SHEAR ZONE DEVELOPMENT AND FRICTIONAL INSTABILITY OF FAULT GOUGE

2017 ◽  
Author(s):  
Momoko Hirata Hirata
Keyword(s):  
Shear Zone ◽  
Fault Gouge ◽  
Zone Development ◽  
Frictional Instability

Free gas distribution and basal shear zone development in a subaqueous landslide – Insight from 3D seismic imaging of the Tuaheni Landslide Complex, New Zealand

2018 ◽  
Vol 502 ◽  
pp. 231-243 ◽  
Author(s):  
Felix Gross ◽  
Joshu J. Mountjoy ◽  
Gareth J. Crutchley ◽  
Christoph Böttner ◽  
Stephanie Koch ◽  
...  
Keyword(s):  
New Zealand ◽  
Shear Zone ◽  
Seismic Imaging ◽  
3D Seismic ◽  
Gas Distribution ◽  
Free Gas ◽  
Zone Development ◽  
Basal Shear

The influence of dikes on auriferous shear zone development within granitoid intrusions: the Bourlamaque pluton, Val-d'Or district, Abitibi greenstone belt

1993 ◽  
Vol 30 (9) ◽  
pp. 1924-1933 ◽  
Author(s):  
Abdelhay Belkabir ◽  
François Robert ◽  
L. Vu ◽  
C. Hubert
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Slip Direction ◽  
Principal Stresses ◽  
Quartz Veins ◽  
Profound Influence ◽  
Complex Shear ◽  
Zone Development ◽  
Granitoid Intrusions ◽  
Geometry And Kinematics

Shear-zone-related gold–quartz veins in granitoid intrusions are commonly intimately associated with mafic dikes, which may have a profound influence on the localization, orientation, and kinematics of auriferous shear zones. The Bourlamaque pluton of the Val-d'Or district contains several economic auriferous shear zones, most of which follow and overprint diorite dikes. Mineralization in all deposits consists of quartz–tourmaline–pyrite veins in reverse- oblique orientation with a significant range of strike, dip, and slip direction. The geometry and kinematics of shear zone and vein array within the pluton is more complex than the simple conjugate pattern predicted for a deforming homogeneous intrusion. The stress tensor determined from the auriferous shear zones within the pluton indicates the same northerly-directed compression recorded by similar shear zones outside the pluton. This indicates that the complex shear zone and vein pattern within the pluton reflects the influence of diorite dikes, which acted as weak layers that were activated during subsequent deformation, showing the importance of layer anisotropy in auriferous shear zone development.The plunges of orebodies bear simple geometric relationships to the slip direction along a host shear zone: these are generally perpendicular to, or in some cases parallel to, the slip direction. Knowledge of the slip directions along activated dikes would therefore allow prediction of the possible plunge(s) of orebodies at early stages of exploration programs. Slip direction along an activated layer is controlled by the orientation of the layer with respect to the stress field and by the relative magnitudes of the three principal stresses. Using techniques developed for analysis of fault slip data, both parameters can be determined, provided there is a sufficient database, and slip direction can be predicted for activated layers of any orientations.

scholarly journals Microstructural, modal and geochemical changes as a result of granodiorite mylonitisation – a case study from the Rolovská shear zone (Čierna hora Mts, Western Carpathians, Slovakia)

Geologos ◽  
2016 ◽  
Vol 22 (3) ◽  
pp. 171-190 ◽  
Author(s):  
Roman Farkašovský ◽  
Katarína Bónová ◽  
Marián Košuth
Keyword(s):  
Shear Zone ◽  
Shear Bands ◽  
Major And Trace Elements ◽  
White Mica ◽  
Western Carpathians ◽  
Lateral Mobility ◽  
Chemical Changes ◽  
Zone Development ◽  
Zone Centre

Abstract Strong tectonic remobilisation and shear zone development are typical features of the easternmost part of the Veporicum tectonic unit in the Western Carpathians. The granodiorite mylonites in the area of the Rolovská shear zone (Čierna hora Mts) underwent a complex polystage evolution during the Hercynian and Alpine orogenies. Deformation during the latter reached greenschist facies under metamorphic conditions. Mylonites are macroscopically foliated rocks with a stretching lineation and shear bands. Structurally different mylonite types, ranging from protomylonites to ulramylonites with typical grainsize reduction from the margins towards the shear zone centre, have been assessed. The modal mineralogy of the different mylonite types changes considerably. Typical is a progressive decrease in feldspar content and simultaneously the quartz and white mica content increases from protomylonites towards the most strongly deformed ultramylonites. The deformation had a brittle character in less deformed rocks and a ductile one in more deformed tectonites. Obvious chemical changes occur in mesomylonites and ultramylonites. During mylonitisation, the original biotite granodiorite was depleted of Mg, Fe, Na, Ca and Ba, while K, Rb and mainly Si increased considerably. Other (major and trace) elements reflect erratic behaviour due to lateral mobility. Chemical changes indicate the breakdown and subsequent recrystallisation of biotite and feldspars and, in turn, the crystallisation of albite and sericite. REE decrease in ultramylonites due to the breakup of accessory minerals during deformation and alteration.

