{"action":"create","ckan_id":null,"date_created":"Sat, 21 Feb 2026 21:03:07 GMT","date_finished":null,"harvest_job_id":"fb591ca5-43f4-4ca4-a149-94fd73e2a6d1","harvest_source_id":"31f41541-38a0-400b-b240-10ebcb0acd9a","id":"298228e7-7e91-4873-b4fc-275c54aefb8c","identifier":"https://dggs.alaska.gov/webpubs/metadata/MP174.xml","parent_identifier":null,"source_hash":"279aa1b0154580a38e56f9e9591393733faad33cedd7eac4a05097ea5bdfecb8","source_raw":"Loewen, M.W.Wallace, K.L.Lubbers, JordanRuth, DawnIzbekov, P.E.Larsen, J.F.Graham, Nathan2023Glass electron microprobe analyses methods, precision and accuracy for tephra studies in AlaskacsvMiscellaneous PublicationMP 174Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys20 p.https://doi.org/10.14509/31045Glass electron microprobe analyses methods, precision and accuracy for tephra studies in Alaska, Miscellaneous Publication 174, reports analytical conditions and secondary standard results for electron probe microanalysis (EPMA) of glass in support of tephra studies in Alaska between 2018 and 2023. Long-term accuracy and precision are evaluated for our standardized method and compared between analytical sessions and instruments at the University of Alaska Fairbanks (UAF) and the U.S. Geological Survey (USGS) Menlo Park, California. Future versions will provide updates with secondary standard results from future analytical sessions and any changes to the analytical routine and conditions. This data is released as a Miscellaneous Publication with an open end-user license. The data are available from the DGGS website: http://doi.org/10.14509/31045.The goal of this standard routine, and in comparing multi-year secondary standard results, is to ensure that data for unknown sample analyses is precise and comparable. This standard will enable us to correlate tephra units from Alaskan volcanos to better understand and detect changes in composition at a volcano over time.>Calibrants: Name of calibration standard, matches values in Conditions table for each analyte, microprobe lab for the calibrant values, where the calibration standard was obtained, type of material, and elemental concentrations\t\r\n>Conditions: Electron microprobe beam conditions, calibration standards, spectrometer assignment, diffraction crystal assignments, analysis order, counting times, and time-dependent intensity correction flag (Y/N) for each element\t\r\n>RepeatUnkns: Microprobe session identifier to link analyses to a set of analytical conditions (usually used on multiple consecutive days)\t\r\n>SecondaryStandardResults: Categorical identification of secondary standards, secondary standard name used in analysis runs, date and time of analysis, and element weight percents\t\r\n>SecondaryStandardValues: Name of secondary standard used in analysis categorization, Y/N flag to indicate whether the standard is part of the traveling AVO standard mount, element reference values, and literature citations for standard reference values20182023ground conditionCompleteNone planned-178.817961-104.06029171.27768443.359849ISO 19115 Topic CategorygeoscientificInformationAlaska Division of Geological & Geophysical SurveysActive VolcanoesAnalyses and SamplingAnalytical Lab ResultsAnalytical ResultsChemistryCorrelationDGGSGeochemical DataGeochemistryGeologicGeologic HazardsGeological ProcessGeologyGlassIgneousLab MethodsPyroclasticsTephraVolcanicVolcanic AshVolcanic EruptionVolcaniclasticsVolcanoesVolcanologyAlaska Division of Geological & Geophysical SurveysAlaskaAlaska, State ofCook InletWalker, J.D., Geissman, J.W., Bowring, S.A, and Babcock, L.E., comp., 2012, Geologic Time Scale v. 4.0: Geological Society of AmericaHoloceneThis report, map, and/or dataset is available directly from the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys (see contact information below).Any hard copies or published datasets utilizing these datasets shall clearly indicate their source. If the user has modified the data in any way, the user is obligated to describe the types of modifications the user has made. The user specifically agrees not to misrepresent these datasets, nor to imply that changes made by the user were approved by the State of Alaska, Department of Natural Resources, Division of Geological & Geophysical Surveys. The State of Alaska makes no express or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.Alaska Division of Geological & Geophysical SurveysMetadata Managermailing and physical
3354 College Road
FairbanksAK99709-3707USA(907)451-5020(907)451-5050dggspubs@alaska.gov8 am to 4:30 pm, Monday through Friday, except State holidaysPlease view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.This article has been peer-reviewed and approved for publication consistent with USGS Fundamental Science Practices (pubs.usgs.gov/circ/1367). We appreciate reviews provided by Heather Lowers and Steve Kuehn, metadata review by Simone Montayne, and editorial handling by Kristen Janssen. