A detailed airborne gravity gradiometry, magnetic, and radiometric survey of Mountain Pass, California was flown by CGG Canada Services Ltd. (CGG). The high-resolution helicopter survey was flown at a flight-line spacing of 100 and 200 m, a flight-line azimuth of 70 degrees, a nominal flight-line elevation above ground of 70 m, and consists of about 1,814 line-kilometers. Tie lines were spaced at a 1-km interval with a flight-line azimuth of 160 degrees. Data were collected using a HeliFALCON airborne gravity gradiometry system, Scintrex CS-3 cesium magnetometer, Radiation Solutions RS-500 spectrometer, and Riegl LMS-Q1401-80n laser scanner and processed by CGG. Gravity gradiometry data include corrections for residual aircraft motion, self gradient, terrain corrections, and tie-line and micro-levelling. Magnetic data were corrected by the contractor for diurnal variations of the Earth’s magnetic field, tie-line leveled, micro-leveled, and an International Geomagnetic Reference Field of the Earth was removed. Radiometric data include corrections for aircraft and cosmic background radiation, radon background, Compton scattering effects, and variations in altitude. Data are provided in ASCII (.csv) and Geosoft database (.gdb) format, database channels and descriptions are listed in the survey report, and grids of gravity and hillshade are in ASCII Grid eXchange Format (.gxf). Maps and grids of magnetic and radiometric data were released by Ponce and Denton (2018a-d). References: Ponce, D.A., and Denton, K.M., 2018a, Aeromagnetic map of Mountain Pass and vicinity, California and Nevada: U.S. Geological Survey Scientific Investigations Map 3412-B, 6 p., 1 pl., scale 1:62,500, https://doi.org/10.3133/sim3412B. Ponce, D.A., and Denton, K.M., 2018b, High-resolution aeromagnetic survey of Mountain Pass, California: U.S. Geological Survey data release, https://doi.org/doi:10.5066/P92XVOOF. Ponce, D.A., and Denton, K.M., 2018c, Airborne radiometric maps of Mountain Pass, California: U.S. Geological Survey Scientific Investigations Map 3412-C, 6 p., 1 pl., scale 1:62,500, https://doi.org/10.3133/sim3412C. Ponce, D.A., and Denton, K.M., 2018d, High-resolution airborne radiometric survey of Mountain Pass, California: U.S. Geological Survey data release, https://doi.org/10.5066/P9ENLS6D.

A detailed aeromagnetic survey of Mountain Pass, California was flown by CGG Canada Services Ltd. (CGG) during November and December, 2016. The high-resolution helicopter survey was flown at a flightline spacing of 100 and 200 m, a flightline azimuthal direction of 70 degrees, a nominal flightline elevation above ground of 70 m, and consists of about 1,814 line-kilometers. Tie lines were spaced at a 1-km interval with a flight-line azimuthal direction of 160 degrees. A Scintrex CS-3 cesium magnetometer was used throughout the airborne survey as well as for the ground base station survey. Data are presented as residual magnetic intensity (RMI) in nanoteslas (nT).

A detailed airborne radiometric survey of Mountain Pass, California was flown by CGG Canada Services Ltd. (CGG). The high-resolution helicopter survey was flown at a flight-line spacing of 100 and 200 m, a flight-line azimuth of 70 degrees, a nominal flight-line elevation above ground of 70 m, and consists of about 1,814 line-kilometers. Tie lines were spaced at a 1-km interval with a flight-line azimuth of 160 degrees. Data were collected using a Radiation Solutions RS-500 spectrometer and processed by CGG using standard radiometric surveying techniques (e.g., International Atomic Energy Agency, 2003) that include corrections for aircraft and cosmic background radiation, radon background, Compton scattering effects, and variations in altitude. Radioelement data are presented as ASCII grids of potassium (K) in per cent, equivalent thorium (eTh) in parts per million (ppm), and equivalent uranium (eU) in ppm. Airborne radiometric maps of Mountain Pass were published by Ponce and Denton (2019).

The U.S. Geological Survey (USGS) collected gravity data in the eastern Mojave Desert, California and Nevada as an aid to characterizing the regional geologic framework. Gravity stations were located between approximately lat 35°10’ and 35°50’ N. and long 115°05’ and 115°50’ W. and were distributed from west to east across parts of Shadow Valley, Clark Mountain Range, Mescal Range, Ivanpah Valley, Lanfair Valley, Bobcat Hills, and New York Mountains. Gravity data were ultimately tied to a World Relative Gravity Reference Network of North America gravity base station at Nipton, California (Jablonski, 1974) and supersede previously published data (Denton and Ponce, 2018). In general, gravity anomalies can be used to infer the subsurface structure of geologic features, provided a physical-property contrast occurs across the geologic boundaries. Gravity anomalies can, for example, reveal variations in lithology and delineate features such as calderas, deep sedimentary basins, and faults, all of which play an important role in defining the geologic framework of a region (Ponce and Denton, 2018). Gravity data were processed using standard geophysical methods (for example; Blakely, 1995; Denton and Ponce, 2018). New gravity data are shown at the top of the data file and their reduction method matches previously published data. Gravity data include the following corrections: (1) earth-tide correction, which corrects for tidal attraction of the Moon and Sun; (2) instrument-drift correction, which compensates for drift in the instrument’s spring; (3) latitude correction, which accounts for variation in the Earth’s gravity with latitude; (4) free-air correction, which accounts for variation in gravity due to elevation relative to sea level; (5) Bouguer correction, which corrects for the attraction of material between the station and sea level; (6) curvature correction, which corrects the Bouguer correction for the effect of the Earth’s curvature; (7) terrain correction, which removes the effect of topography to a radial distance of 167 km from the station; and (8) isostatic correction, which removes long-wavelength variations in the gravity field related to the compensation of topographic loads. Denton, K.M., and Ponce, D.A., 2018, Gravity and magnetic studies of the eastern Mojave Desert, California and Nevada (rev. 1.1): U.S. Geological Survey Open-File Report 2016-1070, 20 p., https://doi.org/10.3133/ofr20161070. Jablonski, H.M., 1974, World relative gravity reference network North America, Parts 1 and 2, with a supplementary section on IGSN 71 gravity datum values (rev. ed.): U.S. Defense Mapping Agency Aerospace Center Reference Publication 25, 1261 p. Ponce, D.A., and Denton, K.M., 2018, Isostatic gravity map of Mountain Pass and vicinity, California and Nevada: U.S. Geological Survey Scientific Investigations Map 3412-A, 6 p., scale 1:62,500, https://doi.org/10.3133/sim3412A.

