The constraints of strain partitioning and geochronology in Luonan-Luanchuan tectonic belts on Qinling orogenic belt

Abstract

The Luonan-Luanchuan tectonic belt lies between the North China Block and QinlingMountains, including the Luonan-Luanchuan fault zone and the strong deformation zone to the north of the fault. The ductile shear zone, imbricate brittle fault and duplex structure in the fault zone now are the expression of the same tectonic event in different depth. Such lineation structure exists in the tectonic belts as mineral lineation, elongation lineation, crenulation lineation, sheath folds and so on, indicating NE-directed plate motion. Fold axes and thrusts in the strong deformation zone are inclined to the Luonan-Luanchuan fault zone at small angles. The structures with different natures show a regular pattern, produced during oblique convergence of plates. The convergence factors are as follows：The direction of plate convergence is 22°, 31° and the angle between the plate convergence direction and plate boundary is 73°, 82° respectively in the west and east segment. The Luonan-Luanchuan tectonic belt was deformed strongly in 372 Ma, resulted from Erlangping back-arc ocean basin subduction sinistrally and obliquely to North China Block during the collision of North China Block and South China Block.

Timing of Orogenic Exhumation Processes of the Qinling Orogen: Evidence From40Ar/39Ar Dating

“…Muscovite and biotite from mylonitic rocks of the LLF, the boundary fault between the S‐NCB and the Kuanping Group, yield 40 Ar/ 39 Ar ages of 373–371 Ma (C. Z. Song et al, ).…”

Structural analysis of ductile shear zones in the North Qinling Orogen and its implications for the evolution of the Proto‐Tethys Ocean

“…This shear zone extends northwestwards to disappear under the Quaternary strata and is exposed in the Tongbai Orogen after being partly covered by the Nanyang Basin (Liu et al, ; Zhao et al, ; Figure b). Previous studies suggested that the Luonan‐Luanchuan shear zone developed deformations of ductile shearing and overthrusting, with the latter deformation cutting through the former one (Ren et al, ; Song, Zhang, Wang, et al, ; Song, Zhang, Ren, Li, & Huang, ). The bookshelf structure developed at outcrop indicates dextral strike‐slip movement of the Luonan‐Luanchuan shear zone (Figure a).…”

“…Previous studies suggested that the Luonan‐Luanchuan shear zone was formed due to the collision between the NCB and the North Qinling Terrane during the Neoproterozoic (e.g., Dong et al, ), or during the Early Paleozoic (e.g., Liu et al, 2013; Zhao et al, ). The 40 Ar/ 39 Ar ages for muscovite and biotite obtained from mylonite and mylonitic gneiss collected from the Luonan‐Luanchuan shear zone reveal that the shear zone underwent intensive ductile deformation at ~372 Ma (Song, Zhang, Wang, et al, ). In general, the 40 Ar/ 39 Ar ages for mica record the cooling age when the subducted slab was exhumed to a shallow depth (Dong, Genser, et al, ).…”

“…Significant advancements have been made in the studies concerning the petrology, geochronology, geochemistry, and structural geology in the NQO (e.g., Cao et al, ; Cheng et al, ; Diwu et al, ; Dong, Zhang, Neubauer, et al, ; Dong et al, , ; Li, Zhao, et al, ; Liu, Li, et al, ; Liu, Jahn, Li, & Liu, ; Liu et al, ; Wang, Wang, & Zhang, ; Wang, Wu, et al, ; Wu & Zheng, ; Yu et al, ; Zhang et al, , ; Zhang et al, ; Zhao et al, ; Zheng, Zhou, Wu, & Xie, ). It has been proved that the border faults of the NQO, that is, the Luonan‐Luanchuan Fault and the Shangdan Suture, and the secondary faults that bound the lithotectonic sub‐units of the NQO, that is, the Guanpo‐Qiaoduan and the Zhuyangguan‐Xiaguan faults, have undergone ductile shear deformation (Li, Zhang, & Song, ; Liu, Li, et al, ; Song, Zhang, Wang, et al, ; Wang, Wang, et al, ; Zhang et al, ; Zhao et al, ; Figure b). However, the sense and forming environment of the four ductile shear zones in the NQO are still vague due to a lack of detailed research.…”

The Structural Framework of the Erlangping Group in North Qinling, Central China

“…The Erlangping Group, neighbouring the Qinling Group to the south by the Zhuyangguan-Xiaguan boundary shear zone along where ultra high pressure metamorphic rocks were found near the Guanpo Town, and connecting with the Kuanping Group by the Waxuezi-Qiaoduan shear zone ( Figure 1). In recent years, with continuously enriched inner and regional related research achievements [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20], the Erlangping Group is gradually becoming a hot research area.…”