Ore deposits of the western United States in relation to mass distribution in the crust and mantle

Abstract

Colored, digital residual Bouguer gravity maps of the conterminous United States at different cutoff wavelengths reveal significant compositional heterogeneities in the lithosphere, providing a new tool for the studies of controls of mineralization. Examples are presented showing correlations between main endogenic ore deposits of the western United States and gravity anomalies in the residual Bouguer gravity maps at 250-, 625-, and 1,000-km wavelength cutoffs. Some of the clusters of ore deposits are in or adjacent to regions of gravity lows (for example, the majority of deposits of the Colorado mineral belt). Most of the high-amplitude gravity lows reflect low-density igneous masses emplaced along zones of tectonic weakness which guided the ascent of magmatic fluids and caused major geochemical changes in the lithosphere. Some clusters of ore deposits (for example, the group of Tertiary deposits of the Salt Lake City area, Utah, including Bingham, Tintic, Park City, and others) are along the flanks of major zones of gravity highs. In the Salt Lake City area, the major concentrations of metals occur near the eastern edge of a broad gravity high that correlates with crustal thinning. These relations (and others) between the location of major ore deposits and mass distribution in the crust and upper mantle may serve as general guidelines in mineral exploration on a regional scale.