Palaeomagnetism and geochronology of mid-Neoproterozoic Yanbian dykes, South China: implications for a c. 820–800 Ma true polar wander event and the reconstruction of Rodinia
Published:January 01, 2016
Jiawen Niu, Zheng-Xiang Li, Weiguang Zhu, 2016. "Palaeomagnetism and geochronology of mid-Neoproterozoic Yanbian dykes, South China: implications for a c. 820–800 Ma true polar wander event and the reconstruction of Rodinia", Supercontinent Cycles Through Earth History, Z. X. Li, D. A. D. Evans, J. B. Murphy
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We 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).
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Supercontinent Cycles Through Earth History
The supercontinent-cycle hypothesis attributes planetary-scale episodic tectonic events to an intrinsic self-organizing mode of mantle convection, governed by the buoyancy of continental lithosphere that resists subduction during the closure of old ocean basins, and the consequent reorganization of mantle convection cells leading to the opening of new ocean basins. Characteristic timescales of the cycle are typically 500 to 700 million years. Proposed spatial patterns of cyclicity range from hemispheric (introversion) to antipodal (extroversion), to precisely between those end members (orthoversion). Advances in our understanding can arise from theoretical or numerical modelling, primary data acquisition relevant to continental reconstructions, and spatiotemporal correlations between plate kinematics, geodynamic events and palaeoenvironmental history. The palaeogeographic record of supercontinental tectonics on Earth is still under development. The contributions in this Special Publication provide snapshots in time of these investigations and indicate that Earth’s palaeogeographic record incorporates elements of all three end-member spatial patterns.