This data release contains the whole-rock major and trace element analyses of 51 samples of intrusive igneous rocks from the Wet Mountains area of Custer and Fremont counties of south-central Colorado, collected by U.S. Geological Survey (USGS) geologists. The samples were collected from breccias, veins and thin dikes, and a variety of carbonatite, felsic, mafic, and ultramafic intrusions across the area. The first 41 samples listed in this data release were collected in July 2007, originally as part of a reconnaissance study of the thorium deposits of the area (Van Gosen and others, 2009). The samples are grab samples from outcrops, shallow open-pit excavations, and mineral prospect trenches. The last 10 samples listed in this data release were originally collected and geochemically analyzed in 1976 as part of a USGS study of carbonatites in this area (Armbrustmacher, 1976, 1979; Armbrustmacher and Brownfield, 1978). These 10 carbonatite samples were reanalyzed by modern analytical methods in 2007, and the new data are included in this data release. The Wet Mountains area hosts a variety of alkaline intrusions (Armbrustmacher, 1984), which includes three Cambrian-age alkaline complexes (Olson and others, 1977) that intruded the surrounding Precambrian terrane. These are (1) the McClure Mountain Complex (Shawe and Parker, 1967; Armbrustmacher, 1984), (2) the Gem Park Complex (Parker and Sharp, 1970), and (3) the complex at Democrat Creek (Armbrustmacher, 1984). In the Wet Mountains area, elevated concentrations of thorium and rare earth elements (REEs) occur in veins, syenite dikes, fracture zones, breccias, and carbonatite dikes (Armbrustmacher, 1988). These thorium-REE deposits are distal to the alkaline complexes but are thought to be genetically associated. Characteristics of the thorium and REE deposits in the area, as well as typical concentrations and resource estimates, are detailed in the publications listed in the supplementary file “Wet Mountains area publications.pdf”. Armbrustmacher (1988) determined that vein and fracture zone deposits contain most of the thorium and REE resources in the area. These are linear features, typically 1–2 meters thick, but a few are as much as 15 meters thick. Some individual thorium veins can be traced in outcrop for 1,500 m and some radioactive fracture zones for as much as 13 kilometers. Most of these vein- and fracture-zone deposits occur within a 57 square kilometers tract of Precambrian gneiss and migmatite (Scott and others, 1976) located south and southeast of the quartz syenite complex at Democrat Creek; in this area Christman and others (1953, 1959) mapped nearly 400 veins. Most of the samples in this data release are examples of unaltered alkaline igneous rocks of the intrusive complexes rather than the mineral deposits. These samples were selected in the field to study possible relationships between the magmatic complexes and the thorium-REE deposits. All samples included in this data release were analyzed by laboratories contracted by the USGS. Major and trace element concentrations were determined by inductively coupled plasma-atomic emission spectrometry (ICP-AES) and inductively coupled plasma-mass spectrometry (ICP-MS). An acceptable criteria for the data has been identified based on (1) if recovery of each element is within a designated percentage at five times the lower limit of determination, and (2) the calculated relative standard deviation of duplicate samples is no greater than that percentage. The reported laboratory percentages for the acceptance criteria are +/- 15 percent for ICP-AES and ICP-MS. Ten carbonatite samples were additionally analyzed by wavelength dispersive X-ray fluorescence (WDXRF) to determine the concentrations of major elements as oxides. The reported laboratory percentages for the acceptance criteria are +/- 5 percent for WDXRF. Data are reported in a comma-separated values (CSV) file that lists the samples that were analyzed,

