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 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.

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 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 contains analytical data and images for a suite of drill core samples from the Mineral Hill alkaline complex (MHAC), northeastern Wyoming. Geochemistry data include major and trace element analytical results for 103 alkaline igneous rock samples. Images include hand sample photographs of halved core and full thin section images captured in transmitted, plane-polarized and cross-polarized light. Samples are from two core holes drilled by Humble Oil Company in 1970, and subsequently acquired and stored by Felix Mutschler at Eastern Washington University. The two skeletonized (incomplete) drill cores were acquired by the U.S. Geological Survey Geology, Minerals, Energy, and Geophysics Spokane office in 2019, through a co-operative agreement with Eastern Washington University. The collection contains full-core pieces from select intervals representative of the different lithologies and textures in the complex. Mineral Hill is a Paleogene-age, ring-shaped, multi-phase alkaline (miaskitic) igneous complex that intrudes Precambrian schists and lower Paleozoic units of the Tinton uplift on the northwest flank of the broader Black Hills uplift (Welch, 1974; Ray, 1979). The outer ring of the complex is composed of foid syenite and compositionally similar rocks, whereas clinopyroxenite (jacupirangite) and other foid-bearing mafic rocks (ijolite and melteigite) form an irregular inner ring. The center of the complex is composed of a central feldspathic diatreme breccia pipe that exhibits pervasive potassic and sulfidic alteration (DeWitt and others, 1986). Alkali feldspar trachyte/latite porphyry is exposed as large masses in a steep-walled, columnar-jointed zone peripheral to foid syenite of the Mineral Hill dome and as high-angle sills within the central area (Ray, 1979). Alkalic lamprophyres throughout the complex are thought to be related to clinopyroxenite and may have formed from a volatile-rich fraction of the pyroxenite magma (Ray 1979). Pseudoleucite porphyry and melteigite/feldspathic ijolite may be variations of foid syenite and foid clinopyroxenite, respectively. Historic mineral production in the area occurred between the 1870s and 1930s: principally alluvial gold, gold and silver at the Treadwell Mine, and gold and copper at the Interocean Mine. Exploration since 2000 has shown that gold and silver at the Treadwell Mine is related to epithermal-style mineralization and adularia-bearing potassic alteration (Eurasian Minerals Inc., 2016). Higher temperature, porphyry-style potassic alteration associated with gold and copper was identified near the Interocean Mine. Investigations of critical mineral potential in the area have focused on Precambrian pegmatites in the Tinton district which produced some cassiterite (Sn) and tantalite-columbite (Ta) ore, and the Spotted Tail and Sand Creek gold placers which produced some cassiterite (Sn) (Smith and Page, 1941; Hausel, 1990). The critical mineral potential of Paleogene intrusive rocks of the Mineral Hill complex has received comparatively little attention. All samples were analyzed by the U.S. Geological Survey contract laboratory, AGAT Laboratories. Major and trace element concentrations were determined by wavelength dispersive X-ray fluorescence, inductively coupled plasma-optical emission spectrometry or inductively coupled plasma-mass spectrometry (ICP-MS). Additional analytical methods included determination of carbonate carbon by combustion and infrared detection (IR); gold, platinum and palladium by lead fusion fire assay and ICP-MS; fluoride by ion-selective electrode; ferrous iron by titration; non-essential and essential water by gravimetric methods; total sulfur by IR; and gold and platinum group elements by nickel sulfide fire-assay followed by instrumental neutron activation analysis. For each method outlined above, an acceptable criteria for the data has been identified based on 1) if recovery of each element is within a designated percentage at

This data release contains analytical data and images for a suite of drill core samples from the Mineral Hill alkaline complex (MHAC), northeastern Wyoming. Geochemistry data include major and trace element analytical results for 103 alkaline igneous rock samples. Images include hand sample photographs of halved core and full thin section images captured in transmitted, plane-polarized and cross-polarized light. Samples are from two core holes drilled by Humble Oil Company in 1970, and subsequently acquired and stored by Felix Mutschler at Eastern Washington University. The two skeletonized (incomplete) drill cores were acquired by the U.S. Geological Survey Geology, Minerals, Energy, and Geophysics Spokane office in 2019, through a co-operative agreement with Eastern Washington University. The collection contains full-core pieces from select intervals representative of the different lithologies and textures in the complex. Mineral Hill is a Paleogene-age, ring-shaped, multi-phase alkaline (miaskitic) igneous complex that intrudes Precambrian schists and lower Paleozoic units of the Tinton uplift on the northwest flank of the broader Black Hills uplift (Welch, 1974; Ray, 1979). The