New Silurian and Devonian palaeomagnetic results from the Hexi Corridor terrane, northwest China, and their tectonic implications

A total of 239 orientated drill-core samples from 23 sites were collected for palaeomagnetic study from Silurian and Devonian red beds, marlaceous sandstone, and limestone rocks in the eastern part of the Hexi Corridor, southwest Ningxia, North China. The characteristic high-temperature component resides in both haematite and magnetite. It clusters around a northwesterly and shallow to moderate downward direction and its antipode after tilt correction. The primary origin of this characteristic remanent magnetization (ChRM) is ascertained by positive fold and reversal tests at the 95 per cent confidence level. The corresponding palaeopoles, at 339.0 degrees E, 60.1 degrees N with A(95) = 11.2 degrees (Silurian) and 336.0 degrees E, 56.0 degrees N with A(95) = 9.2 degrees (Devonian), imply that the North China Block (NCB) had a low palaeolatitude of around 15 degrees N in the Northern Hemisphere during the Silurian-Devonian period. Comparison with the Early-Middle Ordovician palaeopole of the NCB suggests that the NCB moved rapidly northwards by 30.8 degrees +/-10.9 degrees to cross the palaeo-equator during the Early-Middle Ordovician to Silurian. In combination with the palaeobiogeographical data from Ningxia, our palaeomagnetic results suggest that the NCB was located close to Australia during the Late Devonian.