Geochemical-Thermo-Mechanical Modeling Applied to Plume-induced Subduction Initiation Along the Caribbean Large Igneous Province

Recent geochemical (Whattam and Stern, 2015) and geodynamical (Gerya et al., 2015) evidence suggest that plume-induced subduction initiation (PISI) instigated the Central American Volcanic Arc system circa 100-90 Ma. The Caribbean is a natural example to study PISI and may provide more information on the advent of plate tectonics on Earth. Here, we relate geodynamical processes to real chemical data to test the viability of PISI.

For this purpose a geochemical thermo-mechanical 3D high-resolution model has been developed, tracing physical parameters, source lithologies and geochemical signatures. Based on a large database consisting of partition coefficients and reference geochemistry the forward modeling approach uses hydration, dehydration and melt partitioning algorithms to show the chemo-temporal progression of trace elements (Ba, Ce, Nb, Zr, Y, Th) and isotopes (Hf, Sr, Nd, Pb), and the tectono-magmatic evolution of PISI on a regional scale. The model shows a loss of enriched, fertile plume-sourced lavas at early stages, and heterogeneous geochemistry of the oceanic plateau. Trace elements ratios trace magmatic and geodynamic processes and isotopes make it possible to more accurately interpret the interplay of different source components.

Early-stage enriched products can be related to high-temperature komatiites from the Tortugal Suite (Trela et al., 2015). We link and explain Caribbean geochemistry with locations in the geodynamic model. We also show that a heterogeneous plume is not necessary for heterogeneous surface geochemistry. Based on the model we also propose a process for the evolution from primitive mantle to a depleted upper mantle and an enriched lower mantle by means of PISI paired with large-scale drip tectonics.

Advances made in this project address the possibility of PISI in prompting modern plate tectonics on Earth, and are a first step to an integrated geochemical-geodynamical approach to solve cross-disciplinary problems concerning Earth's evolution. It may also prove useful to investigate geodynamic processes of other planets based on the surface chemistry.