Orogenic gold systems in 3‐D space and time

Lode gold deposits (structurally hosted gold-bearing quartz vein systems) occur in deformed, lowto medium-grade metamorphosed rocks of ages ranging from Archean to Cenozoic. They commonly form clusters along regional-scale faults or fault systems, deposited by low salinity, mixed H2O-CO2 fluids, representing a distinct mineral system1. Hronsky et al.2 proposed a unifying model for orogenic systems in which three key variables must coincide in order to concentrate significant gold resources to economic grades: 1) long-term fertilization of the upper mantle through subduction-related fluids and magmas; 2) lithosphere-scale structures providing mantle-to-crust pathways; and 3) a transient remobilization event in which gold is transported upward by fluids or magmas. Additionally, changes in ambient stress such as extensional collapse may be necessary to both trigger variables 2 and 3, and to prevent erosion of the high structural levels at which gold is trapped3.