地幔柱影响大陆板块漂移速率的数值模拟研究--对印度板块晚白垩世快速漂移的启示

Numerical Modeling of the Effect of Mantle Plume on Continental Drift: Revelation of the Rapid Drift of the Indian Tectonic Plate in Late Cretaceous

本文利用二维地球动力学数值模拟方法研究地幔柱与大陆岩石圈相互作用,着重探讨上覆大陆岩石圈结构、地幔柱规模及二者间的相对位置等参数对上覆大陆漂移速率的影响。模拟结果表明,在地幔柱作用下,大陆是否含厚的岩石圈根对其自身的漂移速率有一定影响;在相同规模地幔柱作用下,大陆的漂移速率随着岩石圈根的增厚而减小。另外,大陆岩石圈越长其漂移速率越小,最终漂移距离越短。且随着地幔柱直径的增加,上覆大陆漂移速率和持续漂移时间都会随之增加。对于含岩石圈根模型而言,岩石圈根位置越靠近地幔柱上涌中心,上覆大陆的漂移速率越大,最终漂移距离越长。而对于不含岩石圈根模型,上覆大陆与地幔柱的相对位置同样影响较大。地幔柱越靠近上覆大陆岩石圈的边缘,其对于大陆漂移的影响越显著。上涌地幔柱对于上覆大陆漂移普遍起到10 cm/a以上的增速作用。模型结果对认识印度大陆在晚白垩世的快速向北漂移提供了重要的动力学约束和地质启示。

Numerical modeling is used to investigate the interaction between mantle plume and continental lithosphere,especially the effect of the continental lithosphere structure,the scale and position of mantle plume on the rate of continental drift.Numerical results show that,under the effect of mantle plume,the existence of a thick root of the continental lithosphere affects the rate of continental drift.Moreover,under identical scale of mantle plume,the drift rate decreases with increasing thickness of the root.Besides,the velocity and distance of a continental plate drift are negatively correlated in scale of the continental lithosphere,but correlated with the scale of the mantle plume.For the model without lithospheric root,the mantle plume has a more appreciable impact on the plate drift rate when it comes closer to edge of the continental plate.Our models show that mantle plume can accelerate the continental drift by more than 10 cm/a.The modelling results can provide significant dynamical constraint and geological enlightenment.