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Browsing by Author "Morata, Diego"

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Effects of hydrogeochemistry on the microbial ecology of terrestrial hot springs
(2023) Barbosa, Carla; Tamayo Leiva, Javier Alejandro; Alcorta Loyola, Jaime Andrés; Salgado Salgado, Oscar Alexis; Daniele, Linda; Morata, Diego; Diez Moreno, Beatriz
Temperature, pH, and hydrochemistry of terrestrial hot springs play a critical role in shaping thermal microbial communities. However, the interactions of biotic and abiotic factors at this terrestrial-aquatic interface are still not well understood on a global scale, and the question of how underground events influence microbial communities remains open. To answer this, 11 new samples obtained from the El Tatio geothermal field were analyzed by 16S rRNA amplicon sequencing (V4 region), along with 191 samples from previous publications obtained from the Taupo Volcanic Zone, the Yellowstone Plateau Volcanic Field, and the Eastern Tibetan Plateau, with their temperature, pH, and major ion concentration. Microbial alpha diversity was lower in acid-sulfate waters, and no significant correlations were found with temperature. However, moderate correlations were observed between chemical parameters such as pH (mostly constrained to temperatures below 70°C), SO4 2− and abundances of members of the phyla Armatimonadota, Deinococcota, Chloroflexota, Campilobacterota, and Thermoplasmatota. pH and SO4 2− gradients were explained by phase separation of sulfur-rich hydrothermal fluids and oxidation of reduced sulfur in the steam phase, which were identified as key processes shaping these communities. Ordination and permutational analysis of variance showed that temperature, pH, and major element hydrochemistry explain only 24% of the microbial community structure. Therefore, most of the variance remained unexplained, suggesting that other environmental or biotic factors are also involved and highlighting the environmental complexity of the ecosystem and its great potential to test niche theory ecological associated questions.
Episodic construction of the early Andean Cordillera unravelled by zircon petrochronology
(2021) Jara, Jose Joaquin; Barra, Fernando; Reich, Martin; Leisen, Mathieu; Romero, Rurik; Morata, Diego
The subduction of oceanic plates beneath continental lithosphere is responsible for continental growth and recycling of oceanic crust, promoting the formation of Cordilleran arcs. However, the processes that control the evolution of these Cordilleran orogenic belts, particularly during their early stages of formation, have not been fully investigated. Here we use a multi-proxy geochemical approach, based on zircon petrochronology and whole-rock analyses, to assess the early evolution of the Andes, one of the most remarkable continental arcs in the world. Our results show that magmatism in the early Andean Cordillera occurred over a period of similar to 120 million years with six distinct plutonic episodes between 215 and 94 Ma. Each episode is the result of a complex interplay between mantle, crust, slab and sediment contributions that can be traced using zircon chemistry. Overall, the magmatism evolved in response to changes in the tectonic configuration, from transtensional/extensional conditions (215-145 Ma) to a transtensional regime (138-94 Ma). We conclude that an external (tectonic) forcing model with mantle-derived inputs is responsible for the episodic plutonism in this extensional continental arc. This study highlights the use of zircon petrochronology in assessing the multimillion-year crustal scale evolution of Cordilleran arcs.
