Earth's copper resources estimated from tectonic diffusion of porphyry copper deposits

Improved estimates of global mineral endowments are relevant to issues ranging from strategic planning to global geochemical cycling. We have used a time-space model for the tectonic migration of porphyry copper deposits vertically through the crust to calculate Earth's endowment of copper in mineral deposits. The model relies only on knowledge of numbers and ages of porphyry copper deposits, Earth's most widespread and important source of copper, in order to estimate numbers of eroded and preserved deposits in the crust. Model results indicate that approximately 125,895 porphyry copper deposits were formed during Phanerozoic time, that only approximately 47,789 of these remain at various crustal depths, and that these contain approximately 1.7X10 (super 11) tonnes (t) of copper. Assuming that other types of copper deposits behave similarly in the crust and have abundances proportional to their current global production yields an estimate of 3X10 (super 11) t for total global copper resources at all levels in Earth's crust. Thus, approximately 0.25% of the copper in the crust has been concentrated into deposits through Phanerozoic time, and about two-thirds of this has been recycled by uplift and erosion. The amount of copper in deposits above 3.3 km, a likely limit of future mining, could supply current world mine production for 5500 yr, thus quantifying the highly unusual and nonrenewable nature of mineral deposits.