This data release includes new major and trace element geochemical data acquired by the U.S. Geological Survey (USGS) for igneous rocks in the Cripple Creek district in Colorado. Cripple Creek is among the largest epithermal districts in the world, with more than 800 metric tons (t) Au (>26.4 Moz). The ores are associated spatially, temporally, and genetically with ~34 to 28 Ma alkaline igneous rocks that were emplaced into an 18 km2- diatreme complex and surrounding Proterozoic rocks (Kelley and others, 2020). Igneous rocks associated with Cripple Creek are part of a regionally extensive episode of Oligocene alkaline magmatism that extended southward along the axis of the Rio Grande rift through New Mexico and into the Trans Pecos region of Texas and northern Mexico (McLemore, 1996; Kelley and Ludington, 2002). The deposits at Cripple Creek are known as alkalic-type gold deposits, but they have been referred to as alkalic-related and Great Plains margin deposits in previous literature (McLemore, 1996). Many of the deposits in this class are enriched in critical elements, the most common of which is tellurium (Kelley and Spry, 2016). However, not all deposits are characterized by enriched tellurium concentrations. Cripple Creek is highly enriched, whereas other deposits in New Mexico are less enriched. The objective of the USGS study was to characterize the tellurium contents (and other trace elements) of predominantly unaltered alkaline igneous rocks that are genetically associated with mineralization in order to better understand possible source(s) and mechanism of enrichment of tellurium in these systems. This data release provides the analytical results of 25 rock hand samples collected by USGS geologists in collaboration with the New Mexico Bureau of Geology and Mineral Resources (NMBGMR) during site visits to Cripple Creek in 1989, 2015, and 2016. In addition, 50 samples collected in 2013 by Anne Rahfeld (Rahfeld, 2013) were submitted and analyzed by the USGS. The mapped rock units from which the samples were collected are described in Wobus and others (1976) and brief descriptions of rock types are given in Kelley and others (1998). Several analytical methods were used and include 55 major and trace elements using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and 42 elements using inductively coupled plasma-atomic emission spectrometry (ICP-AES). Some samples were also analyzed for major elements using wavelength dispersive x-ray fluorescence spectrometry (WDXRF), for Au by fire assay ICP-MS and Au and PGE by fire assay.

This data release includes new major and trace element geochemical data acquired by the U.S. Geological Survey (USGS) for igneous rocks in the Cripple Creek district in Colorado. Cripple Creek is among the largest epithermal districts in the world, with more than 800 metric tons (t) Au (>26.4 Moz). The ores are associated spatially, temporally, and genetically with ~34 to 28 Ma alkaline igneous rocks that were emplaced into an 18 km2- diatreme complex and surrounding Proterozoic rocks (Kelley and others, 2020). Igneous rocks associated with Cripple Creek are part of a regionally extensive episode of Oligocene alkaline magmatism that extended southward along the axis of the Rio Grande rift through New Mexico and into the Trans Pecos region of Texas and northern Mexico (McLemore, 1996; Kelley and Ludington, 2002). The deposits at Cripple Creek are known as alkalic-type gold deposits, but they have been referred to as alkalic-related and Great Plains margin deposits in previous literature (McLemore, 1996). Many of the deposits in this class are enriched in critical elements, the most common of which is tellurium (Kelley and Spry, 2016). However, not all deposits are characterized by enriched tellurium concentrations. Cripple Creek is highly enriched, whereas other deposits in New Mexico are less enriched. The objective of the USGS study was to characterize the tellurium contents (and other trace elements) of predominantly unaltered alkaline igneous rocks that are genetically associated with mineralization in order to better understand possible source(s) and mechanism of enrichment of tellurium in these systems. This data release provides the analytical results of 25 rock hand samples collected by USGS geologists in collaboration with the New Mexico Bureau of Geology and Mineral Resources (NMBGMR) during site visits to Cripple Creek in 1989, 2015, and 2016. In addition, 50 samples collected in 2013 by Anne Rahfeld (Rahfeld, 2013) were submitted and analyzed by the USGS. The mapped rock units from which the samples were collected are described in Wobus and others (1976) and brief descriptions of rock types are given in Kelley and others (1998). Several analytical methods were used and include 55 major and trace elements using inductively coupled plasma-atomic emission spectrometry (ICP-AES) and 42 elements using inductively coupled plasma-atomic emission spectrometry (ICP-AES). Some samples were also analyzed for major elements using wavelength dispersive x-ray fluorescence spectrometry (WDXRF), for Au by fire assay ICP-MS and Au and PGE by fire assay.

