Andy Van Cleave (2003) - Bioprecipitates in Mg-silicate/carbonate systems: insights into ALH84001 carbonate genesis.

Judy Harden - (2005) B.S. Li isotope and B-Be-Li studies of "hotspot" and other intraplate volcanic rocks, and an educational application

The science I do is very strongly instrument-based: I examine unusual and often difficult-to-measure elemental and isotopic tracers in rocks and waters as a means of gaining new insights into the origins and history of these materials, and to characterize and understand large-scale geochemical processes in the Earth. Toward these ends I manage the Geology department's rock analysis laboratories, which currently include a DC plasma emission spectrometer, our primary in-house tool for elemental analysis in rocks; and an X-ray powder diffractometer for the identification of minerals. We also prepare rock samples for trace metal analysis, particularly for Rare Earth Element (REE) studies, making use of ICP-MS facilities at the University of Boston, and other labs.  My ongoing collaborations with researchers at the Department of Terrestrial Magnetism of the Carnegie Institution of Washington, and at the University of Maryland at College Park, provides us with access to these extensive analytical labs, including thermal ionization mass spectrometry facilities for traditional radiogenic isotopes, and their new doubly focusing, multicollector ICP-source MS instruments for B and Li isotopic analyses. A new addition to our in-house analytical capabilities (funded by NSF) is a regional electron microprobe/SEM facility. The instruments are housed at Florida International University, in the Florida Center for Analytical Electron Microscopy , and we have remote operation capabilities at USF via an Internet 2 operational link, which means that we run the instrument in real time off of our desktop computers in Tampa.

I currently maintain active research programs on modern subduction zones, and on the origins and metamorphic/tectonic evolution of igneous rock units in the southern Appalachians.

My subduction zone studies follow two separate, but related tracks:
1) Elemental fluxes in subduction zones. Tracers such as Li, B, ^11/10B and ^10/9Be indicate that materials and particularly fluids from the subducting plate are involved in the generation of lavas at volcanic arcs. I am examining a wide variety of volcanic and metamorphic materials to constrain the physical processes behind fluid-mediated slab/mantle chemical exchanges, and to quantify chemical fluxes between the Earth's surface and its deep interior. My most recent efforts have involved examining lithium isotope variations in suites of arc lavas, volcanic rocks from several different "hotspot" settings, and in arc mantle-derived ultramafic xenoliths with the goal of characterizing both subduction-related fluxes of Li into the mantle, and to try and identify subduction-generated Li reservoirs in the mantle.

2) The petrogenesis of igneous and metamorphic rocks at subduction zones. I am studying the origins of igneous rocks from a variety of volcanic arcs (the Woodlark Basin/New Georgia volcanic arc, the Mexican Volcanic Belt, Kuril-Kamchatka arc, the Central American volcanic arc, and the Aleutians, among others). I have also been examining the origins and history of subduction-related metamorphic rocks, including samples from the "subduction complex" association of the Catalina Schist (Calif.), and in particular samples of diapiric serpentinites extruding as seamounts in the forearc regions of the Marianas and Izu-Bonin arcs.

The mass transfer pathways indicated by our forearc and cross-arc studies have led us to examine the role that subduction plays in defining the chemical signature of the deep mantle. A recently funded project examined the B and Li isotopic systematics of lavas from Mt. Erebus, Antarctica, with the intention of identifying subducted components in the deep mantle sources of intraplate lavas.  Newly funded research will use Li isotope systematics along with B-Be-Li abundance systematics to assess the development of mantle heterogeneities in subduction systems, focusing on off-axis volcanism in Mexico and Guatemala; and to fully characterize the OIB-source mantle reservoirs for Li isotopes.