Browsing by Author "Perez-Flores, Pamela"

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    Decoding the state of stress and fluid pathways along the Andean Southern Volcanic Zone
    (2023) Perez-Estay, Nicolas; Ruz-Ginouves, Javiera; Perez-Flores, Pamela; Sielfeld, Gerd; Roquer, Tomas; Cembrano, Jose
    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 similar to 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.
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    Tectonic setting, structures, and Au-Cu mineralization age of the Indiana deposit: An example of ore deposit formation controlled by Andean transverse faults, Atacama region, Chile
    (2024) Reinoso, Felipe; Marquardt, Martin; Cembrano, Jose; Perez-Flores, Pamela; Diaz-Alvarado, Juan; Folguera, Andres
    The Indiana Deposit corresponds to a Cu-Au (Mo-Co) fault-vein deposit located in the Central Andes Coastal Cordillera Belt (similar to 27 degrees S). It is hosted by strongly altered volcanic and intrusive rocks located between the NNE-striking central and principal branches of the Atacama Fault System (AFS) in northern Chile. The Indiana Deposit is part of a 10 km-long and 5 km-wide mine district that includes the Iron-Copper bearing Cerro Negro Norte (CNN) deposits and the Cu-Au Galleguillos vein system, termed the CNN-Indiana District in this study. The district provides insights into the mid-Cretaceous structural and lithological control of iron, copper and gold mineralization in northern Chile.Mineralization in the Indiana Deposit is spatially and temporally related to NW- and ENE-striking fault-vein systems, which are kinematically unrelated to the AFS. Three main mineralized ENE-striking, hundred-meter-long structures have been identified in Indiana. Structural and kinematic data suggest that mineral precipitation took place at dilation zones (e.g. extensional jogs, transtensional fault terminations) generating steeply-plunging ore shoots, and reactivating pre-existing structures (NW fault-vein system).Sinistral transtensional kinematics observed in ENE-striking fault-vein structures postdate the activity of the margin-parallel Atacama fault system, which has for long been regarded as accommodating the strike-slip component of plate convergence during the Jurassic to middle Cretaceous neglecting the role of Andean Transverse Faults (ATF), such as the ones recognized in this study. Sinistral transtension along ENE-striking faults gave rise to a local NE-striking maximum principal stress, different from that arising from displacement along the main margin-parallel faults, which in turn is consistent with far field stresses at that time.The CNN-Indiana district evolved from an early Ca-Na high temperature system related to Iron-bearing deposits to a brittle mineralized fault-vein copper-gold-bearing quartz-sericite (k-feldspar-calcite) corridor associated with a lower temperature environment along the Costal belt.Re-Os ages yielded 109-108 Ma obtained along the mineralized ENE-striking structures in Indiana Deposit and are slightly younger than those obtained from similar deposits associated with deformation along the AFS, which is consistent with our field observations indicating that at least part of the strike slip displacement on transverse faults hosting mineralization outlasts that of the AFS.
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    The orientation of intra-arc crustal fault systems influences the copper budget of magmatic-hydrothermal fluids
    (2024) Tardani, Daniele; Tassara, Santiago; Sanchez-Alfaro, Pablo; Reich, Martin; Perez-Flores, Pamela; Robidoux, Philippe; Contreras, Claudio; Pinti, Daniele L.; Cembrano, Jose; Ague, Jay. J.
    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.