An Investigation into Thermochemical Piles beneath Africa and the Pacific

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Seismological studies have revealed the presence of large, low velocity anomaliesin the lower mantle beneath Africa and the Pacific, and there is growing evidence thatthese anomalies may be caused by chemical heterogeneity, possibly due to a more-densemantle component. A comprehensive geodynamical study into the development ofthermochemical piles in the lower mantle will be undertaken by performing fully 3Dspherical thermochemical convection calculations at Earth-like convective vigor whichincludes Earth's Cretaceous to present day subduction history. The proposed workinvolves a joint geodynamics-tomography approach to impose constraints uponheterogeneous mantle models by direct comparisons between geodynamically-predictedand seismically-observed tomography. The objectives of this work are to:(1) develop a method of 'tomographic filtering' and spatial correlation which willtransform geodynamic output to more closely resemble what it is expected toappear as from observational tomography.(2) Investigate the necessity of thermochemical models by determining whetherisochemical models can predict observations from seismology. Previous workhas hinted that this is not likely, however, only limited parameter sets havebeen observed.(3) To perform a comprehensive parameter search to understand how rheological,thermodynamic, and material properties affect the geographic position, arealextent, and height of dense thermochemical piles.(4) To ultimately place constraints upon the density and volume of dense pilesthat have been proposed to reside beneath Africa and the Pacific.Broader impacts associated with this work include providing resulting data to theGEON project which has been active in developing new, interactive methods to visualize3D geodynamical data sets with the ultimate goal of fostering collaborative efforts inscience and education. In addition, new code development will be shared with theComputational Infrastructure for Geodynamics (CIG). The proposed research will alsoform the basis of a Ph.D. student's dissertation, and will involve collaboration betweenseismology and geodynamics.-- Robin Reichlin Geophysics Program Director National Science Foundation 4201 Wilson Blvd., Room 785 Arlington, VA 22230 PHONE (703)-292-8556 FAX (703)-292-9025Upcoming Deadlines:GEOPHYSICS: December 1, 2004 (NEW EAR Program Announcement NSF 04-613)http://www.nsf.gov/pubsys/ods/getpub.cfm?nsf04613CSEDI: August 25, 2005 (Program Announcement NSF 04-593) http://www.nsf.gov/pubs/2004/nsf04593/nsf04593.htmGuidelines:NSF's latest Grant Proposal Guide is NSF 04-23 http://www.nsf.gov/pubsys/ods/getpub.cfm?gpg