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.Cameron, C.E.Crass, S.W.AVO Staff2022Geologic Database of Information on Volcanoes in Alaska (GeoDIVA)Digital Data SeriesDDS 20Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveyshttps://doi.org/10.14509/30901Mulliken, K.M.Schaefer, J.R.Cameron, C.E.2018Geospatial distribution of tephra fall in Alaska: a geodatabase compilation of published tephra fall occurrences from the Pleistocene to the presentMiscellaneous PublicationMP 164Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys46 phttps://doi.org/10.14509/29847Wallace, K.L.Cameron, C.E.Waythomas, C.F.Perreault, J.M.2020Major-oxide and trace-element geochemical data from the tephra collected on Veniaminof volcano, AlaskaRaw Data FileRDF 2020-17Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys5 phttps://doi.org/10.14509/30578Wallace, K.L.Hayden, L.A.Neal, C.A.2017Major-element glass compositions of tephra from the circa 3.6 ka eruption of Aniakchak volcano, Alaska Peninsula, AlaskaRaw Data FileRDF 2017-9Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys9 phttps://doi.org/10.14509/29777Worden, A.K.Schaefer, J.R.Mulliken, K.M.2018Tephra occurrence in Alaska: a map-based compilation of stratigraphic tephra dataMiscellaneous PublicationMP 165Fairbanks, Alaska, United StatesAlaska Division of Geological & Geophysical Surveys19 phttps://doi.org/10.14509/30059This data release covers analyses made between 2018 and 2023, during which an effort was made to standardize the analytical setup, although slight variations in calibration and processing did occur. Multiple secondary standard basalts and rhyolite glasses were run throughout all analytical sessions, and individual secondary standard point analyses are provided in the data file. The accompanying report and data files provide additional detail and are intended to streamline reporting by providing a detailed explanation of the methodology and to ensure that data for unknown sample analyses is precise and comparable.Not applicableThis data releaase is complete.Samples were collected from the Cook Inlet area and sampling locations are available via the Geological Database of Information on Volcanoes in Alaska (GeoDIVA; Cameron and others, 2022).Analytical setup - We prepared a traveling mount of secondary standards that can be used on multiple instruments in different laboratories because microbeam standards or reference materials often suffer heterogeneities at small scales and between individual aliquots (chips of materials or single crystals; Jarosewich and others, 1980). Thus, we can ensure our standard analyses are directly comparable and independently verify compositions of internal lab standards. This mount includes five natural volcanic glasses: two low-silica glasses (VG-2, A-99) and three high-silica glasses (VG-568, RLS-132, KN-18). Three of these standards (VG-2, A-99, VG-568) were provided by the Smithsonian Museum of Natural History and are readily available to the analytical community. We mounted unknown tephra samples with epoxy in 25-mm-diameter rounds (hereafter called round mounts) or on commercially produced polished petrographic sections. We progressively polished round mounts with diamond grit to 1 \u00c2\u00b5m and a final polish with 0.05 \u00c2\u00b5m colloidal silica or 0.1 \u00c2\u00b5m alumina suspension. Petrographic section preparation followed vendor protocols but typically included a final polish of 0.1 \u00c2\u00b5m or finer. Our traveling standard mount was in a 25 mm-diameter round mount. Samples and calibration standards were all carbon-coated to ~22 nm thickness (indigo-blue interference on brass monitors). Analyses were performed at the UAF Advanced Instrumentation Laboratory and the USGS Electron Microprobe in Menlo Park, California. UAF analyses reported here used a JEOL JXA 8530F electron microprobe. Tephra matrix analyses were performed at 15 kV, 10 nA, and a 5 \u00c2\u00b5m defocused beam. Identical beam conditions were used on the Menlo Park JEOL JXA 8530F+ electron microprobe. Calibration standards, spectrometer assignments, peak and background count times, and time-dependent intensity corrections are summarized for each analyte in Conditions and Calibrants data tables, and attempts were made to keep these values constant over all sessions. However, some variations occurred and are noted. All elements were measured on K alpha lines with linear background corrections. Data were collected and processed with Probe for EPMA software (Probe Software 2023). In UAF analyses, Na, K, and Al were measured first and corrected with a time-dependent intensity correction (TDI; Nielsen and Sigurdsson, 1981). Menlo Park analyses did not implement a TDI correction for the analyses reported here. All cations were obtained from raw intensities using the Phi-Rho-Z intensity corrections (Armstrong, 1988), while oxygen was calculated by cation stoichiometry; however, oxygen equivalent for halogens (Cl) was not used. Additional detail, results, and complete reference list can be found in the accompanying report and data tables.2022Analytical methods - Multiple secondary standard basalts and rhyolite glasses were run throughout all analytical sessions, and individual secondary standard point analyses are provided in the SecondaryStandardResults data file. We consider precision after normalization to 100 percent anhydrous (but including Cl), with Fe concentrations calculated as the total Fe (denoted by FeOT) and compared to normalized accepted values (SecondaryStandardValues data table) to determine accuracy. Normalization corrects many anomalously low or high totals (above or below a 100 percent total), which, through our examination, appear to affect all elements proportionally. Normalization is often necessary for analyzing unknown tephra that may