This data release includes geochemical, x-ray diffraction mineralogical, and electron probe microanalysis (EPMA) data on rocks, soils, and sediments collected near the Orange Hill and Bond Creek porphyry copper deposits, Nabesna quadrangle, Alaska. Geochemical analyses were completed by a laboratory under contract with the U.S. Geological Survey (USGS). Electron microprobe and x-ray diffraction mineralogical analyses were completed by personnel of the Central Region Minerals Program in Denver, Colorado. The samples were collected and analyzed during 2014 to 2016, selected to help characterize the distribution and composition of mineralized and unmineralized geologic materials in this remote part of the eastern Alaska Range. These results provide important information for interpreting airborne imaging spectroscopy data that were collected as part of the U.S. Geological Survey (USGS) Mineral Resources Program (MRP) project, 'Hyperspectral Remote Sensing Data and a Multi-proxy Investigation for Characterizing Mineral Resources in Alaska'. A discussion and interpretation of these data and their relationship to the airborne spectroscopy results are provided in: Graham, G.E., Kokaly, R.F., Kelley, K.D., Hoefen, T.M., Johnson, M.R., and Hubbard, B.E., Application of imaging spectroscopy for mineral exploration in Alaska: A study over porphyry Cu deposits in the eastern Alaska Range, Economic Geology, in press.

This data release includes geochemical, x-ray diffraction mineralogical, and electron probe microanalysis (EPMA) data on rocks, soils, and sediments collected near the Orange Hill and Bond Creek porphyry copper deposits, Nabesna quadrangle, Alaska. Geochemical analyses were completed by a laboratory under contract with the U.S. Geological Survey (USGS). Electron microprobe and x-ray diffraction mineralogical analyses were completed by personnel of the Central Region Minerals Program in Denver, Colorado. The samples were collected and analyzed during 2014 to 2016, selected to help characterize the distribution and composition of mineralized and unmineralized geologic materials in this remote part of the eastern Alaska Range. These results provide important information for interpreting airborne imaging spectroscopy data that were collected as part of the U.S. Geological Survey (USGS) Mineral Resources Program (MRP) project, 'Hyperspectral Remote Sensing Data and a Multi-proxy Investigation for Characterizing Mineral Resources in Alaska'. A discussion and interpretation of these data and their relationship to the airborne spectroscopy results are provided in: Graham, G.E., Kokaly, R.F., Kelley, K.D., Hoefen, T.M., Johnson, M.R., and Hubbard, B.E., Application of imaging spectroscopy for mineral exploration in Alaska: A study over porphyry Cu deposits in the eastern Alaska Range, Economic Geology, in press.

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.

Key mineral assemblages help determine pressure, temperature and depth of emplacement for mineralized veins of the Keno Hill district, as well as for local Cretaceous pluton emplacement. New electron microprobe analyses are presented on samples collected in the field, enabling further characterization of the hydrothermal and plutonic regimes. Staurolite-garnet-albite-biotite schist along the margins of the Cretaceous Roop Lakes stock record contact metamorphic conditions, averaging 518°C and 3450 bar. To the west, hydrothermal veins of the Keno Hill district containing pyrite-pyrrhotite-sphalerite-arsenopyrite, indicate hydrothermal conditions of approximately 400°C and 1500 bar. Lithostatic conditions for the pluton, and likely hydrostatic conditions for the veins, are interpreted to indicate a similar depth of emplacement for the two systems, near 10-13 km below the surface.

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 dataset contains results from electron microprobe analyses of cassiterite from the Sullivan Pb-Zn-Ag deposit, British Columbia. These data were collected from two samples and may not reflect the overall variability present at the deposit. An ASCII text file of results is provided in comma-separated by value (csv) format. The file has the name “2019-07-09_Sullivan_Cassiterite”.

This dataset contains results from electron microprobe analyses of cassiterite from the Sullivan Pb-Zn-Ag deposit, British Columbia. These data were collected from two samples and may not reflect the overall variability present at the deposit. An ASCII text file of results is provided in comma-separated by value (csv) format. The file has the name “2019-07-09_Sullivan_Cassiterite”.

Geologic map of Okmok Volcano, Report of Investigation 2023-1, provides 40Ar/39Ar and radiocarbon geochronology data from Okmok Volcano and its eruptive products. Okmok Volcano is one of 54 historically active volcanoes in the Alaska-Aleutian volcanic arc that stretches across southern mainland Alaska and the Aleutian Islands. Okmok Volcano dominates the northeastern portion of Umnak Island, which is 100 km southwest of Unalaska/Dutch Harbor and 1,400 km southwest of Anchorage. Okmok Volcano is one of the most frequently active volcanoes in the Aleutian volcanic arc. In 1998, the Alaska Volcano Observatory (AVO) began a multi-year effort to expand geophysical monitoring in the central Aleutians Islands, including at Okmok Volcano. These data support the development of a modern geologic map of Okmok Volcano and related investigation of its eruptive history and hazards. 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/10.14509/31015.

This data release is part of a 2016-2019 study on the geology, geochemistry and geochronology of ore systems in the eastern Yukon-Tanana Upland region, Alaska. Whole rock chemistry was conducted on 185 samples, mostly from Au prospects, with lesser samples from porphyry Cu prospects. Geographically, most samples are from gold prospects near the Pogo Au mine and east to Black Mountain in the Big Delta quadrangle. Fewer samples are from prospects in the Eagle and Tanacross Quadrangles. Samples were submitted to the USGS contract laboratory and analyzed for select trace elements and gold. Sixty elements were determined by inductively coupled plasma-optical emission spectroscopy-mass spectroscopy (ICP-OES-MS), sodium peroxide fusion (ICP-60). Gold was determined by lead fusion fire assay.