Interactions of Buoyant Upwellings with Subduction Induced Mantle Wedge Flow

One of the primary modes of thermal-chemical transport in subduction zones controlling the growth of crust and the evolution of ocean-atmosphere system through geologic time is buoyant upwellings or diapirs. Typical process models developed from surface data depict vertical ascent paths in two-dimensional cross-sections through convergent margins. In this investigation we show that compositionally buoyant diapirs sourced from the slab-wedge interface have significantly more complex communication pathways as they interact with three-dimensional, time-varying mantle circulation driven by plates. Analogue fluid dynamical laboratory experiments, capable of representing the needed range in length scales (106 orders of magnitude), are used to characterize diapir dynamics for a range in plate-driven and buoyancy-driven parameters. Circulation patterns are recorded in traditional cross-sectional and map-view planes using photogrammetry to measure deflections from vertical ascent and parallel to the strike of the trench imposed by the creeping wedge flow. Results show a) the style of plate subduction produces different diapir paths, with spatial-temporal complexity (95% non-vertical paths) b) up-slab and down-slab buoyancy fluxes lead to three basic surfacing modes in arcs and c) three-dimensionality of subduction-driven wedge flow, specifically trench-parallel motion, leads to complex diapir-conduit interaction scenarios, with strong implications for geochemical models of arc volcanics. Diapir thermal models produce a complex range of evolution scenarios, from no-melt, to partial-melt and to full-melt outcomes depending on individual paths.