Ductile Shearing in Attur Shear Zone and its Relation with Moyar Shear Zone, South India

2000 ◽  
Vol 3 (3) ◽  
pp. 361-369 ◽  
Author(s):  
B.K. Bhadra
Keyword(s):  
Shear Zone ◽  
South India ◽  
Ductile Shearing ◽  
Moyar Shear Zone

scholarly journals SHRIMP U–Pb zircon ages of granitoids adjacent to Chitradurga shear zone, Dharwar craton, South India and its tectonic implications

2015 ◽  
Vol 110 (5) ◽  
pp. 224-234 ◽  
Author(s):  
Abdulla NASHEETH ◽  
Takamoto OKUDAIRA ◽  
Kenji HORIE ◽  
Tomokazu HOKADA ◽  
Madhusoodhan SATISH–KUMAR
Keyword(s):  
Shear Zone ◽  
South India ◽  
Dharwar Craton ◽  
Tectonic Implications

The Role of a Transcrustal Shear Zone in Orogenic Gold Mineralization at the Ajjanahalli Mine, Dharwar Craton, South India

2004 ◽  
Vol 99 (4) ◽  
pp. 743-759 ◽  
Author(s):  
J. Kolb ◽  
A. Hellmann ◽  
A. Rogers ◽  
S. Sindern ◽  
T. Vennemann ◽  
...  
Keyword(s):  
Shear Zone ◽  
South India ◽  
Gold Mineralization ◽  
Dharwar Craton ◽  
Orogenic Gold ◽  
Orogenic Gold Mineralization

Pan-African charnockite formation in Kerala, South India

1992 ◽  
Vol 129 (3) ◽  
pp. 257-264 ◽  
Author(s):  
A. K. Choudhary ◽  
N. B. W. Harris ◽  
P. van Calsteren ◽  
C. J. Hawkesworth
Keyword(s):  
Sri Lanka ◽  
Shear Zone ◽  
South India ◽  
Metamorphic Event ◽  
Isotopic Ratios ◽  
Sr Isotope ◽  
Pan African ◽  
Granulite Metamorphism ◽  
History Of

AbstractSm-Nd mineral ages of gneisses and associated granulites from the Ponmudi incipient charnockite locality (South India) indicate that granulite metamorphism occurred at, or shortly after, 558 Ma. Proterozoic ages recorded by garnet separates reflect a detrital age or an earlier metamorphic event preserved by inclusions within garnet. The age of post-metamorphic uplift (440–460 Ma) is constrained by Sr isotope equilibration between biotite and plagioclase. Since charnockite formation and subsequent uplift north of the Palghat-Cauvery shear zone had terminated by earliest Proterozoic time, these results confirm two distinct periods of granulite formation in South India and suggest that the Palghat-Cauvery shear zone represents the boundary between two blocks of strongly contrasting geological histories. Both incipient charnockite formation and subsequent uplift at Ponmudi may be correlated with the tectonothermal evolution of the Highlands Group in Sri Lanka. The similarity between Nd and Sr model ages for charnockites and gneisses from Ponmudi indicates that no significant Rb-Sr fractionation has occurred during the crustal history of these incipient charnockites. Pb isotopic ratios suggest that Th-U ratios were fractionated during charnockite formation at about 500 Ma. In contrast to charnockites found north of the Palghat-Cauvery shear zone, fractionation of U-Pb during the Archaean did not occur in the Ponmudi granulites.

Exhumation of HP/UHP rocks by normal ductile shearing on top of the Eocene extruding wedge

2020 ◽  
Author(s):  
Michel Ballèvre ◽  
Paola Manzotti
Keyword(s):  
Shear Zone ◽  
Kinematic Model ◽  
Geological Mapping ◽  
Greenschist Facies ◽  
Western Boundary ◽  
Frontal Part ◽  
Ductile Shearing ◽  
Shear Sense ◽  
Eclogite Facies ◽  
Ductile Shear

<p>A popular model for the exhumation of HP-UHP rocks is the ‘extruding wedge’ model, where a crustal slice is bounded at its base by a ‘thrust shear-sense’ fault and to the top by a ‘normal shear-sense’ fault. In the Western Alps, the late Eocene Combin Shear Zone (CSZ) allowed extrusion of a wedge made by the Briançonnais-Piemonte-Liguria (‘Penninic’) stack.</p><p>Geological mapping has established the geometry and continuity of the CSZ from the frontal part of the Dent Blanche Tectonic System to the western boundary of the Sesia Zone. The CSZ has been cut during the Miocene by the brittle Aosta-Ranzola Fault, with an estimated downthrow of the northern block of c. 2.5 km with respect to the southern block. Consequently, the sections observed north (Monte Rosa) and South (Gran Paradiso) of the Aosta Fault display different structural levels in the Alpine nappe stack. The CSZ has been folded (Vanzone phase) during the final part of its history (i.e. when displacement along the CSZ was no more taking place), due to the indentation of the Adriatic mantle. This offers us the unique opportunity to study the change in deformation mechanisms along the shear zone (for a distance parallel to its displacement of about 50 km).</p><p>Salient characteristics of the CSZ are the following. (i) The thickness of the ductile shear zone increases from NW (frontal part of the Dent Blanche) to SE (frontal part of the Sesia Zone), from a few hundred metres to several kilometres. The type of lithologies pervasively reworked by the ductile shear changes along strike (dominantly calcschists from the topmost oceanic units in the Combin Zone, possibly up to the whole of the ‘Gneiss Minuti’ in the frontal Sesia Zone). (ii) The main ductile deformation along the CSZ was taking place at greenschist-facies conditions, overprinting eclogite-facies to greenschist-facies deformations of Cretaceous to Middle Eocene age. The CSZ is cutting and reworking eclogite-facies structures developed in its hangingwall (Sesia) as well as in its footwall (Zermatt). (iii) Ductile displacement along the CSZ is associated with the development in its footwall of south-east-verging, kilometre-scale, folds (Mischabel phase). The sedimentary sequences of the Pancherot-Cime Bianche-Bettaforca Unit may be used to estimate the minimum amount of ‘normal shear sense’ displacement of the order of 15-20 km.</p><p>A kinematic model integrating slab roll-back, ‘thrust shear-sense’ at the base and ‘normal shear-sense’ displacement on top of the Eocene eclogite-facies stack will be presented.</p>

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