Regional crustal structures and their relationship to the distribution of ore deposits in the western United States, based on magnetic and gravity data

Upgraded gravity and magnetic databases and associated filtered-anomaly map s of western United States de fine regional crustal fractures or faults tha t ma) have guided die emplacement of plutonic rocks and large metallic ore deposits. Fractures, igneous intrusions, and hydrothermal circulation tend to be localized along boundaries of crustal blocks. with geophysical expres sions that are enhanced here by wavelength filtering, In particular, we exp lore the utility. of regional gravity and magnetic data to aid in understan ding the distribution of large Mesozoic and Cenozoic ore deposits, primaril y epithermal and porphyry precious and base metal deposits and sediment-hos ted gold deposits in the western United States cordillera. On the broadest scale, most ore deposits lie within areas characterized by low magnetic properties. The Mesozoic Mother Lode gold belt displays charac teristic geophysical signatures (regional gravity high, regional low-to-mod erate background magnetic field anomaly: and long curvilinear magnetic high s) that might serve as an exploration guide. Geophysical lineaments charact erize the Idaho-Montana porphyry belt and the La Caridad-Mineral Park belt (from northern Mexico to western Arizona) and thus indicate a jeep-seated c ontrol for these mineral belts. Large metal accumulations represented by th e giant Bingham porphyry copper and the Butte polymetallic vein and porphyr y coppers systems lie at intersections of several geophysical lineaments. A t a more local scale, geophysical data define deep-rooted faults and magmat ic zones that correspond to patterns of epithermal precious metal deposits in western and northern Nevada. Of particular interest is an interpreted de nse crustal block with a shape that resembles the elliptical deposit patter n partly formed by the Carlin trend and the Battle Mountain-Eureka mineral belt. We support previous studies, which on a local scale, conclude that structur al elements work together to localize mineral deposits within regional zone s or belts. This study of mineral deposits of the western United States dem onstrates the ability of magnetic and gravity data to elucidate the regiona l geologic framework or structural setting and to contribute in locating fa vorable environments for hydrothermal mineralization.