Pamela Pérez-Flores

Many epithermal ore deposits form in fault-veins that channel large volumes of vertical fluid flow synkinematic with fault slip. A key genetic process is the interplay among fluid flow, fault activation, and mineral precipitation; however, significant questions remain regarding the mechanics of fault slip under high fluid-flux conditions and its impact on mineralisation. A fundamental question is whether ore deposition is coseismic, post-seismic, or interseismic—specifically, whether pressure drops during seismic rupture are the dominant trigger for mineral precipitation, or whether mineralisation occurs during longer-lived, aseismic creep and sealing cycles. A deeper understanding of these processes is essential for predicting ore grade and spatial distribution.The Cretaceous Indiana deposit, located in the Coastal Cordillera of northern Chile, is a Cu–Au (Mo–Co) fault-vein system composed of several subvertical NW- or ENE-striking fault veins, with lengths ranging from 300 m to 2 km. Artisanal tunnels provide access to multiple structural levels in oxides and sulphides mineralization, offering exceptional three-dimensional exposure. NW-striking fault-veins host Au–Cu-Fe–Co-rich mineral assemblages associated with pyrite, chalcopyrite, magnetite, actinolite, albite, garnet, epidote, quartz, tourmaline, and late jarosite, clay and hematite. These are cross-cut by ENE-striking fault-veins containing Au–Cu–Mo-Co mineralisation in pyrite and chalcopyrite paragenetically associated with garnet, epidote, actinolite, quartz, and less sericite. High-grade ore shoots commonly occur in dilatational jogs and at the intersections between these two structural sets.Fault-veins are 1–3 m wide and display complex internal structures. Fault zones of variable thickness occur along the vein margins and mainly record strike-slip motion, expressed as thin (

Decoding means decrypting a hidden message. Here, the encrypted messages are the state of stress, fluid pathways, and volcano tectonic processes occurring in volcanoes of the Andean Southern Volcanic Zone (SVZ). To decode these messages, we use earthquake focal mechanisms, fault slip data, and a Monte Carlo simulation that predicts potential pathways for magmatic and hydrothermal fluids. From this analysis, we propose that SVZ volcanoes have three end-member stress patterns: (i) Stress-A, a strike-slip regime coupled with the regional far-field tectonic stress; (ii) Stress-B, an extensional regime that may be promoted by volcanic edifice loading and upward pressure due to magma inflation occurring within the upper brittle-crust; and (iii) Stress-C, a local and transient fluid-driven stress rotated ~90 degrees from Stress-A. Notoriously, Stress-C pattern was observed in most volcanoes with historical eruptions. We propose that volcanoes presenting Stress-B are attractive geothermal targets, while Stress-C could be used as a predicting signal for impending eruptions.