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X-ray Microprobe for Fluorescence and Absorption Spectroscopy Matt Newville, Steve Sutton, Mark Rivers Chemical composition, speciation, and local atomic structure for elements in heterogeneous materials at a micron scale. •Techniques: X-ray Fluorescence Chemical composition, elemental correlations, 2dimensional mapping, fluorescence tomography (1ppm) XANES Chemical speciation / oxidation state (10ppm) EXAFS Near-neighbor distances and coordination environment of selected element. (100ppm) • Applications: Environmental Sciences: Speciation, mobility, and bio-availability of metals in soils, plant tissues, and at mineral surfaces. Planetary Sciences Elemental abundance and correlations and oxidation state of metals in meteorites. Geochemistry: Elemental partitioning and metal speciation in hydrothermal fluids. GeoSoilEnviroCARS 2002-02-28 GSECARS Fluorescence and XAFS Microprobe Station Beamline13-ID-C is a world-class micro-beam facility for x-ray fluorescence (XRF) and x-ray absorption spectroscopy (XAS) studies: Incident Beam: Monochromatic x-rays from LN2-cooled Si (111) Sample Stage: x-y-z(-q) stage, 1mm resolution Fluorescence detector: 16-element Ge detector [shown], Ion Detector, or Wavelength Dispersive Spectrometer Optical Microscope: (5x to 50x) with external video system Data Collection: Flexible software for x-y mapping, XAFS, tomography scans. GeoSoilEnviroCARS Focusing: Horizontal and Vertical Kirkpatrick-Baez mirrors 2002-02-28 Metal Speciation in Hydrothermal Fluid Inclusions John Mavrogenes, Andrew Berry (Australian National University) Hydrothermal ore deposits are the main source of Cu, Au, Ag, Pb, Zn, and U. Metal complexes in high-temperature, highpressure solutions are transported until cooling, decompression, or chemical reaction cause precipitation and concentration in deposits. To further understand the formation of these deposits, the nature of the starting metal complexes need to be determined. XRF and XAFS are important spectroscopic tools for studying the chemical speciation and form of these metal complexes in solution. This is challenging to do at and above the critical point of water (22MPa, 375oC). Fluid inclusions from hydrothermal deposits can be re-heated and used as sample cells for high temperature spectroscopies. GeoSoilEnviroCARS Natural Cu and Fe-rich brine fluid inclusions in quartz from Cu ore deposits from New South Wales, Australia were examined at room temperature and elevated temperatures by XRF mapping and XAFS. 2002-02-28 Cu Speciation in Hydrothermal Fluid Inclusions: XRF Maps John Mavrogenes, Andrew Berry (Australian National University) Natural Cu and Fe-rich brine fluid inclusions in quartz from Cu ore deposits were examined at room temperature and elevated temperatures by XRF mapping: Cu 25oC Fe 25oC Cu 495oC Fe 495oC Cu and Fe Ka fluorescence intensities were recorded as a function of x-y position across a fluid inclusion by moving the sample in 5mm steps with an x-ray beam of 5mm x 5mm. Initial Expectation: chalcopyrite (CuFeS2) would be precipitated out of solution at low temperature, and would dissolve into solution at high temperature. We would study the dissolved solution at temperature XRF mapping showed that a uniform solution at room temperature was becoming less uniform at temperature. This was reversible. GeoSoilEnviroCARS 2002-02-28 Cu Speciation in Hydrothermal Fluid Inclusions: XAFS John Mavrogenes, Andrew Berry (Australian National University) XAFS measurements at low and high temperature were also very different, with a very noticeable differences in the XANES indicating a change in speciation Low temp: Cu2+ O 2.35Å Cu2+ High temp: Cu1+ O Cl 2.09Å Cu1+ 1.96Å Low temp High temp EXAFS from the high temperature phase (below) is also consistent with the model of Fulton et al: Cu1+ with Cl (or S) at 2.09Å, These results are consistent with Fulton et al [Chem Phys Lett. 330, p300 (2000)] study of Cu solutions near critical conditions: Cu2+ solution at low temperature, and Cu1+ associated with Cl at high temperatures. GeoSoilEnviroCARS 2002-02-28