Reconnaissance Crustal Assessment of Metallogenic Occurrence in the Central U.S.: Geotectonic Application of Satellite Magnetic Anomaly Data
Carmichael, R. S.
published: Jan 1, 1993
ArtNo. ESP136000403005, Price: 19.00 €
Deep-seated and broad-scale crustal geologic features can play an important role in the genesis and localization of metallogenic provinces. This is because of crustal tectonism, the intracratonic structural and thermal evolution of deep geologic terranes, and reactivation of major basement fracture zones. Such events can be accompanied by deep magmatism, and upwelling and circulation of mineralizing hydrothermal fluids. Long-wavelength magnetic anomaly data, from NASA's MAGSAT satellite, have been combined here with other geophysical and geological data sets to aid in interpreting the crustal framework for economic resources in the U.S. central Midcontinent. Satellite magnetometry can help define major crustal structure, past tectonic development, geologic provinces and their boundaries, and lower-crustal composition and physical properties. In the U.S. Midcontinent, the major metallic-mineral province (lead/zinc/copper/iron) is centered in the Missouri region. It lies over and around the periphery of lower-crustal terrane, as interpreted from satellite data, of very strong magnetization and thus anomalous petrology, properties, and metamorphic state. This interpreted elongate zone that deeply underlies much of the state of Missouri is the most magnetic region of the mafic lower-crustal layer in the central U.S. It has a calculated magnetization intensity of 5 to 6 amp/m (5-6 x 10-3 emu/cm3), compared to the U.S. continental lower-crustal average of 3.5 amp/m. If there is a causative relationship between paleotectonism and deep structural control of the geological emplacement of resources, then satellite magnetometry can aid reconnaissance exploration to investigate known metallogenic provinces and the potential extent of mineral resources at greater depths.