My research efforts are currently focused on quantifying the concentration and distribution of tungsten and other siderophile elements in the Earth and its reservoirs (i.e., core, mantle, crust). Tungsten (W) is a refractory, moderately siderophile trace element whose initial abundance in the Earth can be estimated from chondritic abundances. In silicate systems, though, W behaves like a highly incompatible trace element, such as U, Ba or Th. Due to this incompatible behavior of W, it is difficult to precisely estimate the absolute concentration of W in the bulk silicate Earth (BSE). However, several published scientific papers have attempted to constrain the amount of W in the BSE by normalizing W to a similarly behaving incompatible lithophile element, most notably Ba and Th, and determining a representative W/Ba or W/Th ratio for the continental crust and the depleted mantle (Sims et al., 1990; Newsom et al., 1996). Unfortunately, representative samples of the upper mantle, such as peridotite xenoliths, massif peridotites and primitive high temperature melts, are considerably uncommon and can thus be argued to not accurately characterize the bulk of the depleted mantle. Mid-ocean ridge basalts (MORB’s), on the other hand, are extremely abundant, have been widely studied for the past 50 years and are derived directly from the upper mantle. Regrettably, though, few MORB’s have been analyzed for W (n=3) because of previously existing analytical challenges. For my first major project as a graduate student, I have begun analyzing W concentrations at the tens to hundredss ng/g level (±<10%) in fresh mid-ocean ridge basaltic glasses. In turn, these data will then be used to develop a model for abundance of W in the upper mantle, the source region of MORB’s.

Further along in my graduate studies I intend to use W isotopes in order to evaluate proposed models that have reported on detecting core-mantle interactions in the deep mantle-source regions of ocean-island basalts (OIB’s). W isotopes provide a new test for core interaction due to the extinct ¹⁸²Hf-¹⁸²W system. ¹⁸²Hf decays to ¹⁸²W via beta emission and yields a half-life of ~9 Myr. Because of the short-lived nature of this system, differences in W isotopes are imparted only at the beginning of Earth history and further differentiation processes do not affect them. This is not true for the long-lived Pt-Os and Re-Os systems, as parent-daughter fractionation could have occurred at any time in Earth history and will yield variable present-day Os isotopic anomalies depending on time, degree of fractionation and parent half-life. Collectively, these features make W isotopes particularly powerful as an independent test of core-contribution modeling, as concluded by Scherstén et al (2004).