Anne E. McCafferty 20250331 raster digital data Denver, CO U.S. Geological Survey Additional information about Originator: McCafferty, A.E, https://orcid.org/0000-0001-5574-9201. Suggested Citation: McCafferty, A.E., 2023, Gravity and related derivative GeoTIFF grids and data for the United States and Canada, in McCafferty, A.E., San Juan, C.A., Lawley, C.J.M., Graham, G.E., Gadd, M.G., Huston, D.L., Kelley, K.D., Paradis, S., Peter, J.M., and Czarnota, K., National-scale geophysical, geologic, and mineral resource data and grids for the United States, Canada, and Australia: Data in support of the tri-national Critical Minerals Mapping Initiative: U.S. Geological Survey data release, https://doi.org/10.5066/P970GDD5. https://doi.org/10.5066/P970GDD5 Several evidential layers calculated from a compilation of gravity data from the national-scale gravity anomaly map of the conterminous United States (Phillips and others, 1993), Alaska (Saltus and others, 2006) and Canada (Geological Survey of Canada, 2017) are presented here. This directory includes GeoTIFF grids of Bouguer gravity, the horizontal gradient magnitude of the Bouguer gravity, the Bouguer gravity upward continued 30 km, and the horizontal gradient magnitude of the upward continued gravity, The directory also includes shapefiles of locations that trace the maxima of the horizontal gradient magnitude of the gravity and of the maxima of the horizontal gradient magnitude of the upward continued gravity. Otherwise known as “worms”, the points tracking the maxima mark the edges of shallow density sources (in the case of the Bouguer gravity) and deeper density sources (calculated from the upward continued gravity). The shapefile of worms also includes attribute fields related to the steepness of the gradient and to the trend or strike of the gradient. The reader is encouraged to read the metadata provided in the zip file that is specific to each data layer for details related to the calculation and derivation of each gravity grid and derivative products. References Geological Survey of Canada, 2017, Canada-gravity data compilation: Natural Resources Canada, https://open.canada.ca/data/en/dataset/5a4e46fe-3e52-57ce-9335-832b5e79fecc. Phillips, J.D., Duval, J.S., and Ambroziak, R.A., 1993, National geophysical data grids; gamma-ray, gravity, magnetic, and topographic data for the conterminous United States: U.S. Geological Survey Data Series 9, https://doi.org/10.3133/ds9. Saltus, R.W., Brown, P.J. II, Morin, R.L., and Hill, P.L., 2008, 2006 compilation of Alaska gravity data and historical reports: U.S. Geological Survey Data Series 264, https://doi.org/10.3133/ds264. The GeoTIFF grids and shapefiles of the gravity data and derivative products for the United States and Canada were used as evidential layers in mineral prospectivity models for predicting sedimentary-hosted Pb-Zn mineralization described in Lawley and others (2021). This effort was part of a tri-national collaboration between the federal geological surveys of the United States (USGS), Canada (Canadian Geological Survey), and Australia (Geoscience Australia) called the Critical Minerals Mapping Initiative. References Lawley, C.J.M., McCafferty, A.E., Graham, G.E., Gadd, M.G., Huston, D.L., Kelley, K.D., Paradis, S., Peter, J.M., and Czarnota, K., 2021, Datasets to support prospectivity modelling for sediment-hosted Zn-Pb mineral systems: Natural Resources Canada Open File 8836, https://doi.org/10.4095/329203. The data are provided in two file formats. The first is GeoTIFF, which is used for gridded data and is a public domain geospatial tagged image file format that maintains the original data values as grid cells. The GeoTIFF grids can be read and written by many common geographic software tools including ArcMap and QGIS. GeoTIFFs are provided as zip files consisting of a .tif (image file), a .tfw (world file), a .png (preview image) and a .xml (metadata file). The second file format is Esri shapefile. Esri shapefiles are used for geospatial vector data such as points, lines, and polygons and can be read with a wide variety of