CSEDI Collaborative Research: Application of siderophile elements to mantle geodynamics

Carnegie Institution Of Washington, Washington DC

Investigators

Abstract

We propose to conduct collaborative, synergistic research combining observations of siderophile element compositions with geodynamic modeling to study the evolution of elemental and isotopic heterogeneities in the mantle. Siderophile elements are those with a preference to enter metal rather than silicates, and are thus, elements that are largely concentrated in planetary cores. The objectives of this study will be to develop a better understanding of the global processes that led to the establishment of siderophile element abundances in the mantle, assess the extent of and possible mechanisms for the long-term preservation of the siderophile elemental and isotopic heterogeneities observed in the terrestrial rock record, and combine this information with geodynamic modeling to provide new insights to develop a better understanding of the formation and early chemical evolution of the Earth. In part, this project will be accomplished via study of the petrologic and chronologic extents of 182W isotopic anomalies in terrestrial systems using a newly-developed, high precision mass spectrometry technique. Ancient rocks, such as komatiites for which we have already identified isotopic anomalies, as well as modern rocks, such as MORB, oceanic peridotites, and ocean island basalts, will be examined as part of this task. Where necessary, complementary concentration and isotopic data for other elements, such as Os and Nd, will be generated. To better understand the causes and implications of the isotopic systematics revealed, we will test, via different geodynamic models, mechanisms for the formation and dispersal of the geochemical reservoirs with the appropriate characteristics. By tracking hafnium and tungsten in models of a range of possible early Earth states, then comparing model results with observations, we will be able to rule out some early Earth formation models and also better understand mantle mixing over the evolution of the Earth.