Browsing by Author "Lopez-Contreras, Camila"

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    Integration of Near-Surface Complementary Geophysical Techniques for the Study of Ancient Archaeological Areas in the Atacama Desert (Pampa Iluga, Northern Chile)
    (2023) Gallegos-Poch, Fernanda; Viguier, Benoit; Menanno, Giovanni; Mandakovic, Valentina; Yanez, Gonzalo; Gutierrez, Sergio; Lizarde, Catalina; Araya, Jaime Vargas; Lopez-Contreras, Camila; Mendez-Quiros, Pablo; Maldonado, Antonio; Uribe, Mauricio
    Near-surface geophysical techniques are useful for the characterization of archaeological areas because of their ability to rapidly cover wide extensions and obtain high-resolution data to identify the location for archaeological excavations. However, in hyperarid environments usual geophysical techniques may fail to obtain the expected results due to the dry near surface. This study proposes an integration of ground penetrating radar (GPR) and electromagnetic induction (EMI) techniques, to elucidate the origin of thousands of aligned circular features located at the Iluga archaeological area emplaced on one of the driest places on Earth (Pampa del Tamarugal, Atacama Desert). The GPR was useful to recognize alluvial deposits, sandy aeolian filling in pre-existing holes and roots right underneath circular features. Magnetic susceptibility data derived from the EMI in-phase component, usually considered a complementary result, were useful to identify fireplaces in the vicinity of the alignments. These geophysical findings were verified with an archaeological excavation. It has been found that circular features resulted from an extensive deforestation process in the Pampa del Tamarugal, consisting in the extraction of both trunk and roots of algarrobos (Prosopis chilensis) or tamarugos (Prosopis tamarugo), likely for recent charcoal production. The proposed methodology delivers promising results for archaeological and shallow geological studies in hyperarid and dry environments.
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    Numerical modeling of the Nevados de Chillan fractured geothermal reservoir
    (2025) Oyarzo-Cespedes, Isa; Arancibia, Gloria; Browning, John; Crempien, Jorge G. F.; Morata, Diego; Mura, Valentina; Lopez-Contreras, Camila; Maza, Santiago
    Numerical models can be utilized to understand and anticipate the future behavior of a geothermal reservoir, and hence aid in the development of efficient reservoir engineering strategies. However, as each system has a unique geological context, individual characterization is required. In this research, the Nevados de Chillan Geothermal System (NChGS) in the Southern Volcanic Zone of the Andes is considered. The NChGS is controlled by the geology of the active Nevados de Chillan Volcanic Complex (NChVC) including their basement units (Miocene lavas and volcaniclastic layers from Cura-Mall & iacute;n Formation and the Miocene, Santa Gertrudis granitoids) as well as the key structural control from crustal scale faults, all of which combine to influence the reservoir characteristics. The presence of faults acts to generate a high secondary permeability which favors the circulation of hydrothermal fluids. Based on previous studies in the NChGS, we designed a thermo-hydraulic model in COMSOL Multiphysics (R) combining equations of heat transfer and Darcy's law in order to determine the distribution of isotherms and surface heat flux. The boundary conditions of the model were informed by a conceptual model of depth 3 km and width of 6.6 km which considers a highly fractured granitic reservoir, a clay cap behavior of Miocene lavas and volcaniclastic units, and transitional zones between a regional zone and the reservoir. A lowangle reverse fault affecting the clay cap unit was also incorporated into the models. Results indicate convective behavior in the reservoir zone and a surface heat flux of 0.102 W/m2 with a local peak up to 0.740 W/m2 in the area affected by the low-angle reverse fault zone. The models suggest hydrothermal fluid residence times of around 9-15 thousand years are required to reach a steady-state thermal configuration, which is consistent with the deglaciation age proposed for the NChVC latitude of the complex (c. 10-15 ka). Permeability in the fractured reservoir is one of the most complex parameters to estimate and the most sensitive and hence requires further constraint. Finally, using the volumetric method and the results obtained in this research, we estimate a geothermal potential of 39 +/- 1 MWe for the NChGS.