Neoarchean ductile deformation of the Northeastern North China Craton: The Shuangshanzi ductile shear zone in Qinglong, eastern Hebei, North China

2017 ◽  
Vol 139 ◽  
pp. 224-236 ◽  
Author(s):  
Boran Liu ◽  
Franz Neubauer ◽  
Junlai Liu ◽  
Wei Jin ◽  
Weimin Li ◽  
...  
Keyword(s):  
Shear Zone ◽  
North China Craton ◽  
North China ◽  
Ductile Deformation ◽  
Ductile Shear Zone ◽  
Ductile Shear

Two Paleoproterozoic metamorphic events in the Zhujiafang ductile shear zone of the Hengshan Complex: Insights into the tectonic evolution of the North China Craton

2020 ◽  
Author(s):  
Jiahui Qian
Keyword(s):  
Shear Zone ◽  
North China Craton ◽  
Tectonic Evolution ◽  
North China ◽  
Shear Zones ◽  
Ductile Shear Zone ◽  
Garnet Amphibolite ◽  
Inclusion Type ◽  
Mineral Assemblages ◽  
Ductile Shear

<p>Ductile shear zones <span>usually record mineralogical and isotopic changes that are not apparent in the surrounding host rocks and thus may preserve a complete evolutionary record in a single locale from relatively undeformed to highly deformed rocks. </span>The Zhujiafang ductile shear zone is situated in the central Hengshan Complex, a key area for understanding the Paleoproterozoic tectonic evolution of the Trans-North China Orogen, North China Craton. Detailed metamorphic and geochronological analyses were carried out on metapelite and garnet amphibolite from the Zhujiafang ductile shear zone. The metapelite preserves two phases of mineral assemblages: early kyanite-rutile-bearing assemblage and late chlorite-staurolite-bearing assemblage in garnet–mica schist, and inclusion-type muscovite (high-Si) + kyanite assemblage and late sillimanite-bearing assemblage in sillimanite–mica gneiss. Garnet in the metapelite occasionally exhibits pronounced two-stage zoning characteristic of a diffusion core with irregular pyrope (X<sub>py</sub>) and grossular (X<sub>gr</sub>) contents and a growth rim with X<sub>py</sub> and X<sub>gr</sub> increasing outwards. The isopleths of the maximum X<sub>gr</sub> in garnet core and Si content in inclusion-type muscovite in the P–T pseudosections suggest that the early mineral assemblages underwent medium-high-pressure type metamorphism with pressures up to 12–14 kbar at 700–750 °C. The late assemblages and the growth zoning of garnet rim predict a late separated clockwise P–T path with peak conditions of 6.5 ± 0.2 kbar/620 ± 10 °C (medium-low-pressure type). The garnet amphibolite is mainly composed of garnet, hornblende, plagioclase, ilmenite and quartz, without overprinting of late mineral assemblages except for localized corona textures. Phase modeling suggests that the rock has experienced high-amphibolite facies metamorphism with peak conditions of 10.5 ± 0.8 kbar/770 ± 50 °C, which is broadly consistent with the early-phase metamorphism of metapelite. Zircon U–Pb dating on metapelite yields two metamorphic age groups of 1.96–1.92 Ga and 1.87–1.86 Ga which are interpreted to represent the timing of the two separated phases of metamorphism. Two separated orogenic events may have occurred respectively at ~1.95 Ga and ~1.85 Ga in the Hengshan–Wutai area. The older orogeny was resulted from continental collision and the younger one may be caused by within-plate deformation. The final exhumation of the high-grade rocks formed in the older (i.e. 1.95 Ga) orogeny should be related with the younger deformation/metamorphic event. For more details, please refer to <span>https://doi.org/10.1016/j.lithos.2019.02.001.</span></p>

40Ar/ 39Ar laser dating of Zongwulong ductile shear zone in northeastern Tibetan Plateau ：Constrains on the closure time of the northmost Paleo-Tethys ocean

