Comparison of petrofabrics with composite magnetic fabrics of S–C mylonite in paramagnetic granite

Ono, Takaaki; Hosomi, Yukinobu; Arai, Hiroyoshi; Takahashi, Hideo

doi:10.1016/j.jsg.2009.04.009

Cited by 17 publications

(13 citation statements)

References 26 publications

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“…[Gleizes et al, 2001], [Gleizes et al, 2006] and [Ono et al, 2009]) show that there is a good correlation between magnetic lineation (K1) and foliation (plane normal to K3) and mineral lineation and foliation, respectively. Moreover, in these granites Km is proportional to the iron content of the iron-bearing silicates and thus it can be directly correlated to the modal content in biotite, amphibole and pyroxene.…”

Section: Petrostructural Microstructural and Kinematic Characteristimentioning

confidence: 92%

Granite intrusion in a metamorphic core complex: The example of the Mykonos laccolith (Cyclades, Greece)

et al. 2011

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The Aegean domain is a well-suited place to study the formation of metamorphic core complex (MCC) and to investigate the role of syn-tectonic granites on their development. In the northern Cyclades, the Mykonos-Delos-Rhenia MCC is characterized by the intrusion of a kilometer-scale Late Miocene pluton of I-type granitoids within a migmatitic gneiss dome. New combined AMS (anisotropy of magnetic susceptibility) and microstructural studies on the Mykonos granitoids together with recently published thermochronological data allow us to use the granitoids as strain markers.The Mykonos granitoids form a laccolith-like intrusion with a N70°E long axis. The laccolith is strongly asymmetric with an outlying root zone to the SW and a major body mainly developed to the NE. The laccolith construction is due to successive pulses of more or less differentiated magma that intruded the Cycladic Blueschist Unit. The attitude of stretching markers suggests an important (about 60°) vertical-axis local rotation phenomenon in the cycladic upper crust during the exhumation of the Mykonos MCC. Structural data suggest a four-stage evolution of the Mykonos MCC: (i) a first stage characterized by flat shearing toward the N-NE and by the formation of a domal structure in migmatitic paragneisses with multi-scale generation of folds with axes either perpendicular or parallel to the regional stretching, as a result of the interplay between regional N20°E-directed extension and EW shortening; (ii) a second stage marked by the emplacement of the Mykonos laccolith at 13.5 ± 0.3 Ma at the top of the migmatitic paragneisses; (iii) the third stage corresponding to the development of protomylonitic foliations and lineations in the whole laccolith in high to medium temperature conditions; and (iv) the late stage marked by an acceleration of the exhumation of the Mykonos MCC. This exhumation was accommodated by important rotations of upper crustal blocks. During the end of the exhumation processes, around 10 Ma, deformation localized at the top of the laccolith in semi-ductile conditions and then in brittle conditions in the major detachment plane.Our study shows that the Cycladic plutonism event had no role on the initiation of the MCC. However, the geometry of the Mykonos intrusion supports that the magmas are "sucked" into the direction of regional extension and that the intrusion of magmas has caused an acceleration of the last stages of the MCC development. This acceleration was marked by a very fast exhumation of the laccolith after its emplacement.

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Section: Petrostructural Microstructural and Kinematic Characteristimentioning

confidence: 92%

Granite intrusion in a metamorphic core complex: The example of the Mykonos laccolith (Cyclades, Greece)

et al. 2011

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“…Parés and van der Pluijm (2002) carried out detailed magnetic analysis of mudstone, slates and schists and concluded that orientation of the magnetic lineation along the tectonic extension is dependent on the original AMS fabric, lithology and the intensity of deformation. As mentioned earlier, for granitic mylonites, the magnetic fabric may represent an intermediate fabric between the 'S' and 'C' fabric (Aranguren et al, 1996;Tomezzoli et al, 2003) or weakly mimic a fabric developed at later stages (Ono et al, 2010).…”

Section: Significance Of Composite Mesoscopic and Magnetic Fabricmentioning

confidence: 86%

“…However, for granitic gneisses that have undergone a considerable amount of post-emplacement solid state deformation, especially in the Himalaya, the magnetic fabric is difficult to interpret as it can be a combined effect of various deformation episodes (Jayangondaperumal et al, 2010;Tripathi et al, 2012). Past studies have shown that for granitic mylonites, the magnetic fabric may represent an intermediate fabric between the 'S' and 'C' fabric (Aranguren et al, 1996;Tomezzoli et al, 2003) or weakly mimic a fabric developed at later stages (Ono et al, 2010). These studies confirm that for granitic gneisses, the mesoscopic and magnetic foliation may not be concordant and magnetic fabric may result from superposed deformation.…”

