In December of 2018, the U.S. Geological Survey (USGS) signed a Technical Assistance Agreement with a third party to reanalyze 2,324 archived sample splits collected as part of the National Uranium Resource Evaluation (NURE) Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) project from selected areas in Idaho and Montana. A small amount (approximately 0.25 grams [g]) of sieved <75-micron sample material was retrieved from the USGS National Geochemical Sample Archive for geochemical analysis. These samples were analyzed for 48 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, Zr). These data are comparable to those reported by Smith and others (2018, 2019). A subset of these samples, as identified by the collaborating party, was additionally analyzed by ALS Global laboratories for stable lead isotopes (204Pb, 206Pb, 207Pb, and 208Pb, using the MS61L-PbIS method). Blind standard reference materials (SRM) 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

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

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

Selected archived sample splits collected as part of the National Uranium Resource Evaluation (NURE) Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) program, were reanalyzed by the U.S. Geological Survey (USGS) as part of a NURE-HSSR Reanalysis project (Smith and others, 2018). A small amount (approximately 0.25 grams [g]) of sieved less than 75-micron sample material was retrieved from the USGS National Geochemical Sample Archive for geochemical analysis. These samples were analyzed for 51 elements under a Technical Assistance Agreement with a third party by ALS Global laboratories using their ultra-trace four-acid-digestion dual-mode inductively coupled plasma-optical emission spectrometry/mass spectrometry (ICP-OES/MS) (ALS ME-MS61L) method (Ag, Al, As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, 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, Hf_p, Zr_p, Au_sq, Pt_sq, Pd_sq). Blind standard reference materials (SRM), 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 United States. As one of nine components of the NURE program, the HSSR project systematically sampled the United States 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 also 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 only, and a few samples were never analyzed at all. Funding cuts after 1980 curtailed the NURE-HSSR sampling

Selected archived sample splits collected as part of the National Uranium Resource Evaluation (NURE) Hydrogeochemical and Stream Sediment Reconnaissance (HSSR) program, were reanalyzed by the U.S. Geological Survey (USGS) as part of a NURE-HSSR Reanalysis project (Smith and others, 2018). A small amount (approximately 0.25 grams [g]) of sieved less than 75-micron sample material was retrieved from the USGS National Geochemical Sample Archive for geochemical analysis. These samples were analyzed for 51 elements under a Technical Assistance Agreement with a third party by ALS Global laboratories using their ultra-trace four-acid-digestion dual-mode inductively coupled plasma-optical emission spectrometry/mass spectrometry (ICP-OES/MS) (ALS ME-MS61L) method (Ag, Al, As, Ba, Be, Bi, Ca, Cd, Ce, Co, Cr, Cs, Cu, Fe, Ga, Ge, 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, Hf_p, Zr_p, Au_sq, Pt_sq, Pd_sq). Blind standard reference materials (SRM), 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 United States. As one of nine components of the NURE program, the HSSR project systematically sampled the United States 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 also 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 only, and a few samples were never analyzed at all. Funding cuts after 1980 curtailed the NURE-HSSR sampling

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 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 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.

Geochemical data for aqueous, mine tailings, and sediment samples collected from the Big River and Meramec River drainage basins in southeastern Missouri are presented. The Big River drains historical lead, zinc, and barite mining districts, including the Old Lead Belt (OLB). Underground mining in the OLB resulted in large mine-waste chat piles and tailings impoundments that have released material laden with lead, zinc, and other trace elements to the Big River drainage basin. The Meramec River has also been affected by mining-related material transported by the Big River. Since the late 1980s, the U.S. Geological Survey (USGS) has been involved in investigations into the effects of mining on the Big River. The data presented here were generated as part of collaborations between the USGS Central Midwest Water Science Center, the USGS Mineral Resources Program, the U.S. Environmental Protection Agency, and the Missouri Department of Natural Resources. Flood deposit sediments were collected immediately after major flooding of the Big and Meramec Rivers in December 2016 and April 2017. Bed sediments and suspended sediments were collected by various methods during several field efforts from 2018 through 2022. Mine tailings were collected by coring on the former Federal mine tailings impoundment within St. Joe State Park in 2018. Concentrations of major and trace elements were determined for multiple particle size fractions of solid-phase samples, and multi-element analyses of deionized water leaches and sequential extractions were performed on select samples. Aqueous samples were collected from the Big River, tributaries, and mine and mine-waste seeps at near baseflow conditions during three different field efforts in 2018, 2019, and 2021. Aqueous samples were analyzed for anions and major and trace elements. Concentrations of major and trace elements in streambed and suspended sediments collected from the Big River drainage basin in 1988 and 1999 are also reported; these data were previously published in a USGS report but are provided here for convenient comparison.