Geospatial analysis delineates lode gold prospectivity in Alaska

Geospatial Analyses Delineate Lode Gold Prospectivity in AlaskaData-driven geospatial analyses of geological data delineate lode gold potential for Alaska.Analyses indicate new potential lode source areas in gold placer districts and identify new areas in Alaska prospective for lode gold deposits.Adaptable geospatial analytical techniques can focus future investigations, data collection, and exploration strategies for gold and associated byproduct critical minerals, such as As, W, Sb, and Te. GIS-Based Method of AnalysisFor the geographic information system (GIS) analysis used to determine lode gold prospectivity in Alaska, key quantifiable characteristics of gold deposit types were identified using seven geologic, geochemical, and geophysical datasets, which we scored with respect to their importance for indicating gold potential.A data scoring and ranking process was tailored to critical parameters for 3 conventional lode gold deposit types, 2 lode gold system types, and 1 overarching undivided gold deposit group; scores were applied to drainage basins approximately 100 square kilometers in area statewide.For a detailed discussion of the scoring criteria for datasets of each deposit type and to access the geospatial data files, see https:// doi.org/10.3133/ofr20211041.Criteria and scoring weights can be modified to implement different analyses of the datasets to address other types of inquiries.A Python script combines individual parameter scores into cumulative scores for each drainage basin.The cumulative scores for each drainage basin were divided into three levels of prospectivity for gold potential (High, Medium, Low) on the basis of natural statistical breaks (qualified by the certainty of the analysis on the basis of the presence and abundance of favorable attributes for each deposit type); a fourth category of Unknown potential was applied to drainage basins that lack data.Owing to the uneven distribution of some datasets, our method assigns scores for certainty that are based on the number of datasets that contribute to each score.The product of each analysis is a map that indicates the relative level (High, Medium, Low) of gold potential, represented by red, yellow, and green, respectively, and the relative level (High, Medium, Low) of certainty, represented by dark, medium, and light shades of the colors, respectively, for each prospectivity exercise.The Unknown class is colored gray.The format and coding of the analytical criteria and data permit users to query individual scores for each drainage basin on the digital map products and compare with known gold occurrences.Photograph of Independance Mine northeast of Anchorage, Alaska, by S. Karl, U.S. Geological Survey (banner).Estimated resource potential and certainty for lode gold in undivided deposits (top right) and undivided deposits with Alaska Resource Data File locality type labeled (lower right).AAXXXX_fig 01 Alaska Albers Equal Area Conic projection North American Datum of 1983 120° 135° 150° 165° 180° 66° 62° 58° 54° 66° 62° 58° 54° EXPLANATION High potential