Volume 97, Issue 1 pp. 13-34
Original Article

Triassic Nappe in the Central Part of the Southern Central Asian Orogenic Belt (Ejinaq, NW China): Evidence from Structural Analysis and Geothermochronology

He SU

He SU

School of Earth Sciences and Resources, China University of Geosciences, Beijing, 100083 China

SinoProbe Center, Chinese Academy of Geological Sciences and China Geological Survey, Beijing, 100037 China

Search for more papers by this author
Xuanhua CHEN

Corresponding Author

Xuanhua CHEN

SinoProbe Center, Chinese Academy of Geological Sciences and China Geological Survey, Beijing, 100037 China

Corresponding author. E-mail: [email protected]Search for more papers by this author
Xinqi YU

Xinqi YU

School of Earth Sciences and Resources, China University of Geosciences, Beijing, 100083 China

Search for more papers by this author
Zhaogang SHAO

Zhaogang SHAO

SinoProbe Center, Chinese Academy of Geological Sciences and China Geological Survey, Beijing, 100037 China

Search for more papers by this author
Wei YU

Wei YU

SinoProbe Center, Chinese Academy of Geological Sciences and China Geological Survey, Beijing, 100037 China

School of Resources and Environmental Engineering, Hefei University of Technology, Hefei, 230009 China

Search for more papers by this author
Yiping ZHANG

Yiping ZHANG

SinoProbe Center, Chinese Academy of Geological Sciences and China Geological Survey, Beijing, 100037 China

Search for more papers by this author
Yongchao WANG

Yongchao WANG

SinoProbe Center, Chinese Academy of Geological Sciences and China Geological Survey, Beijing, 100037 China

Search for more papers by this author
First published: 07 October 2022
Citations: 9

About the first author:

SU He, male, born in 1987 in Wuhai, Inner Mongolia, China; master; graduated from Earth Sciences and Resources, China University of Geosciences, Beijing; he is currently interested in the study of geotectonics, structural geology and tectonogeophysics. E-mail: [email protected].

About the corresponding author:

CHEN Xuanhua, male, born in 1967 in Wenzhou, Zhejiang Province; Ph.D.; graduated from the Chinese Academy of Geological Sciences; professor at the SinoProbe Center, Chinese Academy of Geological Sciences. He is currently working on structural geology, tectonics and deep earth science. E-mail: [email protected].

Abstract

The thrust nappe played an important role in the Mesozoic tectonic evolution of the middle part of the Central Asian Orogenic Belt (CAOB). However, the timing, structural style and kinematic processes of the thrust nappe remain controversial, particularly the detail of the thrust nappe in the Guaizihu region (110 km east of Ejinaq). In this study, we investigate new field mapping, seismic sections, geochronology and low-temperature thermochronometric dating to provide constraints on the history of this thrust nappe in the Chaheilingashun area (northwestern Guaizihu region). The field mapping, seismic sections and structural analysis reveal that the autochthonous system had developed a series of strong fold structures in the upper Permian strata. The allochthonous system mainly contains Devonian monzogranite (U-Pb age, ranges from 386.7 to 389.0 Ma) and Meso–Neoproterozoic schists (the maximum depositional age, ∼880 Ma), which were thrust upon the upper Permian strata during Middle to Late Triassic. Based on similar rocks, geochronological dating and the Yagan thrust, we suggest that the postulated root zone of this allochthon might have originated from the Huhetaoergai area (40–60 km northwest of the study area). The geochronological results reveal that the lower age limit of this thrust nappe is constrained by the Lower–Middle Triassic syntectonic sediments (tuffaceous sandstone, ∼247 Ma), which is the sedimentary response of the fold structure., The timing of the termination of this thrust nappe is defined by the cooling age (40Ar/39Ar data, 217–211 Ma) of the Devonian monzogranite and Meso–Neoproterozoic schists. Thus, we consider this thrust event in the study area to potentially have occurred in the period from 247 Ma to 211 Ma, which may represent the tectonic response to the closure of the Paleo-Asian Ocean.

The full text of this article hosted at iucr.org is unavailable due to technical difficulties.