Glass 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.

This Raw Data File presents major-oxide glass geochemical results from the ca. 3.6 ka caldera-forming eruption of Aniakchak volcano, Alaska. These data are part of a larger effort to identify and characterize tephra deposits from the largest eruptions in Alaska for use as geochronological marker horizons. Aniakchak is one of at least 29 volcanoes in Alaska that has had multiple large tephra-producing eruptions. Other deposit and sample metadata including geospatial distributions of this tephra deposit are held in the Alaska Volcano Observatory's online database, the Geologic Database of Information on Volcanoes in Alaska (GeoDIVA), and will be linked to these new geochemical data once published. Products included in this data release are background information on the larger project, methods of sample collection, processing, analysis, and data reduction spreadsheets showing 1) raw point major-oxide data, 2) normalized and averaged major-oxide data, and 3) basic sample metadata. Users can access the complete report and digital data from the DGGS website: http://doi.org/10.14509/29777 and from the Alaska Volcano Observatory's online database, the Geologic Database of Information on Volcanoes in Alaska (GeoDIVA)

Alaska Volcano Observatory (AVO) geologists from the U.S. Geological Survey (USGS) and the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted fieldwork at Mount Veniaminof during field excursions between 2001 and 2016. The primary purpose of the fieldwork was geologic investigation of Veniaminof volcano to elucidate its eruptive history and understand its eruptive behavior. Teams of geologists focused on 1) edifice lava flows, 2) flowage deposits (lahars and pyroclastic flows), and 3) tephra-fall deposits. This Raw Data File comprises 61 whole-rock analyses of pumices from Holocene-age tephra deposits collected from 36 field stations on the flanks of Veniaminof volcano in 2001-2004, 2010, and 2016. All but four samples in this report were collected by geologists Kristi Wallace and Chris Waythomas during 1- to 2-week summer fieldwork campaigns. Thomas Miller and Charles Bacon contributed four pumice samples of a young dacite-composition tephra collected in 2001 and 2002. Mount Veniaminof is an ice-clad, basalt-to-dacite stratovolcano topped by an ice-filled caldera 10 km (about 6 mi) in diameter, located 775 km (482 mi) southwest of Anchorage on the Alaska Peninsula. With a volume of approximately 350 km3 (approximately 84 mi3) Veniaminof is one of the largest and most active volcanoes of the Aleutian Arc. Two Holocene caldera-forming eruptions are recorded in extensive pyroclastic-flow deposits around the volcano. Veniaminof has had at least 15 eruptions in the past 200 years, all from the approximately 300-m-high (about 984-ft-high) intracaldera cone and all largely basaltic-basaltic andesite composition, producing small lava flows and minor tephra deposits mostly confined to the caldera boundaries. The most recent explosive eruption was in 2018. Geochemical characterization of tephra deposits is most commonly executed by using glass-phase chemistry rather than whole-rock (bulk) geochemistry. The bulk composition of a tephra may change over fallout distance by eolian fractionation and therefore cannot be used to correlate tephra deposits over long distances. Whole-rock composition is commonly used to characterize juvenile material from flowage deposits (lahars and pyroclastic flows) and lavas. In order to readily compare (correlate) juvenile material from proximal tephra-fall deposits with other proximal deposits, tephra whole-rock analysis is required. This Raw Data File is focused only on whole-rock geochemical analyses of significant coarse-grained tephra deposits exposed on the flanks of Veniaminof volcano for use in correlating tephra deposits across the large volcanic edifice, and with proximal flowage deposits and edifice lava flows. Results of glass geochemistry of Veniaminof tephra and all other whole-rock analyses of samples collected is part of an ongoing study and not included in this report. Files can also be downloaded from the DGGS website (http://doi.org/10.14509/30578) and is also available in .html and .csv from the AVO Geochemical Database (https://avo.alaska.edu/geochem). Sample descriptions, locations, and sample types are included in the analytical data table. Samples collected during this project, including hand sample material, remaining powder from these whole-rock analyses, and partially crushed sample remains are stored at the Alaska Geologic Materials Center or at the USGS Alaska Tephra Laboratory in Anchorage.

