Reduced As Components in Highly Oxidized Environments: Evidence from Full Spectral XANES Imaging using the Maia Massively Parallel Detector

Journal Article · Fri Jan 01 04:00:00 EST 2010 · American Mineralogist

DOI:https://doi.org/10.2138/am.2010.3469· OSTI ID:1019699

Etschmann, B; Ryan, C; Brugger, J; Kirkham, R; Hough, R; Moorhead, G; Siddons, D; De Geronimo, G; Kuczewski, A

Synchrotron X-ray fluorescence (SXRF) and X-ray absorption spectroscopy (XAS) have become standard tools to measure element concentration, distribution at micrometer- to nanometer-scale, and speciation (e.g., nature of host phase; oxidation state) in inhomogeneous geomaterials. The new Maia X-ray detector system provides a quantum leap for the method in terms of data acquisition rate. It is now possible to rapidly collect fully quantitative maps of the distribution of major and trace elements at micrometer spatial resolution over areas as large as 1 x 5 cm{sup 2}. Fast data acquisition rates also open the way to X-ray absorption near-edge structure (XANES) imaging, in which spectroscopic information is available at each pixel in the map. These capabilities are critical for studying inhomogeneous Earth materials. Using a 96-element prototype Maia detector, we imaged thin sections of an oxidized pisolitic regolith (2 x 4.5 mm{sup 2} at 2.5 x 2.5 {micro}m{sup 2} pixel size) and a metamorphosed, sedimentary exhalative Mn-Fe ore (3.3 x 4 mm{sup 2} at 1.25 x 5 {micro}m{sup 2}). In both cases, As K-edge XANES imaging reveals localized occurrence of reduced As in parts of these oxidized samples, which would have been difficult to recognize using traditional approaches.

• Research Organization: Brookhaven National Laboratory (BNL) National Synchrotron Light Source
• Sponsoring Organization: DOE - OFFICE OF SCIENCE
• DOE Contract Number: AC02-98CH10886
• OSTI ID: 1019699
• Report Number(s): BNL--95545-2011-JA
• Journal Information: American Mineralogist, Journal Name: American Mineralogist Journal Issue: 5-6 Vol. 95; ISSN AMMIAY; ISSN 0003-004X
• Country of Publication: United States
• Language: English

Related Subjects

58 GEOSCIENCES
ABSORPTION
ABSORPTION SPECTROSCOPY
ARSENIC
DATA ACQUISITION
DISTRIBUTION
ELEMENTS
FLUORESCENCE
SPATIAL RESOLUTION
SYNCHROTRONS
TRACE AMOUNTS
VALENCE
national synchrotron light source