Structural analysis of mylonitic rocks in the Cougar Creek Complex, Oregon–Idaho using the porphyroclast hyperbolic distribution method, and potential use of SC′-type extensional shear bands as quantitative vorticity indicators

Kurz, Gene A.; Northrup, C.J.M.

doi:10.1016/j.jsg.2008.04.003

Cited by 62 publications

(60 citation statements)

References 12 publications

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“…The Cougar Creek Complex contains dikes and small plutons that range in bulk compositions from gabbro to tonalite and their metamorphosed and deformed equivalents (Vallier, 1995;Kurz, 2001;Kurz and Northrup, 2008). Metamorphism and deformation occurred under lower-to upper-greenschist-facies conditions (Avé Lallemant, 1995;Vallier, 1995;Kurz, 2001;Kurz and Northrup, 2008;Kohn and Northrup, 2009).…”

Section: Cougar Creek Complexmentioning

confidence: 99%

U-Pb geochronology and geochemistry of intrusive rocks from the Cougar Creek Complex, Wallowa arc terrane, Blue Mountains Province, Oregon-Idaho

Kurz

Schmitz

Northrup

et al. 2011

Geological Society of America Bulletin

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Section: Cougar Creek Complexmentioning

confidence: 99%

U-Pb geochronology and geochemistry of intrusive rocks from the Cougar Creek Complex, Wallowa arc terrane, Blue Mountains Province, Oregon-Idaho

Kurz

Schmitz

Northrup

et al. 2011

Geological Society of America Bulletin

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“…The five vertical solid-lines represent the half-conjugate angles measured in central Tibet ➀ ; the Qaidam Basin ➁ ; mid-Asia ➂ ; the "Three-Rivers" ➃ ; and Indochina ➄. The four vertical dotted-lines represent the measurements (Kurz and Northrup, 2008;Zheng et al, 2009) for conjugate extensional crenulation cleavages in low-and high-strained rocks, all of which are close to the maximum value of 54.7 .…”

Section: Figurementioning

confidence: 76%

“…The angles between the conjugate shear bands provided by Kurz and Northrup (2008) show that all of them, either in high-strained or in low-strained rocks, fall into the range predicted by the MEM Criterion (the four vertical dotted-lines in Fig. 7) and also that the angle of 110 does not increase with progressive strain (Zheng et al, 2009).…”

Section: Mem-criterionmentioning

confidence: 80%

A challenge to the concept of slip-lines in extrusion tectonics

Zheng

Wang

Zhang

et al. 2011

Geoscience Frontiers

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Wide-open V-shaped conjugate strike-slip faults in Asia are typically related to extrusion tectonics. However, the tectonic model based on the slip-line theory of plasticity has some critical problems associated with it. The conjugate sets of slip-lines in plane deformation, according to the theory of plasticity should be normal to each another but, in reality, the angles between the conjugate strike-slip faults, which are regarded as slip-lines in extrusion tectonics in the eastern Mediterranean, Tibet-middle Asia, China and the Indochina Peninsular regions, are always more than 90 (on average w110 ) in the direction of contraction. Another problem is that the slip-line theory fails to explain how, in some cases, e.g., in the Anatolian area in the eastern Mediterranean, the extrusion rate is much higher than the indent rate. The two major problems are easy to solve in terms of the Maximum-Effective-Moment (MEM) Criterion that predicts that orientations of the shear zones are theoretically at an angle of 54.7 and practically at angles of 55 AE10 with the s 1 -or contractional direction. The orientations of the strike-slip faults that accommodate extrusion tectonics are, therefore, fundamentally controlled by the MEM Criterion. When extrusion is along the MEM-orientations, the extruding rate is normally higher than the indenting rate. ª 2011, China University of Geosciences (Beijing) and Peking University. Production and hosting by Elsevier B.V. All rights reserved.

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“…Fossen and Tikoff 1993;Grasemann et al 1999), and rigid clasts (Xypolias and Doutsos 2001;Bailey and Eyster 2003;Law et al 2004;Jessup et al 2007;Marques et al 2007;Kurz and Northrup 2008;Sarkarinejad and Azizi 2008;Sarkarinejad et al 2009;Zhang et al 2009;Langille et al 2010;Thigpen et al 2010), have been widely used for kinematic vorticity estimation, certain problems still exist: (1) the method using deformed dikes or veins requires distinguishing the deformation sequence of the dikes or veins, and dikes or veins in an ideal geometry are not always available;…”

Section: Methodsmentioning

confidence: 99%

Formation of Late Jurassic–Early Cretaceous metamorphic core complexes in Northeast China: insight from a structural study of the Yiwulüshan ductile detachment zone

Wang

Guo

et al. 2016

International Geology Review

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Late Jurassic to Early Cretaceous extensional structures are widespread in Northeast China and the eastern part of the Asian continent. The Yiwulüshan ductile detachment shear zone, the master ductile detachment zone of the Yiwulüshan metamorphic core complex (MCC), occurs in the northern North China Craton. This shear zone dips to the northwest on the western flank and to the southeast on the eastern flank of the MCC and consists of brittle faults, breccia, chloritized microbreccia, and ductile (mylonite) zones. The well-developed mylonitic foliation and stretching lineation are characterized by oriented minerals (quartz and feldspar) that exhibit ductile deformation, including undulose extinction, deformation bands, subgrain formations, and recrystallized grains. The shear indicators, such as asymmetric porphyroclasts, S-C fabrics, and shear bands, suggest consistent top-to-the-NW shear on both the western and eastern flanks of the MCC. Strain measurements using feldspar porphyroclasts show that the strain intensity (Es), Lode's parameter (υ), and Flinn parameter (k) range from 0.46 to 1.03, −0.23 to 0.62, and 0.23 to 1.6, respectively. Kinematic vorticity (W k ) values, estimated by the Polar Mohr diagram and the C′ methods, range from 0.61 to 0.96, with an average of 0.80, for the mylonitic deformation, and from 0.24 to 0.53, with an average of 0.37, for extensional crenulation cleavage (ecc) domains. The kinematic vorticity values, together with the regional structural background, suggest the Yiwulüshan ductile detachment zone experienced simple-shear-dominated general shearing that formed the mylonitic fabric in the early stages of extension. Later in the deformation history, pure-shear-dominated general shearing dominated when ecc developed. Strain measurements and kinematic vorticity estimates indicate that the Yiwulüshan ductile detachment zone is a lengthening-thinning shear zone. It is proposed that simple-shear-dominated general shear developed during crustal extension and that pure-shear-dominated general shear is related to the upward flow of Precambrian basement and Jurassic plutons. ARTICLE HISTORY

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Structural analysis of mylonitic rocks in the Cougar Creek Complex, Oregon–Idaho using the porphyroclast hyperbolic distribution method, and potential use of SC′-type extensional shear bands as quantitative vorticity indicators

Cited by 62 publications

References 12 publications

U-Pb geochronology and geochemistry of intrusive rocks from the Cougar Creek Complex, Wallowa arc terrane, Blue Mountains Province, Oregon-Idaho

U-Pb geochronology and geochemistry of intrusive rocks from the Cougar Creek Complex, Wallowa arc terrane, Blue Mountains Province, Oregon-Idaho

A challenge to the concept of slip-lines in extrusion tectonics

Formation of Late Jurassic–Early Cretaceous metamorphic core complexes in Northeast China: insight from a structural study of the Yiwulüshan ductile detachment zone

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