COPPER 



181 



coveries and estimated mine production, respec- 

 tively. Low-grade deposits are not included here but 

 are discussed under "Subeconomic Resources" of 

 this chapter. 



Hypothetical resources given in table 39 are those 

 that have not been found but whose existence is 

 suspected, as in concealed parts of known mineral 

 districts, in projections of incompletely explored 

 mineral belts, and in areas near important isolated 

 new discoveries that suggest the possibility of a 

 future mining district. The largest hypothetical re- 

 serves are in the Western United States, South 

 America, Africa, and the U.S.S.R., all areas of 

 favorable geologic setting and much recent success- 

 ful exploration. 



Hypothetical resources in the Western United 

 States comprise the concealed deposits under basin 

 fill in the major porphyry copper regions, a possible 

 new porphyry copper province in the Absaroka 

 Range of Wyoming, and the great resources of sedi- 

 mentary copper in the Belt Supergroup of Idaho and 

 Montana. Alaskan hypothetical resources are based 

 on favorable evaluation of porphyry deposits in 

 eastern Alaska and of replacement deposits in car- 

 bonate rocks on the south slope of the Brooks Range. 

 Canadian hypothetical resources are in British 

 Columbia and Yukon Territory. South American 

 resources are in the Andes of Chile, Peru, Ecuador, 

 and Argentina, and the estimate is probably con- 

 servative. African hypothetical resources are in the 

 copper belt region and in the Precambrian rocks of 

 southwest Africa. U.S.S.R. hypothetical resources 

 are large, and the estimate of 50 million tons may be 

 conservative; the resources comprise undiscovered 

 porphyry deposits in the Kazakhstan and Uzbekstan 

 regions and copper-bearing sedimentary strata in 

 several areas. Another area where future discovery 

 of important copper porphyry deposits can be rea- 

 sonably expected is in the central Iranian volcanic 

 belt northwest from the known porphyry occur- 

 rences near Kerman through the area near Hama- 

 dan and Tabriz and then westward across northern 

 Turkey. In this area some types of copper minerali- 

 zation related to intrusions have been reported by 

 Superceanu. (1971, p. 395). The areas of copper 

 prospects in northeastern and east-central Iran that 

 may have potential for large copper deposits are 

 discussed under "Speculative Resources." 



The identified resources in the United States, 76 

 million tons of copper metal, are enough to last the 

 country 45 years at the constant-use rate of 1.7 

 million tons per year; the world identified resource 

 of 344 million tons will last 50 years at the rate of 

 6.9 million tons per year. At the same use rates. 



hypothetical resources add 60 years supply to the 

 United States and 58 years supply to the world. 



SPECULATIVE RESOURCES 



During the last decade many new mineral prov- 

 inces and districts were discovered and developed. 

 Important examples of these are the porphyry cop- 

 per deposits of the Canadian cordillera, the South- 

 west Pacific, and Iran. These areas had previously 

 received little attention, and deposits of the por- 

 phyry type were thought to be limited mostly to 

 Southwestern North America and the Andes. Simi- 

 larly, sedimentary copper deposits, previously con- 

 sidered as rather unique occurrences, have been dis- 

 covered in the Western United States and in eastern 

 U.S.S.R. The development of these new provinces 

 has drastically increased the resources. 



There is considerable likelihood of finding even 

 more new copper provinces given the new knowledge 

 of copper metallogeny and perhaps aided by the 

 same combination of economic boom and high metal 

 prices that existed in the last decade. Future dis- 

 coveries of porphyry copper and sedimentary cop- 

 per deposits are more likely to have a major impact 

 on the world's copper resources, and these types 

 will receive the greatest attention. Unfortunately, 

 not enough is known of the stratigraphic and paleo- 

 tectonic controls of sedimentary copper deposits to 

 be able to point to many areas with potential re- 

 sources of this type. 



In the United States, the greatest likelihood of 

 new discoveries lies in the Southwest. In Arizona, 

 the search for new porphyry copper deposits has 

 been concentrated in the southeastern part of the 

 State because of the greater number of known de- 

 posits and because more is known about the geology, 

 geophysics, and geochemistry. Most of the south- 

 western, western, and northwestern parts of the 

 Basin and Range province has not been evaluated 

 adequately in reconnaissance, much less in detaill. 

 Adequate geologic maps exist for only a few widely 

 separated areas. The reasons for this are many and 

 include inaccessibility, restricted access to military 

 bombing ranges and Indian reservations, and in- 

 hospitable climate. Nevertheless, from what is 

 known, these are pristine exploration areas, and 

 must be considered to contain many copper deposits. 

 On the basis of a simple comparison with the con- 

 centration of copper deposits in southeastern Ari- 

 zona, and generally favorable regional geology, an 

 order of magnitude of 10** tons is estimated for 

 these areas. 



Elsewhere in the Western United States, the 

 Mountain City copper deposit in Elko County* Nev., 