Fluid flow in the Nevados de Chillán Geothermal System as an example of fractured reservoir, Southern Andes
(2024) Arancibia Hernández, Gloria Cecilia; Mura Toledo, Valentina Rossana; López Contreras, Camila Andrea; Oyarzo Cespedes, Isa Paz Belen; Browning, John; Healy, David; Maza, Santiago; Morata, Diego
Fluid-Assisted Aggregation and Assembly of Magnetite Microparticles in the Giant El Laco Iron Oxide Deposit, Central Andes
(2023) Ovalle, J. Tomais; Reich, Martin; Barra, Fernando; Simon, Adam C.; Godel, Belinda; Le Vaillant, Margaux; Palma, Gisella; Deditius, Artur P.; Heuser, Gert; Arancibia, Gloria; Morata, Diego
The El Laco iron oxide mineral deposit in the CentralAndes ofChile has attracted significant attention because of its uniquelypreserved massive magnetite orebodies, which bear a remarkable similarityto volcanic products. To date, the outcropping highly vesicular andporous massive magnetite orebodies have received little attentionfrom a microtextural point of view, limiting our understanding aboutthe role of volcanogenic processes on iron mineralization. Here, wereport the chemical composition of vesicular magnetite at El Lacousing EPMA and LA-ICP-MS methods and provide detailed 2D and 3D imagingof the internal structure of these texturally complex magnetite oresby combining SEM observations, synchrotron radiation micro-X-ray fluorescencechemical mapping, and high-resolution X-ray computed microtomography.Our observations reveal the presence of abundant magnetite microsphereswith diameters ranging from & SIM;100 to & SIM;900 & mu;m, aswell as dendritic microstructures forming interconnected networksup to a few millimeters in size. Two-dimensional microtextural andgeochemical imaging of the microspheres show that these features areformed by multiple euhedral magnetite crystals growing in all directionsand occur immersed within a porous matrix conformed by smaller-sized(& SIM;2-20 & mu;m) and irregularly shaped magnetite microparticles.These types of morphologies have been reported in hydrothermal ventsassociated with hydrovolcanic processes and commonly described inhydrothermal synthesis experiments of magnetite microspheres, suggestingprecipitation from iron-rich fluids. A hydrothermal origin for themagnetite microparticles reported here is further supported by theirgeochemical signature, which shows a strong depletion in most minorand trace elements typical from magnetite precipitated from hydrothermalfluids in ore-forming environments. We propose that decompression,cooling, and boiling of fluids triggered massive iron supersaturation,resulting in the nucleation of magnetite microparticles or colloids,followed by self-assembly into larger and more complex microstructures.Our data from El Laco deposit agree with models invoking magmatic-hydrothermalfluids to explain the origin of the deposit and provide new insightson the potential role of iron colloids as agents of mineralizationin volcanic systems.
Geochronology and petrogenesis of intrusive rocks in the Coastal Cordillera of northern Chile: Insights from zircon U-Pb dating and trace element geochemistry
(2021) Joaquin Jara, Jose; Barra, Fernando; Reich, Martin; Morata, Diego; Leisen, Mathieu; Romero, Rurik
Two models have been proposed to explain the early Andean evolution of the southwestern margin of Gondwana; a model that assumes continuous subduction-related magmatism since the Carboniferous and a second involving subduction cessation during the pre-Andean stage (similar to 280-200 Ma) followed by subsequent reactivation at ca. 200 Ma. Here we provide new constraints regarding the onset of the Andean tectonic cycle and the transition between pre-Andean and early Andean stages (210-100 Ma) by performing a comprehensive study of the geochronology and petrogenesis of plutonic complexes from the Coastal Cordillera of northern Chile. We present the first zircon U-Pb geochronology and trace element dataset of intrusive rocks combined with whole-rock geochemistry for the early Andean stage. The oldest unit identified is a syenogranite dated at 246.7 +/- 3.9 Ma with a subduction signature, i.e., slightly peraluminous, enriched in LILE over HFSE, negative Nb-Ta and positive Pb anomalies, and strong REE fractionation, but also shows anorogenic features with an alkali-rich composition and high enrichment in rare earth and HFS elements compared to chondritic values. These characteristics are interpreted as representing a transitional, anorogenic event from the pre-Andean stage. In contrast, the second oldest magmatic eventwas dated at 211.4 +/- 1.2Ma and has a chemical composition consistent with Andean-related magmatismand its zircon composition is similar to those fromLate Triassic-Early Cretaceous units. Consequently, we conclude that the Andean orogeny started at ca. 210 Ma, before earlier estimates. Our study also supportsworks that indicate episodic high-flux magmatism and the eastward migration of themagmatic arc during the Mesozoic. Furthermore, the whole-rock Th/Yb and zircon U/Yb ratios show a trend fromthe Late Triassic to Late Jurassic of increasing depletion of themantle source. However, during the Early Cretaceous more variable and enriched signatures are observed, possibly related to changes in the tectonic regime. (C) 2021 International Association for Gondwana Research. Published by Elsevier B.V. All rights reserved.
