Discovery of Giant Metal Deposits and Districts

摘要

It is a popular belief that exceptional metallic deposits have been formed first, that is earlier than the bulk of lesser-size deposits, because of their supposedly striking appearance. The reality is, however, different and only about 13 locations out of a population of 337 had been found by the end of 15th century. The graph of discovery dates of the giant and supergiant deposits (i.e. those with tonnage-accumulation index of the order of 10" and 10'2) shows an almost exponential increase of giant ore discoveries after the year 1800, culminating around 1975. The rate of finding new giants has declined since than time. The sharp increase in the discovery rate iri the modern period is due to the increasing market demand for metals that were not sought earlier, growth of industrial output, new ore types, and greatly improved geological knowledge and exploration technology. About 30% of all giant discoveries have been made by chance, but only 5.5% between 1965 and 1995. 14.5% of finds are due to government workers and enterprises; 24% to "unsophisticated" prospecting; and 31% to comnplex exploration by predomianntly private corporations.