Validation data for a scanning electron microscope-energy dispersive spectrometry (SEM-EDS) method for the analysis of common volcanic phases

Introduction This dataset contains data that underlie the development and validation of the quantitative scanning electron microscope-energy dispersive spectrometry (SEM-EDS) analytical routine implemented at the U.S. Geological Survey Cascades Volcano Observatory (CVO). The data comprise SEM-EDS analyses of plagioclase, olivine, pyroxene, magnetite, ilmenite, and volcanic glass reference materials to optimize the analytical setup and document the precision and accuracy of the method. Please cite the associated journal article for references to our analytical routine. Supplemental tables containing the reference material expected concentrations (Tables S1 and S2), summaries of the results of parameter testing (Table S3), and the reproducibility of mineral and glass standards (Tables S4 and S5) are provided together in a single Excel workbook (supplemental summary tables S1-S5.xlsx). The underlying data are contained in separate comma-separated values (csv) files, each with an associated file of field definitions. The information in Tables S3, S4, and S5 is derived from the data reported in Table S6. The contents of each supplemental table are: Table S1: The expected compositions of all mineral standards used for calibration and verification, and a list of the standards used to calibrate each element in each phase. Table S2: The expected concentration of all glass standards. Table S3: A summary of the results of testing the total spectrum counts, process time, and standardized versus standardless quantification. Table S4: A summary of the long-term reproducibility of mineral standards. Table S5: A summary of the glass analyses for which we judged the beam damage to be mitigated. TableS6.csv: All spot and raster analyses of the mineral and glass standards. TableS7.csv: The line scan data used to determine the collimator width. TableS8.csv: The peak resolution data used to compare the process times. Methods summary All data were collected at CVO using a JEOL IT510 W-source SEM, an Oxford Instruments Ultim Max 40 mm2 EDS detector, and the Oxford Instruments AztecLive (OIA) EDS software, version 6.0 SP2 (Oxford Instruments, 2023). Mineral and pure oxide reference materials used for calibration and verification are from the Smithsonian Microbeam Standards Collection (SMS) or purchased from Micro Analytical Consultants (MAC). All materials were mounted in epoxy-filled wells in 25-mm-diameter brass or leucite disks, ground and polished flat using 1 µm diamond followed by 0.25 µm alumina for the final polishing steps, and coated with approximately 20 nm of carbon prior to analysis. Our preferred protocol for mineral analysis utilizes an accelerating voltage of 15 kV, working distance of 10 mm, process time of 16 µs, a beam current scaled to a dead-time of 45–55% (generally produced by a current of 2–3 nA), a 30 µm final aperture, and applies the pulse pileup correction implemented in OIA. At these conditions, typical output count rates were 20–25 kilo-counts per second (kcps). Spectra are collected with 1.5 million total counts (typically acquired within 35 s live time) using 4048 channels with 5 eV per channel. As described in detail in the accompanying article, we performed analyses using 0.25–2.5 x106 total spectrum counts, currents of 0.6–11 nA, process times of 2–16 µs, and point versus area raster analyses to optimize the analytical setup and investigate mitigation strategies for beam damage in volcanic glass. The instrument settings for each analysis are recorded in Table S6. Disclaimers This database, identified as “Data to support a scanning electron microscope-energy dispersive spectrometry (SEM-EDS) method for the quantitative analysis of common volcanic phases”, has been approved for release by the U.S. Geological Survey (USGS). Although this database has been subjected to rigorous review and is substantially complete, the USGS reserves the right to revise the data pursuant to further analysis and review. Furthermore, the database is released on condition that neither the USGS nor the U.S. Government shall be held liable for any damages resulting from its authorized or unauthorized use. Although these data have been processed successfully on a computer system at the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. The USGS or the U.S. Government shall not be held liable for improper or incorrect use of the data described and/or contained herein. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.