Browsing by Author "Marquardt Roman, Carlos Jorge"
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- ItemDevelopment of a geomechanical model based on suitable estimations of GSI and UCS in mining production slopes at the TilTil district, central Chile(2023) Félix Del Pozo; Eduardo Cordova; Marquardt Roman, Carlos Jorge; Rodolfo Cabezas G; Philip Benson; Nick Koor; John Browning; Rocío Rudloff
- ItemInclination and heterogeneity of layered geological sequences influence dike-induced ground deformation(2023) Matías Clunes; John Browning; Marquardt Roman, Carlos Jorge; Jorge Cortez; Kyriaki Drymoni; Janine KavanaghAbstractConstraints on the amount and pattern of ground deformation induced by dike emplacement are important for assessing potential eruptions. The vast majority of ground deformation inversions made for volcano monitoring during volcanic unrest assume that dikes are emplaced in either an elastic half-space (a homogeneous crust) or a crust made of horizontal layers with different mechanical properties. We extend these models by designing a novel set of two-dimensional finite-element method numerical simulations that consider dike-induced surface deformation related to a mechanically heterogeneous crust with inclined layers, thus modeling a common geometry in stratovolcanoes and crustal segments that have been folded by tectonic forces. Our results confirm that layer inclination can produce localized ground deformation that may be as much as 40× higher in terms of deformation magnitude than would be expected in a non-layered model, depending on the angle of inclination and the stiffness of the rock units that host and are adjacent to the dike. Generated asymmetrical deformation patterns produce deformation peaks located as much as 1.4 km away from those expected in non-layered models. These results highlight the necessity of accurately quantifying both the mechanical properties and attitude of the geology underlying active volcanoes.
- ItemInsights on Prioritization Methods for Mining Exploration Areas: a Case Study of the Tiltil Mining District, Chile(Multidisciplinary Digital Publishing Institute (MDPI), 2024) Molina Catricheo, Claudio Sebastian Ernesto; Marquardt Roman, Carlos Jorge; Jara Donoso, José Joaquin; Faúndez, Patricio IgnacioThis study proposes a simple and replicable methodology to prioritize mining exploration projects based on their geoscientific characteristics and contextual factors, which can be adapted to different mining contexts. Using the Tiltil Mining District in Central Chile as a case study, where over 100 small and medium-sized Au and Cu prospects exist, this research outlines three key stages: (1) collection of relevant data; (2) selection of the most appropriate multi-criteria decision-making methods (MCDMs); and (3) the application, analysis, and comparison of these methods. This study identifies AHP and PROMETHEE II as the most suitable MCDM for the case study. The application of these methods consistently ranked El Huracán, San Aurelio, and La Despreciada as the top three exploration priorities. The AHP’s weight assignment highlights economic, geological, and social factors as the most critical variables in determining project viability.
- ItemReconciling mechanical models of caldera ring-fault nucleation within the transcrustal magmatic system paradigm(Elsevier B.V., 2024) Villarroel, Matías; Browning, John; Marquardt Roman, Carlos Jorge; Clunes Squella, Matias; Zañartu Torres, Gabriela Antonia; Giordano, GuidoThe formation of a collapse caldera requires the nucleation of circumferential ring-faults that connect an underlying magma chamber with the Earth's surface. The roof of the magma chamber collapses as a consequence of magma withdrawal due to either over- or under-pressure within the chamber. Recent inferences have suggested that calderas may form atop complex transcrustal magma systems with several individual or interconnected magma chambers residing at depth throughout the crust. Whilst there have been several attempts to define the mechanical conditions leading to caldera fault nucleation, the assumptions for these models often rely on a single shallow magma chamber or the combination of a single shallow magma chamber with doming of a deep-seated magma reservoir. There have, so far, been no attempts to reconcile the mechanical conditions leading to ring-fault nucleation and potential collapse caldera formation with inferred geometries and arrangements of complex transcrustal magmatic systems. Here we address this issue using Finite Element Method (FEM) to reconcile mechanical conditions for caldera ring-fault nucleation within the transcrustal magma system paradigm by modeling multiple magma pocket arrangements. Out of the 150 distinct combinations of shallow magma chambers and pressure conditions that were tested, only 15% yielded the necessary conditions for the successful formation of a caldera ring-fault, supporting the need for special or very specific conditions for the occurrence of calderas in nature. Results show that relatively small lateral distances in the position between magma chambers inhibit the stress conditions required for caldera fault nucleation and propagation. Changes in the vertical spacing between stacked magma chambers do not significantly alter the distribution of either tensile or shear stress. This implies that the specified criteria for initiating ring-faults are consistently met, regardless of the number or arrangement of magma chambers. However, vertical offsets between laterally distributed magma compartments lead to an uneven distribution of shear stress, potentially triggering a trapdoor-type collapse. Consistent with the results presented here, the concept of vertically stacked magma compartments has been proposed as an explanation for both contemporary and ancient volcanic systems.
- ItemStresses induced by magma chamber inflation altered by mechanical layering and layer dip(2023) Matías Clunes; John Browning; Jorge Cortez; José Cembrano; Marquardt Roman, Carlos Jorge; Janine Kavanagh; Agust Gudmundsson
- ItemStresses Induced by Magma Chamber Pressurization Altered by Mechanical Layering and Layer Dip(2024) Clunes Squella, Matías; Browning, John; Cortez Campaña, Jorge Osvaldo; Cembrano Perasso, José Miguel; Marquardt Roman, Carlos Jorge; Kavanagh, Janine L.; Gudmundsson, AgustUnderstanding the stress distribution around shallow magma chambers is vital for forecasting eruption sites and magma propagation directions. To achieve accurate forecasts, comprehensive insight into the stress field surrounding magma chambers and near the surface is essential. Existing stress models for pressurized magma chambers often assume a homogenous elastic half-space or a heterogeneous crust with varying mechanical properties in horizontal layers. However, as many volcanoes have complex, non-horizontal, and heterogeneous layers, we enhance these assumptions by considering mechanically stratified layers with varying dips. We employed the Finite Element Method (FEM) to create numerical models simulating three chamber geometries: circular, sill-like and prolate. The primary condition was a 10 MPa excess pressure within the magma chamber, generating the stress field. Layers dips by 20-degree increments, with differing elastic moduli, represented by stiffness ratios of the successive layers (EU/EL) ranging from 0.01 to 100. Our findings validate prior research on heterogeneous crustal modeling, showing that high stiffness ratios disrupt stress within layers and induce local stress rotations at mismatched interfaces. Layer dip further influences stress fields, shifting the location of maximum stress concentration over varying distances. This study underscores the significance of accurately understanding mechanical properties, layer dip in volcanoes, and magma chamber geometry. Improving forecasting of future eruption vents in active volcanoes, particularly in the Andes with its deformed, folded, and non-horizontal stratified crust, hinges on this knowledge. By expanding stress models to incorporate complex geological structures, we enhance our ability to forecast eruption sites and magma propagation paths.
- ItemVariability of quaternary marine terraces and uplift rates in the Andean coastal zone at 23°S(2024) P. Vergara; Marquardt Roman, Carlos Jorge; J. Browning; M.P. Rodríguez