Data for: Mechanism of Gd3+ uptake in gypsum (CaSO4*2H2O): Implications for EPR dating, REE recovery and REE bahavior
Description
This submission includes one MsWord document named “Supplementary-Data.docx” and one CIF file entitled “Figure-1-Comodi-2008.txt” from Comodi et al. (2008). All research data are uploaded in three formats: 1) TXT, 2) CSV, and 3) ORIGIN. PXRD analyses were made on a PANalytical X’pert PRO X-ray diffractometer using Cu Kα1 (λ =1.54056 Å) radiation at 40 kV and 45 mA. ICP-MS analyses were made using the HF-HNO3 dissolution method and the calibration protocol of Jenner et al. (1990), on a Perkin Elmer Sciex Elan 5000 spectrometer. Gadolinium L3-edge (7243 eV) XAS spectra of three gypsum samples (pH = 6.5, 7.5 and 8.5) and two model compounds (Gd2O3 and GdCl3.6H2O) were measured at the HXMA beamline, Canadian Light Source (Jiang et al., 2007). A Si(111) monochromator crystal coupled to Rh mirrors (collimating and focusing mirrors) and a wiggler field of 1.9 T were used during data collection. Gypsum samples were measured in fluorescence mode using a 32 element Ge detector, and model compounds were measured in transmission mode. Iron metal foil was introduced for energy calibration. Multiple scans were made for both the gypsum samples (6-7 scans) and the model compounds (2-3 scans). Powder EPR measurements of all gypsum samples, before and after gamma-ray irradiation in a 60Co cell with a dose rate of ~460 Gy/hr for 7 days, were first measured at RT on a Bruker EMX spectrometer, operated at X-band frequencies (~9.87 GHz). Subsequently, a crystal of ~3 mm x ~2 mm x ~1.5 mm from the pH = 6.5 experiment was selected for single-crystal EPR measurements at room temperature in three rotation planes [approximately (100), (010) and (001)] on the same Bruker EMX spectrometer at ~9.38 GHz, a microwave power of 5 mW, modulation amplitude of 1 G, a constant angle interval of 5°, and a spectral resolution of 0.1 G. The same crystal was also measured at room temperature in two planes [~(100) and ~(010)] on a Varian E-15 spectrometer at ~34.8 GHz, a microwave power of 5 mW, a modulation amplitude of 1.6 G, a constant angle interval of 15° and a spectral resolution of 2.44 G. Pulsed X-band single-crystal ENDOR spectra at 9K of the pH = 6.5 gypsum crystal were collected on a Bruker E580-10 Elexsys with a liquid He Oxford CF935 cryostat. ENDOR experiments were made using a Mims three-pulse scheme scheme (/2 – – /2 – T – /2 – – echo, with the RF pulse applied during time T and the frequency of which is varied in time). X-band Mims spectra were collected at a constant angle interval of 10° in a single plane (i.e., normal vector to the rotation plane: θ = 39.6◦, ϕ = 177.8◦, zero rotation vector: θ =101.7◦, ϕ =253.7◦). Because Mims ENDOR gives rise to blind-spots that arise from an oscillating dependence, ENDOR spectra were also recorded as a function of and later summed (8 spectra @ 16ns steps). Pulsed Q-band ENDOR spectra at 20K were collected on a Bruker E580-10 Elexsys with a Bruker EN 5107D2 cavity as part of the Bruker SuperQ-FT accessory.