This data release is part of a study examining the use of near-stream groundwater discharge as a tool for Geochemical Exploration. Handcart Gulch is an unmined alpine watershed in Montezuma Mining District in the Colorado Front Range. The streambed is cemented by deep ferricrete deposits. Stream water, groundwater, and ferricrete samples were collected and analyzed to constrain the location of a possible concealed mineral occurrence identified by previous stream water sampling. Nineteen, near stream mini-boreholes were drilled through ferricrete using a portable, handheld, gasoline powered, rock coring drill manufactured by Shaw Tool. Boreholes were drilled within 2 meters of the stream on the east and west banks to constrain local-scale groundwater variations on either side of the stream. Ferricrete samples were logged and collected during drilling. A subset of ferricrete samples were analyzed for bulk chemistry and a deionized water leach quantified the water-soluble fraction from the ferricrete samples. Groundwater levels and field parameters (temperature, pH, specific conductance, and dissolved oxygen) were measured and groundwater samples were collected using a peristaltic pump for major and trace element chemistry. Environmental tracer samples (stable water isotopes, dissolved noble gases, helium isotopes, and tritium) were collected using a submersible double-valve pump manufactured by Solinst Canada Ltd. Stream water samples were collected adjacent to mini-boreholes over a period of two days with no major precipitation events.

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 U.S. Geological Survey (USGS) data release contains data from stream water, groundwater, and stream sediment samples collected in August 2023 in the East Mancos River watershed in southwestern Colorado. Data were collected as part of a study aimed at identifying sources of elevated metal concentrations in the stream. Eighteen streambank wells were installed in pairs at nine locations to capture the emerging groundwater from the left and right banks (relative to downstream-facing direction) and a synoptic sampling campaign was conducted to quantify stream metal loads. A continuous, instream injection of sodium bromide (NaBr) was initiated at the head of the ~17 km study reach prior to the synoptic sampling campaign and maintained throughout the duration of the study. Bromide concentrations were subsequently used to determine streamflow in the upper ~2.7 km of the stream using the tracer-dilution method. Streamflow was quantified for tributaries and locations farther downstream using data from a series of sodium chloride slug additions wherein specific conductivity readings were used as a surrogate for the tracer concentration. Stream and groundwater samples, including the wells and inflows from the left (LBI) and right (RBI) banks, were collected mainly in the upper ~0.9 km of the stream course (primary study reach). Environmental tracer data were collected to better understand groundwater flowpaths to the stream. Stream sediment samples, including some ferricrete samples, were also collected to help identify potential instream and near-stream metal sources.

This U.S. Geological Survey (USGS) data release contains stream water chemistry and streamflow data collected in late August and early September, 2021 from 28 sites located throughout Colorado, USA. The sampled streams all drain high-elevation mountain watersheds in areas where the bedrock is hydrothermally altered and contains abundant sulfide minerals. Most sampled streams are therefore affected by natural acid-rock drainage. All sites had been sampled in prior years so that the 2021 data could be used to evaluate potential changes in stream water chemistry in recent decades. Streamflow was also quantified at most sites using data from a sodium chloride slug addition wherein specific conductivity readings were used as a surrogate for the tracer concentration.

This U.S. Geological Survey (USGS) data release contains stream water chemistry and streamflow data collected in late August and early September, 2021 from 28 sites located throughout Colorado, USA. The sampled streams all drain high-elevation mountain watersheds in areas where the bedrock is hydrothermally altered and contains abundant sulfide minerals. Most sampled streams are therefore affected by natural acid-rock drainage. All sites had been sampled in prior years so that the 2021 data could be used to evaluate potential changes in stream water chemistry in recent decades. Streamflow was also quantified at most sites using data from a sodium chloride slug addition wherein specific conductivity readings were used as a surrogate for the tracer concentration.

This U.S. Geological Survey (USGS) data release contains data from stream water, groundwater/springs, and sediment samples collected from legacy mine land (LML) sites in central Colorado. The sites were selected using a GIS-based approach that integrated regional geological and geochemical datasets with known mine features and satellite data identifying hydrothermal alteration (ASTER) to identify LML-impacted watersheds with low natural background or metal concentrations slightly above aquatic life standards. The central Colorado watersheds selected for preliminary investigation included 1) McNasser Gulch, 2) upper South Fork Lake Creek, 3) Saints John Creek, and 4) Hall Valley (north fork of South Platte River). Reconnaissance sampling of surface water, groundwater, and sediment (August 2019) to identify sources of trace element contamination in each watershed. Follow-up sampling in the Hall Valley watershed (August 2020) provided flow and concentration data for the four largest surface inflows to a headwater pond and additional locations below the pond outlet. Metal loads at these locations were calculated as the product of flow and concentration.

