CHEM 0226

eworsha1 [at] umd [dot] edu

Richard Walker

My research interests are focused broadly on using the geochemistry of meteorites to understand nebular and planetary geologic processes in the early solar system. Specifically, I am interested in the nature of genetic relationships between and among meteorite groups representing specific planetary bodies, and in the accretion, differentiation, and early evolution of planetesimals. I primarily use isotopic and trace element abundances in iron meteorites to address these research concentrations. The IAB complex of iron meteorites is of particular interest in that it likely had a more complicated history than other iron meteorite groups, which originated in the cores of differentiated planetesimals. Much of my research is concerned with using the trace element abundances in IAB complex meteorites to elucidate the crystallization process or processes of the IAB metallic melt(s). I also use the Hf-W radiogenic isotope system, coupled with Os isotopic compositions, to understand the relative timing of metal-silicate segregation in the IAB complex, and Mo isotopes to understand how subgroups within the complex are related to one another. In order to determine Mo isotopic compositions in both meteoritic and terrestrial materials, I am developing procedures for high-precision analyses of Mo isotopes by thermal ionization mass spectrometry. Highly precise Mo isotope data can be used as fingerprints in a variety of geologic materials to address issues related to nebular mixing, planetary genetics, and late accretion.

Walker R.J., Bermingham, K., Liu J., Puchtel I.S., Touboul M. and Worsham E. (2015) In search of late-stage planetary building blocks. Chemical Geology. 411 125-142. DOI: 10.1016/j.chemgeo.2015.06.028

Worsham, E. A., Bermingham, K. R., Walker, R. J. (2016) Siderophile element systematics of IAB complex iron meteorites: New insights into the formation of an enigmatic group. Geochimica et Cosmochimica Acta. 188 261-283. DOI: 10.1016/j.gca.2016.05.019

Worsham E.A., Walker R.J. and Bermingham K.R. (2016) High-precision molybdenum isotope analysis by negative thermal ionization mass spectrometry. International Journal of Mass Spectrometry. 407 51-61. DOI: 10.1016/j.ijms.2016.06.005

Bermingham K., Walker R.J. and Worsham E.A. (2016) Refinement of high precision Ru isotope analysis using negative thermal ionization mass spectrometry. International Journal of Mass Spectrometry. 403 15-26. DOI: 10.1016/j.ijms.2016.02.003

Worsham, E.A., Bermingham, K.R. and Walker, R.J. (2017) Characterizing cosmochemical materials with genetic affinities to the Earth: Genetic and chronological diversity within the IAB meteorite complex. Earth and Planetary Science Letters. 467 157-166. DOI: 10.1016/j.epsl.2017.02.044