Browsing by Author "Pineda Ramírez, Camila Andrea"

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    Mafic Enclaves Reveal Multi-Magma Storage and Feeding of Shangri-La Lavas at the Nevados de Chillán Volcanic Complex
    (2025) Pineda Ramírez, Camila Andrea; Arancibia Hernández, Gloria Cecilia; Mura Toledo, Valentina Rossana; Morata, Diego; Maza, Santiago; Browning, John
    The Nevados de Chillán Volcanic Complex is one of the most active of the Southern Volcanic Zone. It is formed by NW-SE-aligned eruptive centers divided into two subcomplexes, namely Cerro Blanco (basaltic andesitic) and Las Termas (dacitic), and two satellite cones (to the SW and NE of the main alignment). Our study of the Shangri-La volcano, which is located between the two subcomplexes, in alignment with the satellite cones, and which produced dacitic lavas with basaltic andesitic enclaves, sheds light on the compositional and structural diversity of the volcanic complex. Detailed petrography along with mineral chemistry allows us to suggest partial hybridization between the enclaves and the host lavas and that mixing processes are related to the generation of the Shangri-La volcano and to other volcanic products generated in the complex. This is supported by mixing trends between the enclaves and the most differentiated units from Las Termas. We argue the presence of two main magma storage areas genetically related to crustal structures. A dacitic reservoir (~950 °C) is fed along NW-SE structures, whereas a deeper mafic reservoir (>1100 °C) utilizes predominantly NE-SW structures. We suggest that the intersection between these sets of structures facilitates magma ascent and controls the Nevados de Chillán plumbing system dynamics.
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    Microstructural controls on geothermal reservoir host rock responses to elevated pressures and temperatures
    (ESS Open Archive, 2025) Mura Toledo, Valentina Rossana; Browning, John; Arancibia Hernández, Gloria Cecilia; Healy, David; Farrell, Natalie Jane Charlotte; Bigaroni, Nico; Pineda Ramírez, Camila Andrea; Morata, Diego; Mecklenburgh, Julian
    Rock microstructure controls the nature of geothermal fluid flow within reservoirs hosted in active volcanic environments and as such it is necessary to constrain the microstructural evolution of rocks at elevated pressure and temperature conditions. Despite Andean geothermal systems hosting numerous high enthalpy geothermal plays, there remains a paucity of experimentally derived seismic velocity and porosity data at crustal relevant in-situ conditions. Here, we provide novel constraints on the evolution of rock physical properties of five main representative lithologies of the Nevados de Chillán Geothermal System under dry conditions with confining pressures up to 150 MPa and following heat treatment up to 600°C. The variability of P-wave velocity changes with elevated confinement reveals the presence of both different densities of pre-existing cracks and different distributions of pore aspect ratios within the tested lithologies. Two target units, crystalline granodiorite and diorite, were further subjected to heat treatment to recreate potential temperature conditions within and around the geothermal reservoir. The heat treatment generated new populations of low aspect ratio cracks in both rocks, but this pore space was apparently more difficult to close in the diorite than in the granodiorite when resubjected to confinement. This difference is explained in a conceptual model whereby a combination of crack realignment and mineral alteration in the diorite allows pore space to remain open and potentially connected at greater levels of confining pressure, at greater depths in the geothermal reservoir. These results have implications for the propensity for fluid flow in crystalline geothermal reservoir host rocks.