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Understanding Our Planet Through Chemistry

Keeping Track of the Resources of Our Country

Congress has mandated the USGS to assess the mineral-resource potential of public lands, especially those lands set aside as wilderness or proposed wilderness. These assessments provide an inventory of mineral resources for future generations. In 1964, the Wilderness Act was passed, and a 20-year program to assess the mineral resources of U.S. Forest Service wilderness areas began. A large amount of this work involved the analysis of stream sediments to determine the presence or absence of halos. Subsequent laws have required mineral-resource assessments on additional public lands. The USGS also works with the Bureau of Indian Affairs and individual tribes to assess the mineral resources on Indian lands.

By relating ore-deposit models and geochemical data to geologic observations and plate tectonic theory, geologists can predict what types of ore deposits may be found in a given geographic area. The USGS supplies this information to the public and to other government agencies. Assessments are published by the USGS for use by land-use planners, Federal, state, and local government agencies, environmentalists, and private individuals. Many maps, such as the map of lead in stream sediments of Colorado, are useful for both resource evaluations and environmental assessments.

Map of Colorado showing lead concentration in stream sediments. This map of lead in Colorado stream sediments was generated with existing data from the National Geochemical Data Base. It shows the presence of a geochemical halo from the Colorado Mineral Belt and also the lead caused by industry in some cities.[12k] [20k]

It is important to weigh the mineral-resource potential of a tract of land against other potential uses such as water resources, grazing, forestry, recreation, tourism, and scenic value. Chemistry plays a vital role in this assessment process.

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