Hydrothermal Alteration in the Nevados de Chillan Geothermal System, Southern Andes: Multidisciplinary Analysis of a Fractured Reservoir
(2023) Morata, Diego; Gallardo, Romina; Maza, Santiago; Arancibia Hernández, Gloria Cecilia; López Contreras, Camila Andrea; Mura Toledo, Valentina Rossana; Cannatelli, Claudia; Reich, Martin
The interplay between a heat source, primary plus secondary permeability, and hydrothermal fluids makes geothermal systems a highly dynamic environment where evolving physico-chemical conditions are recorded in alteration mineralogy. A comprehensive characterization of hydrothermal alteration is therefore essential to decipher the major processes associated with geothermal system development. In this study, we defined the hydrothermal mineralogical evolution of the Nevados de Chillan Geothermal System (NChGS), located in the Southern Volcanic Zone (SVZ) of the central Andes, where the regional framework of the system is formed by a direct association with a currently active volcanic complex, a favorable structural control, and vertically inhibited fluid circulation. To characterize the secondary mineralogy present in the NChGS, we integrated optical petrography, Scanning Electron Microscopy (SEM) observations, X-ray Diffraction (XRD) analysis, and microthermometric measurements along a drill core with a depth of 1000 m at the Nieblas-1 well. These mineralogical approaches were combined with a structural field analysis to highlight the relevance of multidisciplinary study in understanding active geothermal systems. The results indicated that the evolution of the system involved four paragenetic stages, with the main processes in each phase being the heating, boiling, and mixing of fluids and re-equilibration to new physico-chemical conditions. Additionally, three hydrothermal zones were recognized: an upper argillic section, an intermediate sub-propylitic zone, and a deep propylitic domain. Sampled thermal springs are characterized by pH values of 2.4-5.9 and high SO4= concentrations (>290 ppm). These acid-sulfate steam-heated waters suggest the contribution of primary magmatic volatiles to the hydrothermal system. Alunite recorded in the alteration halos of veinlets presents at depths of 170-230 m denote the circulation of acidic fluids at these levels which were favored by reverse faults. These findings indicate that, at this depth range, the condensation of magmatic volatiles into shallow aquifers controls the recharge area of the superficial thermal manifestations. Conversely, deep-seated hydrothermal fluids correspond to near-neutral chloride fluids, with salinities ranging from 0.1 to 6.9 wt.% NaCl eq. The distribution of illite/smectite and chlorite/smectite mixed-layered minerals outline the presence of a significant clay cap, which, in this system, separates the steam-heated domain from the deep hydrothermal realm and restricts fluid circulation to existing permeable channels. Our mineralogical and structural study provides critical data for the interpretation of heat-fluid-rock interaction processes in the NChGS. The interplay between hydrothermal fluids and active faults is also discussed in the context of the complex of geological processes in active geothermal systems along the Chilean Southern Volcanic Zone.
Magmatism and Polyphase Deformation in the Middle Jurassic Arc of Central Chile: Implications for the Tectonic Development of the Early Andean Margin
(2024) Singleton, John S.; Arancibia, Gloria; Morata, Diego; De La Maza, Ignacia Perez
The similar to 173-164 Ma Papudo-Quintero plutonic complex near 32.5 degrees S in central Chile records three deformation events that provide insight into the tectonic development of the early Andean margin. The first event (D-1) includes: (a) high-temperature (>600 degrees C), coaxial-dominated strain along NE- to N-striking subvertical shear zones; (b) widespread emplacement of granitic dikes that dip gently to steeply NE; and (c) development of narrow (<10 cm thick) strike-slip and oblique-reverse shear zones. These D-1 structures record NW-SE to WNW-ESE transpressional shortening with a component of sinistral shear parallel to the N-S trending magmatic arc. Zircon and apatite U-Pb dates and cross-cutting relations constrain most D-1 deformation to similar to 166-164 Ma. The second event (D-2) occurred during postmagmatic cooling in the Late Jurassic and was characterized by development of pervasive E-W-striking veins with alteration halos and minor strike-slip and normal faults that record N-S extension in a transtensional regime. Structures associated with the last deformation event (D-3) include Late Jurassic to Early Cretaceous mafic dikes, veins, and conjugate strike-slip faults that record NW-SE to N-S shortening in a strike-slip regime. D-1 deformation is consistent with studies from other areas that document NW-SE shortening +/- sinistral transpression along the arc throughout the Jurassic, suggesting this deformation was regional in scale and driven by oblique subduction convergence. Deformation associated with oblique convergence was localized within the active magmatic arc, which was an important process in the early Andean orogeny. As the arc migrated eastward, D-2 and D-3 structures formed in a low-stress regime in an arc margin or forearc setting.
Multi-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, Diego
The 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.
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.
