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.

DGGS Raw Data File 2022-6, Electron probe microanalytical data of minerals and glass from rock samples from Okmok volcano, Alaska, provides electron probe microanalytical data (EPMA) from minerals and glasses from samples collected at Okmok volcano by Alaska Volcano Observatory (AVO) geologist Jessica Larsen. AVO geologists conducted fieldwork at Okmok volcano between 1998 and 2016. The samples included in this report are from the 2050 +/-50 yBP Okmok II eruption of Okmok caldera. All files are available from the DGGS website: http://doi.org/10.14509/30853.

During the summers of 2017 and 2018, Alaska Volcano Observatory (AVO) geologists from the University of Alaska, Fairbanks (UAF), the U.S. Geological Survey (USGS), and the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted fieldwork at Pavlof Volcano (55.4173 N, -161.8937 W), on the Alaska Peninsula, Alaska. The fieldwork was conducted in support of geologic mapping and tephrostratigraphy, to improve the documentation of recent Pavlof eruptions, and to better assess hazards associated with Pavlof eruptions. As a result, samples of lava and various pyroclasts (mainly bombs and lapilli) were collected for whole rock geochemistry analyses. This report includes whole rock major- and trace-element data from lava and bomb samples from the 1996, 2013, 2014, and 2016 eruptions, along with samples of lava and lapilli fall deposits, presumed to be of Holocene age, collected from outcrops around Pavlof and Pavlof Sister volcanoes. We also include electron probe microanalyzer (EPMA) data from tephra glass samples from the 1986 (AT-2822), 1996 (AT-2823), 2007 (AT-2824), and 2013 (AT-2821) eruptions. These samples were initially analyzed at the USGS office in Menlo Park and were re-analyzed for this report in the Advanced Instrumentation Laboratory (AIL) at UAF for comparison. Tephra EPMA glass data from the 2016 eruption, analyzed in the AIL, is also included from sample AT-3680. The analytical data tables associated with this report are available in digital format as comma-separated value (CSV) files. Users can access the complete report and digital data from the DGGS website: http://doi.org/10.14509/30580.

The exploration for porphyry deposits in some parts of Alaska may require unconventional exploration geochemical methods, depending on type of cover. The Taurus deposit and others in the region are mostly concealed by residual soils that in part include ash and loess, and therefore traditional stream sediment samples typically contain subdued geochemical signatures. 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, and include apatite, rutile, and titanite. The electron probe data in this data release were collected for apatite, rutile, and titanite by personnel of the Geology, Geophysics, and Geochemistry Science Center in Denver, Colorado, for the U.S. Geological Survey (USGS) Mineral Resources Program (MRP). Appreciable differences in chemistry were noted for these minerals in mineralized rock and stream sediment samples draining these rocks compared to sediment samples away from mineralization.

The exploration for porphyry deposits in some parts of Alaska may require unconventional exploration geochemical methods, depending on type of cover. The Taurus deposit and others in the region are mostly concealed by residual soils that in part include ash and loess, and therefore traditional stream sediment samples typically contain subdued geochemical signatures. 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, and include apatite, rutile, and titanite. The electron probe data in this data release were collected for apatite, rutile, and titanite by personnel of the Geology, Geophysics, and Geochemistry Science Center in Denver, Colorado, for the U.S. Geological Survey (USGS) Mineral Resources Program (MRP). Appreciable differences in chemistry were noted for these minerals in mineralized rock and stream sediment samples draining these rocks compared to sediment samples away from mineralization.

Mineral compositions are reported for Quaternary volcanic rocks of the Matan volcanic center, northern Harrat Rahat, Saudi Arabia. Compositions were measured by wavelength-dispersive methods with the 5-spectrometer JEOL-8900 electron microprobe at the USGS facility in Menlo Park, California; background-corrected X-ray intensities were reduced to oxide weight concentrations with the JEOL proprietary version of the CITZAF reduction schema. These results are part of a collaborative study by the U.S. Geological Survey and Saudi Geological survey to assess the volcanic and seismic hazards associated with the northern Harrat Rahat volcanic field.

Mineral compositions are reported for Quaternary volcanic rocks of the Matan volcanic center, northern Harrat Rahat, Saudi Arabia. Compositions were measured by wavelength-dispersive methods with the 5-spectrometer JEOL-8900 electron microprobe at the USGS facility in Menlo Park, California; background-corrected X-ray intensities were reduced to oxide weight concentrations with the JEOL proprietary version of the CITZAF reduction schema. These results are part of a collaborative study by the U.S. Geological Survey and Saudi Geological survey to assess the volcanic and seismic hazards associated with the northern Harrat Rahat volcanic field.

This data release provides geochemical results of in situ electron probe microanalyses of hydrothermal muscovite associated with gold-bearing quartz veins from the Klamath Mountains, California. Samples were collected from eight different mines in the summer of 2013 and electron probe microanalyses were carried out May 27, 2014 and November 12, 2019.