The dataset comprises analyses of core and surface samples collected in and around the Red Mountain porphyry Cu-Mo deposit, Santa Cruz County, Arizona. The dataset includes: analyses for 13 minerals in 245 core samples (Appendix 1); analyses for 44 elements in 818 core samples (Appendix 2); analyses for 54 elements in 122 rock samples (Appendix 3); analyses for 55 elements in 119 soil samples (Appendix 4); and analyses for percent ash and 66 elements in 57 mesquite ash (Appendix 5), 68 oak ash (Appendix 6), and 68 juniper ash (Appendix 7) samples, respectively. The samples were collected and analyzed between 1980 and 2000.

The dataset comprises analyses of core and surface samples collected in and around the Red Mountain porphyry Cu-Mo deposit, Santa Cruz County, Arizona. The dataset includes: analyses for 13 minerals in 245 core samples (Appendix 1); analyses for 44 elements in 818 core samples (Appendix 2); analyses for 54 elements in 122 rock samples (Appendix 3); analyses for 55 elements in 119 soil samples (Appendix 4); and analyses for percent ash and 66 elements in 57 mesquite ash (Appendix 5), 68 oak ash (Appendix 6), and 68 juniper ash (Appendix 7) samples, respectively. The samples were collected and analyzed between 1980 and 2000.

The geochemical data included here were generated as part of a Technical Assistance Agreement between the U.S. Geological Survey (USGS) and Rio Tinto Exploration based in Salt Lake City, Utah. Beginning in November of 2015, we began a project to reanalyze up to 60,000 archived sample splits originally collected as part of the National Uranium Resource Evaluation (NURE) Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) project from selected areas in Arizona, California, Idaho, Montana, Nevada, New Mexico, and Utah. A small amount (approximately 0.25 g) of sieved <75 micron sample material was retrieved from the USGS National Geochemical Sample Archive for geochemical analysis. These samples were analyzed for 51 elements by ALS Global laboratories using their ultra-trace four-acid-digestion dual-mode inductively coupled plasma mass spectrometry (ICPMS) (ALS ME-MS61L) method (Ag, Al, As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, Hf, In, K, La, Li, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Rb, Re, S, Sb, Sc, Se, Sn, Sr, Ta, Te, Th, Ti, Tl, U, V, W, Y, Zn, and Zr plus Au, Pt, and Pd). Blind geologic reference materials (GRM), blanks, and sample duplicates were inserted by the USGS into every job of 36 samples to ensure the quality of the data. The results from these quality control (QC) samples, along with QC samples inserted by the laboratory, were evaluated for every job by a QC Manager. Only data that passed these checks were approved for release. Samples with analytical results that failed to pass the QC checks were reanalyzed and re-evaluated before the data were approved for release. The archived sample splits came from the NURE program, which began in 1973 with a primary goal of identifying uranium resources in the U.S. As one of nine components of the NURE program, the HSSR project systematically sampled the U.S. between 1976 and 1980 under the direction of four U.S. Department of Energy (DOE) national laboratories. Although there was some collaboration, each DOE laboratory developed its own sample collection, analytical, and data management methodologies, and hired contractors to do much of the actual work. Initially, Lawrence Livermore Laboratory (LLL) was responsible for the western states of Arizona, California, Idaho, Nevada, Oregon, Utah, and Washington; Los Alamos Scientific Laboratory (LASL) was responsible for the Rocky Mountain States (Colorado, Montana, New Mexico, and Wyoming) as well as Alaska; the Oak Ridge Gaseous Diffusion Plant (ORGDP) was responsible for 12 central Plains and upper Great Lakes States; and Savannah River Laboratory (SRL) was responsible for the remaining 23 states along the Eastern Seaboard, lower Great Lakes, Appalachians, and Gulf Coast. However, by 1979 the areas of responsibility had changed from state lines to 2-degree quadrangle boundaries and SRL had taken over the responsibility for completing the seven western states formerly assigned to LLL. Thus, quadrangles in the western third of the U.S. were variously sampled and analyzed by LLL, LASL, and SRL. Due to the enormous number of samples collected by these laboratories, some were sent to ORGDP for additional chemical analyses (Information Systems Programs, 1985; Smith, 1997). Geochemical samples were collected from multiple sources (78 percent stream-, 8 percent lake-, and 2 percent spring-sediments, and 12 percent soils). Analytical methods differed between laboratories and evolved over time so that 29 single- and multi-element analytical procedures, or variations thereof, were used during the project. The NURE-HSSR sediment and soil database compiled by Smith (1997) provides analytical results for 54 different elements (Ag, Al, As, Au, B, Ba, Be, Bi, Br, Ca, Cd, Ce, Cl, Co, Cr, Cs, Cu, Dy, Eu, F, Fe, Hf, Hg, K, La, Li, Lu, Mg, Mn, Mo, Na, Nb, Ni, P, Pb, Pt, Rb, Sb, Sc, Se, Sm, Sn, Sr, Ta, Tb, Th, Ti, U, V, W, Y, Yb, Zn, and Zr). However, no sample was analyzed for more than 46 elements, some were analyzed for uranium