Modeling Mantle Circulation, Temperatures and Melting Processes Beneath Back-Arc Spreading Centers

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ABSTRACT (Kincaid - 0453656) The Earth's interior represents a convective engine that generated our continents, oceans and atmosphere and continues to reshape them over time. Spreading ridges, where plates move apart, and subduction zones where plates converge, represent the dominant sites for energy and chemical exchange between Earth's interior and our oceans and atmosphere. Subduction zones, in particular, are important because they occur near continental margins where a large and growing percentage of Earth's population resides. Subduction zones have also produced all of the great earthquakes in recorded history, along with a variety of subduction-induced hazards including lava flows; pyroclastic flows; and devastating tsunamis. This research tests the hypothesis that the presence of a spreading center above a subducting plate dramatically modifies the system in terms of mantle flow (and stress fields), temperatures, and the production of melt and new crust. Two-dimensional (2-D) numerical models and a novel apparatus for three-dimensional (3-D) laboratory analog models of subduction with back-arc spreading are used. Results will characterize relationships between mantle circulation patterns, mantle temperatures, and variability in the types and volumes of melt that are produced and extracted from within these complex systems. Numerical models will be generated to show how different subduction parameters observed in the global arc system influence mantle processes and crustal growth in a 2-D sense. These results will be used to calculate the characteristics of melt leaving the mantle and, through comparisons with available chemical data, will allow focus to be brought on scenarios that are possible for the actual system. Laboratory models, developed with prior NSF funding that scale well to the mantle, will be used to characterize the 3-D spatial and temporal patterns in mantle flow, stress, temperature, and melt production in complex regions where subduction and plate spreading processes interact. The 3-D aspects of the laboratory models allow for effective comparisons with existing data sets, going beyond what is possible with 2-D computer models. Broader Impacts