Distribution of Principal Gold Producing Districts of the United States
About one-half of the gold mined in the United States has come from the 25 districts listed in figure 2.
FIGURE 2. - Gold production (to nearest 1,000 ounces) of 25 principal gold-mining districts of the United States - through 1959.
GEOLOGIC RELATIONS
In general, gold is derived from three types of ore: (1) ore in which gold is the principal metal of value, (2) base-metal ore which yields gold as a byproduct, and (3) placers.
Most of the principal gold-producing districts are in the mountainous areas of the United States, where folding, faulting, and igneous intrusions have deformed the rocks. In contrast, many large base-metal deposits are found in the large relatively un-deformed areas of the Central and Eastern States, but gold is not even a byproduct of these ores. Large parts of the Western States, such as the Colorado Plateau, the Columbia Plateau, and much of Wyoming, have not been subjected to violent tectonic forces and consequently contain very few gold deposits.
The occurrence of gold is erratic and many rich ore deposits have yielded relatively little or no gold. Foremost among these are the large silver-lead de¬posits of Coeur d'Alene, Idaho, Aspen, Colo., and Magdalena, N. Mex.; the copper deposits of Copper Mountain (Morenci), Ray, Miami, and Superior in Arizona; and the copper deposits of Santa Rita, N. Mex., and the Keweenaw Peninsula, Mich.
Most of the gold deposits in the United States are associated with and are perhaps genetically related to small batholiths, stocks, and satellitic intrusive bodies of quartz monzonitic composition that range in age from Jurassic to Tertiary. Some deposits, such as those in the Southeastern States, may be genetically related to granitic bodies that were in¬truded at the close of Paleozoic time, and a few deposits, as at Jerome, Ariz., are Precambrian in age.