East-west patterns of Cenozoic igneous rocks, aeromagnetic anomalies, and mineral deposits, Nevada and Utah

Abstract

In Nevada and western Utah, Cenozoic igneous rocks within several age increments crop out in arcuate, generally east-trending belts, each successively younger to the south. Broad aeromagnetic highs with superimposed short-wavelength anomalies are associated with some of these outcrop belts. Mineral deposits are aligned along the belts in easternmost Nevada and western Utah. The east-west patterns are the result of a southward-migrating front of igneous activity that, in Nevada and Utah, started about 43 to 34 m.y. ago near lat 40°N and ended about 17 to 6 m.y. ago near lat 37°N. During any one time interval, igneous activity was concentrated near the leading edge of the east-trending front. The volcanic front may be related to igneous activity localized along a southward-propagating transverse break or structural warp in a subducting plate.