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.

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 iron oxide-apatite (IOA) deposits near Mineville in the Adirondack Mountains, New York, have been of interest for their rich magnetite ore since the mid-1700s but have attracted renewed attention due to their potential as rare earth element (REE) resources (McKeown and Klemic, 1956; Lupulescu and others, 2016; Taylor and others, 2018). Apatite is the main REE-host and is found in variable concentrations within ore seams of the regional magnetite deposits. Some apatite crystals are unaltered, relatively homogenous, and inclusion-free, whereas other deposits contain heterogenous apatite with zones of abundant secondary mineral inclusions that were formed through metasomatic reactions with the apatite after initial precipitation. The heterogeneous apatite crystals may have inclusion-free bright zones and intermediate zones in back-scattered electron imagery (BSE), and dark BSE zones that contain inclusions of monazite and thorite. Apatite crystals from twenty-seven samples, including twenty-four ore and three rock samples from a total of nineteen different ore deposits, were analyzed by electron microprobe to obtain their major and minor element geochemistry. Additionally, some magmatic apatite crystals from the ore-hosting Lyon Mountain Granite Gneiss were analyzed for comparison with the ore apatite. The electron microprobe data was collected by personnel of the Southwest Region Geology, Geophysics, and Geochemistry Science Center in Denver, Colorado, for the U.S. Geological Survey (USGS) Mineral Resources Program (MRP). A JEOL 8900 Electron Microprobe with five wavelength dispersive analyzers operated at 20keV accelerating voltage, a 50-nA current (measured on the Faraday cup), and an electron beam diameter of 10 micrometers was utilized. All analyzed crystals are considered fluorapatite, with fluorine contents ranging from approximately 3.5 to 6.6%. Some apatite crystals from ore contain greater than 15% total REE, whereas some others contain less than 1%. Commonly, Y, La, Ce, and Nd are the most abundant REE in the apatite crystals. The magmatic apatite crystals are notably purer with low contents of actinides, REE, and other common minor impurities. Analyses that contained total elemental weight percentages between 97% to 103% were accepted; those analyses with poor totals falling outside of this range were rejected. The different zones within heterogeneous apatite crystals contained lower concentrations of REE and other minor element components in the dark BSE zones than in the bright BSE zones, but both zones had nearly parallel REE profiles. The zones of differing BSE brightness are interpreted to be caused by metasomatic alteration. Although the REE profiles were consistent for a given sample, variations in total REE content and overall chemistry were noted between different deposits and even different ore seams within a given deposit.

The iron oxide-apatite (IOA) deposits near Mineville in the Adirondack Mountains, New York, have been of interest for their rich magnetite ore since the mid-1700s but have attracted renewed attention due to their potential as rare earth element (REE) resources (McKeown and Klemic, 1956; Lupulescu and others, 2016; Taylor and others, 2018). Apatite is the main REE-host and is found in variable concentrations within ore seams of the regional magnetite deposits. Some apatite crystals are unaltered, relatively homogenous, and inclusion-free, whereas other deposits contain heterogenous apatite with zones of abundant secondary mineral inclusions that were formed through metasomatic reactions with the apatite after initial precipitation. The heterogeneous apatite crystals may have inclusion-free bright zones and intermediate zones in back-scattered electron imagery (BSE), and dark BSE zones that contain inclusions of monazite and thorite. Apatite crystals from twenty-seven samples, including twenty-four ore and three rock samples from a total of nineteen different ore deposits, were analyzed by electron microprobe to obtain their major and minor element geochemistry. Additionally, some magmatic apatite crystals from the ore-hosting Lyon Mountain Granite Gneiss were analyzed for comparison with the ore apatite. The electron microprobe data was collected by personnel of the Southwest Region Geology, Geophysics, and Geochemistry Science Center in Denver, Colorado, for the U.S. Geological Survey (USGS) Mineral Resources Program (MRP). A JEOL 8900 Electron Microprobe with five wavelength dispersive analyzers operated at 20keV accelerating voltage, a 50-nA current (measured on the Faraday cup), and an electron beam diameter of 10 micrometers was utilized. All analyzed crystals are considered fluorapatite, with fluorine contents ranging from approximately 3.5 to 6.6%. Some apatite crystals from ore contain greater than 15% total REE, whereas some others contain less than 1%. Commonly, Y, La, Ce, and Nd are the most abundant REE in the apatite crystals. The magmatic apatite crystals are notably purer with low contents of actinides, REE, and other common minor impurities. Analyses that contained total elemental weight percentages between 97% to 103% were accepted; those analyses with poor totals falling outside of this range were rejected. The different zones within heterogeneous apatite crystals contained lower concentrations of REE and other minor element components in the dark BSE zones than in the bright BSE zones, but both zones had nearly parallel REE profiles. The zones of differing BSE brightness are interpreted to be caused by metasomatic alteration. Although the REE profiles were consistent for a given sample, variations in total REE content and overall chemistry were noted between different deposits and even different ore seams within a given deposit.

Electron probe microanalytical data of minerals and glass from rock samples from Pavlof Volcano, Alaska, Raw Data File 2022-7, presents electron microprobe analytical data from minerals from lava samples collected at Pavlof Volcano by Alaska Volcano Observatory (AVO) geologist Jessica Larsen during fieldwork in 2017 and from tephra samples described in Waythomas and others (2017). Samples include those produced during recent eruptions of Pavlof in 1986, 1996, 2007, 2013, 2014, and 2016. Pavlof Volcano is an undissected stratovolcano located approximately 58 km northeast of Cold Bay, in the southwestern portion of the Alaska Peninsula. Electron probe micro-analysis (EPMA) data are reported from the major mineral phases: orthopyroxene, clinopyroxene, olivine, plagioclase, and magnetite. Sample descriptions, locations, and types are included in the metadata associated with the analytical data table. The data are available from the DGGS website: http://doi.org/10.14509/30854.

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”.

This data release comprises geochemical point analyses of magnetite by electron probe microanalyzer (EPMA) and sample imagery acquired by a combination of scanning electron, reflected light, and transmitted light microscopy. Analyzed elements include Fe, Ti, Al, Mn, Mg, V, Si, Ni, Cr, and Ca. Samples are from the Taurus porphyry Cu-Mo(-Au) deposit in the Yukon-Tanana upland of eastern interior Alaska and compose two types of magnetite. The first subset of EPMA analyses (n=771 individual points) are from detrital magnetite obtained from sediments of streams that drain the deposit and its environs. A second subset of EPMA analyses (n=203) are from hydrothermal, igneous, and metamorphic magnetite associated with porphyry style mineralization and its host lithologies. Complementary sample imagery documents grain-by-grain microstructures, inclusion assemblages, and sample context which are also tabulated herein.