Explained by Alan R. Wallace
On the choice of deposit models
Modern hot springs are common in New Mexico, and geothermal activity was undoubtedly associated with the many Tertiary volcanic centers in New Mexico. Erosion has probably stripped away many potential deposits, but others many be concealed in volcanic piles such as the Mogollon volcanic field or still preserved due to their relative youth. We used the descriptive model of Berger (1986) and the grade and tonnage model of Berger and Singer (1992).
On the delineation of permissive tracts
Two broad areas were deemed permissive for hot-spring gold-silver deposits: (1) thick volcanic piles, such as the Mogollon and Jemez volcanic fields, where hot-spring deposits related to volcanic activity could have been concealed by subsequent eruptions, and (2) areas of modern geothermal activity, principally along the Rio Grande rift but also in the Jemez volcanic field, some of which may be generating or have already generated a gold deposit.
Important examples of this type of deposit
No true hot-springs gold-silver deposits have been reported in the State. Possible examples may include parts of the Wilcox, Mogollon, and Gila districts.
On the numerical estimates made
Parts of New Mexico are known for their past and present high heat flow, and the permissive tracts easily could conceal a geothermal center, although very few such centers produce gold-silver deposits of the size consistent with the grade and tonnage model. Nevertheless, the presence of concealed volcanic rocks in the various volcanic fields and the presence of modern geothermal activity permits some chance for the existence of a hot-spring gold-silver deposit in the permissive areas. For the 90th, 50th, 10th, 5th, and 1st percentiles, the team estimated 0, 0, 0, 1, and 2 or more deposits consistent with the grade and tonnage model for hot-spring gold-silver deposits (Berger and Singer, 1992).
Berger, B.R., 1986, Descriptive model of hot-spring Au-Ag deposits, in Cox, D.P., and Singer, D.A., eds., Mineral deposit models: U.S. Geological Survey Bulletin 1693, p. 143.
Berger, B.R., and Singer, D.A., 1992, Grade and tonnage model of hot-spring Au-Ag, in Bliss, J.D., ed., Developments in mineral deposit modeling: U.S. Geological Survey Bulletin 2004, p 23-25.