A GEOGRAPHIC INFORMATION SYSTEM ON THE GEOLOGY AND MINERAL RESOURCES OF THE MIDCONTINENT RIFT SYSTEM

A cooperative effort by the Minnesota Geological Survey, Ontario Geological Survey, and U.S. Geological Survey, assisted by several university cooperators, is developing a Geographic Information System (GIS) for the geology, geochemistry and mineral resources of the Midcontinent Rift System in the Lake Superior region. We are compiling a series of digital map and data layers relating to the bedrock lithology and structure, geochemistry of volcanic and intrusive rocks, and mineral deposits in Ontario, Minnesota, Wisconsin, and Michigan. Layers include a digital geologic map compilation based on numerous original source maps, a data layer containing more than 4,000 chemical analyses, isotopically determined ages for about 250 sites, and information on about 600 mineral deposits and occurrences. The data are compiled in formats which can be displayed and analyzed using standard commercial GIS software. The geologic data base provides the ability to generate maps based on variables such as map unit, age, and lithology at several levels of detail. Geochemistry files include both major and trace element analyses and related information on analytical technique, laboratory, and date of analyses. Geochronology files include data for all isotopic systems, standardized to current decay constants, although in most instances U/Pb zircon and baddeleyite ages provide the most reliable ages. Mineral deposit information includes data on location, commodities, deposit type, size, status, and production, including the famous native copper deposits as well as magmatic Cu-Ni-PGE sulfide deposits of present-day exploration and development interest. This GIS product allows, for the first time, a quick and easy search of most publicly available earth science information on this geologically and economically important province. This presentation highlights the features of the database, including the digital map compilation.