Deep ductile shear zone facilitates near‐orthogonal strike‐slip faulting in a thin brittle lithosphere

2020 ◽  
Author(s):  
Chao Liang ◽  
Jean‐Paul Ampuero ◽  
Daniel Pino Muñoz
Keyword(s):  
Shear Zone ◽  
Strike Slip ◽  
Ductile Shear Zone ◽  
Ductile Shear

scholarly journals Polyphase deformation along the South Bohemian Batholith-Moldanubian nappes boundary – The Freyenstein Fault System (Bohemian Massif/Austria)

2020 ◽  
Vol 113 (1-2) ◽  
pp. 139-153
Author(s):  
Gerit E. U. Griesmeier ◽  
Christoph Iglseder ◽  
Ralf Schuster ◽  
Konstantin Petrakakis
Keyword(s):  
Shear Zone ◽  
Bohemian Massif ◽  
Potassium Feldspar ◽  
Strike Slip ◽  
Greenschist Facies ◽  
Fault System ◽  
Ductile Shear Zone ◽  
The South ◽  
Shear Sense ◽  
Ductile Shear

AbstractThis work describes the Freyenstein Fault System, which extends over 45 km in the southeastern part of the Bohemian Massif (Lower Austria). It represents a ductile shear zone overprinted by a brittle fault located at the eastern edge of the South Bohemian Batholith towards the Moldanubian nappes. It affects Weinsberg- and a more “fine-grained” granite, interlayered aplitic granite and pegmatite dikes as well as paragneiss of the Ostrong Nappe System. The ductile shear zone is represented by approximately 500 m thick greenschist-facies mylonite dipping about 60° to the southeast. Shear-sense criteria like clast geometries, SCC`-type shear band fabrics as well as abundant microstructures show top to the south/ southsouthwest normal shearing with a dextral strike-slip component. Mineral assemblages in mylonitized granitoid consist of pre- to syntectonic muscovite- and biotite-porphyroclasts as well as dynamically recrystallized potassium feldspar, plagioclase and quartz. Dynamic recrystallization of potassium feldspar and the stability of biotite indicate upper green-schist-facies metamorphic conditions during the early phase of deformation. Fluid infiltration at lower greenschist-facies conditions led to local sericitization of feldspar and synmylonitic chloritisation of biotite during a later stage of ductile deformation. Finally, a brittle overprint by a north-south trending, subvertical, sinistral strike-slip fault that shows a normal component is observed. Ductile normal shearing along the Freyenstein Shear Zone is interpreted to have occurred between 320 Ma and c. 300 Ma. This time interval is indicated by literature data on the emplacement of the hostrock and cooling below c. 300°C inferred from two Rb-Sr biotite ages measured on undeformed granites close to the shear zone yielding 309.6 ± 3 Ma and 290.9 ± 2.9 Ma, respectively. Brittle sinistral strike-slip faulting at less than 300°C presumably took place not earlier than 300 Ma. Early ductile shearing along the Freyenstein Fault System may be genetically, but not kinematically linked to the Strudengau Shear Zone, as both acted in an extensional regime during late Variscan orogenic collapse. A relation to other major northeast-southwest trending faults of this part of the Bohemian Massif (e.g. the Vitis-Pribyslav Fault System) is indicated for the phase of brittle sinistral movement.

Tectonic significance of the northeastern Gander Zone, Newfoundland: an Acadian ductile shear zone

1981 ◽  
Vol 18 (1) ◽  
pp. 120-135 ◽  
Author(s):  
Simon Hanmer
Keyword(s):  
Shear Zone ◽  
Strike Slip ◽  
Vertical Shear ◽  
Ductile Shear Zone ◽  
Tectonic Significance ◽  
Southeastern Margin ◽  
Thrust Zone ◽  
Appalachian Orogen ◽  
Geologic Model ◽  
Ductile Shear

Penetrative deformation and granite intrusion in the northeastern Gander Zone, Newfoundland, represent a progressive Acadian event. Interference between ductile, strike–slip shearing along the southeastern margin of the Appalachian orogen and the emplacement of syntectonic granite diapirs results in the formation of a vertical, northeast–southwest strike–slip ductile shear zone where granites come to outcrop and a ductile strike–slip thrust zone where granites are absent at the surface. Sinistral movement along the vertical shear zone is compatible with recent palaeomagnetic models for the Appalachians and the British Caledonides. The constraints that the geologic model places on the symmetry of the Appalachian orogen in Newfoundland and the definition and extrapolation of the Gander tectonostratigraphic zone are discussed.

scholarly journals Kinematics and Geochronology of Late Paleozoic–Early Mesozoic Ductile Deformation in the Alxa Block, NW China: New Constraints on the Evolution of the Central Asian Orogenic Belt

Lithosphere ◽  
2021 ◽  
Vol 2021 (1) ◽  
Author(s):  
Beihang Zhang ◽  
Jin Zhang ◽  
Heng Zhao ◽  
Junfeng Qu ◽  
Yiping Zhang ◽  
...  
Keyword(s):  
Shear Zone ◽  
Shear Zones ◽  
Strike Slip ◽  
Late Paleozoic ◽  
Ductile Shear Zone ◽  
Early Mesozoic ◽  
Central Asian ◽  
Ductile Shear Zones ◽  
Dextral Shear ◽  
Ductile Shear

Abstract Strike-slip faults are widely developed throughout the Central Asian Orogenic Belt (CAOB), one of the largest Phanerozoic accretionary orogenic collages in the world, and may have played a key role in its evolution. Recent studies have shown that a large number of Late Paleozoic–Early Mesozoic ductile shear zones developed along the southern CAOB. This study reports the discovery of a NW–SE striking, approximately 500 km long and up to 2 km wide regional ductile shear zone in the southern Alxa Block, the Southern Alxa Ductile Shear Zone (SADSZ), which is located in the central part of the southern CAOB. The nearly vertical mylonitic foliation and subhorizontal stretching lineation indicate that the SADSZ is a ductile strike-slip shear zone, and various kinematic indicators indicate dextral shearing. The zircon U-Pb ages and the 40Ar/39Ar plateau ages of the muscovite and biotite indicate that the dextral ductile shearing was active during Middle Permian to Middle Triassic (ca. 269–240 Ma). The least horizontal displacement of the SADSZ is constrained between ca. 40 and 50 km. The aeromagnetic data shows that the SADSZ is in structural continuity with the coeval shear zones in the central and northern Alxa Block, and these connected shear zones form a ductile strike-slip duplex in the central part of the southern CAOB. The ductile strike-slip duplex in the Alxa Block, including the SADSZ, connected the dextral ductile shear zones in the western and eastern parts of the southern CAOB to form a 3000 km long E-W trending dextral shear zone, which developed along the southern CAOB during Late Paleozoic to Early Mesozoic. This large-scale dextral shear zone was caused by the eastward migration of the orogenic collages and blocks of the CAOB and indicates a transition from convergence to transcurrent setting of the southern CAOB during Late Paleozoic to Early Mesozoic.

Structural analysis of the Nanchang-Wanzai sinistral ductile shear zone (Jiangnan region, South China)

1991 ◽  
Vol 6 (1) ◽  
pp. 13-23 ◽  
Author(s):  
Liangshu Shu ◽  
Jacques Charvet ◽  
Yangshen Shi ◽  
Michel Faure ◽  
Dominique Cluzel ◽  
...  
Keyword(s):  
Structural Analysis ◽  
Shear Zone ◽  
South China ◽  
Ductile Shear Zone ◽  
Ductile Shear
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