Goldschmidt Conference Abstracts 2005

Abstract

4 MS 954, U.S. Geological Survey, Reston, VA (imchou@usgs.gov)Fluid-solid and fluid-melt interactions up to 850 °C and 500 MPa in a hydrothermal diamond anvil cell were monitored using X-ray microspectroscopy. The high spatial resolution of the X-ray microprobe permits separate in situ analyses of different phases at a given temperature and pressure. Spectra were collected continuously for periods of up to 12 hours on beam lines 13ID-C or 201D-B at the Advanced Photon Source, Argonne National Laboratory, Chicago. The local structure or partial composition of the aqueous fluid or melt is determined using X-ray absorption fine structure (XAFS) and X-ray fluorescence (XRF) spectra, respectively. Quantitative elemental analysis of the aqueous fluid is achieved by using an internal spike. Analytical sensitivity is enhanced by reducing the path length of the Xrays in diamond to 80 micrometers by laser-milling a sample chamber and grooves in the culet face of one of the diamond anvils. The potential of this technique will be demonstrated using examples involving zircon-fluid and melt-fluid interaction.