This data release is part of a study designed to test geochemical methods that best delineate known mineral deposits in the northeast part of the Tanacross 1° x 3° quadrangle, within the Yukon-Tanana Upland region, Alaska. The total area sampled is about 3,200 km2. Extensive tundra cover and patchy spruce/alder vegetation and very limited outcrop exposure characterize the area. Soils and stream sediments contain mixtures of weathered bedrock, sand derived from dunes developed during the Pleistocene, and volcanic ash deposits from the 1.2 Ky eruption of the nearby Mount Churchill volcano. Several mineral deposits are known in the area, including the Late Cretaceous to earliest Tertiary porphyry Cu (+/-Mo-Au) deposits at Taurus, Bluff, and Oreo; and poorly understood epithermal(?) Cu-Au (+/- Pb-Zn) deposits at Pika, Fishhook, and Pushbush. Stream water and sediment samples were collected near these occurrences, as well as in surrounding areas, to determine methods that most effectively enhance geochemical signals related to mineralization. Sediment samples were collected during two sampling campaigns (2017 and 2018). Each sample was dried, homogenized, and split into multiple aliquots. One aliquot of sediment was subsequently sieved to recover the minus-80 mesh portion of the sample, whereas a second was sieved to recover the minus-230 mesh portion of the sample. Both aliquots were analyzed by three techniques, all of which included ICP-OES/ICP-MS analysis following (1) sodium peroxide fusion, 2) leaching by aqua regia; and 3) leaching by cold hydroxylamine-HCL. Stream water samples were collected from select sites in August 2018 and analyzed for cation and anion concentrations using high-resolution ICP-MS for cations and Ion Chromatography (IC) for anions.

This set of data files contains analyses of samples representing Triassic units (Shublik and Ivishak Formations and Karen Creek Sandstone) in Alaska. The samples were collected from 20 outcrop localities in northeastern Alaska. The data set includes total organic carbon (TOC) and geochemical data from inductively coupled plasma-optical emission spectroscopy-mass spectroscopy (ICP-OES-MS) and portable X-ray fluorescence (p-XRF). The data presented here are described and interpreted in a paper titled "Facies Variation within Outcrops of the Triassic Shublik Formation, Northeastern Alaska".

This set of data files contains analyses of samples representing Triassic units (Shublik and Ivishak Formations and Karen Creek Sandstone) in Alaska. The samples were collected from 20 outcrop localities in northeastern Alaska. The data set includes total organic carbon (TOC) and geochemical data from inductively coupled plasma-optical emission spectroscopy-mass spectroscopy (ICP-OES-MS) and portable X-ray fluorescence (p-XRF). The data presented here are described and interpreted in a paper titled "Facies Variation within Outcrops of the Triassic Shublik Formation, Northeastern Alaska".

In 2016, geologists from the Alaska Division of Geological & Geophysical Surveys (DGGS) and University of Alaska Fairbanks carried out a two-part geologic mapping and geochemical sampling project in the Tok River area of the Tanacross A-5 and A-6 quadrangles (June 12-26 and July 8-26). This report provides results of stream-sediment sampling for trace-element geochemistry. An initial suite of sediment samples was collected from streams draining known gold occurrences, including the Stibnite Creek and Noah prospects, and numerous prospects in the White Gold area. These samples were split in half and the two splits were sieved to -200 mesh and -80 mesh, respectively. The splits were then both analyzed to determine which size fraction was best for identifying gold anomalies in this part of the Alaska Range. In most samples, the -200 mesh fraction showed higher gold levels, and hence, all additional samples we collected were analyzed at -200 mesh. In some -80 mesh samples, gold and tungsten appear to show "nugget" effects not seen in the -200 mesh samples. The other trace elements are largely equivalent between the two mesh sizes. The second suite of samples was collected throughout the map area from streams draining color anomalies, from areas where DGGS mapping identified igneous rocks upstream, and from areas with suspected potential for base-metal or gold mineralization. Highlights of the analytical results include two samples draining the Noah prospect with greater than 1 part per million gold. The analytical data tables associated with this report are available in digital format as comma-separated value (CSV) files.

This U.S. Geological Survey (USGS) data release contains data from stream water, groundwater, and soil samples collected in 2019 and 2020 in the North Quartz Creek watershed in central Colorado. Fourteen streambank wells were installed in pairs at seven locations in August 2020 to capture the emerging groundwater from the left bank and right banks (relative to downstream-facing direction) and a synoptic sampling campaign was conducted to quantify metal contributions to the stream. A continuous, instream injection of sodium bromide (NaBr) was initiated at the head of the 5 km study reach several days prior to the synoptic sampling campaign and maintained throughout the duration of the study. Bromide concentrations were subsequently used to determine streamflow in the primary study reach (upper 1.3 km) using the tracer-dilution method, and as an indicator of hydrologic connections between North Quartz Creek and subsurface water. Streamflow was quantified in a secondary study reach (lower 3.7 km) using data from a series of sodium chloride slug additions wherein specific conductivity readings were used as a surrogate for the tracer concentration. Surface water samples were collected along North Quartz Creek including inflows from the left (LBI) and right (RBI) banks. Soil and sediment samples were collected along the transport path from source material (natural weathering and mine tailings/mine drainage) to the stream.

