{| class="wikitable"

{| class="wikitable"

|-

|-

=== Example ===

=== Example ===

Rocks that contain incompetent (mechanically weak) minerals such as micas and more competent (mechanically stronger) minerals such as quartz or feldspars, may develop a shear band fabric.<ref name=GoodwinTikoff /><ref name=Japan /> The [[incompetent mineral]]s will preferentially form the C-surfaces and competent minerals will form along the S-surfaces.<ref name=GoodwinTikoff /><ref name=Japan />

Rocks that contain incompetent (mechanically weak) minerals such as micas and more competent (mechanically stronger) minerals such as [[quartz]] or feldspars, may develop a shear band fabric.<ref name=GoodwinTikoff /><ref name=Japan /> The [[incompetent mineral]]s will preferentially form the C-surfaces and competent minerals will form along the S-surfaces.<ref name=GoodwinTikoff /><ref name=Japan />

==Individual deformation mechanisms==

==Individual deformation mechanisms==