Browsing by Author "Arancibia, Gloria"
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- ItemGroundwater resources and recharge processes in the Western Andean Front of Central Chile(ELSEVIER, 2020) Taucare, Matias; Daniele, Linda; Viguier, Benoit; Vallejos, Angela; Arancibia, GloriaIn Central Chile, the increment of withdrawals together with drought conditions has exposed the poor understanding of the regional hydrogeological system. In this study, we addressed theWestern Andean Front hydrogeology by hydrogeochemical and water stable isotope analyses of 23 springs, 10 boreholes, 5 rain-collectors and 5 leaching-rocks samples at Aconcagua Basin. From the upstream to the downstream parts of the Western Andean Front, most groundwater is HCO3-Ca and results from the dissolution of anorthite, labradorite and other silicate minerals. The Hierarchical Cluster Analysis groups the samples according to its position along the Western Andean Front and supports a clear correlation between the increasing groundwater mineralization (31-1188 mu S/cm) and residence time. Through Factorial Analysis, we point that Cl, NO3, Sr and Ba concentrations are related to agriculture practices in the Central Depression. After defining the regional meteoric water line at 33 degrees S in Chile, water isotopes demonstrate the role of rain and snowmelt above similar to 2000 m asl in the recharge of groundwater. Finally, we propose an original conceptual model applicable to the entire Central Chile. During dry periods, water releases fromhigh-elevation areas infiltrate in mid-mountain gullies feeding groundwater circulation in the fractured rocks of Western Andean Front. To the downstream, mountain-block and -front processes recharge the alluvial aquifers. Irrigation canals, conducting water from Principal Cordillera, play a significant role in the recharge of Central Depression aquifers. While groundwater in the Western Andean Front has a high-quality according to different water uses, intensive agriculture practices in the Central Depression cause an increment of hazardous elements for human-health in groundwater. (C) 2020 Elsevier B.V. All rights reserved.
- ItemMulti-scale flow structure of a strike-slip tectonic setting: A self-similar model for the Liquine-Ofqui Fault System and the Andean Transverse Faults, Southern Andes (39-40 degrees S)(PERGAMON-ELSEVIER SCIENCE LTD, 2022) Roquer, Tomas; Arancibia, Gloria; Crempien, Jorge G. F.; Mery, Domingo; Rowland, Julie; Sepulveda, Josefa; Veloso, Eugenio E.; Nehler, Mathias; Bracke, Rolf; Morata, DiegoThe flow structure of a brittle crustal volume is defined by the multi-scale geometric and hydraulic properties of its fracture meshes. The length density distribution n(L,l) and the transmissivity distribution K(L,l) control the hydrologic scaling, where l is fracture length and L is the system size. The flow structure might display at most three key hydrologic scales: the connection scale, above which flow is focused in few critical paths; the channeling scale, above which flow is distributed in several paths; and the homogenization scale, above which permeability approaches a constant value. According to these scales, the hydrological structure could be distributed or clustered, thus having a clear impact in geothermal exploration campaigns and reservoir modeling. In this work, we determine the multi-scale flow structure for the Liquine-Ofqui Fault System (LOFS) and the Andean Transverse Faults (ATF) in the Southern Andes, by establishing the hydrologic scaling they follow. Using fractal statistics, we integrated geological data at the regional, meso-and micro-scale, including image analysis from X-ray microtomography. Our results suggest a self-similar, dense network with n(L,l)similar to l(-a) and a = 2.6-2.9, from the regional scale where the LOFS and ATF interact to the meso-and micro-scale within highly fractured areas of the LOFS. Scaling models are constrained by the length distribution, and other power-law functions reflecting the geometric arrangement of fractures, as well as the spatial distribution of superficial geothermal occurrences. Thus, we expect the hydrologic scaling to depend on the transmissivity distribution. Lognormal transmissivity distribution yields a permeability increase with scale, from the connection to the homogenization scales; whereas power-law transmissivity distribution yields a permeability increase from the connection scale without a limiting value. Approximations of the connection scale are around 10(-3)-10(0) m; the channeling scale, around 100-104 m; and if the homogenization scale exists, it should be equal or greater than 10(3)-10(4) m. Finally, the results presented here could to define the internal architecture of fracture meshes in fault-controlled fluid flow, and be used to select an appropriate hydrologic model according to the analyzed scale. Therefore, these findings must be taken into consideration in future geothermal prospecting, modeling and exploitation.
