PRISE Annual Report 2004

Prise operates as a unique entity within the Research School, with the principal charter to provide external access to the Research School’s specialised equipment and expertise in the areas of geochronology, isotope geochemistry and trace element geochemistry. During 2004 Prise continued to compete successfully in an increasingly competitive market; the main areas of such activities being SHRIMP projects, with significant LA- and solution ICPMS components and TIMS analyses.

Collaborative research projects have been undertaken with colleagues from Europe, southeast Asia, southern Africa and both North- and South America as well as that conducted with staff of other Australian universities and institutions. A small proportion of purely commercial work has been carried out, mainly for Australian clients.

Prise staff also conduct their own research and have been successful in obtaining a number of ARC Discovery and Linkage grants. They are also significantly involved with numerous successful grant applications to international funding agencies. Prise staff effected 40 publications and hosted 22 visitors to the Research School during 2004.

Research highlights include:

Timing of the Snowball Earth – Mr C.M.Fanning The concept of a Snowball Earth has stimulated much discussion and ongoing research. A fundamental criterion is the absolute timing of the glaciogene events on a global scale. From a study of stratigraphically well constrained rocks near Pocatello Idaho, USA absolute age constraints can be placed on the glaciogene events and so enable one to draw comparisons and contrasts with other correlated horizons. From this and other studies it is clear that some glacigene events are globally coincident, whilst others are clearly outside the bounds of a single coeval, coincident Snowball Earth event.

Chalcophile element volatility - Dr. M.D. Norman The volatility of chalcophile metals rhenium (Re), cadmium (Cd), and bismuth (Bi) in basaltic magmas was proven by a study of submarine glasses recovered from offshore landslide deposits around the Hawaiian volcanoes Ko'olau and Moloka’i. This research was done in collaboration with Prof. Michael Garcia, University of Hawaii, using the laser ablation ICPMS facilities at RSES. Rhenium, Cd, and Bi contents of these glasses correlate with S abundances, demonstrating volatile loss of these metals during volcanic eruptions. Rhenium appears to be considerably more volatile than previously thought, and may be the most volatile chalcophile metal in basaltic magma systems. This discovery may explain the unexpectedly low Re contents of many subaerial lavas, and help resolve the ‘missing Re’ problem by showing that mantle plumes have higher Re contents than the depleted mantle.

Advancing diamond indicator interpretation – mantle redox condtions and diamond stability - Dr G.M. Yaxley (in collaboration with Dr A.J. Berry, RSES and Prof. A.B. Woodland, Uni Frankfurt) We have advanced application of a synchrotron-based technique called XANES (X-ray Absorption Near Edge Structure) spectroscopy to the measurement of Fe 2+ and Fe 3+ contents of pyrope garnets transported from the deep lithosphere to the surface in kimberlites. Calibration measurements, undertaken during 2004 at the Australian National Beamline Facility at the Tsukuba synchrotron in Japan (funded by ANSTO), indicated that with further development, Fe K-edge XANES spectroscopy applied to garnet in garnet peridotite xenoliths will allow determination of lithospheric redox state, an important parameter in assessing the diamond potential of individual kimberlites.

Research Highlights

Mark Fanning - K-bentonites in the Argentine Precordillera contemporaneous with rhyolite volcanism in the Famatinian Arc

Mark Fanning - U-Pb SHRIMP ages of Neoproterozoic (Sturtian) glaciogenic Pocatello Formation, southeastern Idaho

Richard Armstrong - U-Pb and fission track ages from Oceanic Crust at Macquarie Island

Marc Norman - Trace element distribution coefficients for pyroxenes, plagioclase, and olivine in evolved tholeiites from the 1955 eruption of Kilauea Volcano, Hawai`i, and petrogenesis of differentiated rift zone lavas

Greg Yaxley - High pressure partial melting of gabbro and the preservation of “ghost plagioclase” signatures

Greg Yaxley - Calibration of a synchrotron-based XANES technique for determination of Fe3+/∑Fe in garnet