Rock magnetic properties of the Upper Silurian Longmu Co Upper Formation in the North Qiangtang Terrane

Abstract

Objective Palaeomagnetic study of the early Palaeozoic North Qiangtang Terrane can quantitatively constrain its palaeogeographic location since the Palaeozoic, which serves as an important foundation and key constraint for studying of the palaeotectonic pattern of the Qinghai-Tibet Plateau, the evolution of the Phanerozoic Tethys and palaeogeographic reconstruction. Methods Prior to palaeomagnetic study, it is essential to investigate the magnetic properties of rocks to identify the types and assemblages of magnetic carriers present in rocks, which will facilitate the selection of demagnetization experimental protocols and discussions on the primary nature of remanent magnetization. This paper focuses on the magnetic properties of limestone and sandstone from the Late Silurian Longmu Co Upper Formation in the North Qiangtang Terrane, through analyses of isothermal remanence acquisition curves, magnetic susceptibility with temperature(χ-T) curves, triaxial thermal demagnetization experiments, low-temperature magnetic properties tests, scanning electron microscopy (SEM) and energy dispersive spectral (EDS) analysis. Results Results show that magnetite is the predominant magnetic carrier in the limestone samples of the Longmu Co Upper Fm, with small amounts of pyrrhotite. The magnetic assemblage in the sandstone samples is more complex, dominated by magnetite, possibly with other magnetic minerals such as pyrrhotite. Conclusion Moreover, it demonstrates that stable high-temperature remanent magnetization components can be isolated from the limestone samples in the Longmu Co Upper Formation, making them suitable for further palaeomagnetic researches.

Keywords

• qinghai-tibet plateau
• rock magnetism
• north qiangtang terrane
• upper silurian
• longmu co upper formation