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Remagnetization of Carboniferous Limestone in the Zaduo Area, Eastern Qiangtang Terrane, and Its Tectonic Implications

Remagnetization of Carboniferous Limestone in the Zaduo Area, Eastern Qiangtang Terrane, and Its Tectonic Implications

Authors :
Yu, Liang
Yan, Maodu
Guan, Chong
Li, Bingshuai
Fu, Qiang
Xu, Wanlong
Feng, Zhantao
Zhang, Dawen
Shen, Miaomiao
Xu, Zunbo
Niu, Zhichao
non-UU output of UU-AW members
non-UU output of UU-AW members
Source :
Frontiers in Earth Science, 10, 1. Frontiers Research Foundation
Publication Year :
2022
Publisher :
Frontiers Media SA, 2022.

Abstract

Robust paleomagnetic results through geological time are one of the keys to understand the drift history of the eastern Qiangtang terrane (EQT). Here, we presented comprehensive petrographic observations and rock magnetic and paleomagnetic analyses of the early Carboniferous Upper Zaduo (ZD) limestone Formation (C1z2) from the Sulucun (SLC) section in the Zaduo area, EQT, to investigate its magnetic originality and geological significance. A total of 12 sites (131 samples) were collected. Photomicrograph observations indicate that the limestone samples were characterized by widespread carbonate veinlets. Electron microprobe and energy dispersive spectrometry analyses confirm that authigenic magnetite formed after pyrite. Rock magnetic analyses reveal the dominant magnetic minerals of pyrite and magnetite, with ‘wasp-waisted’ hysteresis loops and close to the “remagnetization trend” hysteresis parameters. Based on both thermal and alternating field demagnetizations, the characteristic remanent magnetization directions for most samples were isolated: Dg = 6.3°, Ig = 50.1°, kg = 54.9, α95 = 6.2° in-situ, and Ds = 330.2°, Is = 58.9°, ks = 5.9, and α95 = 20.5° after 2-step tilt correction. The κ (α95) value decreases (increases) after tilt-correction, and the ChRM directions failed both the McFadden (1990), Watson and Enkin (1993) fold tests, indicating post-folding magnetizations. The 11 site-mean directions yield a mean in-situ paleopole of 84.4°N, 200.3°E, and A95 = 6.8°, which is coincident with the post ∼53 Myr (especially around 40 Ma) paleopoles of the region. We therefore interpreted that these early Carboniferous limestone samples contain remagnetized magnetizations and that they were obtained after 53 Ma, most likely around 40 Ma, due to the far-field effect of the India–Eurasia collision.

Details

ISSN :
22966463
Volume :
10
Database :
OpenAIRE
Journal :
Frontiers in Earth Science
Accession number :
edsair.doi.dedup.....4de8372e47c8aeaa549e5e632bc6c9e4
Full Text :
https://doi.org/10.3389/feart.2022.825943