The U.S. Geological Survey (USGS) and the Department of Energy (DOE) have collaborated to acquire high-resolution airborne magnetic and radiometric data, over northern and western Nevada and eastern California, to support geologic and geophysical mapping and modeling that will assist geothermal and critical mineral studies. The surveys, referred to as GeoDAWN (Geoscience Data Acquisition for Western Nevada), span areas of major resource potential associated with the Walker Lane and western Great Basin. They were conducted under the USGS’s Earth Mapping Resource Initiative (EarthMRI), with support from the DOE’s Geothermal Technologies Office (GTO), and involved acquisition of aeroradiometric and aeromagnetic data that provide key information on surface geology and soil composition, and subsurface structure and geology, respectively. Coordinated with this effort was the collection of airborne lidar (light detection and ranging) data (conducted through the USGS 3DEP Program) that yield detailed surface topographic models of the terrain over a similar extent spanned by the geophysical surveys. The GeoDAWN surveys were performed by EDCON-PRJ, Inc., under contract with the USGS from November 1, 2021 to November 20, 2022, and consisted of two different, overlapping surveys with different flight specifications (Area 1 and Area 2; Figure 1). Area 1, centered over Clayton Valley in western Nevada was selected primarily with a focus on the region’s Li-clay and brine resources. It was flown with rank 1 specifications (following criteria outlined by Drenth and Grauch, 2019) that met EarthMRI survey requirements. Area 2, consisting of the remainder of the GeoDAWN extent, was selected primarily with a focus on geothermal resources. Lower resolution flight specifications designated for Area 2 (falling between rank 1 and 2) enabled data collection across a substantially larger area (spanning numerous known, prospective, and undiscovered geothermal and mineral systems) than would have been possible with rank 1 specifications. The combined GeoDAWN area (consisting of a total of 149,030 line-km spanning an area of 51,857 sq km), was divided into four separate acquisition blocks (from north to south: Winnemucca, Fallon, Hawthorne, and Tonopah; Figure 1). The Tonopah block, which includes Area 1 and the southern part of Area 2 surveys, was flow by Precision GeoSurveys Inc. (under subcontract to EDCON-PRJ, Inc.), with a Bell Jet Ranger helicopter. Area 1 was flown with a nominal flight height targeted at 100 m above terrain over low-relief areas and 150 m over mountainous areas. Flight lines were spaced 200 m apart at an azimuth of 90 degrees, and tie lines were spaced 2000 m apart at an azimuth of 180 degrees. Area 2 was flow at a nominal flight height targeted at 150 m above terrain over low-relief areas and 200 m over mountain ranges. The survey was flown with flight lines spaced 400 m apart at an azimuth of 90 degrees, and tie lines spaced 4000 m apart at an azimuth of 180 degrees. The portion of Area 2 contained within the Tonopah acquisition block was flown with the Precision GeoSurveys’ Bell Jet Ranger, while the remainder was collected by Cloudstreet Flying Service (under subcontract to EDCON-PRJ, Inc.) and flown with a Cessna 180 and Turbo 206 fixed-wing aircraft. Nominal flight heights for both surveys were based on a best fit, pre-planned, three-dimensional draped surface designed with a maximum 22-degree climb/descent angle to follow terrain as closely as possible while maintaining a safe survey. Actual flight heights were subject to aircraft climb and descent limitations. In areas of steep terrain, the aircraft may have required deviating from the planned drape surface, and therefore variable terrain clearance should be considered when modeling and interpreting these data. Magnetic data (Figure 2) were processed by EDCON-PRJ, Inc. and include corrections for diurnal variations of the Earth’s magnetic field, magnetic field of the

This dataset consists of 65 magnetotelluric (MT) stations collected in 2015 near Mountain Pass, California. The U.S. Geological Survey acquired these data to create a regional conductivity model near the Mountain Pass mine. This work is in support of characterizing mineral deposits.

This dataset consists of 65 magnetotelluric (MT) stations collected in 2015 near Mountain Pass, California. The U.S. Geological Survey acquired these data to create a regional conductivity model near the Mountain Pass mine. This work is in support of characterizing mineral deposits.

This dataset consists of 65 magnetotelluric (MT) stations collected in 2015 near Mountain Pass, California. The U.S. Geological Survey acquired these data to create a regional conductivity model near the Mountain Pass mine. This work is in support of characterizing mineral deposits.

This dataset consists of 65 magnetotelluric (MT) stations collected in 2015 near Mountain Pass, California. The U.S. Geological Survey acquired these data to create a regional conductivity model near the Mountain Pass mine. This work is in support of characterizing mineral deposits.

This dataset consists of 65 magnetotelluric (MT) stations collected in 2015 near Mountain Pass, California. The U.S. Geological Survey acquired these data to create a regional conductivity model near the Mountain Pass mine. This work is in support of characterizing mineral deposits.