Giant Metallic Deposits–a Century of Exponential Progress

Abstract

A magnitude of metallic deposits can be rationally defined by reference to mean crustal contents of elements (Clarkes), thus: “economic” metal content in a deposit divided by Clarke of the metal that equals the tonnage of continental crust that would contain the same amount of trace metal in Clarke concentration” (Laznicka, 2010, 2014). There, by convention, a “giant” deposit starts at n x 10 crustal tonnage equivalent, supergiant deposit starts at n x 10. Because metal Clarkes vary, metal “giants” magnitudes vary as well so Au “giant” starts at 250 t Au, Cu “giant” at 2.5 Mt Cu, Fe “giant” at 4 Gt Fe. These metal magnitude thresholds vary with Clarke values published by the various authorities; ours are based on Wedepohl (1995). The main advantage of this “macrogeochemical” approach is that it provides rational means for comparison of all metallic deposits with very different Clarke values, free of economic factors, thus compatible with quantitative (macro)geochemical studies of ore deposit formation and distribution. One can thus numerically evaluate efficacies of metal accumulating systems in nature. Based on continuously updated database (Giantdep 3), there are now 1,308 giant and supergiant metal accumulations (1171 giants and 137 supergiants) reported, in 915 deposits and some districts (this is because some deposits contain more than one metal accumulation; the Olympic Dam deposit has five: Cu,Au,U,Ag,REE). As definition of the “ore giants” depends on published quantitative data, those deposits lacking such data are not yet included (about 50 deposits). Fig. 1 shows the distribution of “giants” and “supergiants” Peter LAZNICKA, 2014. Giant Metallic Deposits--a Century of Exponential Progress. Acta Geologica Sinica (English Edition), 88(supp. 2): 90-92.