TIN 



647 



tin deposits in areas they penetrated. 

 4. Finally, with the possible exception of commer- 

 cial deposits of chromite, tin displays such a 

 well-marked geologic association — with acid 

 granitic rocks or rhyolite — that speculation as 

 to the finding of major tin reserves and re- 

 sources in entirely new geologic environments 

 is without any redeeming value; it is like 

 speculation as to the possibility of the seventh 

 dimension, and the planning of structures 

 based upon the speculative existence of it. 

 In assembling the table of undiscovered resources, 

 it has been assumed that but a few new tin deposits 

 will be found. For instance, the estimate of U.S. 

 resources includes the assumption that tin deposits 

 may be found on the Aleutian Islands, whose geology 

 is roughly comparable to the Japanese Islands, which 

 have produced moderate amounts of lode tin. Some 

 tin deposits may be found in the southern Alaska 

 Range, where placer tin has long been known and 

 where Reed and Elliot (1970) have found tin anoma- 

 lies in stream sediments near biotite granites. Analy- 

 ses of placer concentrates collected between 1900 

 and 1954 from many Alaskan streams have shown 

 that noteworthy tin occurs in numerous localities 

 where tin deposits are not known (J. C. Hamilton, 

 written commun., 1972). Tin-bearing lodes may be 

 found, but no major new districts are believed likely 

 to exist near such areas. In Canada, perhaps a few 

 more mines similar to the Sullivan will be found, as 

 will be more mines similar to the Mount Pleasant in 

 eastern Canada. But speculation about the finding 

 of large reserves in North America faces one rigid 

 fact — there are no known large tin deposits, lode or 

 placer, even in areas with favorable rock types. 

 Again, most of these areas have been panned by the 

 gold seekers. , 



On the basis of the above factors, one cannot 

 reasonably expect to find speculative resources of 

 any magnitude in the United States, and areas fav- 

 orable for new deposits in North America are vir- 

 tually limited to areas such as the Canadian Shield 

 or the rhyolite areas of Mexico. Such deposits likely 

 will be small. 



In South America, areas may remain in Rondonia, 

 possibly even in easternmost Bolivia, in which many 

 new deposits similar to those now known may be 

 found. This leads to large speculative resources in 

 South America. Inasmuch as the large Rondonian 

 deposits occur in and near Precambrian granites, 

 one can speculate that the Precambrian Shield areas 

 in the Guianas and eastern Colombia may also 

 contain tin deposits. Perhaps a field even as large 

 as the Nigerian tin fields could exist there. Else- 



where in South America, speculative placer resources 

 in Bolivia would exist near some lode tin deposits 

 and hypothetical resources would be in deeper, un- 

 known ore bodies in known districts. 



In Europe, there is little likelihood for the dis- 

 covery of large new districts. However, it is as- 

 sumed that at least 10 more Wheal Jones, or South 

 Croftys, will ultimately be found in the old estab- 

 lished Cornish mining district. In Spain and Portu- 

 gal, because of the favorable geology, the known 

 deposits, and the archaic state of mining and ex- 

 ploration, large amounts of tin are assumed to 

 remain in unknown deposits. Nowhere else in Europe 

 can one postulate substantial tin resources, even in 

 the Erzgebirge, because the intensive exploration 

 and mining by the Germans during World War II 

 have exhausted that possibility. 



In Asia, the long history of mining, the great ex- 

 tent of the placer deposits, and the remoteness of 

 much of the jungle country probably insure that 

 new lode and placer deposits will be found. Large 

 reserves undoubtedly lie offshore on the Sunda Shelf 

 and ultimately will be found and mined. Tin will be 

 found in Burma, perhaps mostly associated with 

 tungsten deposits, but most of this tin will be in 

 the known tin belt. 



Because of the remoteness, the jungle cover, and 

 the relative recency of the discovery of the tin 

 fields of Zaire, both sufficient area and favorable 

 geology indicate the possibility for discovery of an- 

 other tin field the size of the Nigerian field. In 

 northern Africa, the scattered known deposits, asso- 

 ciated with biotite granite, the remoteness of the 

 area, and the poor state of geologic knowledge all 

 suggest that tin deposits may be found there. 



In Australia, the rapid resurgence of tin mining 

 since 1965 proves that new deposits will be found, 

 principally in Tasmania and possibly in Western 

 Australia. 



In Communist China, it is assumed that new de- 

 posits will be found in the remote ranges of the 

 Himalayas, as well as in known districts, when 

 modern mining and exploration techniques become 

 available, but elsewhere in China the long occu- 

 pancy by civilized people who have used tin suggests 

 that major new districts probably will not be found. 



In the U.S.S.R., tin deposits not yet known prob- 

 ably exist in the tundra-covered areas of Siberia 

 and in the Magadan area of eastern Siberia, for 

 numerous deposits have been found in these areas 

 since World War II. Despite the large number of 

 Soviet geologists actively employed in economic 

 geology, it is unlikely that Asiatic Russia has yet 

 been adequately explored, though it is unlikely, too, 