Observation of shear zone development in ring-shear apparatus with a transparent shear box

Landslides ◽  
2006 ◽  
Vol 3 (3) ◽  
pp. 239-251 ◽  
Author(s):  
Hiroshi Fukuoka ◽  
Kyoji Sassa ◽  
Gonghui Wang ◽  
Ryo Sasaki
Keyword(s):  
Shear Zone ◽  
Ring Shear ◽  
Zone Development ◽  
Ring Shear Apparatus ◽  
Shear Box

scholarly journals A Mélange of Subduction Ages: Constraints on the Timescale of Shear Zone Development and Underplating at the Subduction Interface, Catalina Schist (CA, USA)

2021 ◽  
Vol 22 (9) ◽  
Author(s):  
K. M. Harvey ◽  
S. Walker ◽  
P. G. Starr ◽  
S. C. Penniston‐Dorland ◽  
M. J. Kohn ◽  
...  
Keyword(s):  
Shear Zone ◽  
Zone Development ◽  
Catalina Schist

Geochronological evidence for repeated brittle reactivations of a pre-existing plastic shear zone: The Himdalen–Ørje deformation zone, Southern Norway

2021 ◽  
Author(s):  
Espen Torgersen ◽  
Roy Gabrielsen ◽  
Johan Petter Nystuen ◽  
Roelant van der Lelij ◽  
Morgan Ganerød ◽  
...  
Keyword(s):  
Shear Zone ◽  
Deformation Zone ◽  
Shear Zones ◽  
White Mica ◽  
Fault Gouge ◽  
Plastic Shear ◽  
Brittle Deformation ◽  
Sveconorwegian Orogen ◽  
Fault Gouges ◽  
Southern Norway

<p>It is well known that faults, once formed, become permanent weaknesses in the crust, localizing subsequent brittle strain increments. The case of repeated brittle reactivations localized along pre-existing plastic shear zones is less recognized, although this situation is frequently observed in many geologically old terranes.</p><p>We have studied the prolonged deformation history of the Himdalen–Ørje Deformation Zone (HØDZ) in SE Norway by combining K–Ar and <sup>40</sup>Ar–<sup>39</sup>Ar geochronology with structural analysis. The HØDZ consists of a large variation of deformation products from mylonites and cataclasites to pseudotachylites and fault gouge. Several generations of mylonites make up the ductile part of HØDZ, called the Ørje shear zone, a km-think SW-dipping shear zone within the late Mesoproterozoic Sveconorwegian orogen. <sup>40</sup>Ar–<sup>39</sup>Ar dating of white mica from one of these mylonites give a plateau age of c. 908 Ma, interpreted to constrain the timing of late-Sveconorwegian extensionial reactivation of the Ørje shear zone.</p><p>This mylonitic fabric is extensively reworked in a brittle fashion along the SW-dipping Himdalen fault, a 10–25 m thick fault zone of cataclasite, breccia, fault gouge and, in places, abundant pseduotachylite veins. <sup>40</sup>Ar–<sup>39</sup>Ar dating of pseduotachylite material gives several small plateaus between c. 375 and 300 Ma, whereas K-feldspar clasts from the cataclasitically deformed host rock carry a Caledonian signal (plateau at c. 435 Ma). K–Ar dating of three fault gouges constrain the timing of gouge development at c. 270 and 200 Ma. Two of the fault gouges also contain protolithic K-bearing mineral phases that overlap in age with the c. 375 Ma pseudotachylite <sup>40</sup>Ar–<sup>39</sup>Ar plateau age, consistent with field observations of the former reworking the latter.</p><p>In sum, the HØDZ records multiple Paleozoic and Mesozoic brittle reactivations of the early Neoproterozoic (and older) mylonitic Ørje shear zone. Most of the brittle deformation is interpreted to have accumulated during development of the Permian Oslo rift and its subsequent latest Triassic evolution. The suggested late Devonian (c. 375 Ma) initiation of brittle deformation does not have a clear tectonic association, but we speculate that it relates to strike-slip displacements caused by the Variscan orogen, as also suggested for the sub-parallel Tornquist zone to the south.</p>

Shear-induced permeability reduction and shear-zone development of sand under high vertical stress

2018 ◽  
Vol 238 ◽  
pp. 86-98 ◽  
Author(s):  
Sho Kimura ◽  
Hiroaki Kaneko ◽  
Shohei Noda ◽  
Takuma Ito ◽  
Hideki Minagawa
Keyword(s):  
Shear Zone ◽  
Vertical Stress ◽  
Permeability Reduction ◽  
Zone Development
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