Paleomagnetic results of Late Paleozoic rocks from northern Qiangtang Block in Qinghai-Tibet Plateau, China

Abstract

Tectonic evolution of the Tethys and the boundary between the Gondwanaland and the Eurasia during the Carboniferous and Permian remain hotly debated. Qiangtang region in the Qinghai-Tibet Plateau may be a key place to study these problems. A paleomagnetic study was conducted on the Late Paleozoic rocks in the northern Qiangtang region (33.7°N, 86.7°W), Tibet. Two sites (21 samples) in the Upper Carboniferous, eleven sites (101 samples) in the Permian, and two sites (16 samples) in the Lower Triassic were investigated. The rock magnetic data revealed hematite and magnetite as the main magnetic carriers. In stepwise thermal demagnetization and/or combined alternating field (AC) demagnetization, two characteristic components in the majority of the samples were identified as (1) the Low-temperature Component (LTC), characterized by northerly declination and moderate to steep inclination, corresponding to a pole position overlay with the present North Pole. A minority of the samples present single component, and their directions are the same as (2) the High-temperature Component (HTC) of double components. The combined single-component and HTC data of the Permian can pass the R-test at 95% level and the F-test at 99% level, as well as the BC-test. The pole position from the Late Carboniferous is at 31.8°S, 45.7°E with dp=2.1, dm=3.9, that from the Early and Middle (Late) Permian is at 31. 7°S, 46.8°E with dp=9.2, dm=16.9 (34.4°N, 54.1°E with dp=6.9, dm=12.5) respectively, and that from the Early Triassic is at 16.9°S, 22.5°E with dp=4.9, dm=9.2. These pole positions are different from the other poles for the Qiangtang Block, which suggests the single-component and HTC directions are probably a primary magnetization and the northern Qiangtang Block was paleogeographically

Paleomagnetic Study on the Permian Rocks of the Indochina Block and Its Implications for Paleogeographic Configuration and Northward Drifting of Cathaysialand in the Paleo‐Tethys

“…Note that the synthesized apparent polar wander paths of the South China Block in Cocks and Torsvik () should be used cautiously because inclination correction with a factor of 0.6 to all clastic sedimentary rocks and may lead to an unnecessary offset for some data sets. During the Early to Middle Permian, the new paleomagnetic data obtained from the Indochina Block in this study suggests a ~21°S paleolatitude, which is almost the same as that of the North Qiangtang Block (~20°S; Cheng et al, ). The paleolatitude can be corrected to ~26°S with a flatting factor of 0.8 as discussed in section 4.3 and matches well with the South China result.…”

Paleomagnetic Constraints on the Origin and Drift History of the North Qiangtang Terrane in the Late Paleozoic

“…Previous paleomagnetic investigations of Late Permian rocks of the NQT have been performed in the Raggyorcaka area by Cheng et al (), in the Tuotuohe area by Cheng et al (), and in the Tuoba area by Huang et al (). Cheng et al () and Cheng et al () reported two paleopoles from five sedimentary sites and five volcanic sites, respectively, and concluded that the NQT was located at different paleolatitudes of approximately 13.1 and −7.7°N in the Late Permian (Table S4). Other Late Permian paleomagnetic results of 10 sedimentary sites reported by Huang et al () positioned the NQT at ~4.8°N (Table S4).…”

“…These results suggest that our new data set has averaged out paleosecular variation and thus can be used for tectonic reconstruction. Cheng et al (2012), in the Tuotuohe area by Cheng et al (2013), and in the Tuoba area by Huang et al (1992). Cheng et al (2012) and Cheng et al (2013) reported two paleopoles from five sedimentary sites and five volcanic sites, respectively, and concluded that the NQT was located at different paleolatitudes of approximately 13.1 and −7.7°N in the Late Permian (Table S4).…”

“…The secular variation of paleomagnetic field cannot be fully averaged out by only five volcanic sites (Cheng et al, 2013). Besides, the possible inclination shallowing have not been tested and corrected for sedimentary data by Cheng et al (2012) and Huang et al (1992). Moreover, no isotopic ages are available to constrain the precise ages of these poles.…”

Direct Paleomagnetic Constraint on the Closure of Paleo‐Tethys and Its Implications for Linking the Tibetan and Southeast Asian Blocks

“…Abbreviation: SQT (South Qiangtang), NQT (North Qiangtang), TC (Tengchong), WB (West Burma), IBR (Indo-Burma Range), EKL-ANMQS (East Kunlun-A'nyemaqen Suture), JSJS (Jinshajiang Suture), LSS (Longmu Co-Shuanghu Suture), BNS (Bangong Co-Nujiang Suture), ITS (Indus-Tsangbu Suture), MFT (Main Frontal Thrust), XSH-XJ F. (Xiaoshuihe-Xiaojiang Fault), ALS-RR F. (Ailaoshan-Red River Fault), DBPF (Dien Bien Phu Fault), GLG F. (Gaoligong Fault), MJ (Mojiang), CN (Changning), ML (Menglian), CL (Chianglai), and CM (Chiangmai). References of paleomagnetic studies: A2013 (Ali et al, 2013), C2012 (Cheng et al, 2012), C2013 (Cheng et al, 2013), C2016 (Chi et al, 2016), HO1991 (Huang & Opdyke, 1991), H1992 (Huang et al, 1992), HO2016 (Huang & Opdyke, 2016), M2019 (Ma et al, 2019), S2012 (Song et al, 2012), S2015 (Song et al, 2015), S2017 (Song et al, 2017), X2014 (Xu et al, 2014), YB1993 (Yang & Besse, 1993), Y2017 (Yan et al, 2017), Y2018 (Yan et al, 2018), Z2015 , and Z2019 . (b) Geological map and sampling locations in the south Lancangjiang volcanic belt.…”