Institute Professor, Earth and Environmental Sciences | Earth and Environmental Sciences
Troy, NY, UNITED STATES
Specializes in experiments and modeling that allow geoscientists to "reverse engineer" Earth materials and explore planetary history
Michael R. Ackerson, Nicholas D. Tailby, E. Bruce Watson
Titanium can be incorporated either tetrahedrally (IVTi) or octahedrally (VITi) in most silicate minerals. Ti K-edge X-ray absorption fine structure (XAFS) spectroscopy enables observation of Ti coordination in minerals and melts. In this study, XAFS is used to determine the coordination of Ti in synthetic and natural garnets...
M.R. Ackerson, E.B. Watson, N.D. Tailby, F.S. Spear
Garnet is a common and important mineral in metamorphic systems, but the mechanisms by which it incorporates Ti—one of the major elements in the crust—are not well constrained. This study draws upon garnets synthesized at a range of temperatures and pressures to understand Ti solubility and the substitution mechanisms that govern its incorporation into garnet at eclogite and granulite facies conditions. Garnets from these synthesis experiments can incorporate up to several wt% TiO2. Comparison of Ti content with deficits in Al and Si in garnet indicates that Ti is incorporated by at least two substitution mechanisms (VITi4+ + VIM2+ ↔ 2VIAl3+, and VITi4+ + IVAl3+ ↔ VIAl3+ + IVSi4+)...
DustinTrail, Nicholas D.Tailby, Antonio Lanzirotti, Matthew, Newville, Jay B. Thomas, E. Bruce Watson
The potential for zircon to record continuous and evolving magmatic redox conditions is investigated by quantifying Ce valence in natural and synthetic crystals by X-ray Absorption Near Edge Structure (XANES). Valence was determined at high spatial resolution (2 × 4 μm) by analysis of the Ce L3 edge for synthetic zircons and crystals from the Bishop Tuff Ig2E sequence; analyses included both core-to-rim and cross-sector measurements. Core-to-rim zonation among natural grains reveals a systematic increase in Ce4 +/ΣCe, with core regions that range from ~ 0.4 to 0.6 Ce4 +/ΣCe (i.e., ~ 40–60% Ce4 +), while zircon rims range from ~ 0.7 to 1.0 Ce4 +/ΣCe (i.e., ~ 70–100% Ce4 +)...