outer ring of the complex is composed of foid syenite and compositionally similar rocks, whereas clinopyroxenite (jacupirangite) and other foid-bearing mafic rocks (ijolite and melteigite) form an irregular inner ring. The center of the complex is composed of a central feldspathic diatreme breccia pipe that exhibits pervasive potassic and sulfidic alteration (DeWitt and others, 1986). Alkali feldspar trachyte/latite porphyry is exposed as large masses in a steep-walled, columnar-jointed zone peripheral to foid syenite of the Mineral Hill dome and as high-angle sills within the central area (Ray, 1979). Alkalic lamprophyres throughout the complex are thought to be related to clinopyroxenite and may have formed from a volatile-rich fraction of the pyroxenite magma (Ray 1979). Pseudoleucite porphyry and melteigite/feldspathic ijolite may be variations of foid syenite and foid clinopyroxenite, respectively. Historic mineral production in the area occurred between the 1870s and 1930s: principally alluvial gold, gold and silver at the Treadwell Mine, and gold and copper at the Interocean Mine. Exploration since 2000 has shown that gold and silver at the Treadwell Mine is related to epithermal-style mineralization and adularia-bearing potassic alteration (Eurasian Minerals Inc., 2016). Higher temperature, porphyry-style potassic alteration associated with gold and copper was identified near the Interocean Mine. Investigations of critical mineral potential in the area have focused on Precambrian pegmatites in the Tinton district which produced some cassiterite (Sn) and tantalite-columbite (Ta) ore, and the Spotted Tail and Sand Creek gold placers which produced some cassiterite (Sn) (Smith and Page, 1941; Hausel, 1990). The critical mineral potential of Paleogene intrusive rocks of the Mineral Hill complex has received comparatively little attention. All samples were analyzed by the U.S. Geological Survey contract laboratory, AGAT Laboratories. Major and trace element concentrations were determined by wavelength dispersive X-ray fluorescence, inductively coupled plasma-optical emission spectrometry or inductively coupled plasma-mass spectrometry (ICP-MS). Additional analytical methods included determination of carbonate carbon by combustion and infrared detection (IR); gold, platinum and palladium by lead fusion fire assay and ICP-MS; fluoride by ion-selective electrode; ferrous iron by titration; non-essential and essential water by gravimetric methods; total sulfur by IR; and gold and platinum group elements by nickel sulfide fire-assay followed by instrumental neutron activation analysis. For each method outlined above, an acceptable criteria for the data has been identified based on 1) if recovery of each element is within a designated percentage at

This data release provides the U.S. Geological Survey (USGS) Spectral Library Version 7 and all related documents. The library contains spectra measured with laboratory, field, and airborne spectrometers. The instruments used cover wavelengths from the ultraviolet to the far infrared (0.2 to 200 microns). Laboratory samples of specific minerals, plants, chemical compounds, and man-made materials were measured. In many cases, samples were purified, so that unique spectral features of a material can be related to its chemical structure. These spectro-chemical links are important for interpreting remotely sensed data collected in the field or from an aircraft or spacecraft. This library also contains physically-constructed as well as mathematically-computed mixtures. Measurements of rocks, soils, and natural mixtures of minerals have also been made with laboratory and field spectrometers. Spectra of plant components and vegetation plots, comprising many plant types and species with varying backgrounds, are also in this library. Measurements by airborne spectrometers are included for forested vegetation plots, in which the trees are too tall for measurement by a field spectrometer. The related U.S. Geological Survey Data Series publication, "USGS Spectral Library Version 7", describes the instruments used, metadata descriptions of spectra and samples, and possible artifacts in the spectral measurements (Kokaly and others, 2017). Four different spectrometer types were used to measure spectra in the library: (1) Beckman™ 5270 covering the spectral range 0.2 to 3 µm, (2) standard, high resolution (hi-res), and high-resolution Next Generation (hi-resNG) models of ASD field portable spectrometers covering the range from 0.35 to 2.5 µm, (3) Nicolet™ Fourier Transform Infra-Red (FTIR) interferometer spectrometers covering the range from about 1.12 to 216 µm, and (4) the NASA Airborne Visible/Infra-Red Imaging Spectrometer AVIRIS, covering the range 0.37 to 2.5 µm. Two fundamental spectrometer characteristics significant for interpreting and utilizing spectral measurements are sampling position (the wavelength position of each spectrometer channel) and bandpass (a parameter describing the wavelength interval over which each channel in a spectrometer is sensitive). Bandpass is typically reported as the Full Width at Half Maximum (FWHM) response at each channel (in wavelength units, for example nm or micron). The linked publication (Kokaly and others, 2017), includes a comparison plot of the various spectrometers used to measure the data in this release. Data for the