Control of granite emplacement by regional deformation

AbstractIn this paper the authors review various applications of analysing fabric in granites from Indian cratons using anisotropy of magnetic susceptibility (AMS). First the general importance of AMS in identifying the internal fabric in massive granitoids devoid of visible foliations/lineations is highlighted. Subsequently, three important applications of AMS in granitoids are discussed. (a) The case of Godhra Granite (southern parts of the Aravalli Mountain Belt) is presented as an example of the robustness of AMS in working out the time relationship between emplacement/fabric development and regional deformation by integrating field, microstructural and magnetic data. (b) AMS orientation data from Chakradharpur Granitoid (eastern India) are compared with field-based information from the vicinity of the Singhbhum Shear Zone to highlight the use of AMS in kinematic analysis and vorticity quantification of syntectonic granitoids. (c) Magnetic fabric orientations from the Mulgund Granite (Dharwar Craton) are presented to document the application of AMS in recognizing superposed deformation in granitoids. Moreover, AMS data from Mulgund Granite are also compared with data from another pluton of similar age (c. 2.5 Ga) from the Dharwar Craton (Koppal Granitoid; syenitic composition). This highlights the use of AMS from granitoids of similar absolute ages in constraining the age of regional superposed deformation.

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Famenno-Carboniferous (370-320 Ma) strike slip tectonics monitored by syn-kinematic plutons in the French Variscan belt (Massif Armoricain and French Massif Central)

BSGF - Earth Sciences Bulletin ◽

10.2113/gssgfbull.180.3.231 ◽

2009 ◽

Vol 180 (3) ◽

pp. 231-246 ◽

Cited By ~ 11

Author(s):

Patrick Rolin ◽

Didier Marquer ◽

Michel Colchen ◽

Charles Cartannaz ◽

Alain Cocherie ◽

...

Keyword(s):

Large Scale ◽

Western Europe ◽

Shear Zones ◽

Strike Slip ◽

Variscan Belt ◽

French Massif Central ◽

Massif Central ◽

Granite Emplacement ◽

Regional Deformation ◽

Dextral Shear

AbstractThe Variscan continental collision has led to the development of large strike-slip shear zones in western Europe. Our study focuses on the regional deformation and shear zone patterns in the Massif Armoricain and the French Massif Central. The synthesis of granite emplacement ages associated to granite deformation fields, allow us to propose a geodynamic model for the tectonic evolution of this part of the Variscan belt between 370 Ma – 320 Ma (Late Devonian – Namurian).After the first steps of the continental subduction-collision, leading to high temperature and anatexis associated with N-S shortening at 380-370 Ma (Frasnian to Famennian), the southern part of the Massif Armoricain and western part of French Massif Central underwent large dextral shearing along N100-N130 trending shear zones up to early Visean time. These large-scale displacements progressively decreased at around 350-340 Ma, during the first emplacements of biotite bearing granites (Moulins-les Aubiers-Gourgé massif and Guéret massif intrusions).During middle Visean times, the shortening axis direction rotated towards a NNE-SSW direction implying changes in the regional deformation field. The occurrence of N070-N100 sinistral and N110-N130 dextral conjugate shear zones within leucogranites are related to that time. Finally, new N150-N160 dextral shear zones appeared in middle to late Visean times: as for examples, the Parthenay and the Pradines shear zones in the SE Massif Armoricain and the Millevaches massif, respectively. These shear zones were conjugated to the sinistral N020 Sillon Houiller in the French Massif Central. They reflect large scale brittle continental indentation in the French Variscan belt during the middle to late Visean.

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Granite emplacement and its relation with regional deformation in the Aravalli Mountain Belt (India)—inferences from magnetic fabric

Journal of Structural Geology ◽

10.1016/j.jsg.2005.06.004 ◽

2005 ◽

Vol 27 (11) ◽

pp. 2008-2029 ◽

Cited By ~ 61

Author(s):

Manish A. Mamtani ◽

R.O. Greiling

Keyword(s):

Magnetic Fabric ◽

Granite Emplacement ◽

Regional Deformation ◽

Mountain Belt

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Late Pan-African granite emplacement during regional deformation, evidence from magnetic fabric and structural studies in the Hammamat–Atalla area, Central Eastern Desert of Egypt

