Porphyry copper deposits represent an important resource and the dominant source of copper that is mined today to satisfy global demand. Via compilation of geological data, it has been found that the majority of porphyry deposits are Phanerozoic in age and were emplaced at depths of approximately 1 to 6 kilometres with vertical thicknesses on average of 2 kilometres. Throughout the Phanerozoic an estimated 125,895 porphyry copper deposits were formed; however, 62% of them (78,106) have been removed by uplift and erosion. Thus, 38% (47,789) remain in the crust, of which there are 574 known deposits that are at the surface. It is estimated that the Earth's porphyry copper deposits contain approximately 1.7×1011 tonnes of copper, equivalent to more than 8,000 years of global mine production.