In 2021 the United States Geological Survey (USGS) sampled the lower part of the Upper Cretaceous Lewis Shale in the eastern part of the Southwestern Wyoming Province to better characterize its petroleum source rock potential for an upcoming resource assessment. Ninety-five samples from 24 wells were collected from well cuttings of the lower part of the Lewis Shale stored at the U.S. Geological Survey Core Research Center in Lakewood, Colorado. The selected wells are located near the shallow margins of the basin to obtain samples that were not subjected to the effects of deep burial and subsequent organic carbon loss due to thermal maturation as described by Daly and Edman (1987) (fig, 1). The sample intervals were selected based on high gamma ray responses that Pyles and Slatt (2007) interpreted to be organic-rich condensed sections. Special emphasis was given to the Asquith marker bed which represents the maximum transgression of the Lewis Shale (Pasternack, 2005) (fig. 2).

In 2021 the United States Geological Survey (USGS) sampled the lower part of the Upper Cretaceous Lewis Shale in the eastern part of the Southwestern Wyoming Province to better characterize its petroleum source rock potential for an upcoming resource assessment. Ninety-five samples from 24 wells were collected from well cuttings of the lower part of the Lewis Shale stored at the U.S. Geological Survey Core Research Center in Lakewood, Colorado. The selected wells are located near the shallow margins of the basin to obtain samples that were not subjected to the effects of deep burial and subsequent organic carbon loss due to thermal maturation as described by Daly and Edman (1987) (fig, 1). The sample intervals were selected based on high gamma ray responses that Pyles and Slatt (2007) interpreted to be organic-rich condensed sections. Special emphasis was given to the Asquith marker bed which represents the maximum transgression of the Lewis Shale (Pasternack, 2005) (fig. 2).

This dataset includes thin section images, automated mineralogy mineral maps, whole-rock geochemical data, and whole-rock Nd-Sr-Pb isotopic analysis of samples collected from nine mafic-ultramafic outcrops in the Wet Mountains, southern Colorado, during the summer of 2022. These data will accompany an upcoming journal publication and are intended to supplement recently collected airborne magnetic and ground gravity data that indicate a mostly buried mafic-ultramafic intrusion of unknown age (Grauch et al., 2023; Magnin and Anderson, 2023; Magnin et al., 2023). Outcrop locations were identified based on previous mapping by Taylor (1974). A single thin section was made from each sample, and both plain- and cross-polarized light (PPL and XPL, respectively) images were taken of the entire section using a flatbed film scanner. Automated mineralogy (AM) scans were collected from half of each thin section using a TESCAN Integrated Mineral Analyzer (TIMA) at the Colorado School of Mines Mineral and Materials characterization facility. Whole-rock major and trace element geochemistry of samples used for thin sections and of separate compositional layers in thin section JWM-129 (i.e., JWM-129.1, -129.2) were analyzed by Activation Laboratories Ltd., Ancaster, Ontario. Platinum group element chemistry was collected and analyzed by AGAT Laboratories, Calgary, Alberta. Five whole-rock samples and two mineral separates were analyzed using Sm-Nd thermal ionization mass spectrometry (TIMS) at the University of Colorado Boulder TIMS Facility and Clean Room. The same five whole-rock samples were also analyzed for Rb-Sr and Pb-Pb isotopes using TIMS at the same lab. All analyses were performed between October 2022 and February 2024. The images contained in the zip file are categorized by sample name and additionally labeled with PPL, XPL, and AM categories. Automated mineralogy image names end with a letter indicating whether the top (T), bottom (B), left (L), or right (R) half of the thin section was scanned. A csv file of the modal mineral percentages from automated mineralogy is also included in the zip file. Sample locations/descriptions, whole rock geochemistry, Nd-Sr-Pb isotopes, and a data dictionary are included in csv files.

