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

Abstract

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).

Lab Case Study of Microbiologically Influenced Corrosion and Rietveld Quantitative Phase Analysis of X-ray Powder Diffraction Data of Deposits from a Refinery

“…Subsequently, when Rietveld refinement was used to determine quantitative phase analysis of the identified phases, 9 − 16 the results indicated that the major phase is anhydrite with the addition of calcite, aragonite, halite, quartz, and dolomite phases, see Figure 5 . The findings are supported by the elemental composition (wt %) 37 results obtained from WDXRF spectrometry and Omnian software ( Figure 4 ) for deposits from both reboilers C and D. Therefore, the Rietveld quantitative phase analysis results can guide the engineers at the affected refineries and gas plants to overcome the problems by devising the appropriate corrective procedures. 2 − 5 …”

“…In contrast, the filtrated deposits from reboiler B showed the presence of different irregularly shaped microscopic particles ( Figures 2 and 3 ). The element concentration (wt %) 37 obtained from high-resolution PANalytical Advanced AXIOS WDXRF spectrometry and the instrument’s standardless software (i.e., Omnian) revealed that the major elements are Ca and S and the minor elements are Cl, Sr, Si, Mg, Fe, Mn, and Na ( Figure 4 ). The Ca element is formed from water.…”

Qualitative and Semiquantitative Determination of the Atomic and Molecular Tungsten Distributions in Hybrid Hydroxyurethanes–Poly(dimethylsiloxane) Films Containing Phosphotungstates ([PW12O40]3–)

“…31 SR-GIXRF, unlike SR-μXRF, a bulk analysis method, depends on the quality of the surface of the material. 26 Kawai et al., using a combination of TXRF/XPS and assisted by an X-ray synchrotron beam, reported the angle dependence of photoelectron peak intensity for a system of bilayers tungsten–silicon (W/Si) on an Si wafer. 32 SR-GIXRF was already used in qualitative determination of hybrid nanomaterials in our research group.…”

“…25 If a conventional X-ray source (such as the X-ray tube) is used for this purpose, the collimation would result in an X-ray flow too low to be useful in XRF experiments. 26 Our research group earlier published the SR-mXRF mapping of phosphotungstates ([PW 12 O 40 ] 3À ) in the characterization of hybrid nanomaterials. 27,28 In grazing angle X-ray fluorescence (GIXRF), the X-ray incident beam is almost parallel to surface of the sample at angles equal or slightly larger (two to three times) than the value of the critical angle of sample's support.…”

In situ analysis of garnet inclusion in diamond using single-crystal X-ray diffraction and X-ray micro-tomography

“…The reported absolute uncertainties in the Ca contents of Ca-silicate minerals were AE5-6 wt%. So, this technique appears to be more useful for mineral identification rather than for full chemical analysis (Sitepu et al, 2005). More recently, Yasuzuka et al (2009) proposed a method to estimate the Mg# value [¼ 100ÁMg mol /(Mg þ Fe) mol ] of olivine inclusions from their Raman spectra with an uncertainty of AE0.8.…”