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 f or palaeomagnetic study from Silurian and Devonian red beds, marlaceous san dstone, and limestone rocks in the eastern part of the Hexi Corridor, south west Ningxia, North China. The characteristic high-temperature component re sides in both haematite and magnetite. It clusters around a northwesterly a nd shallow to moderate downward direction and its antipode after tilt corre ction. The primary origin of this characteristic remanent magnetization (Ch RM) is ascertained by positive fold and reversal tests at the 95 per cent c onfidence level. The corresponding palaeopoles, at 339.0 degrees E, 60.1 de grees N with A(95) = 11.2 degrees (Silurian) and 336.0 degrees E, 56.0 degr ees 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 Hemi sphere during the Silurian-Devonian period. Comparison with the Early-Middl e Ordovician palaeopole of the NCB suggests that the NCB moved rapidly nort hwards by 30.8 degrees +/-10.9 degrees to cross the palaeo-equator during t he Early-Middle Ordovician to Silurian. In combination with the palaeobioge ographical data from Ningxia, our palaeomagnetic results suggest that the N CB was located close to Australia during the Late Devonian.