software. Shapefiles are provided as zip files consisting of a .shp (feature geometry), a .dbf (attribute information), a .shx (index file), a .prj (coordinate system information) and a .xml (metadata file). All data are in geographic coordinates using a WGS84 datum. Also provided are .jpg files that provide an image to visualize the GeoTIFF or shapefile data. DATA FILES--GeoTIFFs GeophysicsGravity_USCanada: Bouguer gravity anomaly grid for the US and Canada. GeophysicsGravity_HGM_USCanada: Horizontal gradient magnitude (HGM) of the Bouguer gravity for the US and Canada. GeophysicsGravity_Up30km_USCanada: Bouguer gravity anomaly upward continued 30 kilometers (km) for the US and Canada. GeophysicsGravity_Up30km_HGM_USCanada: Horizontal gradient magnitude of the Bouguer gravity upward continued 30 km for the US and Canada. DATA FILES--Shapefiles ShallowGravitySources_Worms_USCanada: Coordinate locations tracking the horizontal gradient magnitude maxima of the Bouguer gravity, commonly known as 'worms'. DeepGravitySources_Worms_USCanada: Coordinate locations tracking the horizontal gradient magnitude maxima of the Bouguer gravity upward continued 30 km, commonly known as 'worms'. 1993 2017 publication date Complete None planned -173.0353 -50.3905 83.6697 23.5755 ISO 19115 Topic Category geoscientificInformation None U.S. Geological Survey USGS Geological Survey of Canada GSC Geoscience Australia GA Critical Minerals Mapping Initiative CMMI Mineral Resources Program MRP Geology, Geophysics, and Geochemistry Science Center GGGSC Targeted Geoscience Initiative TGI Exploring for the Future Program Bouguer gravity gravity anomaly ground gravity horizontal gradient magnitude horizontal gradient magnitude maxima USGS Thesaurus critical minerals metallic mineral resources mineral resources gravity lead zinc geophysics maps and atlases upward continued gravity magnetic field (earth) gravity worms USGS Metadata Identifier USGS:619a9f02d34eb622f692f96c Common geographic areas United States Canada None. Please see 'Distribution Info' for details. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government. Although these data have been processed successfully on a computer system at the U.S. Geological Survey (USGS), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. The USGS or the U.S. Government, GA or the Australian Government, and GSC or the Canadian Government shall not be held liable for improper or incorrect use of the data described and/or contained herein. Anne E McCafferty U.S. Geological Survey Research Geophysicist mailing

Mail Stop 964, W 6th Ave and Kipling St

Denver CO 80225 USA 303-236-1397 anne@usgs.gov This release of the dataset was funded by the U.S. Geological Survey Mineral Resources Program (MRP). The authors would like to thank the Geological Survey of Canada’s Targeted Geoscience Initiative and Geoscience Australia’s Exploring for the Future Program for providing data for this study. Acknowledgment of the U.S. Geological Survey, the Geological Survey of Canada and Geoscience Australia would be appreciated in products derived from these data. In addition, acknowledgment of the original authors listed under "Related External Resources” at https://doi.org/10.5066/P970GDD5 should occur for non-governmental data. The data were generated on a Dell Precision 7550 laptop computer using Geosoft Oasis Montaj v. 9.9.1 and Esri ArcMap v.10.8.1. Christopher J.M. Lawley Anne E. McCafferty Garth E. Graham David L. Huston Karen D. Kelley Karol Czarnota Suzanne Paradis Jan M. Peter Nathan Hayward Mike Barlow Poul Emsbo Joshua Coyan Carma A. San Juan Michael G. Gadd 202202 publication Ore Geology Reviews volume 141 n/a Elsevier BV Lawley, C.J.M., McCafferty, A.E, Graham, G.E., Huston, D.L., Kelley, K.D., Czarnota, K., Paradis, S., Peter, J.M., Hayward, N., Barlow, M., Emsbo, P., Coyan, J., San Juan, C.A., and Gadd, M.G., 2022, Data-driven prospectivity modelling of sediment-hosted Zn-Pb mineral systems and their critical raw materials: Ore Geology Reviews, v. 141, no. 104635, https://doi.org/10.1016/j.oregeorev.2021.104635. https://doi.org/10.1016/j.oregeorev.2021.104635 