Paleomagnetic studies of Jurassic and Cretaceous rocks in the Eastern Qiangtang Terrane, Tibetan Plateau, China

Abstract

This thesis presents research on the paleogeographic data of Early Cretaceous granites and Mid-Late Jurassic limestones in the Zaduo area, Eastern Qiangtang Terrane, Tibetan Plateau, China. The granite study provides further insight into the Lhasa-Qiangtang collision, while the limestones have been remagnetized due to the India-Eurasia collision. The magnetic fabric of the remagnetized limestones documented the NNE-SSW oriented compression during the remagnetization. A comparative study of the remagnetized and unremagnetized rocks, which mainly concentrates on their rock magnetic properties, was also carried out. The combination of gravity and paleomagnetic data reveals a coupled lithosphere-scale oroclinal deformation of the eastern ending of the Qiangtang Terrane. The thesis consists of five chapters. Chapter 1 investigates an Early Cretaceous granite in the Zaduo area and presents a new paleomagnetic investigation on the granite. Chapter 2 discusses the remagnetization of the Jurassic limestones in the Zaduo area and its implications for the India-Eurasia collision. Chapter 3 is about the lithosphere-scale oroclinal deformation of the eastern ending of the Qiangtang Terrane. Chapter 4 focuses on the remagnetization of the limestones and the NNE-SSW oriented compression during the India-Eurasia collision, and Chapter 5 is about the comparative study of the remagnetized and unremagnetized rocks.

Middle Jurassic Paleolatitude of the Tethyan Himalaya: New Insights Into the Evolution of the Neo‐Tethys Ocean

“…Although remagnetization occurred widely in the TH limestones (e.g., Appel et al., 2012; Huang et al., 2015), some Mesozoic limestones could still preserve a primary remanent magnetization such as the Cretaceous limestones in the TH (Meng et al., 2020), the Cretaceous limestones in the LT (Ma et al., 2018), and the upper Triassic limestones in the Qiangtang terrane (Yu, 2022). Notably, the remagnetized Tethyan Himalayan limestones always include a large number of framboidal Fe oxides (magnetite), which are widely distributed along cracks or instead formed as pseudomorphs after pyrite (Huang et al., 2017).…”

“…The HystLab software package (Paterson et al, 2018(Paterson et al, , 2023 was used for analyzing the hysteresis data, available at https://github.com/greigpaterson/HystLab. FORCinel 3.08 software package (Harrison & Feinberg, 2008, 2022 was used for simulating the first order reversal curve diagrams, available at https://nanopaleomag.esc.cam.ac.uk/nanopaleomag-home/forcinel. The web application MAX UnMix was used for unmixing magnetic coercivity distributions (Maxbauer et al, 2016), available at http://shinyapps.its.carleton.…”