GeoSoilEnviroCARS 2002-02-28 Matt Newville, Steve Sutton, Mark Rivers Applications: XANES EXAFS Techniques: Near-neighbor distances and coordination environment.

2002-02-28 GeoSoilEnviroCARS

Matt Newville, Steve Sutton, Mark Rivers

• Applications:

XANES

EXAFS

•Techniques:

Near-neighbor distances and coordination environment of selected element.

Chemical speciation / oxidation state

X-ray Microprobe for Fluorescence and Absorption Spectroscopy

X-ray Fluorescence Chemical composition, elemental correlations, 2-dimensional mapping, fluorescence tomography

Chemical composition, speciation, and local atomic structure for elements in heterogeneous materials at a micron scale.

Environmental Sciences:

Geochemistry:

Planetary Sciences

(1ppm)

(10ppm)

(100ppm)

Speciation, mobility, and bio-availability of metals in soils, plant tissues, and at mineral surfaces.

Elemental abundance and correlations and oxidation state of metals in meteorites.

Elemental partitioning and metal speciation in hydrothermal fluids.

2002-02-28 GeoSoilEnviroCARS

Beamline13-ID-C is a world-class micro-beam facility for x-ray fluorescence (XRF) and x-ray absorption spectroscopy (XAS) studies:

Focusing: Horizontal and Vertical Kirkpatrick-Baez mirrors

Incident Beam:Monochromatic x-raysfrom LN2-cooled Si (111)

Sample Stage: x-y-z(-) stage, 1m resolution

Fluorescence detector:16-element Ge detector [shown], Ion Detector, or Wavelength Dispersive Spectrometer

Data Collection:Flexible software for x-y mapping, XAFS,tomography scans.

Optical Microscope:

(5x to 50x) with external video system

GSECARS Fluorescence and XAFS Microprobe Station

2002-02-28 GeoSoilEnviroCARS

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, high-pressure 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 andXAFS 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.

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.

Metal Speciation in Hydrothermal Fluid Inclusions

100m

2002-02-28 GeoSoilEnviroCARS

John Mavrogenes, Andrew Berry (Australian National University)

Cu 25oC

Cu 495oC

Fe 25oC

Fe 495oC

65m

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 and Fe K fluorescence intensities were

recorded as a function of x-y position across a fluid inclusion by moving the sample in 5m steps with an x-ray beam of 5m x 5m.

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.

Cu Speciation in Hydrothermal Fluid Inclusions: XRF Maps

Cu 495oC

2002-02-28 GeoSoilEnviroCARS

John Mavrogenes, Andrew Berry (Australian National University)

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.

Cu Speciation in Hydrothermal Fluid Inclusions: XAFS

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+ High temp: Cu1+ Cu2+

O

O

2.35Å

1.96Å

Cl

2.09Å

Cu1+

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,