My work in this area involves the present-day composition of the earth's mantle and the processes governing its recent evolution. An example is the study I published in 1992 (see below), in which we used the Th and Sr isotopic compositions in mid-ocean ridge basalts (MORB) to constrain the time scales and processes of recent upper mantle modification events. The following figure shows a) the range in Th and Sr isotopic compositions in a variety of mantle derived lavas; b) the range in Th and Sr isotopic compositions in MORB; and c) and d) two possible scenarios (mixing and multiple melting events) for casuing this compositional dispersion. The data shown in filled symbols is ours, whereas open-symbol data is from the literature.

For more info on this topic, please see:

K.H. Rubin and J.D. Macdougall, (1992) Th-Sr isotopic relationships in MORB Earth Planet. Science Lett., 114, 149-158.

See also:

Ken Rubin and John Mahoney, (1993) What's on the plume channel? Nature (News and Views), 362, 109-110.

K.H. Rubin (1991) Timing, extent and sources of marine volcanism through U-series disequilibrium, Ph.D. Thesis, University of California, San Diego, pp. 168.

K.H. Rubin, G.E. Wheller, M.O. Tanzer, J.D. Macdougall, R. Varne and R.C. Finkel, (1989) 238U decay series systematics of young lavas from Batur volcano, Sunda Arc, J. Volcan. Geother. Res., 38, 215-226.

K.H. Rubin and J.D. Macdougall, (1988) 226Ra excesses in mid-ocean-ridge basalts and mantle melting, Nature 335, 158-161.

Papers in preparation on this subject:

K.H. Rubin, J.D. Macdougall and J.-G. Schilling, Actinide series isotopes in Easter microplate MORB: recent geochemical heterogeneity at a site of mantle plume-mid ocean ridge interaction.

K.H. Rubin, J.D. Macdougall, J.M. Sinton and J.J. Mahoney, 238U-230Th-226Ra radioactive disequilibria and Th isotopes in EPR MORB from 13oS-23oS: axial variations in lava age, source chemistry, trace element fractionation and magmatic transport.