Metal provinces and metal finding in the western United States

The metal provinces are believed to outline a primitive or precrustal heterogeneity of metal distribution in the upper mantle, and the well established space and time relationship between ores and intrusive bodies is a structural rather than a genetic control. The distribution of the metal deposits of the western United States in space and time is governed by some as yet unknown deep-seated source of heat; it cannot, however, be related to current theories of ‘the new global tectonics’. Although we lack a full understanding of the processes of ore deposition, we can use the assembled data in an empirical way to guide exploration. This is outlined for the porphyry copper deposits of the southern Arizona Copper Quadrilateral. Most of the deposits are of Laramide age; one is Jurassic. Post-Laramide deformations, mainly Basin and Range orogeny, removed part of the deposits and buried the others; these are now being found where they are emerging at the eroding edges of the basins as the basin fill is being removed by erosion.