Christopher J.M. Lawley Anne E. McCafferty Garth E. Graham Michael G. Gadd David L. Huston Karen D. Kelley Suzanne Paradis Jan M. Peter Karol Czarnota 2021 publication n/a Natural Resources Canada/CMSS/Information Management Lawley, C.J.M., McCafferty, A.E., Graham, G.E., Gadd, M.G., Huston, D.L., Kelley, K.D., Paradis, S., Peter, J.M., and Czarnota, K., 2021, Datasets to support prospectivity modelling for sediment-hosted Zn-Pb mineral systems: Natural Resources Canada Open File 8836, https://doi.org/10.4095/329203. https://doi.org/10.4095/329203 These data have been peer reviewed and compared with related ancillary data. Data were reviewed for consistency and analyses results were checked for validity and fidelity of relationships. Data set is considered complete for the information presented, as described in the abstract. Users are advised to read the rest of the metadata record carefully for additional details. All data as part of this collection were included in this data release for the region and time period specified in this metadata. Spatial locations were determined from previously published national grids of the gravity field. No formal positional accuracy tests were conducted. Geological Survey of Canada 2017 raster digital data n/a Natural Resources Canada/CMSS/Information Management Geological Survey of Canada, 2017, Canada-gravity data compilation: Natural Resources Canada, https://open.canada.ca/data/en/dataset/5a4e46fe-3e52-57ce-9335-832b5e79fecc. https://open.canada.ca/data/en/dataset/5a4e46fe-3e52-57ce-9335-832b5e79fecc Digital and/or Hardcopy 2017 publication date Geological Survey of Canada, 2017 Gravity data for Canada Richard W. Saltus Philip J. Brown Robert L. Morin Patricia L. Hill 2008 publication Data Series 264 n/a U.S. Geological Survey Saltus, R.W., Brown, P.J. II, Morin, R.L., and Hill, P.L., 2008, 2006 compilation of Alaska gravity data and historical reports: U.S. Geological Survey Data Series 264, https://doi.org/10.3133/ds264. https://doi.org/10.3133/ds264 Digital and/or Hardcopy 2006 compilation date Saltus and others, 2008 Gravity data for Alaska Jeffrey D. Phillips Joseph S. Duval Russell A. Ambroziak 1993 publication Data Series 9 n/a U.S. Geological Survey Phillips, J.D., Duval, J.S., and Ambroziak, R.A., 1993, National geophysical data grids; gamma-ray, gravity, magnetic, and topographic data for the conterminous United States: U.S. Geological Survey Data Series 9, https://doi.org/10.3133/ds9. https://doi.org/10.3133/ds9 Digital and/or Hardcopy 1993 publication date Phillips and others, 1993 Gravity data for the conterminous United States GeophysicsGravity_USCanada.tif: National-scale grids of Bouguer gravity for Alaska (Saltus and others, 2008), the conterminous United States (Phillips and others, 1993), and Canada (Geological Survey of Canada, 2017) were merged to create a seamless 2-kilometer (km) composite Bouguer gravity anomaly grid using Geosoft Oasis Montaj. The composite grid was projected to a geographic coordinate system (WGS 1984) and converted to FLT format using Oasis Montaj. The FLT grid was then converted to GeoTIFF format using Esri ArcMap. Saltus and others, 2008 Phillips and others, 1993 (Geological Survey of Canada, 2017 2022 GeophysicsGravity_HGM_USCanada.tif: The horizontal gradient magnitude (HGM) of the Bouguer gravity for the conterminous United States and Canada was calculated using Geosoft Oasis Montaj. 2022 GeophysicsGravity_Up30km_USCanada.tif: The Bouguer gravity upward continued 30 km for the conterminous United States and Canada was calculated using Geosoft Oasis Montaj. 2022 GeophysicsGravity_Up30km_HGM_USCanada.tif: The horizontal gradient magnitude (HGM) of the Bouguer gravity upward continued 30 km for the conterminous United States and Canada was calculated using Geosoft Oasis Montaj. 2022 ShallowGravitySources_Worms_USCanada.tif: The coordinate locations of the HGM maxima of the grid of Bouguer gravity for the United States and Canada were calculated using Geosoft Oasis Montaj and output as an Esri shapefile. 