X-Ray Absorption Spectroscopic and Magnetic Investigations on the Garnet Mn3Al2-xCrxGe3O12

Gunßer, W.; Lemke, Th.; Röhl, B.R.; Denecke, Melissa A.

doi:10.1006/jssc.1995.1342

Cited by 3 publications

(1 citation statement)

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“…This is reasonable based on the crystallography and compositions of the minerals analyzed. Synthetically prepared garnets at 1200 °C have chromium K-edge XANES spectra suggesting Cr 3+ in distorted octahedrons (Gunsser et al 1994). Olivine minerals have both distorted and regular octahedrons (Klein and Hurlbut 1993), both of which can contain Cr 3+ (Taura et al 1998) and could yield Cr K-edge XANES spectra similar to that of either spinel or corundum structure.…”

Section: μXanes Analysismentioning

confidence: 96%

Synchrotron micro-X-ray fluorescence analysis of natural diamonds: First steps in identification of mineral inclusions in situ

Sitepu

Kopylova

Quirt

et al. 2005

American Mineralogist

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Diamond inclusions are of particular research interest in mantle petrology and diamond exploration as they provide direct information about the chemical composition of upper and lower mantle and about the petrogenetic sources of diamonds in a given deposit. The objective of the present work is to develop semi-quantitative analytical tools for non-destructive in situ identifi cation and characterization of mineral inclusions in diamonds using synchrotron micro-X-ray Fluorescence (μSXRF) spectroscopy and micro-X-ray Absorption Near Edge Structure (μXANES) spectroscopy at a focused spot size of 4 to 5 micrometers. The data were collected at the Pacifi c Northwest Consortium (PNC-CAT) 20-ID microprobe beamline at the Advanced Photon Source, located at the Argonne National Laboratory, and yielded the fi rst high-resolution maps of Ti, Cr, Fe, Ni, Cu, and Zn for natural diamond grains, along with quantitative μSXRF analysis of select chemical elements in exposed kimberlite indicator mineral grains. The distribution of diamond inclusions inside the natural diamond host, both visible and invisible using optical transmitted-light microscopy, can be mapped using synchrotron μXRF analysis. Overall, the relative abundances of chemical elements determined by μSXRF elemental analyses are broadly similar to their expected ratios in the mineral and therefore can be used to identify inclusions in diamonds in situ. Synchrotron μXRF quantitative analysis provides accurate estimates of Cr contents of exposed polished minerals when calibrated using the concentration of Fe as a standard. Corresponding Cr K-edge μXANES analyses on selected inclusions yield unique information regarding the formal oxidation state and local coordination of Cr. FIGURE 4. Cr K-edge XANES Spectra for reference standards (Cr 2 O 3 , K 2 CrO 4 ), reference chromite (Chromite 9-12) and chrome diopside minerals (Cr-Diopside, YK-2416) and micro-inclusions from diamond samples 280RS, 344X, and 372X. Locations of inclusions in diamonds are shown in Figures 1 to 3. Solid vertical lines designate photon energy positions for (a) pre-edge Cr 6+ absorption peak, (b) Cr 3+ pre-edge absorption peak, (c) main absorption edge for Cr 3+ in spinel structure (~6008.5 eV; Levy et al. 1999) and (d) main absorption edge for Cr 3+ in corundum structure (~6011 eV; Levy et al. 1999).

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Section: μXanes Analysismentioning

confidence: 96%