caa a22 4500 445301252 CHVBK 20180317142558.0 cr unu---uuuuu 170323e20101101xx s 000 0 eng 10.1007/s11430-010-4041-9 doi (NATIONALLICENCE)springer-10.1007/s11430-010-4041-9 Strain and kinematic vorticity analysis of the Louzidian low-angle ductile shear detachment zone in Chifeng, Inner Mongolia, China [Elektronische Daten] [JianBo Li, Tao Wang, ZhiXia Ouyang] The Louzidian low-angle ductile shear detachment zone at the south of Chifeng is a SE-dipping, low-angle normal fault system. It is composed mainly of ductile shear zone, ductile-brittle shear zone and brittle fault zone. The ductile shear zone consists of, from bottom to top, mylonitic rocks, protomylonites and mylonites. Finite strain measurement of feldspar strain markers from those rocks using the R f /ϕ method shows that strain intensities (Es) of the mylonite at core of the ductile shear zone (Es=0.65-0.96) are higher than those of the mylonitic rocks close to the granite intrusions (Es=0.59-0.62) and of the protomylonites at top of the ductile shear zone (Es= 0.47-0.70), and the strain types of the protomylonites and mylonties are elongate strain and plane-flattening strain, respectively. The kinematic vorticity values (W k ) estimated by the Polar Mohr diagram and the Rigid Grain Net range from 0.81 to 0.90 with an average of 0.85 for the protomylonites, and from 0.53 to 0.80 with 0.66 on average for the mylonites; Wk values of the extensional crenulation cleavage, i.e., C′, estimated by C′ method range from 0.63 to 0.37 with an average of 0.50. The angles between the maximum principal stress and shearing direction determined using the Maximum effective moment criterion evolved from 61° to 69° and to 75°, and finally normal to shearing direction. The results of strain and kinematic vorticity measurements suggest that high strain corresponds to low kinematic vorticity. Kinematic vorticity measurements show that the Louzidian low-angle ductile shear detachment zone is a result of a combination of simpledominated general shearing at the early stage and pure-dominated general shearing at the late stage. All these, together with isotope geochronology and regional tectonic background, suggest that the Louzidian ductile shear detachment zone resulted from a combination of crust extension and magma intrusion. The model of simple shear at the early stage and pure shear at the late stage in the formation of metamorphic core complex has probably general significance. Science China Press and Springer-Verlag Berlin Heidelberg, 2010 Louzidian nationallicence low-angle ductile shear detachment zone nationallicence mylonite nationallicence strain intensity nationallicence kinematic vorticity nationallicence principal stress nationallicence Li JianBo Institute of Geology, Chinese Academy of Geological Sciences, 100037, Beijing, China aut Wang Tao Institute of Geology, Chinese Academy of Geological Sciences, 100037, Beijing, China aut Ouyang ZhiXia Institute of Geology, Chinese Academy of Geological Sciences, 100037, Beijing, China aut Science China Earth Sciences SP Science China Press 53/11(2010-11-01), 1611-1624 1674-7313 53:11<1611 2010 53 11430 https://doi.org/10.1007/s11430-010-4041-9 text/html Onlinezugriff via DOI 1 research-article jats NATIONALLICENCE 856 40 https://doi.org/10.1007/s11430-010-4041-9 text/html Onlinezugriff via DOI NATIONALLICENCE 700 1- Li JianBo Institute of Geology, Chinese Academy of Geological Sciences, 100037, Beijing, China aut NATIONALLICENCE 700 1- Wang Tao Institute of Geology, Chinese Academy of Geological Sciences, 100037, Beijing, China aut NATIONALLICENCE 700 1- Ouyang ZhiXia Institute of Geology, Chinese Academy of Geological Sciences, 100037, Beijing, China aut NATIONALLICENCE 773 0- Science China Earth Sciences SP Science China Press 53/11(2010-11-01), 1611-1624 1674-7313 53:11<1611 2010 53 11430 Metadata rights reserved Springer special CC-BY-NC licence nationallicence BK010053 XK010053 XK010000 NATIONALLICENCE NATIONALLICENCE NL-springer