CSEDI Research - Fine Structure of the Lower Mantle

California Institute Of Technology, Pasadena CA

Investigators

Abstract

This is a collaborative study of the deep mantle between the disciplines of body wave seismology, computational geodynamics, and isotope geochemistry. The project will systematically survey seismic data sets and compare waveform data with synthetics for a range of models (including tomographic, hybrid, and convection models). An assortment of modeling techniques have been assembled to take advantage of many different types of seismic phases to constrain dynamic models. With the release of two large datasets (South African array and Saudi Arabian network) along with the ever expanding IRIS and East African PASSCAL experiments, there will be an excellent opportunity to study the underpinning of the African continent from bottom-to-top. A concerted effort will be made to formulate, study, and apply dynamic models of the lower most mantle, especially the upwellings African superplume. Both 2-D (including a cylindrical geometry) and 3-D Cartesian finite element, mantle convection codes will be used to understand lower mantle and core mantle boundary dynamics. Spherical models of convection that have the history of plate motions imposed as boundary conditions will also be used. Model quantities (such as temperature, chemistry, phase, melt, and anisotropy) will be mapped into two and three dimensional seismic velocity fields. These predictions will be tested directly with body wave phases. Previous interdisciplinary work between seismology and geodynamics has allowed has supported the hypothesis that there are three types of structures within the lower most mantle where plumes arise: thermo-chemical super plumes, thermal upwellings which have ULVZ at their base, and thermal plumes which erupt through old subducted slabs. A new goal of this continuing research project is to use seismological observations and dynamical models as new organizing principles for interpreting the geochemistry of plume-related basaltic lavas. The seismology and geodynamics will be used to predict maps (predicted plume provinces) which will be tested with the geochemistry of MORBs and OIBs.