Alaska is dominated by a history of tectonic events that foster mobilization and concentration of a wide variety of mineral commodities that are critical to the US economy and are vital to national defense, renewable-energy, and emerging electronics technologies.
This project uses a recently developed, data-driven geographic information system (GIS)-based method to evaluate the potential of various mineral deposit types across the state of Alaska. The method systematically analyzes pre-existing, geospatially referenced datasets to generate a map, which provides a visual indication of the estimated potential (low, medium, high) and the certainty of that estimate (low, medium, high) for each watershed for a given group of mineral deposits or deposit types. Probabilities are calculated with set criteria based on lithology, geochemistry, and geophysical data. The datasets used include the USGS Alaska Geochemical Database, the Alaska Division of Geological and Geophysical Surveys web-based geochemical database, data from the recently released USGS geologic map of Alaska, the USGS Alaska Resource Data File, and airborne radiometric surveys from the National Uranium Resource Evaluation.
Examples of the various mineral deposit groups currently being evaluated by this method include placer gold, rare earth elements-thorium-niobium, sandstone uranium, platinum group elements-nickel-cobalt-chrome, copper-cobalt-silver-gallium-germanium, and tin-tungsten-molybdenum-tantalum-indium-fluorspar. The method is highly adaptable for the needs of diverse users, including scientific researchers, industry, land mangers such as the Bureau of Land Management and the State of Alaska, and Alaska Native corporations.
Examples of how this GIS analysis can be applied:
The current project is a continuation of a successful pilot study completed in 2015, which used the same scoring and mapping method for the Central Yukon Planning Area in central and northern Alaska. The scoring and mapping method was developed by the USGS in cooperation with the Alaska Division of Geological and Geophysical Surveys. The Bureau of Land Management requested that the study be conducted in the Central Yukon Planning Area to aid in their resource management planning. This pilot study evaluated potential for six different deposit types known to occur in specific rock types:
The scoring system uses a number of parameters based on key characteristics specific to each deposit type. The key characteristics were chosen based on known occurrences of the mineral deposits around the world, known occurrences in Alaska, and previous research relating to the geologic processes responsible for the formation of these deposit types. The parameters are then scored and weighted for each of the different mineral deposit types. The confidence or certainty of the score is then calculated taking into consideration factors such as quantity of data and completeness of the datasets. Each deposit type has different parameters and different point values assigned to the parameters.
As an example, the scoring system for placer gold deposits uses five parameters: pan concentrate mineralogy, sediment geochemistry, rock type, geographical location, and whether the Alaska Resource Data File has any reports for the specific area mentioning placer gold as a keyword. Each parameter has a set number of possible points which allows for the parameters to weigh in differently to the total score. For example, pan concentrate data was assigned point values of up to 10, while the presence of plutonic rocks in the watershed only scored up to 3 points. In other words, if pan concentrate data for the area contains gold, there is a high probability of finding gold in the area; however, the presence of plutonic rocks in an area may often correlate with placer gold deposits, but not always, and thus weighs less on the overall score. After each parameter is assigned a score and a total score is calculated for the watershed, the certainty of the overall score is determined based on whether complete datasets are available for each of the parameters.
Jones, J.V., III, Karl, S.M., Labay, K.A., Shew, N.B., Granitto, M., Hayes, T.S., Mauk, J.L., Schmidt, J.M., Todd, E., Wang, B., Werdon, M.B., and Yager, D.B., 2015, GIS-based identification of areas with mineral resource potential for six selected deposit groups, Bureau of Land Management Central Yukon Planning Area, Alaska: U.S. Geological Survey Open-File Report 2015–1021, 78 p., 5 appendixes, 12 pls., https://dx.doi.org/10.3133/ofr20151021.
Karl, S.M., Jones, J.V., III, and Hayes, T.S., eds., 2016, GIS-based identification of areas that have resource potential for critical minerals in six selected groups of deposit types in Alaska: U.S. Geological Survey Open-File Report 2016–1191, 99 p., 5 appendixes, 12 plates, scale 1:10,500,000, https://dx.doi.org/10.3133/ofr20161191.
Karl, S.M., and Labay, K.A., Geospatial analysis identifies critical mineral-resource potential in Alaska: U.S. Geological Survey Fact Sheet 2017–3012, 4 p., https://doi.org/10.3133/fs20173012.
Karl, S.M., Jones, J.V., Labay, K.A., Shew, N.B., Granitto, M., Hayes, T.S., Mauk, J.L., Schmidt, J.M., Todd, E., Wang, B., Werdon, M.B., and Yager, D.B., 2016, Identification of areas with critical minerals resource potential in six groups of mineral deposit types in Alaska: Alaska Miners Association 2016 Annual Convention, November 6-12, Anchorage, AK. View 2016 AMA abstract book. [PDF file, 7.2 MB]
Karl, S.M., Jones, J.V., Labay, K.A., Shew, N.B., Granitto, M., Hayes, T.S., Mauk, J.L., Schmidt, J.M., Todd, E., Wang, B., Werdon, M.B., and Yager, D., 2016, GIS-based identification of areas that have mineral potential in northern Alaska: Alaska Miners Association Spring Convention, April 4-9, 2016, Fairbanks, AK, p. 10-11. View Karl 2016 AMA presenstation. [PDF file, 15.6 MB]
Karl, S.M., Jones, J.V., Labay, K.A., Shew, N.B., Granitto, M., Hayes, T.S., Mauk, J.L., Schmidt, J.M., Todd, E., Wang, B., Werdon, M.B., and Yager, D., 2015, GIS-based identification of areas that have mineral potential in Alaska: Alaska Miners Association 2015 Annual Convention, p. 13-14. View AMA 2015 Abstract Book. [PDF file, 2 MB] View Karl 2015 AMA presentation. [PDF file, 35.8 MB]
Karl, S.M., Labay, K.A., Shew, N.B., Wang, B., and Granitto, M., 2017, GIS-based identification of areas that have potential for lode gold deposits in Alaska: Association for Mineral Exploration Roundup 2017 Conference, January 23-26, 2017, Vancouver, British Colombia, p. 26-27. View Roundup 2017 abstract book. [PDF file, 2 MB] View poster. [PDF file, 19.6 MB]
Wang, B., Karl, S.M., Labay, K.A., Jones, J.V. III, Shew, N.B., Granitto, M., Hayes, T.S., Mauk, J.L., Schmidt, J., Todd, E., Werdon, M.B., and Yager, D.B., 2016, Identification ofareas with critical minerals resource potential in six groupd of mineral deposit types in Alaska: Geological Society of America Abstracts with Programs, Vol. 48, No. 7, doi:10.1130/abs/2016AM-286305.