A new estimate of the conditions for transition from basal 〈a〉 to prism [c] slip in naturally deformed quartz

Okudaira, Takamoto; Takeshita, Toru; Hara, Ikuo; Ando, Jun–ichi

doi:10.1016/0040-1951(95)00039-4

Cited by 129 publications

(67 citation statements)

References 30 publications

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“…Thermal conditions of this intracrystalline flow are consistent with the metamorphic evolu tion described previously (e.g. Okudaira et al 1995;Kurz et al 2002;Toy et al 2008).…”

Section: Kinematic and Deformation Analysessupporting

confidence: 70%

“…Subgrain boundaries lying at a low angle to coaxes are consistent with intracrystalline flow parallel to the (0001) quartz basal plane. Stereographic projection of subgrain boundary poles (nSBG) has been considered an approximation to the distribution of quartz a-axes (Bouchez 1978;Trepied et al 1980;Okudaira et al 1995). Crystallographic fabrics were processed using Stere032 v.l.O.l software (ROller & Trepmann 2008).…”

Section: Kinematic and Deformation Analysesmentioning

confidence: 99%

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Upper crust reworking during gravitational collapse: the Bembibre–Pico Sacro detachment system (NW Iberia)

Barreiro

Catalán

Fernández

et al. 2010

JGS

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The kinematics of the basal allochthon in the SW of the O rdenes Complex is analysed to constraint its evolution during collisional and postcollisional stages of the Variscan orogeny. Two distinct sequences have been identified in the basal allochthon of this sector: the upper and lower sequences, in close correlation with the subdivision of the basal allochthon in the Malpica-Tui Complex. Three main tectonic episodes have been established in the basal allochthon: a high-pressure event related to continental subduction, a mesozonal event of regional exhlUllation by thrusting and reclUllbent fo lding, and a regional-scale extensional episode that resulted in the development of the Bembibre -Pico Sacro detachment system. The Bembibre-Pico Sacro system rejuvenated pre-existing shear zones, whose weakness favoured the nucleation of the detachments. Shear zones associated with the detachments overprinted the previous tectonic fabrics lUlder conditions ranging fr om lower amphibolite to greenschist fa cies, and with heterogeneously distributed ductile to brittle defonnation. The detachment system is coeval with late oTOgenic collapse and widespread magmatism, and represents its upper CTUstal expression. It correlates with mid-and lower crustal flow and the development of gneiss domes at depth in such a way that the basal allochthon can be considered a rh eological bOlUldary between the more rigid allochthonous sequences above and the more viscous Schistose Domain and autochthon below.Continental lithosphere is characterized by cumulative gwwth during orogenic periods. Long-term persistence of the structural architecture, particularly shear zones and faults, and the over lapping of fabrics, metamorphic events and magmatic episodes, determines the -way in which the lithosphere reacts to every new tectonothermal event (Neil & Houseman 1997;Holdsworth et al. 2001;Houseman & Molnar 2001). The existence of mechanical discontinuities and the variation of lithospheric thermal state seem to be essential controls that potentia11y shape subsequent episodes Holdsworth et al. 1997). Regional studies in co11isional scenarios on tectonic rene-wal of both discrete structures (reactivation) and, at a larger scale, litho spheric or crustal volmnes (reworking) are critical to under standing the rheological behaviom of an orogenic belt with time.In this context, the geodynamic evolution of the basal a11och thon in the NW Iberian Massif is examined. The basal a11ochtho nous lUlits are key pieces of the intricate and long-standing Va riscan orogenic puzzle. They represent the outermost edge of the Gondwana supercontinent, having lUldergone distinct tecto nothermal events related to the continental subduction (Dl) and subsequent co11isional deformation (D2) during the Va riscan orogeny. However, their role dming late orogenic extensional co11apse (D3) remains obscme. Here we focus on this third event (D3), dming which regional-scale extensional detachments par tia11y rejuvenated previous structures and dominated the defor mation o...

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“…Thermal conditions of this intracrystalline flow are consistent with the metamorphic evolu tion described previously (e.g. Okudaira et al 1995;Kurz et al 2002;Toy et al 2008).…”

Section: Kinematic and Deformation Analysessupporting

confidence: 70%

Section: Kinematic and Deformation Analysesmentioning

confidence: 99%

Upper crust reworking during gravitational collapse: the Bembibre–Pico Sacro detachment system (NW Iberia)

Barreiro

Catalán

Fernández

et al. 2010

JGS

View full text Add to dashboard Cite

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“…The diagrams obtained (Fig. 5b) show asymmetric single girdles which suggest temperatures in the range 300±6008C (Gapais, 1989;Okudaira et al, 1995). The asymmetry of the girdles is also consistent with a left-lateral sense of movement.…”

