Inside Porphyry and Epithermal Deposits: The Geology of Earth’s Most Productive Mines

From Mining Visuals

In March 2025, the USGS published an updated global database cataloguing every known porphyry copper deposit on Earth, a remarkable cartographic exercise for a deposit type that already supplies the planet with about 60% of its copper. What the database does not show is that the same magmatic engine produces a second, very different ore type immediately above: epithermal gold-silver veins, which the corresponding USGS model credits with about 8% of global gold supply. The accompanying infographic shows both halves in cross-section. The deeper story is that this single architecture, replicated along convergent plate margins for hundreds of millions of years, has built the world’s largest copper mines and its richest precious-metal veins, often stacked vertically in the same district.