Section: Introductionmentioning

confidence: 99%

Composite mesoscopic and magnetic fabrics of the Paleo-Proterozoic Wangtu Gneissic Complex, Himachal Himalaya, India: Implications for ductile deformation and superposed folding of the Himalayan basement rocks

Sen

Dubey

Tripathi

et al. 2012

Journal of Geodynamics

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“…The quality of the obtained results is strongly dependent on the magnetic properties of materials, the type of fault rocks, and the number of samples used for determining the average magnetic foliation and lineation. In shear zones, the resultant maximum axis of the magnetic susceptibility ellipsoid is assumed to be parallel to the transport direction on C planes (see Parés and Van der Pluijm 2002), although case studies also indicate (1) intermediate orientations at the bisector between S and C planes (Aranguren et al 1996) and (2) opposite geometrical relationships, with k max perpendicular to the transport direction and, consequently, parallel to the intersection lineation between C and S planes (Oliva-Urcia et al 2009;Ono et al 2010). Because of these ambiguous relationships, it is extremely important to determine in each particular case the type of geometrical relationship between AMS and kinematic indicators both at the outcrop and microscopic scales (Debacker et al 2004(Debacker et al , 2010Haerinck et al 2015).…”

Section: Introductionmentioning

confidence: 99%

Multidisciplinary approach to constrain kinematics of fault zones at shallow depths: a case study from the Cameros–Demanda thrust (North Spain)

Sáinz

Román‐Berdiel

Oliva‐Urcia

et al. 2016

Int J Earth Sci (Geol Rundsch)

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Thrusting at shallow depths often precludes analysis by means of structural indicators effective in other geological contexts (e.g., mylonites, sheath folds, shear bands). In this paper, a combination of techniques (including structural analysis, magnetic methods, as anisotropy of magnetic susceptibility and paleomagnetism, and paleothermometry) is used to define thrusting conditions, deformation, and transport directions in the Cameros–Demanda thrust (North Spain). Three outcrops were analyzed along this intraplate, large-scale major structure having 150 km of outcropping length, 30 km of maximum horizontal displacement, and 5 km of vertical throw. Results obtained by means of the different techniques are compared with data derived from cross sections and stratigraphic analysis. Mixed-layer illite–smectite and vitrinite reflectance indicating deep diagenetic conditions and mature stage of hydrocarbon generation suggests shallow depths during deformation, thus confirming that the protolith for most of the fault rocks is the footwall of the main thrust. Kinematic indicators (foliation, S/C structures, and slickenside striations) indicate altogether a dominant NNW movement of the hanging wall in the western zone and NE in the eastern zone of the thrust, thus implying strain partitioning between different branches of the main thrust. The study of AMS in fault rocks (nearly 400 samples of fault gouge, breccia, and microbreccia) indicates that the strike of magnetic foliation is oblique to the transport direction and that the magnetic lineation parallelizes the projection of the transport direction onto the kmax/kint plane in sites with strong shear deformation. Paleomagnetism applied to fault rocks indicates the existence of remagnetizations linked to thrusting, in spite of the shallow depth for deformation, and a strong deformation or scattering of the magnetic remanence vectors in the fault zone. The application of the described techniques and consistency of results indicate that the proposed multidisciplinary approach is useful when dealing with thrusts at shallow crustal levels

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Comparison of petrofabrics with composite magnetic fabrics of S–C mylonite in paramagnetic granite

Cited by 17 publications

References 26 publications

Granite intrusion in a metamorphic core complex: The example of the Mykonos laccolith (Cyclades, Greece)

Granite intrusion in a metamorphic core complex: The example of the Mykonos laccolith (Cyclades, Greece)

Composite mesoscopic and magnetic fabrics of the Paleo-Proterozoic Wangtu Gneissic Complex, Himachal Himalaya, India: Implications for ductile deformation and superposed folding of the Himalayan basement rocks

Multidisciplinary approach to constrain kinematics of fault zones at shallow depths: a case study from the Cameros–Demanda thrust (North Spain)

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