Occurrence and Distribution of Silver in the World-Class Rio Blanco Porphyry Cu-Mo Deposit, Central Chile
(2020) Crespo, Jorge; Reich, Martin; Barra, Fernando; Jose Verdugo, Juan; Martinez, Claudio; Leisen, Mathieu; Romero, Rurik; Morata, Diego; Marquardt, Carlos
Porphyry Cu-Mo deposits (PCDs) are the world's major source of Cu, Mo, and Re and are also a significant source of Au and Ag. Here we focus on the world-class Rio Blanco PCD in the Andes of central Chile, where Ag is a by-product of Cu mining. Statistical examination of an extensive multielemental inductively coupled plasma-mass spectrometry data set indicates compositional trends at the deposit scale, including Ag-Cu (r = 0.71) and Ag-In (r = 0.53) positive correlations, which relate to Cu-Fe sulfides and Cu sulfosalts in the deposit. Silver is primarily concentrated in Cu ores in the central core of the deposit, and significant variations in the Ag concentration are related to the different hydrothermal alteration types. The concentration of Ag is highest in the potassic core (avg 2.01 ppm) and decreases slightly in the gray-green sericite (phyllic) zone (avg 1.72 ppm); Ag is lowest in the outer propylitic alteration zone (avg 0.59 ppm). Drill core samples from major hydrothermal alteration zones were selected for in situ analysis of Ag and associated elements in sulfide and sulfosalt minerals. To ensure representativeness, sample selection considered the spatial distribution of the alteration types and ore paragenesis. Chalcopyrite is the most abundant Cu sulfide in Rio Blanco, with Ag concentration that ranges from sub-parts per million levels to hundreds of parts per million. The highest concentration of Ag in chalcopyrite is associated with the high-temperature potassic alteration stage. Bornite is less abundant than chalcopyrite but has the highest Ag concentration of all studied sulfides, ranging from hundreds of parts per million up to similar to 1,000 ppm. The Ag concentration in bornite is higher in lower-temperature alteration assemblages (moderate gray-green sericite), opposite to the behavior of Ag in chalcopyrite. Pyrite has the lowest Ag content, although concentrations of other critical elements such as Co, Ni, and Au may be significant. The highest Ag concentrations, i.e., thousands of parts per million up to weight percent levels, were detected in late-stage Cu sulfosalts (enargite, tennantite, and tetrahedrite). The Ag content in these sulfosalts increases with increasing Sb concentrations, from the Sb-poor enargite to the Sb-rich tetrahedrite. The earliest Ag mineralization event is related to the potassic alteration stage represented by early biotite and transitional early biotite-type veinlets and where the predominant sulfides are chalcopyrite and bornite. Silver mineralization during this stage was predominantly controlled by crystallization of Cu-Fe sulfides. The second Ag mineralization event at Rio Blanco is associated with the transitional Cu mineralization stage, which is represented by the gray-green sericite alteration (C-type veinlets). In this alteration type, Ag was partitioned preferentially into chalcopyrite, bornite, and to a lesser extent pyrite. The last Ag mineralization event is related to the late quartz-sericite alteration stage, characterized by D- and E-type veinlets with pyrite-chalcopyrite and enargite-tennantite-tetrahedrite. Our data indicate that Ag was associated with several Cu mineralization episodes at Rio Blanco, with Ag concentration apparently controlled by cooling, changes in pH, fo(2) and fs(2) of the hydrothermal fluids, and the intensity of alteration. Overall, our results provide information on critical metal partitioning between sulfides, plus the distribution of critical element resources at the deposit scale.
Palaeopermeability anisotropy and geometrical properties of sealed-microfractures from micro-CT analyses: An open-source implementation
(2019) Gomila, Rodrigo; Arancibia Hernández, Gloria Cecilia; Mery Quiroz, Domingo; Nehler, Mathias; Bracke, Rolf; Morata, Diego
Peraluminous 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. Mark
Combined 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.
Physical, chemical and mineralogical evolution of the Tolhuaca geothermal system, southern Andes, Chile : Insights into the interplay between hydrothermal alteration and brittle deformation
(2016) Sánchez Alfaro, Pablo; Reich, Martin; Arancibia Hernández, Gloria Cecilia; Pérez Flores, Pamela; Cembrano, José; Driesner, Thomas; Lizama, Martin; Rowland, Julie; Morata, Diego; Heinrich, Christoph A.
Understanding hydrothermal alteration pathways in active geothermal systems: a look from clay mineralogy on the Chilean Andes Nevados de Chillán Geothermal System
(2024) Morata, Diego; Maza, Santiago; Abad, Isabel; Cuevas, Cristóbal; Arancibia Hernandez, Gloria Cecilia

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