Transient Hotspot Motion Induced by Plume-Migrating Ridge Interaction

Paleomagnetic data obtained from the Emperor Seamount Chain shows that the Hawaiian hotspot moved rapidly (~40 mm/yr) southward relative to the Earth's magnetic poles during the period of 81- 47 Ma before coming to rest at its present latitude, suggesting that this abrupt change in the motion of the hotspot created the prominent bend in the Hawaii-Emperor Seamount Chain (HESC) [Tarduno et al., 2003]. Tarduno et al. [2009] proposed that this period of rapid hotspot motion might have been the surface expression of the conduit of the presumed Hawaiian plume being entrained and tilted by the passage of a migrating mid-ocean ridge (the Pacific-Kula ridge system) over the plume. While geophysical and geochemical observations have suggested that ridges can influence the dispersion of plumes in the upper mantle at great distances (>1000 km), much about the interaction between mantle plumes and mid-ocean ridges remains poorly understood. We report on a series of 2-D numerical and 3-D analog geodynamic experiments in which a mid-ocean ridge migrates over a mantle plume. These experiments were undertaken to characterize variations in the location of plume-derived melt as the system evolves through time. A range of values for plume excess temperature, plume conduit width, spreading rate and ridge migration rate were investigated so as to fully evaluate the behavior of the system. We find that both the location of the maximum flux of plume-derived melt and the total area over which plume melt is generated vary systemically over the course of the experiments. Most notably, as the ridge moves away from the plume conduit, the area from which plume-derived melts are generated gradually expands in the direction of ridge migration until it reaches a maximum extent, after which it rapidly collapses back towards the plume conduit. The edge of this zone of plume-derived melting can extend as much as 1500 km from the plume conduit, and upon reaching its maximum extent it retreats towards the conduit at speeds ranging from 2 to 25 cm/yr. We suggest that the rapid contraction of this region of plume-derived melting could produce a pattern of surface volcanism that would be consistent with a rapidly migrating hotspot, similar to the Hawaiian hotspot between 81 and 47 Ma.