From rocks to ore

Metal enrichment to ore grade is the ultimate outgrowth of large-scale and long-term fractionation processes of the thermally driven and unique water-cooled geological evolution of the Earth. Silicic magmatism along convergent margins is the most important lithospheric fractionation process for the formation of the continental crust and porphyry/intrusion-related ore deposits. Reconnaissance microanalysis of melt inclusions from Central Andean porphyry systems refines a metallogenic model for copper–gold and tin porphyry mineralization. Magmatic mixing and early exsolution of a fluid phase are important ingredients for porphyry Cu–Au systems in association with silicic rocks of moderate levels of fractionation (such as diorites and monzonites), whereas extended magmatic fractionation with late-stage fluid evolution characterize lithophile-element-enriched tin porphyry systems.