2021 ◽  
Author(s):  
Wanli Gao ◽  
Zongxiu Wang
Keyword(s):  
Shear Deformation ◽  
Shear Zone ◽  
Ductile Deformation ◽  
Low Grade ◽  
Ductile Shear Zone ◽  
The South ◽  
Oblique Collision ◽  
Ductile Shear ◽  
Tethys Ocean ◽  
Tectonic Belt

<p><strong><img src="https://contentmanager.copernicus.org/fileStorageProxy.php?f=gepj.67d6c7216eff55356050161/sdaolpUECMynit/12UGE&app=m&a=0&c=5572aca4b392eef83f52919e1be673e9&ct=x&pn=gepj.elif&d=1" alt="">Abstract</strong>：The Zongwulong tectonic belt (ZTB) is located between the northern Qaidam tectonic belt and the south Qilian orogenic belt and contains Late Paleozoic and Early- Middle Triassic strata. Structural features and geochronology of Zongwulong ductile shear zone have key implications for the tectonic property of the ZTB. This study integrated field structure, microscopic structure and <sup>40</sup>Ar/<sup>39</sup>Ar laser probe analysis. The shear zone strikes ~NEE-SWW and dips at a high angle, with a NWW-SEE trending and WE stretching lineation, indicating the shear zone as a thrust- slip shear ductile shear. The asymmetric folds, rotating porphyroclast,structural lens and crenulation cleavage can be seen in the field. Mica fish, S − C fabrics, σ type quartz porphyroclastic and quartz wire drawing structure can also be observed under microscope, indicating that the strike- slip- related ductile deformation and mylonitization occurred under low- grade greenschist facies conditions at temperatures of <em>300° C − 400° C</em>.  The highly deformed<br>mylonite schist yielded <sup>40</sup>Ar/<sup>39</sup>Ar ages <em>(245.8±1.7)Ma </em>and <em>(238.5±2.6)</em>Ma for muscovite and biotite, respectively, indicating that the shear deformation occurred during the Early- Mid Triassic. Combined with comprehensive analysis of regional geology and petrology, the authors hold that the age of ductile shear deformation represents the time of Triassic orogeny in the ZTB. The oroginic activity was probably related to the oblique collision between the South Qilian block and the Oulongbuluke block after the closure of the northermost Paleo-Tethys ocean.</p>

Macro- and microstructural analysis of the Zhujiafang ductile shear zone, Hengshan Complex: Tectonic nature and geodynamic implications of the evolution of Trans−North China orogen

2020 ◽  
Author(s):  
Lingchao He ◽  
Jian Zhang ◽  
Guochun Zhao ◽  
Changqing Yin ◽  
Jiahui Qian ◽  
...  
Keyword(s):  
Shear Zone ◽  
North China ◽  
Shear Zones ◽  
Crustal Thickening ◽  
Slip Systems ◽  
High Grade ◽  
Ductile Shear Zone ◽  
Crustal Rocks ◽  
Ductile Shear ◽  
Lower Crustal

In worldwide orogenic belts, crustal-scale ductile shear zones are important tectonic channels along which the orogenic root (i.e., high-grade metamorphic lower-crustal rocks) commonly experienced a relatively quick exhumation or uplift process. However, their tectonic nature and geodynamic processes are poorly constrained. In the Trans−North China orogen, the crustal-scale Zhujiafang ductile shear zone represents a major tectonic boundary separating the upper and lower crusts of the orogen. Its tectonic nature, structural features, and timing provide vital information into understanding this issue. Detailed field observations showed that the Zhujiafang ductile shear zone experienced polyphase deformation. Variable macro- and microscopic kinematic indicators are extensively preserved in the highly sheared tonalite-trondhjemite-granodiorite (TTG) and supracrustal rock assemblages and indicate an obvious dextral strike-slip and dip-slip sense of shear. Electron backscattered diffraction (EBSD) was utilized to further determine the crystallographic preferred orientation (CPO) of typical rock-forming minerals, including hornblende, quartz, and feldspar. EBSD results indicate that the hornblendes are characterized by (100) <001> and (110) <001> slip systems, whereas quartz grains are dominated by prism <a> and prism <c> slip systems, suggesting an approximate shear condition of 650−700 °C. This result is consistent with traditional thermobarometry pressure-temperature calculations implemented on the same mineral assemblages. Combined with previously reported metamorphic data in the Trans−North China orogen, we suggest that the Zhujiafang supracrustal rocks were initially buried down to ∼30 km depth, where high differential stress triggered the large-scale ductile shear between the upper and lower crusts. The high-grade lower-crustal rocks were consequently exhumed upwards along the shear zone, synchronous with extensive isothermal decompression metamorphism. The timing of peak collision-related crustal thickening was further constrained by the ca. 1930 Ma metamorphic zircon ages, whereas a subsequent exhumation event was manifested by ca. 1860 Ma syntectonic granitic veins and the available Ar-Ar ages of the region. The Zhujiafang ductile shear zone thus essentially record an integrated geodynamic process of initial collision, crustal thickening, and exhumation involved in formation of the Trans−North China orogen at 1.9−1.8 Ga.

