The dynamics of off-axis plume-ridge interaction in the uppermost mantle
Date of Original Version
Two decades of geochemical and geophysical observations have led to the plume channel model whereby buoyant, off-axis mantle plumes feed and interact with diverging plates at mid-ocean ridge axes which act as sinks of upper mantle material. Here we present results from two-dimensional (2-D) numerical experiments which incorporate the essential physics and fluid dynamic aspects of the plume-ridge-upper mantle system in order to test the feasibility of this plume-ridge interaction model. Specifically, experiments test the relative importance of physical effects such as strong viscosity variations and thermal and chemical buoyancy forcing in plume-ridge dynamics. Results indicate that both transient and steady-state connections may be established between off-axis plumes and ridges for a range of realistic mantle conditions. The presence of a strongly sloping Theological boundary layer (RBL) is a necessary condition for long-term communication between an off-axis buoyant upwelling and a spreading ridge. The flux of buoyant material to the ridge is also shown to increase with increasing plume-to-mantle density contrast, decreasing plume viscosity and smaller plume-ridge separation distances. Plume-ridge interaction regimes are defined based on the competing effects of plate-driven and buoyancy-driven flow. Thermal erosion of the viscous lithosphere strongly inhibits long-term plume-ridge interaction by enhancing the plates ability to deflect the plume, both head and conduit, away from the ridge axis.
Publication Title, e.g., Journal
Earth and Planetary Science Letters
Kincaid, C., J. G. Schilling, and C. Gable. "The dynamics of off-axis plume-ridge interaction in the uppermost mantle." Earth and Planetary Science Letters 137, 1-4 (1996). doi: 10.1016/0012-821x(95)00201-m.