Glen Rose XRF data - Godet et al
Description
This file include elemental geochemical data for samples of the Albian Glen Rose Formation from central and west Texas. Results were obtained using XRF spectrometry, as described in the Methods section of the manuscript.
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Samples were cut into 0.5 x 0.5 cm pieces to be powdered using a SPEX Shatterbox 8515 at the UTSA Rock Preparation Laboratory. Each powdered sample was collected in plastic tubes. To account for the loss of material during fusion, the amount of volatiles was calculated for each sample using a Loss On Ignition (LOI). A tare weight was acquired for a porcelain crucible and then weighed with ca. 2.0 g of sample before being placed at 1050°C in a muffle furnace for 90 minutes. Samples were then removed from the furnace, cooled, and re-weighed to find the post-calcination weight. The LOI value was calculated using the formula: LOI = (Cf-Cc)/(Cf -Ce)×100 where Cf = weight of the crucible with sample; Cc = weight of crucible with samples after calcination; Ce = weight of the crucible empty (Dean, 1974). All samples were prepared using the method below at UTSA, except samples from GCSNA that were prepared and analyzed at the University of Lausanne, Switzerland. At UTSA, glass beads were produced by mixing 9.0 +/- 0.001g of lithium tetraborate (Li2B4O7) with 1.8 +/- 0.001 g of powdered sample into a Pt-Au crucible. Fusion at 1050°C was performed with a Claisse© LeNeo fusion machine using a 22 minutes-long automatized program. Pellets of pressed powdered samples were produced by mixing 6.65 +/- 0.001 g of sample with 0.35 +/- 0.001 g of SpectroBlend® binder; at the University of Lausanne, GCSNA samples were mixed with a different binder, Mowoil polyvinyl alcohol (2%). The sample and the binder were transferred to a plastic vial with two plastic mixing balls, then homogenized for 5 minutes using an automatic, tabletop SPEX mixer. The powder was subsequently transferred into an evacuable die set (30 mm diameter, stainless steel) and pressed in an aluminum cup at 5 tons for 60 seconds. Glass beads and pressed pellets were analyzed for their major and trace elements concentration, respectively, using a Rigaku Primus II Wavelength Dispersive X-Ray Fluorescence spectrometer at UTSA, and a PANalytical PW2400 at the University of Lausanne. The power of the X-ray beam was set at 3.6 kW, with current voltage and intensity ranging between 40-60 kV and 60-90 mA, respectively, depending on the atomic number of the element targeted (40 kV for elements lighter than Ti, 50 kV from Ti to Rb, 60 kV for elements heavier than Rb). The detection limit was better than 0.01 wt% and 10 ppm for major and trace elements, respectively. The standard deviation calculated on triplicate analysis of randomly selected samples is better than 0.3 % (CaO) for major elements and varies between 0.58 (Zn) and 22.81 (Ba) ppm for trace elements.