Michelle Bonnin-Mosbah

Fluid inclusions in quartz from oceanic hydrothermal specimens and the Bingham, Utah porphyry-Cu deposit: a study with PIXE and SXRF

Abstract Individual natural fluid inclusions in quartz were selected for non-destructive microprobe analysis by synchrotron X-ray fluorescence (SXRF) and proton-induced X-ray emission (PIXE) in order to compare and contrast the compositions of porphyry-type ore forming brines and two types of ocean crustal brines. The inclusions contained brines with high salt concentrations (typically 20–40 wt.% total), and one or more daughter crystals. The X-ray and proton beams produced detectable characteristic X-rays for many elements and allowed the quantification of concentrations for many elements with atomic number Z >14. Fluid inclusions associated with the core of the Bingham, UT, porphyry-Cu(Mo) deposit contain NaCl brines that also contain (element, typical range in ppm): K, 12,000–100,000; Ca, ≤17,000; Mn, ≤8000; Fe, ≤120,000; Cu, ≤8000; Zn, ≤5000; Br, ≤2000. These values are in good agreement with published estimates, and results from SXRF and PIXE experiments are generally consistent. The Bingham fluid compositions closely resemble brines from the porphyry-Mo(Cu) deposit at Questa, NM. Inclusions from two suites of oceanic plutonic rock samples gave PIXE results consistent with published SXRF analyses from other inclusions in the same samples. New inclusion analyses from the Mathematician Ridge locality indicate the NaCl brines also contain, on average (element, ppm): K, 3500; Ca, 35,000; Mn, 4900; Cu, 400; Zn, 200; Br, 1000. New inclusion analyses from the Oceanographer Transform locality indicate NaCl brines that also contain, on average: K, 37,000; Ca, 35,000; Mn, 10,000; Cu, ≤400; Zn, 2200; Br, 1000. These values are calculated on the assumption that Fe in the inclusions is 50,000 ppm. Compared to continental ore forming brines, the oceanic brines have higher Ca and lower K and Cu concentrations.

Micro X-ray absorption near edge structure at the sulfur and iron K-edges in natural silicate glasses

Both sulfur and iron chemical environments were studied in natural compounds; sulfides, sulfates and silicate basaltic glasses which are supposed to have variable oxidation states, using XANES (X-ray absorption near edge structure) spectroscopy. Although X-ray absorption methods are well suited for such investigations, the size of natural glass inclusions trapped in volcanic minerals, ranging from a few micrometers to several tenths of micrometers, makes micro-spectroscopy necessary. Hence, we present the μ-XANES spectra at the sulfur and iron K-edges of olivine-hosted glass inclusions containing from 1000 to 1650 ppm S, and between 5.5 and 7.8 wt.% Fe. By combining both high energy and spatial resolutions, we demonstrate the ability of the μ-XANES to produce quantitative determination of sulfur and iron valence states. We have identified various species for sulfur, specifically SII−, SVI and possibly SIV, in basaltic glass inclusions hosted in olivine grains. We propose a method to calibrate the proportion of Fe dissolved as Fe3+ in basaltic glasses for which the Fe3+/ΣFe ratio varies between 0.05 and 0.48 with a relative precision of less than 10%.

Iron oxidation states in silicate glass fragments and glass inclusions with a XANES micro-probe

Abstract The iron oxidation states and its environment in volcanic silicate glasses have been studied by combining micro-X-ray absorption near edge structure (XANES) experiments at the iron K-edge in silicate glass fragments and glass inclusions trapped during the crystal growth. Experiments were performed at the ESRF (ID22 beam-line) – a third generation synchrotron – using a focused beam (2×10 μm 2 ) together with a high brilliance and a good energy resolution. The selected silicate glasses, basaltic in composition, contain between 5.5 and 8 wt% total Fe. In all XANES spectra, pre-peaks exhibit a multi-component structure, which is the convolution of information related to the valence state of iron (2+,3+), the site geometry and transition types. The Fe3+/ΣFe ratio of silicate glass fragments deduced from the XANES spectra is correlated to values determined by chemistry on bulk samples within the range 0.05–0.85. XANES spectra from glass inclusions hosted in natural olivine crystals may be interpreted considering the glass fragments as reference samples.

