Palaeomagnetism and geochronology of mid-Neoproterozoic Yanbian dykes, South China: implications for ac.820–800 Ma true polar wander event and the reconstruction of Rodinia

Abstract

AbstractWe present new palaeomagnetic data from two generations of mafic dykes in the Yanbian region of the western South China Block, dated by the zircon U–Pb method at 824±6 and 806±8 Ma, respectively. The primary origin for the characteristic remanent magnetizations is supported by a positive baked contact test, a dyke-tilt test and rock magnetic data. After tilt corrections, 10 dykes from the c. 824 Ma group gave a mean remanent direction of D=230.1°, I=−72.6° with k=16.3 and α95=12.3°, corresponding to a palaeopole at 42.5 °N, 131.8 °E with A95=19.0°. Three dykes from the c. 806 Ma group give a mean direction of D=284.5°, I=42.6° with k=76.5 and α95=14.2, corresponding to a virtual geomagnetic pole (VGP) at 18.2 °N, 31.0 °E with A95=20.4°. After correcting for a 5° vertical-axis rotation of the study region, the two pole positions are at 45.1 °N, 130.4 °E and 14.1 °N, 32.5 °E, respectively. The c. 825–720 Ma palaeopole position from South China, East Svalbard and neighbouring continents fall on great circles on two alternative Rodinia reconstructions, possibly reflecting oscillating inertial interchange true polar wander events (IITPWs).