I am interested in determining the fundamental molecular mechanisms that control ion exchange processes in porous heterosilicates specifically applied to heavy metal sequestration and industrial applications of adsorbed toxic metals. Although the precise ion diffusion pathways vary with mineral species, my work and that of my colleagues have demonstrated that mapping the structural role of H2O within porous frameworks and layered materials is critical for understanding and controlling ion selectivity.
A major question in Earth science, still debated, is what causes sea level change? One way to approach this question is to measure the slight changes in global seawater chemistry that have a profound impact on the crystal chemistry and structure of the minerals, be it calcite or aragonite, which are biologically mineralized. By determining the composition, crystal structures, and crystallization pathways of the organisms’ tests, a detailed proxy record of ocean chemistry through time will be developed.
(Top Left) Stitched reflected light photo mosaic of one ambulacral groove at 500x. (Bottom Left) Corresponding Raman map for the carbonate symmetric strech peak. Color variation reflects amount of calcite in beam. (Right) Stitched transmitted light photo mosaic at 100x showing mapped area in red.
This data shows the Ca/Mg homogeneity of the single crystal crinoid stem which was estimated to be ~1.9(4)% MgCO3 from peak fitting as compared to inornganic calcite standards from Bischoff, Sharma, Mackenzie (1985), Am. Min. p. 581-589. Continued work in this area will calibrate the Raman/Microprobe composition of these crinoid species.
This study characterizes asbestos-form minerals from the a talc mine in Talcville NY, which include tremolite, talc, and actinolite in thin section. Micro-Raman spectroscopy is used to make chemical maps at specified areas on the thin section surface. These maps allow for analysis of crystal morphology, chemical compositions, phase differentiation, phase transitions, and fractional abundances of minerals within the sample. This work will aid in the characterization of mineralogical controls of alteration products of tremolite/actinolite to talc.
Left: Comopositional map of three minerals: tremolite, actinolite, and talc.
Top Right: High spatial resolution map (1x1 micron step size) illustrating the alteration halos around the asbestos talc. Dashed lines represent composition contours from T0 (dark blue) to T100 (reds).
Bottom Right:compositional evolution analysis extracted form the red line in the above image of the actinolite alteration to talc. From right to left, the green line represents the amount of talc alteration. As well as a possible series of staged intervals of increasing talc concentrations represented as thin black lines.
Deep Earth Processes
One project is to trace the role of H2O during mineral formation and evolution in complex igneous systems. Coupled with this research I am using Raman microscopy to determine the compositional zonal patterns orthoclase feldspars, as well as the zonal compostional patterns of zircons, amphiboles, and plagioclases, to determine the dynamics and origin of intrusive and extrusive ignous bodies.
|(Left) Raman line scan of an orthoclase feldspar from the core to the rim. Frequency of sanidine (blue arrow) and anorthoclase (green arrow) are clearly visible in the map. Within each mineral phase, and zonal band, there are suble compositional changes in the K/(Na+K) ratios. This feldspar is from a pluton in Nevada.|