Analysis of individual fluid inclusions using synchrotron X-ray fluorescence microprobe: progress toward calibration for trace elements

Abstract A critical problem for conducting quantitative analysis of individual fluid inclusions using Synchrotron X-Ray Fluorescence (SXRF) technique relates to the standardization and the calibration of the X-ray spectra. In this study, different approaches have been tested for calibration purposes: (a) the use of chlorine when Cl content can be estimated either from melting point depressions of undersaturated fluid inclusions or from saturation limits for halite-bearing fluid inclusions, (b) the use of calcium from synthetic fluid inclusions of known CaCl2 content as an external standard. SXRF analysis was performed on individual fluid inclusions from the Chivor and Guali emerald deposits, Columbia. These well-known samples contain a single fluid inclusion population for which detailed crush-leach analyses are available, thus providing a relevant compositional reference frame. Concentration estimates were also compared to Particle Induced X-ray Emission (PIXE) analysis carried out independently on the same fluid inclusions. Results of the calibration tests indicate that major (Cl, K, Ca, Fe, Mn) and trace element (Cu, Zn, As, Br, Rb, Sr, Ba, Pb) concentration estimates can be performed without precise knowledge of the analytical volume and the inclusion’s 3D geometry. Although the standard deviation of the SXRF results can be relatively high depending on the calibration mode used, mean concentration estimates for most elements are in good agreement with PIXE and crush-leach analysis. Elemental distributions within single fluid inclusions were also established. Associated correlation diagrams argue for the homogeneous distribution of most elements in the fluid inclusion. In contrast, Br shows a bimodal distribution interpreted to reflect a significant enrichment of the vapor portion of the inclusion fluid.

Iron distribution in cancer cells following doxorubicin exposure using proton and X-ray synchrotron radiation microprobes

Chemical studies have shown that doxorubicin, a well-established anticancer agent, is a powerful iron chelator and the resultant iron - drug complex is an efficient catalyst of the conversion of hydrogen peroxide to the highly reactive hydroxyl radical. However, the intracellular complexation of doxorubicin with iron is still debated. Using nuclear microprobe analysis (NMPA), we previously observed in human ovarian cancer cells exposed to 20 μM iodo-doxorubicin (IDX) that iodine and iron cellular distributions were spatially correlated, suggesting a mechanism of intracellular iron chelation by the anthracycline compound. Because maximal plasma drug concentrations in patients are expected to be around 5 μM, NMPA and X-ray absorption near edge spectroscopy (XANES) experiments for iron speciation analysis were performed on cultured cells exposed to pharmacological doses of 2 μM IDX or doxorubicin.

Chromium mapping in male mice reproductive glands exposed to CrCl3 using proton and X-ray synchrotron radiation microbeams

Abstract Preconception exposure to certain chemicals may increase risk of tumors in offspring, especially with regard to occupational metals such as chromium. However, the mechanism of chromium trans-generation carcinogenicity remains unknown. Using scanning proton X-ray microanalysis we have been able to detect chromium in testicular tissue sections from mice treated by intraperitoneal injection of 1 mmol/kg CrCl3. Chromium concentration was about 5 μg/g dry mass in average, but higher concentrations were found within the limiting membrane of the testes, the tunica albuginea. In addition, synchrotron radiation X-ray fluorescence measurements, with microscopic resolution, clearly demonstrated the presence of chromium in the tunica albuginea but also within isolated cells from the interstitial connective tissue.

Fluid inclusion depth and thickness estimates using a Na nuclear reaction resonance and Si elastic scattering

Abstract An important aspect of quantitative fluid inclusion analysis using X-ray emission techniques concerns a knowledge of fluid inclusion depth and geometry to establish reliable absorption correction procedures. The aim of this study is to assess the potential performance of the nuclear reaction 23 Na(p, p ′ γ ) 23 Na in estimating inclusion depth. Na was chosen because of its common occurrence in natural fluids. The nuclear reaction displays a characteristic, low energy resonance peak at 1.283 MeV in its cross-section which, together with recognition that the energy of the incident particles traversing matter decreases predictably with depth, allow estimation of the thickness of quartz traversed by the beam and hence the inclusion depth. Results of the calculation shows accuracy on estimated fluid inclusion depths commonly better than ±0.5 μm. In addition, following the same experimental protocol as defined for Na, we show how the use of the elastic scattering reaction 28 Si(p, p) 28 Si can provide information on the fluid inclusion thickness.

Austenitic steel corrosion in IGCC environment. Characterisation by photon and nuclear microprobes

Abstract An austenitic steel sample was treated simulating particular working conditions of an integrated gasification combined cycle (IGCC) power plant. Several classical characterisation techniques were used to investigate the oxide scales. In addition, micro-particle-induced X-ray emission (PIXE) and Rutherford backscattering spectrometry (RBS) analyses were performed and permit us to identify several phases constitutive of the oxide. Moreover, micro-X-ray absorption near edge structure (XANES) experiments allow us to determine the valence of the vanadium incorporated in the scale in the form of microscopic islets. The comparison of all these results leads to the proposal of a corrosion mechanism for this alloy.