This dataset includes thin section images, automated mineralogy mineral maps, whole-rock geochemical data, and whole-rock Nd-Sr-Pb isotopic analysis of samples collected from nine mafic-ultramafic outcrops in the Wet Mountains, southern Colorado, during the summer of 2022. These data will accompany an upcoming journal publication and are intended to supplement recently collected airborne magnetic and ground gravity data that indicate a mostly buried mafic-ultramafic intrusion of unknown age (Grauch et al., 2023; Magnin and Anderson, 2023; Magnin et al., 2023). Outcrop locations were identified based on previous mapping by Taylor (1974). A single thin section was made from each sample, and both plain- and cross-polarized light (PPL and XPL, respectively) images were taken of the entire section using a flatbed film scanner. Automated mineralogy (AM) scans were collected from half of each thin section using a TESCAN Integrated Mineral Analyzer (TIMA) at the Colorado School of Mines Mineral and Materials characterization facility. Whole-rock major and trace element geochemistry of samples used for thin sections and of separate compositional layers in thin section JWM-129 (i.e., JWM-129.1, -129.2) were analyzed by Activation Laboratories Ltd., Ancaster, Ontario. Platinum group element chemistry was collected and analyzed by AGAT Laboratories, Calgary, Alberta. Five whole-rock samples and two mineral separates were analyzed using Sm-Nd thermal ionization mass spectrometry (TIMS) at the University of Colorado Boulder TIMS Facility and Clean Room. The same five whole-rock samples were also analyzed for Rb-Sr and Pb-Pb isotopes using TIMS at the same lab. All analyses were performed between October 2022 and February 2024. The images contained in the zip file are categorized by sample name and additionally labeled with PPL, XPL, and AM categories. Automated mineralogy image names end with a letter indicating whether the top (T), bottom (B), left (L), or right (R) half of the thin section was scanned. A csv file of the modal mineral percentages from automated mineralogy is also included in the zip file. Sample locations/descriptions, whole rock geochemistry, Nd-Sr-Pb isotopes, and a data dictionary are included in csv files.

During the 2018 field season, geologists from the Alaska Division of Geological & Geophysical Surveys (DGGS) conducted geologic mapping and sampling of part of the Richardson mining district southeast of Fairbanks, including parts of the Big Delta B-5 and B-6 quadrangles. The project area has produced approximately 122,000 ounces of gold (Singh and others, 2017), mostly from placer mines, and it includes the Richardson, Tower, and Hilltop lode gold exploration properties. Rock outcrop accounts for much less than one percent of the study area, consequently, many of the rock samples were collected from up to 1-meter-deep pits dug with shovels into rocky colluvial deposits below the surficial loess. Highlights of the geochemical results include 43.3 and 9.77 parts per million (ppm) gold sampled from arsenopyrite-bearing quartz veins at the Hilltop prospect. At the Democrat prospect, formerly the site of small-scale mining, a sample of sulfide-rich material returned 3,790 ppm silver and 4.72 ppm gold. Other samples from the Democrat prospect assayed 6.81 and 5.01 ppm gold. The analytical data tables associated with this report are available in digital format as comma-separated value (CSV) files. All files can be downloaded from the DGGS website (http://doi.org/10.14509/30119).

This data release is part of a 2016-2019 study on the geology, geochemistry and geochronology of ore systems in the eastern Yukon-Tanana Upland region, Alaska. Whole rock chemistry was conducted on 185 samples, mostly from Au prospects, with lesser samples from porphyry Cu prospects. Geographically, most samples are from gold prospects near the Pogo Au mine and east to Black Mountain in the Big Delta quadrangle. Fewer samples are from prospects in the Eagle and Tanacross Quadrangles. Samples were submitted to the USGS contract laboratory and analyzed for select trace elements and gold. Sixty elements were determined by inductively coupled plasma-optical emission spectroscopy-mass spectroscopy (ICP-OES-MS), sodium peroxide fusion (ICP-60). Gold was determined by lead fusion fire assay.

This data release is part of a 2016-2019 study on the geology, geochemistry and geochronology of ore systems in the eastern Yukon-Tanana Upland region, Alaska. Whole rock chemistry was conducted on 185 samples, mostly from Au prospects, with lesser samples from porphyry Cu prospects. Geographically, most samples are from gold prospects near the Pogo Au mine and east to Black Mountain in the Big Delta quadrangle. Fewer samples are from prospects in the Eagle and Tanacross Quadrangles. Samples were submitted to the USGS contract laboratory and analyzed for select trace elements and gold. Sixty elements were determined by inductively coupled plasma-optical emission spectroscopy-mass spectroscopy (ICP-OES-MS), sodium peroxide fusion (ICP-60). Gold was determined by lead fusion fire assay.