Journal of African Earth Sciences ◽

10.1016/j.jafrearsci.2014.02.015 ◽

2014 ◽

Vol 99 ◽

pp. 109-121 ◽

Cited By ~ 12

Author(s):

R.O. Greiling ◽

H. de Wall ◽

M.F. Sadek ◽

C. Dietl

Keyword(s):

Eastern Desert ◽

Magnetic Fabric ◽

Structural Studies ◽

Granite Emplacement ◽

Regional Deformation ◽

Central Eastern Desert ◽

Pan African ◽

Central Eastern

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Late Caledonian granitoids and timing of deformation in the Iapetus suture zone of eastern Ireland

Geological Magazine ◽

10.1017/s0016756800015946 ◽

1987 ◽

Vol 124 (2) ◽

pp. 135-142 ◽

Cited By ~ 23

Author(s):

Finbarr C. Murphy

Keyword(s):

Bouguer Anomaly ◽

Suture Line ◽

Continental Collision ◽

Suture Zone ◽

Dyke Swarm ◽

Relative Timing ◽

Early Devonian ◽

Granite Emplacement ◽

Regional Deformation ◽

Magnetic Signature

AbstractLate Caledonian granitoids, (c. 400 Ma) in the zone of the Iapetus suture provide a datum against which current models for the relative timing of deformation can be tested. One such granitoid adjacent to the proposed suture ‘line’ in eastern Ireland is now buried by an Upper Palaeozoic cover. It is identified geophysically by a negative Bouguer anomaly with no magnetic signature, and geologically by a hypabyssal dyke swarm and hornfels metamorphism. The timing of intrusion of the granitoid is shown to have occurred during the continuing end-Silurian/early-Devonian deformation. Other members of this widespread suite in Ireland show features consistent with diapiric intrusion during the later stages of the deformation. This evidence brackets the age of regional deformation as continuing during granite emplacement and cooling (c. 400 Ma). The unifying characteristics of the straddling granitoid suite, coupled with a sinistrally transpressive deformation, in this broad suture zone are interpreted in terms of a continental collision which climaxed in late-Silurian/early-Devonian time.

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Carboniferous magmatism related to progressive pull-apart opening in the western French Massif Central

BSGF - Earth Sciences Bulletin ◽

10.2113/gssgfbull.185.3.171 ◽

2014 ◽

Vol 185 (3) ◽

pp. 171-189 ◽

Cited By ~ 1

Author(s):

Patrick Rolin ◽

Didier Marquer ◽

Charles Cartannaz ◽

Philippe Rossi

Keyword(s):

Shear Zones ◽

Strike Slip ◽

Fault System ◽

Normal Faults ◽

Variscan Belt ◽

French Massif Central ◽

Massif Central ◽

Granite Emplacement ◽

Regional Deformation ◽

Northern Border

AbstractThe Variscan continental collision induced the development of large crustal melting in the western French Massif Central, accompanied by emplacement and deformation of syn- to post-tectonic granites spatially related to normal and strike slip faulting. Our study focuses on the regional deformation and shear zone patterns in the Millevaches massif, one of the largest magmatic area of the French Massif Central. In this massif, the syn-tectonic intrusions are related i) to the dextral wrenching along the Treignac-Pradines shear zones and the Creuse faults system, and ii) to the coeval extension along the N000°–N020° normal faults on the western edge of the Millevaches massif (Bourganeuf and Argentat faults). The analysis of deformation and kinematics correlated to new datations of granites allow us to propose a pull-apart model to explain the tectono-magmatic evolution of this part of the Variscan belt from 350 Ma to 325 Ma. At that time, these granites intruded a “pull-apart” system bounded by two major N140°–160° dextral strike-slip zones operating in the middle continental crust during a bulk N020° regional shortening.From 325 Ma to 320 Ma, a clockwise rotation of the regional shortening axis was responsible for the late reactivation of the N020° eastern Millevaches tectonic border as a dextral fault system (Felletin-Ambrugeat fault system). This NE-SW shortening displaced the N140°–160° Creuse fault system and induced a reverse motion along the northern border of the Millevaches massif (St-Michel-de-Veisse fault). This Visean tectono-magmatic event induced the late exhumation of the Millevaches massif with respect to surrounding units and favoured the widespread granite emplacement in this part of the Variscan belt.

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