scholarly journals Supplemental Material: Macro- and microstructural analysis of the Zhujiafang ductile shear zone, Hengshan Complex: Tectonic nature and geodynamic implications of the evolution of Trans–North China orogen

2020 ◽  
Author(s):  
Lingchao He ◽  
Jian Zhang ◽  
et al.
Keyword(s):  
Shear Zone ◽  
Inductively Coupled Plasma ◽  
Mineral Content ◽  
North China ◽  
Microstructural Analysis ◽  
Ductile Shear Zone ◽  
Inductively Coupled ◽  
High Pressure Granulite ◽  
Plasma Mass Spectrometry ◽  
Ductile Shear

Table S1: Checked mineral content and grain size of EBSD samples; Table S2: Representative compositional analyses of minerals; Table S3: Zircon U-Pb isoplot data obtained by laser ablation–inductively coupled plasma–mass spectrometry for samples 17HS06-1 and 14630-1 from Zhujiafang; Table S4: Summary of isotopic ages for the high-pressure granulite of the Trans–North China orogen and Zhujiafang ductile shear zone.

scholarly journals Supplemental Material: Macro- and microstructural analysis of the Zhujiafang ductile shear zone, Hengshan Complex: Tectonic nature and geodynamic implications of the evolution of Trans–North China orogen

2020 ◽  
Author(s):  
Lingchao He ◽  
Jian Zhang ◽  
et al.
Keyword(s):  
Shear Zone ◽  
Inductively Coupled Plasma ◽  
Mineral Content ◽  
North China ◽  
Microstructural Analysis ◽  
Ductile Shear Zone ◽  
Inductively Coupled ◽  
High Pressure Granulite ◽  
Plasma Mass Spectrometry ◽  
Ductile Shear

Table S1: Checked mineral content and grain size of EBSD samples; Table S2: Representative compositional analyses of minerals; Table S3: Zircon U-Pb isoplot data obtained by laser ablation–inductively coupled plasma–mass spectrometry for samples 17HS06-1 and 14630-1 from Zhujiafang; Table S4: Summary of isotopic ages for the high-pressure granulite of the Trans–North China orogen and Zhujiafang ductile shear zone.

scholarly journals Supplemental Material: Macro- and microstructural analysis of the Zhujiafang ductile shear zone, Hengshan Complex: Tectonic nature and geodynamic implications of the evolution of Trans–North China orogen

2020 ◽  
Author(s):  
Lingchao He ◽  
Jian Zhang ◽  
et al.
Keyword(s):  
Shear Zone ◽  
Inductively Coupled Plasma ◽  
Mineral Content ◽  
North China ◽  
Microstructural Analysis ◽  
Ductile Shear Zone ◽  
Inductively Coupled ◽  
High Pressure Granulite ◽  
Plasma Mass Spectrometry ◽  
Ductile Shear

Table S1: Checked mineral content and grain size of EBSD samples; Table S2: Representative compositional analyses of minerals; Table S3: Zircon U-Pb isoplot data obtained by laser ablation–inductively coupled plasma–mass spectrometry for samples 17HS06-1 and 14630-1 from Zhujiafang; Table S4: Summary of isotopic ages for the high-pressure granulite of the Trans–North China orogen and Zhujiafang ductile shear zone.

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