Multistage emplacement of a composite intrusion: magnetic fabric and zircon U–Pb age of the Parnamirim Pluton, NE Brazil
Charles Henrique Fernandes Sales das NevesSérgio P. NevesValderez P. FerreiraAlcídes N. SialBheatriz LimaDiego H. ArdilaR. Siqueira
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Orogeny
Lineation
Batholith
Transpression
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The north–north‐east‐trending (NNE) shear zones, which are defined by the Jiekou shear zone and Huangmao shear zone, are located in the eastern Jiangnan Orogen. This article provides kinematics, geochronological data, and dynamics on the Jiekou and Huangmao shear zones and serves as a reference for understanding the tectonic evolution in the South China Block during the Early Palaeozoic orogeny. All shearing signatures show that the Huangmao shear zone is dextral, and the Jiekou shear zone is sinistral. Both shear zones have certain genetic connections. The rocks from the Jiekou and Huangmao shear zones are metamorphosed and deformed into protomylonite and mylonite. Results of the deformation fabrics of feldspar and quartz and quartz c ‐axis fabric analysis indicate that the ductile deformation temperatures of the Jiekou shear zone sinistral shearing are ~400–500°C. Dextral shearing with medium–high temperature (450–550°C) is mainly recorded in the Huangmao shear zone. In combination with the previous geochronology, NNE‐trending sinistral and dextral shearing in the eastern Jiangnan Orogen occurred at 465–430 Ma, coeval with the Early Palaeozoic orogeny. Therefore, the geodynamics of the NNE‐trending shear zones is related to a major strain transformation from NW to WNW, which is remotely affected by the intracontinental convergence of Yangtze and Cathaysia blocks during the Early Palaeozoic orogeny.
Orogeny
Shearing (physics)
Mylonite
Transpression
Strain partitioning
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The north-north-east-trending (NNE) shear zones, which are defined by the Jiekou shear zone and Huangmao shear zone, are located in the eastern Jiangnan Orogen. This article provides kinematics, geochronological data, and dynamics on the Jiekou and Huangmao shear zones and serves as a reference for understanding the tectonic evolution in the South China Block during the Early Palaeozoic orogeny. All shearing signatures show that the Huangmao shear zone is dextral, and the Jiekou shear zone is sinistral. Both shear zones have certain genetic connections. The rocks from the Jiekou and Huangmao shear zones are metamorphosed and deformed into protomylonite and mylonite. Results of the deformation fabrics of feldspar and quartz and quartzc-axis fabric analysis indicate that the ductile deformation temperatures of the Jiekou shear zone sinistral shearing are similar to 400-500 degrees C. Dextral shearing with medium-high temperature (450-550 degrees C) is mainly recorded in the Huangmao shear zone. In combination with the previous geochronology, NNE-trending sinistral and dextral shearing in the eastern Jiangnan Orogen occurred at 465-430 Ma, coeval with the Early Palaeozoic orogeny. Therefore, the geodynamics of the NNE-trending shear zones is related to a major strain transformation from NW to WNW, which is remotely affected by the intracontinental convergence of Yangtze and Cathaysia blocks during the Early Palaeozoic orogeny.
Orogeny
Shearing (physics)
Transpression
Mylonite
geodynamics
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Three large transcurrent systems, with related magmatism, are identified in southern Peru. A -40-80km wide, N150-trending, dextral corridor (CECLLA =Cusco-Lagunillas-Laraqueri-Abaroa structural corridor) is characterized by thick Oligocene basic lavas and numerous intrusions. The other two systems are oriented -N12S 130 and sinistral, and cartographically related to the CECLLA. Miocene to Quaternary basic magmas are associated to the northeastern system (SFUACC = Urcos-Ayaviri-Copacabana-Coniri faultsystem). In thesouthwestern region, the abundant Late Cretaceous-Paleocene arc magmatism seems related to the Incapuquio-EI Castillo fault system (SFIEC).
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Orogeny
Geochronology
Shearing (physics)
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The Neogene extension in the inner sector of the Northern Apennines has been accompanied, since Late Miocene, by the emplacement of anatectic plutonic bodies. The Campiglia Marittima monzogranite (K/Ar cooling age of 5.7 Ma), outcrops along the Southern Tuscany coast, on the western part of the mesozoic Campiglia Ridge. Field data were collected to study the role of regional tectonics on pluton emplacement. The data shows that N-S subvertical dextral faults border the western part of the mesozoic Campiglia Ridge. This fault zone is associated with NW-SE to N-S subvertical fracture cleavage, locally reactivated as N-S dextral faults. Pluton emplacement induced a N-S elongated thermal aureole. A sub-horizontal schistosity, due to the flattening induced by the rise of the pluton, is present within the aureole; structural data suggests that the development of such schistosity is coeval with strike-slip faulting. Semi-ductile shear zones in the pluton are kinematically compatible with the major N-S dextral shear recognized along the Campiglia Ridge. These evidences suggest that pluton emplacement was coeval with the N-S dextral shear. The sub-horizontal schistosity induced by the pluton culminates in correspondence with a major releasing bend formed by the N-S dextral faults along the western border of the Campiglia Ridge, where the thermal aureole widens. This suggests that pluton emplacement occurred in correspondence with the releasing bend as a consequence of the activity of the dextral faults. The lack of high-temperature shear within the intrusive body suggests a diapir-like ascent within the space created in the releasing bend. During Pliocene, regional extension reactivated the strike-slip faults at the borders of the Ridge and formed new sets of normal faults.
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The north-north-east-trending (NNE) shear zones, which are defined by the Jiekou shear zone and Huangmao shear zone, are located in the eastern Jiangnan Orogen. This article provides kinematics, geochronological data, and dynamics on the Jiekou and Huangmao shear zones and serves as a reference for understanding the tectonic evolution in the South China Block during the Early Palaeozoic orogeny. All shearing signatures show that the Huangmao shear zone is dextral, and the Jiekou shear zone is sinistral. Both shear zones have certain genetic connections. The rocks from the Jiekou and Huangmao shear zones are metamorphosed and deformed into protomylonite and mylonite. Results of the deformation fabrics of feldspar and quartz and quartzc-axis fabric analysis indicate that the ductile deformation temperatures of the Jiekou shear zone sinistral shearing are similar to 400-500 degrees C. Dextral shearing with medium-high temperature (450-550 degrees C) is mainly recorded in the Huangmao shear zone. In combination with the previous geochronology, NNE-trending sinistral and dextral shearing in the eastern Jiangnan Orogen occurred at 465-430 Ma, coeval with the Early Palaeozoic orogeny. Therefore, the geodynamics of the NNE-trending shear zones is related to a major strain transformation from NW to WNW, which is remotely affected by the intracontinental convergence of Yangtze and Cathaysia blocks during the Early Palaeozoic orogeny.
Orogeny
Shearing (physics)
Transpression
Mylonite
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