Open AccessRedox and speciation micromapping using dispersive X‐ray absorption spectroscopy: Application to iron in chlorite mineral of a metamorphic rock thin section
Author(s) -
Muñoz Manuel,
De Andrade Vincent,
Vidal Olivier,
Lewin Eric,
Pascarelli Sakura,
Susini Jean
Publication year - 2006
Publication title -
geochemistry, geophysics, geosystems
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.928
H-Index - 136
ISSN - 1525-2027
DOI - 10.1029/2006gc001381
Subject(s) - xanes , geology , beamline , mineralogy , absorption (acoustics) , spectroscopy , analytical chemistry (journal) , extended x ray absorption fine structure , thin section , materials science , optics , absorption spectroscopy , chemistry , physics , beam (structure) , chromatography , quantum mechanics
The first dispersive μ ‐XANES mapping is presented here. The experiments have been conducted at the iron K ‐edge, on the “Dispersive‐EXAFS” beamline of the European Synchrotron Radiation Facility (France). The mapping has been performed on a polished thin section of 30 μ m of a natural metamorphic rock including different types of minerals. Because of the high X‐ray absorption due to the thickness of the glass sample holder (∼1 mm), the data have been collected in the fluorescence mode using the so‐called “Turbo‐XAFS” design. The effective spot size was approximately 10 × 10 microns, and an area 390 × 180 microns in size was mapped. Improvements of the acquisition process allowed collection of each XANES spectrum in 1.5 s and with a step size of 5 microns so that 2808 spectra with full XANES information were collected. Then, automatic procedures for data reduction and mapping reconstruction were developed using Matlab®. The results are maps of iron content, oxidation state, and speciation, with a 5 μ m spatial resolution after two‐dimensional deconvolution. Subsequent analyses of the reconstructed images provide some quantitative calibrations.