2022 DeepGravitySources_Worms_USCanada.tif: The coordinate locations of the HGM maxima of the grid of upward continued 30 km Bouguer gravity for the United States and Canada were calculated using Geosoft Oasis Montaj and output as an Esri shapefile. 2022 All Geosoft grids were exported to .flt format, then converted to GeoTIFF format using Esri ArcMap. The GeoTIFF files are in geographic coordinates (decimal degrees) using the WGS84 datum. 20211127 Raster 0.00000001 0.00000001 Decimal degrees WGS_1984 WGS 84 6378137.0 298.257223563 GeophysicsGravity_USCanada.tif Bouguer gravity anomaly for the US and Canada. U.S. Geological Survey Value Measure of the Bouguer gravity anomaly field. NoData value is -3.40282346639e+38. U.S. Geological Survey -337.68661499023 111.12740325928 mGal ShallowGravitySources_Worms_USCanada.shp Points tracking the maxima of the horizontal gradient magnitude of the Bouguer gravity anomaly. U.S. Geological Survey FID Internal feature number. ESRI Sequential unique whole numbers that are automatically generated. Shape Feature geometry. ESRI Shape type. Lat_WGS Latitude of feature. U.S. Geological Survey 23.75 83.11 Decimal degrees Lon_WGS Longitude of feature. U.S. Geological Survey -168.05 -52.50 Decimal degrees Steepness Steepness of the gravity field gradient. U.S. Geological Survey 0.000001 0.016017 mGal/m Lon_WGS Strike of the gravity gradients. U.S. Geological Survey -89.999237 90.000000 degrees from north GeophysicsGravity_Up30km_USCanada.tif Bouguer gravity anomaly upward continued to 30 km above the earth's surface. U.S. Geological Survey Value Estimated Bouguer gravity anomaly observed at 30 km altitude. NoData value is -3.40282346639e+38. U.S. Geological Survey -144.90481567383 81.022430419922 mGal DeepGravitySources_Worms_USCanada.shp Points tracking the maxima of the horizontal gradient magnitude of the upward continued Bouguer gravity anomaly. U.S. Geological Survey FID Internal feature number. Esri Sequential unique whole numbers that are automatically generated. Shape Feature geometry. Esri Coordinates defining the features. Lon_WGS Longitude of feature. U.S. Geological Survey -166.90 -51.23 decimal degrees Lat_WGS Latitude of feature. U.S. Geological Survey 23.64 83.67 decimal degrees Steepness Steepness of the gravity field gradient. U.S. Geological Survey -261.413910 144.372253 mGal/m Strike Strike of the gravity gradients. U.S. Geological Survey -89.991104 90.000000 degrees from north GeophysicsGravity_Up30km_HGM_USCanada.tif Horizontal gradient magnitude of the upward continued 30 km Bouguer gravity anomaly. U.S. Geological Survey Value Magnitude (absolute value) of the change in the slope of the upward continued gravity. NoData value is -3.4028235e+38. U.S. Geological Survey 0 21.368011474609 mGal/m GeophysicsGravity_HGM_USCanada.tif Horizontal gradient magnitude of the Bouguer gravity anomaly. U.S. Geological Survey Value Magnitude (absolute value) of the change in the slope of gravity. NoData value is -3.4028235e+38. U.S. Geological Survey 0.0 0.0094849383458495 mGals/m U.S. Geological Survey GS ScienceBase mailing address

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Denver CO 80225 United States 1-888-275-8747 sciencebase@usgs.gov https://www.sciencebase.gov/catalog/item/619a9f02d34eb622f692f96c Unless otherwise stated, all data, metadata and related materials are considered to satisfy the quality standards relative to the purpose for which the data were collected. Although these data and associated metadata have been reviewed for accuracy and completeness and approved for release by the U.S. Geological Survey (USGS), the Geological Survey of Canada, and Geoscience Australia (GA), no warranty expressed or implied is made regarding the display or utility of the data for other purposes, nor on all computer systems, nor shall the act of distribution constitute any such warranty. digital data https://doi.org/10.5066/P970GDD5 none none 20250331 Anne E McCafferty U.S. Geological Survey mailing

Mail Stop 962, W 6th Ave and Kipling St

Denver CO 80225 USA 303-236-1397 anne@usgs.gov Content Standard for Digital Geospatial Metadata FGDC-STD-001-1998