Section: Structural Featuressupporting

confidence: 51%

Three-dimensional shape and emplacement of the Cardenchosa deformed pluton (Variscan Orogen, southwestern Iberian Massif)

Simancas

Galindo-Zaldı́var

Azor

2000

Journal of Structural Geology

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The Cardenchosa pluton is a Lower Carboniferous Variscan granite located in the southwestern Iberian Massif. It intruded along the contact between the Sierra Albarrana and Azuaga tectonic units. To the northwest the pluton connects with the leftlateral Azuaga fault. The pluton appears in the footwall of the low-angle normal Casa del CafeÂ fault, which crops out to the west of the granite. Gravimetric modelling shows the pluton to have a¯at bottom at a depth of 2 km. Strain analysis of postemplacement deformation of the pluton indicates that: (a) the deformation of the pluton accommodates the displacement of the Azuaga fault; and (b) the pluton prior to the solid state deformation was a lens-shaped laccolith of approximately 10 km diameter and 2 km thickness. The Cardenchosa pluton was a single pulse of magma trapped in a rheological discontinuity of the upper crust (the contact between the Sierra Albarrana and Azuaga units). The magma would ascend through dikes since no root has been detected. The tectonic scenario during the intrusion was one of regional extension. #

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“…The quartz C-axes distribution happens predominantly according to the Z-axis of the finite strain ellipsoid, suggesting the activation of basal planes. Based on the studies by Simpson (1986), FitzGerald andStünitz (1993) and Okudaira et al (1995), these characteristics allow the maximum temperature estimation at 550°C for deformation in the studied shear zones. This is compatible with the minimum temperature required for ductile deformations of K-feldspars, i.e.…”

Section: Discussionmentioning

confidence: 99%

Tectonic inversion of compressional structures in the Southern portion of the Paramirim Corridor, Bahia, Brazil

et al. 2015

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ABSTRACT:The Paramirim Corridor represents the maximum inversion zone of the Paramirim Aulacogen. Reverse-to-reverse dextral shear zones and various types of folds dominate such corridor. These structures reflect a stress field that is WSW-ENE oriented, developed in units of Aulacogen basement, as well as in the Lagoa Real Intrusive Suite, of Statherian age, in Espinhaço and São Francisco supergroups, of Statherian-Tonian and Cryogenian ages, respectively, and in the Macaúbas-Santo Onofre Group, of Tonian age at the most. A rich collection of extensional structures truncate compressional structures of the Paramirim Corridor, characterized by normal shear zones and foliation, which is sometimes mylonitic, down-dip stretching lineation, drag folds, traction fractures and S/C structures. In these shear zones, quartz occurs truncated by the foliation, while feldspars are fractured and altered to white mica. Distribution of the quartz c-axes is at a maximum of 14° from the Z-axis. Thus, it suggests that the deformation activated mainly the basal glide planes in the direction. The paleostress study using the Win-Tensor software demonstrated that the regimen ranged between radial and pure distention. The S 1 direction oscillated around a vertical trend, while s 3 was sub-horizontal, with a predominant N230-050° direction. Ar-Ar ages in biotite obtained from the extensional shear zones ranged from 480 and 490 Ma. Together, data obtained for the structures associated with the late extensional regimen described in the present study suggest that its nucleation is associated with distal and brittle-ductile sectors of the gravitational collapse zone of Araçuaí-West Congo Orogen.KEYWORDS: Shear Zone; Paramirim Corridor; Gravitational Collapse. RESUMO: O Corredor do Paramirim representa a zona de máxima inversão do Aulacógeno do Paramirim, no qual predominam zonas de cisalhamento reversas-reversas destrais e vários tipos de dobras. Essas estruturas refletem um campo de tensão segundo WSW-ENE, os quais se desenvolvem nas unidades de embasamento do Aulacógeno, assim como na Suíte Intrusiva Lagoa Real, de idade estateriana, nos supergrupos Espinhaço e São Francisco, de idades estateriana-toniana e criogeniana, respectivamente, bem como no grupo Macaúbas-Santo

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A new estimate of the conditions for transition from basal 〈a〉 to prism [c] slip in naturally deformed quartz

Cited by 129 publications

References 30 publications

Upper crust reworking during gravitational collapse: the Bembibre–Pico Sacro detachment system (NW Iberia)

Upper crust reworking during gravitational collapse: the Bembibre–Pico Sacro detachment system (NW Iberia)

Three-dimensional shape and emplacement of the Cardenchosa deformed pluton (Variscan Orogen, southwestern Iberian Massif)

Tectonic inversion of compressional structures in the Southern portion of the Paramirim Corridor, Bahia, Brazil

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