External authors:

• Daniele Tardani ( Universidad de Chile , Universidad de O'Higgins )
• Santiago Tassara ( Universidad de O'Higgins )
• Pablo Sanchez-Alfaro ( Universidad de Chile , Universidad Austral de Chile )
• Martin Reich ( Universidad de Chile )
• Pamela Perez-Flores ( Consultoria Invest Geol Ambiental Ltda CIGEA Ltda )
• Philippe Robidoux ( Universidad de Chile )
• Claudio Contreras ( Universidad de O'Higgins , University of Bristol )
• Daniele L. Pinti ( University of Quebec Montreal )
• Jay. J. Ague ( Yale University )

Abstract:

Some of the largest magmatic-hydrothermal copper ore deposits and deposit clusters are associated with arc-oblique fault systems. Whether this structural context impacts the geochemistry of hydrothermal fluids, including their copper contents, remains unknown. Here, we investigate the copper concentration and helium isotope signature of geothermal fluids as modern analogs of hydrothermal ore deposits in the Andes of central-southern Chile. We show that fault systems broadly parallel to the regional stress field facilitate the early release of fluids from deep primitive magmas. By contrast, fault systems oblique to the regional stress field prevent the early escape of fluids and promote magmatic enrichment in copper, volatiles, and ligands, enhancing the potential to form copper deposits. We conclude that the orientation of fault systems actively influences the copper budget of ascending hydrothermal fluids, explaining the contrasting distribution of metals along distinct structures often observed in porphyry-epithermal systems and other types of magmatic-hydrothermal deposits.\nThe enrichment of copper in magmatic hydrothermal fluids is influenced by the orientation of fault systems in arcs, according to geochemical analyses of gases and hot spring waters from active fumarole fields in the Southern Volcanic Zone of Chile.