Tephra samples and analyses from Cook Inlet source volcanoes and Anchor Point, Alaska, Raw Data File 2023-25, proivides samples and analyses collected from source volcanoes of the Cook Inlet region, Alaska, including Hayes Volcano, Mount Spurr, Redoubt Volcano, Iliamna Volcano, Augustine Volcano, Mount Douglas, Fourpeaked Mountain, and Kaguyak Crater. The report also includes tephra and soil samples and analyses from a stratigraphic section examined near Anchor Point, Alaska. These samples were collected over many years during geologic investigations of the eruptive histories for these source volcanoes, and in regional studies of eruption impacts, and are compiled here to support research characterizing the composition and impacts of these volcanoes on the Cook Inlet region. The analytical data tables associated with this report are provided in digital format as comma-separated value (CSV) files. They are available from the DGGS website: http://doi.org/10.14509/31090 and are archived in the Geologic Database of Information on Volcanoes in Alaska (GeoDIVA; Cameron and others, 2022, doi.org/10.14509/geodiva).

Laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) analyses of apatite provide trace element concentrations that support indicator mineral studies near the Taurus porphyry Cu-Mo deposit in the eastern Tanacross quadrangle, Alaska. The Taurus deposit and others in the region are mostly concealed, and traditional stream sediment samples typically show subdued geochemical signatures. The indicator mineral studies include collection of stream sediment samples and analysis using automated SEM mineralogical techniques. The presence of select minerals in the stream sediments may indicate mineralization. In addition, the chemistry of specific minerals may be used to distinguish a hydrothermal origin as opposed to others. The LA-ICP-MS data for apatite were collected by personnel of the Geology, Geophysics, and Geochemistry Science Center in Denver, Colorado, for the U.S. Geological Survey (USGS) Mineral Resources Program (MRP). Additional data were obtained at Queens University and Colorado School of Mines. Appreciable differences in chemistry were noted for apatite in mineralized rock and stream sediment samples draining these rocks compared to barren rocks or sediment samples away from mineralization.

Davidof volcano samples and analyses, Raw Data File 2023-22, provides calculations and analytical results from samples collected in the western Aleutian Islands in 2021 by Alaska Volcano Observatory (AVO) geologists Hannah Dietterich and Matt Loewen. The primary target of this sampling was Davidof volcano, a partially submerged 5 km-diameter caldera located in the Rat Islands. Subaerial exposures include Davidof, Khvostof, Lopy, and Pyramid islands. The only prior published work on Davidof volcano was part of the U.S. Geological Survey's post World War II geologic reconnaissance of the Aleutian Islands (Nelson and others, 1959). Nelson and others (1959) only indicate two samples from Davidof volcano that were analyzed petrographically, but prior to this data release no quantitative data for Davidof volcano have been available. This report also includes samples collected during 2021 from the western shore of Little Sitkin Volcano, as well as new electron microprobe analyses from samples previously collected in 2005 and 2015 from Little Sitkin Volcano and 2015 from Segula Volcano. Data associated with this report are archived in the Geologic Database of Information on Volcanoes in Alaska (GeoDIVA; Cameron and others, 2022, doi.org/10.14509/geodiva. This report is released as a Raw Data File with an open end-user license. The data are available from the DGGS website: http://doi.org/10.14509/31084.

This USGS Data Release presents major-oxide glass geochemical results from tephras erupted form Alaska volcanoes. This data set is in support of volcano hazard studies by the Alaska Volcano Observatory (AVO) where tephra (volcanic ash) deposits are used to assess eruption frequency, magnitude, and character of eruption. These data are part of a larger effort to identify and characterize tephra deposits from Alaskan volcanoes and the data set will continue to grow (versioned) as new data are generated.