'G-cubed' joint inversions for the thermochemical environment and melting regime beneath intra-plate volcanic regions

Abstract

Although intra-plate volcanism is commonly attributed to the presence of thermal anomalies in the sublithospheric mantle (e.g. deep mantle plume, small-scale convection), recent geodynamic and geochemistry studies have emphasized the role of the thermochemical structure of the overlying lithosphere in dictating the type, timing and volume of surface volcanism in intra-plate environments. From the observational point of view, however, it has been difficult to formally link geophysical imaging techniques (e.g. seismic tomography) with geochemical data from erupted lavas to obtain an internally-consistent image of the thermochemical environment and melting regime responsible for intra-plate volcanism. Here we present the first geochemical-geophysical-geodynamic (‘G-cubed’) joint inversion approach capable of inverting both major and trace element lava compositions together with multiple geophysical datasets within a fully probabilistic framework. The result of this inversion is a complete thermo-chemical-dynamical model of the subsurface, including the melting regime. We illustrate the benefits and limitations of the method with a case study in eastern China. We show that our approach can successfully derive a thermochemical model that is fully consistent with all the inverted geochemical and geophysical data sets, providing fundamental constraints on the nature of the intra-plate volcanism and the underlaying mantle dynamics.