442 



UNITED STATES MINERAL RESOURCES 



sulfide estimates might be doubled by new discov- 

 eries; the laterite estimate probably will not be as 

 greatly expanded. 



As mentioned above, if a practical method is 

 found to extract the 0.2-0.4 percent of nickel uni- 

 versally disseminated through peridotites and ser- 

 pentinites, vast amounts of nickel will become avail- 

 able. The total of estimates given in the preceding 

 paragraph would be increased by several orders of 

 magnitude. The potential size of nickel resources in 

 unknown areas of deep-sea manganese nodules could 

 be enormous. 



PROSPECTING TECHNIQUES 



Prospecting and exploration techniques are quite 

 different for the sulfide-, laterite-, and nodule-types 

 of nickel deposits. Prospecting for nickel sulfides 

 can be well illustrated by briefly describing the 

 methods used by Inco (International Nickel Co. of 

 Canada, Ltd.) in their discovery of the major 

 Thompson district in Manitoba in 1956. Geologists 

 first studied aerial photos to find major structural 

 lineaments and bodies of favoi-able rocks such as 

 ultramafics with which nickel deposits are known 

 to be associated. Such a lineament was discovered 

 trending southwest from Hudson Bay through the 

 Thompson area. The area was then flown with air- 

 borne magnetometer and electromagnetic equipment. 

 Areas of coincidence of high magnetic anomalies 

 and high electromagnetic conductivity were selected 

 for exploration by diamond drilling. This drilling 

 led to the discovery of two very large deposits of 

 low-grade disseminated nickel sulfides in serpen- 

 tinized peridotite intrusives. Attention was then 

 turned to electromagnetic conductors that coincide 

 with small magnetic anomalies. Such drilling re- 

 sulted in the discovery of the Thompson deposit of 

 nickel and iron sulfides in biotite schist that aver- 

 ages 3 percent nickel and extends for 31/2 miles 

 laterally and over 2,000 feet vertically. 



Prospecting for nickel laterites involves first the 

 identification of large laterite (intensely weathered 

 saprolitic soils) areas overlying ultramafic rocks. 

 Most of the large nickel or nickel-iron laterites have 

 probably been found; they occur in or near the 

 tropics and lie on Tertiary erosion surfaces. The 

 first step in the search for such laterites is the 

 delineation of old erosion surfaces in favorable 

 areas. Then the areas of ultramafic rocks are out- 

 lined and the most promising selected for sampling 

 on 500-foot or smaller centers. Sampling is done by 

 augering or by digging pits. Nickel, iron, and mag- 

 nesium determinations are made for 1- to 5-foot 

 lengths in each hole. Thus areas of ore grade (com- 



monly those of higher than 1 percent nickel) are 

 delineated. 



Nickel-bearing manganese nodules on the deep 

 ocean floor are explored by dredging and bottom 

 photography. 



PROBLEMS FOR RESEARCH 



Problems of developing potential nickel resources 

 come under three headings : scientific, technological, 

 and political. 



Research on the origin of the metamorphosed 

 ultramafic deposits (Thompson type) would almost 

 certainly pay dividends in the form of new discov- 

 eries. How does the nickel occur in these peridotites, 

 and what happens to it during metamorphism ? 

 What are the most favorable environmental factors 

 for the formation of this type of deposit? What 

 criteria can be used in searching for similar depos- 

 its elsewhere in the world? 



The technological breakthrough of greatest po- 

 tential value would be development of a technology 

 for the extraction of nickel that is universally pres- 

 ent in peridotites and serpentinites in small but 

 abnormal amounts. For ocean-bottom manganese 

 nodules, the cost and difficulty of recovery from 

 mid-ocean depths of 3,500-4,500 meters are major 

 problems. The separation and refinement of the 

 nickel and other metals from the nodules also poses 

 a metallurgical problem that has not yet been re- 

 solved. 



REFERENCES CITED 



Cornwall, H. R., 1966, Nickel deposits of North America: 

 U.S. Geol. Survey Bull. 1223, 62 p. 



Fleischer, Michael, 1953, Recent estimates of the abundances 

 of the elements in the earth's crust: U.S. Geol. Survey 

 Circ. 285, 7 p. 



Hawley, J. E., 1962, The Sudbury ores, their mineralogy and 

 origin — Pt. 3, Interpretations — The history and origin 

 of the Sudbury ores: Canadian Mineralogist, v. 7, pt. 

 1, p. 146-207. 



McKelvey, V. E., and Wang, F. F. H., 1969, World subsea 

 mineral resources: U.S. Geol. Survey Misc. Geol. Inv. 

 Map I-632-A, 17 p. 



Mason, B. H., 1958, Principles of geochemistry: New York, 

 John Wiley and Sons (2d ed.), 310 p. 



Michener, C. E., 1957, Genesis of mineral deposits and ex- 

 ploration : Canada Natl. Advisory Comm. Research Geol. 

 Sci. Ann. Rept., 7th, 1956-57, p. 13-14. 



U.S. Bureau of Mines, 1952, Materials surveys on nickel, 

 1950: Washington, U.S. Govt. Printing Office, 301 p. 



Vinogradov, A. P., 1956, The regularity of distribution of 

 chemical elements in the earth's crust: Geochemistry 

 (Geokhimiya), no. 1, p. 1-43 (English ed.). 



Yates, A. B., 1948, Properties of International Nickel Com- 

 pany of Canada [Sudbury area, Ontario] in Canadian 

 Inst. Mining and Metallurgy, Geol. Div., Structural 

 geology of Canadian ore deposits, Jubilee Volume, p. 

 596-617. 



