Preliminary result and its tectonic implications of Middle Cambrian paleomagnetism in the Alashan and Hexi Corridor terrane

This study reports the paleomagnetic results of 107 orientated drill-core M iddle Cambrian samples at 15 sites of the east of the Alashan and Hexi Corr idor terrane. Detailed paleomagnetic and rock magnetic studies yield that s ampled rocks are magnetically predominant of magnetite, and the high temper ature component B4 passed fold test at the 95% confidence level. The direct ions of this component after tilt correction are significantly different fr om post-Silurian ones of the North China Block and the Alashan and Hexi Cor ridor terrane. The corresponding paleomagnetic pole is'. at 349.9 degrees E , 21.1 degrees N with A(95) = 14.9 degrees, which is close to that of the N orth China Block. This implies that no distinct latitudinal displacement oc curred between the Alashan-Hexi Corridor terrane and the North China Block since the Middle Cambrian. Nonetheless, the Alashan and Hexi Corridor terra ne may rotate counterclockwise about 15 with respect to the North China Blo ck during the Middle Cambrian through to Late Cambrian. This rotation may i ndicate that there was an accreting course of the Alashan and Hexi Corridor terrane to the west of the North China Block, and then one united North Ch ina Block was formed in the Late Cambrian.