Structures, kinematic analysis, rheological parameters and temperature-pressure estimate of the Mesozoic Xingcheng-Taili ductile shear zone in the North China Craton. (September 2015)

• Record Type: Journal Article
• Authors: Liang, Chenyue; Liu, Yongjiang; Neubauer, Franz; Bernroider, Manfred; Jin, Wei; Li, Weimin; Zeng, Zuoxun; Wen, Quanbo; Zhao, Yingli
• Is Part Of: Journal of structural geology. Volume 78(2015:Sep.)
• Page Start: 27
• Page End: 51
• Publication Date: 2015-09
• Subjects: Ductile shear zone -- EBSD analysis -- Quartz microfabrics -- Finite-strain determination -- Kinematic vorticity -- Hornblende-plagioclase thermobarometer -- Fractal dimension -- Paleo-piezometry -- North China Craton -- Xingcheng-Taili ductile shear zone; Geology, Structural -- Periodicals; Géomorphologie structurale -- Périodiques; Geology, Structural; Periodicals; 551.805
• DOI: 10.1016/j.jsg.2015.06.007
• Languages: English
• ISSNs: 0191-8141

Abstract

Abstract: The NE to ENE trending Mesozoic Xingcheng-Taili ductile shear zone of the northeastern North China Craton was shaped by three phases of deformation. Deformation phase D1 is characterized by a steep, generally E–W striking gneissosity. It was then overprinted by deformation phase D2 with NE-sinistral shear with K-feldspar porphyroclasts forming a subhorizontal low-angle stretching lineation on a steep foliation. During deformation phase D3, lateral motion accommodated by ENE sinistral strike-slip shear zones dominated. Associated fabrics developed at upper greenschist metamorphic facies conditions and show the deformation characteristics of middle- to shallow crustal levels. In some parts, the older structures have been in turn overprinted by late-stage sinistral D3 shearing. Finite strain and kinematic vorticity in all deformed granitic rocks indicate a prolate ellipsoid (L-S tectonites) near plane strain. Simple shear-dominated general shear during D3 deformation is probably of general significance. The quartz c-axis textures indicate prism-gliding with a dominant rhomb slip and basal slip system formed mainly at low-middle temperatures. Mineral deformation behavior, quartz c-axis textures, quartz grain size and the Kruhl thermometer demonstrate that the ductile shear zone developed under greenschist facies metamorphic conditions at deformation temperatures ranging from 400 to 500 °C. Dislocation creep is the main deformation mechanism at a shallow crustal level. Fractal analysis showed that the boundaries of recrystallized quartz grains had statistically self-similarities. Differential stresses deduced from dynamically recrystallized quartz grain size are at around 20–39 MPa, and strain rates in the order of 10 −12 to 10 −14 s −1 . This indicates deformation of granitic rocks in the Xingcheng-Taili ductile shear zone at low strain rates, which is consistent with most other ductile shear zones. Hornblende-plagioclase thermometer and white mica barometer indicate metamorphic conditions of medium pressures at around ca. 3–5 kbar and temperatures of 400–500 °C within greenschist facies conditions. The main D3 deformation of the ENE-trending sinistral strike-slip ductile shearing is related to the roll-back of the subducting Pacific plate beneath the North China Craton. Highlights: Sinistral strike-slip ductile shearing is related to ongoing Early Cretaceous roll-back of the Pacific Plate beneath NCC. Three phases of deformation were first recognized in the Xingcheng-Taili strike-slip shear zone. The metamorphic conditions of shearing were between ca. 3–5 kbar and 400–500 °C. The strain rates consistent with slow deformation and show a bulk simple shear-dominated general shear. Various paleopiezometers are compared and yield a fast strain rate.