sampling positions and the bandpass values (for each channel in the spectrometers) are included in this data release. These data are in the SPECPR files, as separate data records, and in the American Standard Code for Information Interchange (ASCII) text files, as separate files for wavelength and bandpass. Spectra are provided in files of ASCII text format (files with a .txt file extension). In the ASCII files, deleted channels (bad bands) are indicated by a value of -1.23e34. Metadata descriptions of samples, field areas, spectral measurements, and results from supporting material analyses – such as XRD – are provided in HyperText Markup Language HTML formatted ASCII text files (files with .html file extension). In addition, Graphics Interchange Format (GIF) images of plots of spectra are provided. For each spectrum a plot with wavelength in microns on the x-axis is provided. For spectra measured on the Nicolet spectrometer, an additional GIF image with wavenumber on the x-axis is provided. Data are also provided in SPECtrum Processing Routines (SPECPR) format (Clark, 1993) which packages spectra and associated metadata descriptions into a single file (see the linked publication, Kokaly and others, 2017, for additional details on the SPECPR format and freely-available software than can be used to read files in SPECPR format). The data measured on the source spectrometers are

This data release provides the U.S. Geological Survey (USGS) Spectral Library Version 7 and all related documents. The library contains spectra measured with laboratory, field, and airborne spectrometers. The instruments used cover wavelengths from the ultraviolet to the far infrared (0.2 to 200 microns). Laboratory samples of specific minerals, plants, chemical compounds, and man-made materials were measured. In many cases, samples were purified, so that unique spectral features of a material can be related to its chemical structure. These spectro-chemical links are important for interpreting remotely sensed data collected in the field or from an aircraft or spacecraft. This library also contains physically-constructed as well as mathematically-computed mixtures. Measurements of rocks, soils, and natural mixtures of minerals have also been made with laboratory and field spectrometers. Spectra of plant components and vegetation plots, comprising many plant types and species with varying backgrounds, are also in this library. Measurements by airborne spectrometers are included for forested vegetation plots, in which the trees are too tall for measurement by a field spectrometer. The related U.S. Geological Survey Data Series publication, "USGS Spectral Library Version 7", describes the instruments used, metadata descriptions of spectra and samples, and possible artifacts in the spectral measurements (Kokaly and others, 2017). Four different spectrometer types were used to measure spectra in the library: (1) Beckman™ 5270 covering the spectral range 0.2 to 3 µm, (2) standard, high resolution (hi-res), and high-resolution Next Generation (hi-resNG) models of ASD field portable spectrometers covering the range from 0.35 to 2.5 µm, (3) Nicolet™ Fourier Transform Infra-Red (FTIR) interferometer spectrometers covering the range from about 1.12 to 216 µm, and (4) the NASA Airborne Visible/Infra-Red Imaging Spectrometer AVIRIS, covering the range 0.37 to 2.5 µm. Two fundamental spectrometer characteristics significant for interpreting and utilizing spectral measurements are sampling position (the wavelength position of each spectrometer channel) and bandpass (a parameter describing the wavelength interval over which each channel in a spectrometer is sensitive). Bandpass is typically reported as the Full Width at Half Maximum (FWHM) response at each channel (in wavelength units, for example nm or micron). The linked publication (Kokaly and others, 2017), includes a comparison plot of the various spectrometers used to measure the data in this release. Data for the sampling positions and the bandpass values (for each channel in the spectrometers) are included in this data release. These data are in the SPECPR files, as separate data records, and in the American Standard Code for Information Interchange (ASCII) text files, as separate files for wavelength and bandpass. Spectra are provided in files of ASCII text format (files with a .txt file extension). In the ASCII files, deleted channels (bad bands) are indicated by a value of -1.23e34. Metadata descriptions of samples, field areas, spectral measurements, and results from supporting material analyses – such as XRD – are provided in HyperText Markup Language HTML formatted ASCII text files (files with .html file extension). In addition, Graphics Interchange Format (GIF) images of plots of spectra are provided. For each spectrum a plot with wavelength in microns on the x-axis is provided. For spectra measured on the Nicolet spectrometer, an additional GIF image with wavenumber on the x-axis is provided. Data are also provided in SPECtrum Processing Routines (SPECPR) format (Clark, 1993) which packages spectra and associated metadata descriptions into a single file (see the linked publication, Kokaly and others, 2017, for additional details on the SPECPR format and freely-available software than can be used to read files in SPECPR format). The data measured on the source spectrometers are