be affected by secondary hydration resulting in low totals, or where analysis of thin glass on bubble walls results in low totals. Although this is less of an issue for the secondary standards presented here, we prefer to treat our secondary standards similarly to our unknowns to provide the most accurate representation of unknown analysis accuracy and precision. Our traveling secondary standard mount was incorporated into analyses as an unknown block one or more times per analytical session. It included Smithsonian standard glasses VG-2 (NMNH 111240-52), A-99 (NMNH 113498-1), VG-568 (NMNH 72854), USGS standard RLS-132, and KN-18. Four of the measured standards were part of the UAF EPMA internal standard block and had unique names BG-1 (VG-2_UAF), BG-2 (A-99_UAF), BG-3 (NMNH 113716-1), Rhyolite (VG-568_UAF), and CCNM (also known as Lipari UA5831). An internal aliquot of VG-2 was also analyzed on the USGS Menlo Park microprobe (VG-2_cal) along with an internal rhyolite (RLS-75). Accepted values for Smithsonian glasses are from Jarosewich and others (1980), except for Mg on VG-2 from Helz and others (2014), and Cl concentrations from various sources compiled on the Smithsonian NMNH website5 RLS-132 values are reported in Macdonald and others (1992). All our accepted values and their referenced sources are provided in the SecondaryStandardValues data table.2022point0.0000010.000001decimal degreesNAD83GRS 806378137298.257222101Calibrants.csv, Calibrants-data-dictionary.csvName of calibration standard, matches values in Conditions table for each analyte, microprobe lab for the calibrant values, where the calibration standard was obtained, type of material, and elemental concentrationsAVO, this reportCalibrantsConditions.csv, Conditions-data-dictionary.csvElectron microprobe beam conditions, calibration standards, spectrometer assignment, diffraction crystal assignments, analysis order, counting times, and time-dependent intensity correction flag (Y/N) for each elementAVO, this reportConditionsRepeatUnkns.csv, RepeatUnkns-data-dictionary.csvMicroprobe session identifier to link analyses to a set of analytical conditions (usually used on multiple consecutive days)AVO, this reportRepeatUnknsSecondaryStandardResults.csv, SecondaryStandardResults-data-dictionary.csvCategorical identification of secondary standards, secondary standard name used in analysis runs, date and time of analysis, and element weight percentsAVO, this reportSecondaryStandardResultsSecondaryStandardValues.csv, SecondaryStandardValues-data-dictionary.csvName of secondary standard used in analysis categorization, Y/N flag to indicate whether the standard is part of the traveling AVO standard mount, element reference values, and literature citations for standard reference valuesAVO, this reportSecondaryStandardValuesAlaska Division of Geological & Geophysical SurveysMetadata Managermailing and physical
3354 College Road
FairbanksAK99709-3707USA(907)451-5020(907)451-5050dggspubs@alaska.gov8 am to 4:30 pm, Monday through Friday, except State holidaysPlease view our website (https://www.dggs.alaska.gov) for the latest information on available data. Please contact us using the e-mail address provided above when possible.MP 174The State of Alaska makes no expressed or implied warranties (including warranties for merchantability and fitness) with respect to the character, functions, or capabilities of the electronic data or products or their appropriateness for any user's purposes. In no event will the State of Alaska be liable for any incidental, indirect, special, consequential, or other damages suffered by the user or any other person or entity whether from the use of the electronic services or products or any failure thereof or otherwise. In no event will the State of Alaska's liability to the Requestor or anyone else exceed the fee paid for the electronic service or product.DGGS publications are available as free online downloads or you may purchase paper hard-copies or digital files on CD/DVD or other digital storage media by mail, phone, fax, or email from the DGGS Fairbanks office. To purchase this or other printed reports and maps, contact DGGS by phone (907-451-5020), e-mail (dggspubs@alaska.gov), or fax (907-451-5050). Payment accepted: Cash, check, money order, VISA, or MasterCard. Turnaround time is 1-2 weeks unless special arrangements are made and an express fee is paid. Shipping charge will be the actual cost of postage and will be added to the total amount due. Contact us for the exact shipping amount.Contact DGGS for current pricingcsv20231002tablehttps://doi.org/10.14509/31045Free download20231002Alaska Division of Geological & Geophysical SurveysSimone MontayneMetadata Managermailing and physical
3354 College Road
FairbanksAK99709-3707USA(907)451-5020(907)451-5050dggspubs@alaska.gov8 am to 4:30 pm, Monday through Friday, except State holidaysFGDC Content Standard for Digital Geospatial MetadataFGDC-STD-001-1998If the user has modified the data in any way they are obligated to describe the types of modifications they have performed in the supporting metadata file. User specifically agrees not to imply that changes they made were approved by the Alaska Department of Natural Resources or Division of Geological & Geophysical Surveys.https://dggs.alaska.gov/metadata/dggs.extdggs metadata extensions","source_transform":null,"status":"error"}