- ItemPeraluminous Grenvillian TTG in the Sierra de Pie de Palo, Western Sierras Pampeanas, Argentina: Petrology, geochronology, geochemistry and petrogenetic implications(ELSEVIER, 2010) Morata, Diego; Castro de Machuca, Brigida; Arancibia, Gloria; Pontoriero, Sandra; Fanning, C. MarkCombined petrological, geochemical, isotopic and geochronological data shed light on the origin and evolution of a peraluminous garnet-bearing two-mica granitoid (El Tigre Granitoid: ETG) cropping out in southwestern Sierra de Pie de Palo (31 degrees 31'30 '' S-68 degrees 15'12 '' W), and to constrain the age and petrogenetic conditions of this intrusive event. ETG experienced amphibolite to greenschist facies metamorphism after igneous crystallization, followed by strong deformation restricted to narrow mylonite zones (ETG shear zone) and partial dynamic recrystallization under lower-T conditions. A dextral shear sense is compatible with kinematic observations registered along the NNE striking regional Las Pirquitas overthrust, active at 473 +/- 10 Ma (K/Ar on <2 mu m micaceous fraction for the ETG shear zone). The ETG crops out as small, tabular to lenticular vein-like bodies emplaced into metasedimentary rocks of the Pie de Palo Complex. The ETG ranges from granodiorite to tonalite, with a moderately peraluminous signature (ASI = 1.09-1.33; A/CNK >1.1; normative corundum; low CaO values between 1.72 and 2.41%), plotting mostly in the granite-trondhjemite fields of the Ab-An-Or diagram. The trace element contents show a relatively low abundance of Rb, HFS elements such as Y, Nb, Ta, Ga and Zr, and high concentrations of Ba, Sr, and Sigma LREE. The chondrite-normalized REE pattern has a high slope with [La/Yb](N) = 9.48-55.32 and a negative or absent europium anomaly. Relationships between trace elements suggest the classical setting of granitoids produced in a convergent plate setting.
- ItemSelective reactivation of inherited fault zones driven by stress field changes: Insights from structural and paleostress analysis of the Pocuro Fault Zone, Southern Central Andes (32.8 degrees S)(PERGAMON-ELSEVIER SCIENCE LTD, 2022) Taucare, Matias; Roquer, Tomas; Heuser, Gert; Perez-Estay, Nicolas; Arancibia, Gloria; Yanez, Gonzalo; Viguier, Benoit; Figueroa, Ronny; Morataa, Diego; Daniele, LindaThis study aims to explain the selective reactivation of normal faults during the Andean orogeny at the Southern Central Andes western flank. We conducted a structural mapping and paleostress field reconstruction in the regional-scale Pocuro Fault Zone (PFZ) at 32.8 degrees S. Results reveal that the architecture of the PFZ results from at least two deformation phases, each revealing an individual progressive and gradual evolution. The earliest deformation phase is recorded by two similar to NS-striking normal faults involving a 5 km wide damage zone characterized by quartz-laumontite and calcite veins that were developed under an extensional regime with a WNW-ESE-trending sigma 3-axis. The latest deformation phase is recorded by one NS-striking reverse-dextral fault with goethite-hematite syn-tectonic precipitation and two NW-striking reverse-sinistral faults. Reverse faults were developed under a compressional/transpressional regime characterised by an ENE-WSW-trending sigma 1-axis with a sigma 2-/sigma 3-axis permutation. From a geophysical data reassessment, we inferred that observed faults in the surface within the PFZ are regional-scale deep-seated structures. Considering previous geochronological data, we correlated the earliest and latest phases with the Abanico Basin extension (middle Eocene-early Miocene) and its subsequent inversion (Miocene). Given the neotectonic evidence (geomorphic markers and deformation of unconsolidated deposits), the latter phase likely remains active. Quartz-laumontite cementation of the fault core's cataclastic material promotes mechanical strengthening leading to negative feedback for the reactivation of inherited normal faults as reverse ones. Conversely, the concentration of fractures in the damage zone between the normal faults promotes mechanical weakening resulting in a preferential area for the propagation of reverse fault during the compressive/transpressional phase.