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Cu K-edge X-ray absorption near edge structure (XANES) spectra were recorded from individual synthetic brine fluid inclusions as a function of temperature up to 500 [degrees]C. The inclusions serve as sample cells for high-temperature spectroscopic studies of aqueous Cu-Cl speciation. [Cu.sup.+] and [Cu.sup.2+] can both be identified from characteristic pre-edge features. Mixed oxidation states can be deconvoluted using linear combinations of [Cu.sup.+] and [Cu.sup.2+] spectra. This work illustrates how complex Cu XANES spectra can be interpreted successfully. [Cu.sup.2+] is the stable oxidation state in solution at room temperature and [Cu.sup.+] at high temperatures. The change in oxidation state with temperature was completely reversible. [Cu.sup.+] was found to occur exclusively as the linear species [[Cu[Cl.sub.2]].sup.-] in solutions containing KCl with Cu:Cl ratios up to 1:6. In the absence of [K.sup.+], there is evidence for higher order coordination of [Cu.sup.+], in particular the tetrahedral complex [[Cu[Cl.sub.4].sup.3-]. The importance of such complexes in natural ore-forming fluids is yet to be determined, but may explain the vapor-phase partitioning of Cu as a Cl complex from a Cl-rich brine. Keywords: XAS (XAFS, XANES), Cu in high-temperature brines, high-temperature studies, XANES of fluid inclusions, fluid phase, experimental petrology, synthetic fluid inclusions

Using synchrotron X-ray fluorescence (XRF) microanalysis, including XRF tomography, and X-ray absorption near-edge structure (XANES) analyses, the distribution, and nature of incorporation of Fe and Ni impurities in as-grown diamond crystals, synthesized under high-pressure and high-temperature (HPHT) conditions, have been characterized. We find significantly different behavior for Fe and Ni as impurities in diamond. Nickel is dispersed and sector-zoned, with concentrations in {111} growth sectors at least 3 times those in {100} sectors, whereas Fe exists in the form of micro-aggregates or clusters with no observable sector correlation. Fe K-edge XANES shows that Fe is oxidized in diamond and has a valence of 2+. Comparison of XANES spectra from numerous standard compounds indicates that Fe is very likely bonded with oxygen as FeO.

X-ray fluorescence elemental maps and Cu K-edge X-ray absorption near-edge structure (XANES) spectra were recorded for individual vapor and brine phase fluid inclusions from the Mole Granite, NSW, Australia. The maps indicate that Cu is concentrated in the vapor inclusions and, at room temperature, distributed uniformly in the condensed liquid. Opaque precipitates in these inclusions do not contain Cu. The absorption spectra identify the stable complexes as [[[Cu([H.sub.2]O).sub.6]].sup.2+] at 25[degrees]C, [[Cu[Cl.sub.2]].sup.1-] at 200[degrees]C, and either [Cu[Cl.sub.2].sup.1-] or [CuCl([H.sub.2]O)] at the homogenization temperature of around 400[degrees]C. These changes in Cu coordination and oxidation state are fully reversible. We suggest that the vapor phase partitioning of Cu as a chloride complex from a high-density brine may occur under acidic conditions. Estmates of fluid acidity at the time of boiling may potentially predict the metal distribution between epithermal and porphyry-type environments in hydrothermal systems.

Two clay soil column samples are taken from Almeda County, California and exposed to chromium contamination. The diffusion and reduction of the chromium in the soils is measured using X-ray absorption near edge structure spectroscopy, and graphed for depth of transport.

X-ray fluorescence microtomography is used for imaging the distribution of Pt drugs within multicellular tumour spheroids. Results show that there is no difference between the distributions of the range of Pt(II) and Pt(IV) complexes, indicating that the complexes that are more resistant to cellular uptake is required for ensuring complete distribution throughout a tumor.

This paper describes riesite, a new high-pressure polymorph of TiO2 from the Ries impact structure, Germany. Riesite occurs in shock-induced melt veins within xenoliths of bedrock in suevite. It is structurally closely related to srilankite from which it differs by having two distinct cation sites rather than one and through its monoclinic symmetry. It is indicative that riesite forms only upon release from the shock state upon back transformation from akaogiite. [ABSTRACT FROM AUTHOR]

Eu [L.sub.3] X-ray absorption near edge structure (XANES) spectroscopy was conducted with a wavelength dispersive (WDS) spectrometer to determine the valence state of europium in a natural, Mn-and REE-rich apatite from Llallagua, Bolivia. Europium exists in both the divalent and trivalent states in the Llallagua apatite with a [Eu.sup.2+]/[Eu.sup.3+] ratio between 0.12 and 0.22. With the enhanced energy resolution of WDS the EuL[[Alpha].sub.1] fluorescence line can be resolved from the Mn[K[Alpha] line, allowing for significant reduction of background in the Eu[L.sub.3] absorption edge region and resolution of the Eu XAS, which is difficult by conventional methods because of fluorescence peak interference. The anomalous partitioning behavior of Eu in these samples (Rakovan and Reeder 1996) can be explained by the observed presence of [Eu.sup.2+] and [Eu.sup.3+] and is consistent with the suggested size effect on intrasectoral zoning of REEs in apatite.

The physical and chemical properties of the hydrated [Alpha]-[Al.sub.2][O.sub.3] (0001) surface are important for understanding the reactivity of natural and synthetic aluminum-containing oxides. The structure of this surface was determined in the presence of water vapor at 300 kelvin by crystal truncation rod diffraction at a third-generation synchrotron x-ray source. The fully hydrated surface is oxygen terminated, with a 53% contracted double Al layer directly below. The structure is an intermediate between [Alpha]-[Al.sub.2][O.sub.3] and [Gamma]-Al[(OH).sub.3], a fully hydroxylated form of alumina. A semiordered oxygen layer about 2.3 angstroms above the terminal oxygen layer is interpreted as adsorbed water. The clean [Alpha]-[Al.sub.2][O.sub.3] (0001) surface, in contrast, is Al terminated and significantly relaxed relative to the bulk structure. These differences explain the different reactivities of the clean and hydroxylated surfaces., The interaction of water with solid surfaces plays an important role in many natural and technological processes, from mineral dissolution and adsorption/desorption reactions and the reaction of water with sulfate [...]