Porphyry-Copper Ore Shells Form at Stable Pressure-Temperature Fronts Within Dynamic Fluid Plumes

Abstract

Earning a High Grade Most of the world's copper and molybdenum come from porphyry-type ore deposits in Earth's crust. The metals are deposited either as veins of concentrated metals in fractured rock or in a confined shell, associated with the edges of magma chamber plumes. But it remains unclear why a front of sharp temperature-pressure gradients, which allows the accumulation of high-grade metal deposits, remains stable. Weis et al. (p. 1613 , published online 15 November; see the Perspective by Ingebritsen ) constructed a hydrothermal model of a porphyry-type system given a supply of magmatic fluids with high metal concentrations. The thermodynamic properties of injected volatile fluids and dynamic variations in host rock permeability, driven by injection-induced fracturing, controlled the stability and evolution of the fronts and allowed for the formation of an extensive network of ore veins from within the magmatic chamber.