Australia: The Land Where Time Began

A biography of the Australian continent 

Mantle Plume Head - Influence on Dynamics of Retreating Subduction Zone

The authors¹ say there is evidence from the geological record and seismic tomography containing multiple examples of interacting mantle plumes and subducting oceanic slabs, though the consequences of these interactions and a mechanism that allows plumes to pass from the slab that is subducting to the overriding plate are uncertain. In this article the authors¹ present 3D numerical simulations of a subduction zone that is retreating encountering a mantle plume head, and assess the impact on the geometry of the trench of a plume head, and whether or not it can form a window in the subducting slab. According to the authors¹ in their model they consider interactions between the plume head and the slab to follow naturally from the entrainment of the plume head by motion of the plate combined with the retreat of the slab. Plume heads are prevented from reaching the surface by strong slabs, though for weak slabs plume heads that are strongly buoyant cause the local advance of the trench, slab windowing and accelerated retreat of the slab at the plume head margins. This trench advance may contribute to shortening of the crust in the overriding plate when plume heads are large. A potential conduit for plume material transfer from the subducting plate to the overriding plate, by the opening of a slab window, without terminating a magmatic arc away from the tear in the slab caused by the plume head.

Sources & Further reading

1. Betts, Peter G., Wendy G. Mason, and Louis Moresi. "The Influence of a Mantle Plume Head on the Dynamics of a Retreating Subduction Zone." Geology 40, no. 8 (August 1, 2012 2012): 739-42.