This U.S. Geological Survey (USGS) data release contains data from stream water, groundwater, and soil samples collected in 2019 and 2020 in the North Quartz Creek watershed in central Colorado. Fourteen streambank wells were installed in pairs at seven locations in August 2020 to capture the emerging groundwater from the left bank and right banks (relative to downstream-facing direction) and a synoptic sampling campaign was conducted to quantify metal contributions to the stream. A continuous, instream injection of sodium bromide (NaBr) was initiated at the head of the 5 km study reach several days prior to the synoptic sampling campaign and maintained throughout the duration of the study. Bromide concentrations were subsequently used to determine streamflow in the primary study reach (upper 1.3 km) using the tracer-dilution method, and as an indicator of hydrologic connections between North Quartz Creek and subsurface water. Streamflow was quantified in a secondary study reach (lower 3.7 km) using data from a series of sodium chloride slug additions wherein specific conductivity readings were used as a surrogate for the tracer concentration. Surface water samples were collected along North Quartz Creek including inflows from the left (LBI) and right (RBI) banks. Soil and sediment samples were collected along the transport path from source material (natural weathering and mine tailings/mine drainage) to the stream.

This data release is the result of a hydrogeochemical sampling campaign during summer 2021 to investigate whether high resolution geochemical analysis of waters for element chemistry can be used as an exploration tool for identifying gold-rich occurrences in parts of the Big Delta B-1 and B-2 quadrangles, within the Yukon-Tanana Upland region, Alaska. Historical USGS conventional stream sediment geochemical data yielded variable indications of geochemical anomalies in conventional stream sediment geochemistry results, probably related to relative exposure of mineralized rock. Previous studies of waters in the Pogo area (western part of current study) utilized conventional analytical methods not capable of measuring low concentrations of many elements (Wang et al., 2005). In the current study, water samples were collected from 36 stream sample sites, with a focus on streams around Black Mountain to the east and the Pogo Au deposit area to the west. Both areas have known gold-rich mineral occurrences. In the eastern Black Mountain area, this included the Gray Lead, Blue Lead, and Michigan prospects, among others (U.S. Geological Survey, 1996). Sampling in the Pogo area was restricted to streams outside Leise Creek area due to anthropogenic disturbance as part of mining. Stream water samples were collected in 2021 and analyzed for cation and anion concentrations using high-resolution ICP-MS for cations and ion chromatography (IC) for anions.

This data release is the result of a hydrogeochemical sampling campaign during summer 2021 to investigate whether high resolution geochemical analysis of waters for element chemistry can be used as an exploration tool for identifying gold-rich occurrences in parts of the Big Delta B-1 and B-2 quadrangles, within the Yukon-Tanana Upland region, Alaska. Historical USGS conventional stream sediment geochemical data yielded variable indications of geochemical anomalies in conventional stream sediment geochemistry results, probably related to relative exposure of mineralized rock. Previous studies of waters in the Pogo area (western part of current study) utilized conventional analytical methods not capable of measuring low concentrations of many elements (Wang et al., 2005). In the current study, water samples were collected from 36 stream sample sites, with a focus on streams around Black Mountain to the east and the Pogo Au deposit area to the west. Both areas have known gold-rich mineral occurrences. In the eastern Black Mountain area, this included the Gray Lead, Blue Lead, and Michigan prospects, among others (U.S. Geological Survey, 1996). Sampling in the Pogo area was restricted to streams outside Leise Creek area due to anthropogenic disturbance as part of mining. Stream water samples were collected in 2021 and analyzed for cation and anion concentrations using high-resolution ICP-MS for cations and ion chromatography (IC) for anions.

The State of Alaska's Strategic and Critical Minerals (SCM) Assessment project, a State-funded Capital Improvement Project (CIP), is designed to evaluate Alaska's statewide potential for SCM resources. The SCM Assessment is being implemented by the Alaska Division of Geological & Geophysical Surveys (DGGS), and involves obtaining new airborne-geophysical, geological, and geochemical data. For the geochemical part of the SCM Assessment, thousands of historical geochemical samples from DGGS, U.S. Geological Survey (USGS), and U.S. Bureau of Mines archives are being reanalyzed by DGGS using modern, quantitative, geochemical-analytical methods. The objective is to update the statewide geochemical database to more clearly identify areas in Alaska with SCM potential. For this report, DGGS funded reanalysis of 1,682 historical USGS sediment samples from the statewide Alaska Geochemical Database Version 2.0 (AGDB2; Granitto and others, 2013). Samples were chosen from an area covering northeastern Alaska Range, Healy, Mount Hayes, Nabesna, and Tanacross quadrangles, Alaska. USGS was responsible for sample retrieval from the Denver warehouse through the final quality assurance/quality control (QA/QC) of the geochemical analyses obtained through the USGS contract lab. The new geochemical data are published in this report as a coauthored DGGS report, and will be incorporated into the statewide geochemical databases of both agencies.

The State of Alaska's Strategic and Critical Minerals (SCM) Assessment project, a State-funded Capital Improvement Project (CIP), is designed to evaluate Alaska's statewide potential for SCM resources. The SCM Assessment is being implemented by the Alaska Division of Geological & Geophysical Surveys (DGGS), and involves obtaining new airborne-geophysical, geological, and geochemical data. For the geochemical part of the SCM Assessment, thousands of historical geochemical samples from DGGS, U.S. Geological Survey (USGS), and U.S. Bureau of Mines archives are being reanalyzed by DGGS using modern, quantitative, geochemical-analytical methods. The objective is to update the statewide geochemical database to more clearly identify areas in Alaska with SCM potential. For this report, DGGS funded reanalysis of 1,682 historical USGS sediment samples from the statewide Alaska Geochemical Database Version 2.0 (AGDB2; Granitto and others, 2013). Samples were chosen from an area covering the western half of the Wrangellia Terrane in the Anchorage, Gulkana, Healy, Mt. Hayes, Nabesna, and Talkeetna Mountains quadrangles of south-central Alaska. USGS was responsible for sample retrieval from the Denver warehouse through the final quality assurance/quality control (QA/QC) of the geochemical analyses obtained through the USGS contract lab. The new geochemical data are published in this report as a coauthored DGGS report, and will be incorporated into the statewide geochemical databases of both agencies.