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.

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.

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.

The genetic origin of many gold deposits, including Pogo in Alaska, remains controversial with questions as to whether they formed due to magmatic-hydrothermal or metamorphic-hydrothermal fluids. Gaining a better understanding of the formation mechanisms for these deposits is critical for defining proper exploration criteria in gold-bearing regions and production within these deposits. Monazite are light rare earth (LREE)-bearing and xenotime are heavy rare earth (HREE)-bearing phosphate minerals that are found as alteration products in many gold deposits. In addition to their importance in geochronological investigations, their minor element chemistry may be used to differentiate between metamorphic, magmatic, diagenetic, and hydrothermal origin. This data release provides electron microprobe geochemical data that is used to showcase differences in these phosphates when derived from magmatic-hydrothermal systems compared to metamorphic-hydrothermal systems. The electron microprobe data was collected by personnel of the Central Region Minerals Program in Denver, Colorado, for the U.S. Geological Survey (USGS) Mineral Resources Program (MRP). Appreciable differences in chemistry were noted for deposits associated with alkaline magmatic systems (Taurus, AK, and Cripple Creek, CO), calc-alkaline magmatic systems (Pebble, AK, and Butte, MT), and orogenic gold systems derived from metamorphic-hydrothermal systems (systems from Grass Valley, the Mother Lode, and the Klamath Mountains in CA). These characteristics were then applied to the controversially classified Pogo gold deposit, Alaska, in order to provide evidence for how it formed. Following initial study, new electron microprobe geochemical data for this updated data release were collected from reduced intrusion-related gold deposits at the Geology, Geophysics, and Geochemistry Science Center in Denver, Colorado, to add to the database. This new data allows better comparison between gold deposits formed from reduced magmatic-hydrothermal fluids, oxidized magmatic-hydrothermal fluids, and metamorphic-hydrothermal fluids.

The genetic origin of many gold deposits, including Pogo in Alaska, remains controversial with questions as to whether they formed due to magmatic-hydrothermal or metamorphic-hydrothermal fluids. Gaining a better understanding of the formation mechanisms for these deposits is critical for defining proper exploration criteria in gold-bearing regions and production within these deposits. Monazite are light rare earth (LREE)-bearing and xenotime are heavy rare earth (HREE)-bearing phosphate minerals that are found as alteration products in many gold deposits. In addition to their importance in geochronological investigations, their minor element chemistry may be used to differentiate between metamorphic, magmatic, diagenetic, and hydrothermal origin. This data release provides electron microprobe geochemical data that is used to showcase differences in these phosphates when derived from magmatic-hydrothermal systems compared to metamorphic-hydrothermal systems. The electron microprobe data was collected by personnel of the Central Region Minerals Program in Denver, Colorado, for the U.S. Geological Survey (USGS) Mineral Resources Program (MRP). Appreciable differences in chemistry were noted for deposits associated with alkaline magmatic systems (Taurus, AK, and Cripple Creek, CO), calc-alkaline magmatic systems (Pebble, AK, and Butte, MT), and orogenic gold systems derived from metamorphic-hydrothermal systems (systems from Grass Valley, the Mother Lode, and the Klamath Mountains in CA). These characteristics were then applied to the controversially classified Pogo gold deposit, Alaska, in order to provide evidence for how it formed. Following initial study, new electron microprobe geochemical data for this updated data release were collected from reduced intrusion-related gold deposits at the Geology, Geophysics, and Geochemistry Science Center in Denver, Colorado, to add to the database. This new data allows better comparison between gold deposits formed from reduced magmatic-hydrothermal fluids, oxidized magmatic-hydrothermal fluids, and metamorphic-hydrothermal fluids.

From June 12-21, 2017, the Alaska Division of Geological & Geophysical Surveys (DGGS) geologists carried out geologic mapping and geochemical sampling in the northeastern Tanacross D-1, and parts of the C-1, and D-2 quadrangles. The project area lies within the Yukon-Tanana Uplands, and encompasses the boundary between Fortymile and Lake George assemblages. It includes porphyry copper-molybdenum-gold deposits and prospects including: Taurus, Fishhook (also known as SW Pika), and Pika Canyon, and is adjacent to the Fortymile Mining District to the north. Highlights of this geochemical report include sampling and characterization of the Pika Canyon, Fishhook, and Taurus prospects. This dataset contains four samples with gold in excess of 0.1 parts per million (ppm) in several different locations, including two samples from Fishhook with 2.15 ppm and 0.697 ppm gold, respectively (17MBW119, 17MBW130), and a sample with 4,420 ppm silver and greater than 30 percent lead (17MLW002) collected nearby Pika Canyon. The DGGS Tanacross project area includes a section of Paleozoic and Mississippian- to Devonian-age, metasedimentary and metavolcanic rocks, as well as Jurassic(?) to Tertiary intrusive and volcanic rocks. Major- and trace-element geochemical analyses were obtained for metamorphic rocks to distinguish between igneous and sedimentary protoliths, and for igneous rocks to characterize and differentiate Mesozoic and Cenozoic rocks in the area. The analytical data tables associated with this report are available in digital format as comma-separated value (CSV) files. Additional details about the organization of information are noted in the accompanying metadata file. All files can be downloaded from the DGGS website (http://doi.org/10.14509/29778).

Data for 819 pan concentrated stream-sediment samples, nonmagnetic heavy-mineral concentrate (HMC) samples, and chemical data for 93 of HMC samples. The samples were collected in 2004-2008 as part of a reconnaissance geochemical geological survey of drainage basins mostly in the Taylor Mountains 1:250,000-scale quadrangle in southwestern Alaska. Samples were collected from first- or second-order streams, as shown on USGS 1:63,360-scale maps. The data reported here are from hand lens inspection of the panned concentrate samples in the field, microscopic examination of the non-magnetic fraction of the HMC samples in the lab, and chemical analyses by Inductively Coupled Plasma-Atomic Emission Spectrometry-Mass Spectrometry (ICP-AES-MS) of selected nonmagnetic HMC samples.