Tesis Doctorals - Departament - Mineralogia, Petrologia i Geologia Aplicada

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Dynamic behaviour of salt rocks: exploring the interplay between deformation and recrystallization with full-field numerical simulations
(Universitat de Barcelona, 2024-11-27) Hao, Baoqin; Gómez Rivas, Enrique; Griera i Artigas, Albert; Llorens, Maria-Gema; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] Rock salt, primarily composed of halite, flows in a viscous manner in the solid state under a wide range of geological conditions, strongly affecting the dynamic evolution of sedimentary basins and orogens. The macroscopic physical properties of rock salt are governed by the deformation mechanisms that operate at the microscale and the resulting anisotropy, as rock salt is fundamentally a polycrystalline aggregate. Understanding how microscale deformation mechanisms, like dislocation glide and recrystallization processes (including intracrystalline recovery, subgrain rotation, and grain boundary migration), control the microstructural evolution of polycrystalline aggregates under different temperatures and deformation conditions is crucial for grasping the mechanical behavior of rock salt. Moreover, the interaction between different mineral phases significantly influences grain boundary kinetics, adding complexity to the rock’s microstructural evolution. The overarching aim of this PhD thesis is to systematically analyze and quantify the development of microstructures in rock salt (halite) under different deformation conditions through full-field numerical simulations. The specific objectives are to (i) understand the impact of dynamic recrystallization on pure rock salt, (ii) examine the influence of deformation kinematics on pure rock salt microstructural evolution, and (iii) quantify the effect of a second hard phase on the dynamic recrystallization of polymineralic rock salt. Additionally, the thesis presents the calibration and validation of a state-of-the-art numerical method to simulate rock salt dynamic recrystallization. These objectives are addressed using full-field numerical simulations of halite based on the ELLE- VPFFT approach. The thesis is structured into three main studies. The first one couples dislocation glide and dynamic recrystallization (DRX) processes to simulate the evolution of pure halite polycrystalline aggregates under simple shear deformation, successfully replicating the microstructural evolution observed in laboratory torsion experiments at temperatures ranging from 100 to 300°C. The second study explores simulations across different temperatures and deformation kinematics, in both pure and simple shear boundary conditions. The third study presents simulations incorporating a second hard phase in the halite polycrystalline aggregate, which affects the deformation and recrystallization of halite. The results of the three studies are discussed in an integrated manner. The pure halite deformation models show that temperature governs the competition between grain size reduction driven by dislocation glide and subgrain rotation recrystallization (SGR) at low temperatures, while grain growth produced by grain boundary migration (GBM) dominates at higher temperatures. This leads to either a grain size reduction or increase. When GBM dominates, larger and more equidimensional grains are observed, complicating strain localization assessment from grain morphology, compared to models deformed at lower temperatures. Despite these differences, the crystallographic preferred orientation (CPO) remains consistent across all the modelled temperatures in simple shear. Additionally, the relationship between subgrain misorientation and finite strain follows a power law with a universal exponent of 2/3 at low strain. However, dynamic recrystallization processes produce a progressive deviation from this relationship at high strain. This deviation can be quantified by the average and skewness of the subgrain misorientation distribution, highlighting the need for precise calibration when inferring finite strain or temperature from microstructures. The results also illustrate how the kinematics of deformation control the development of micro-shear bands and the spread direction of crystallographic preferred orientation. Simple shear deformation features a discontinuous evolution of high strain-rate bands, which activate and deactivate periodically, thus causing variation of strain localization and the formation of asymmetric subgrain boundary orientations relative to the grain shape preferred orientation. In contrast, pure shear deformation results in steady high strain-rate bands and more distributed deformation, producing symmetric conjugate subgrain boundaries, small grain bands, and higher grain aspect ratios compared to simple shear scenarios. At high strain, the CPO allows distinguishing between coaxial and non- coaxial deformation and determining the sense of shear. Finally, the presence of a second hard phase under dynamic recrystallization significantly influences halite microstructures, amplifying strain localization. When there is a second hard phase, the steady grain size of the halite matrix is significantly smaller than in single-phase systems, and the CPO intensity of halite is weaker compared to that of pure halite aggregates. The pinning effect of second phases restricts GBM, limiting grain growth, while promoting SGR and strain localization, resulting in further grain size reduction. The load transfer and strain partitioning within polymineralic aggregates are also affected by the second phase content, altering the intensity of the matrix CPO. Therefore, caution is advised when using steady-state recrystallized grain size to predict differential stresses in polymineralic rocks, as smaller grain sizes may lead to overestimated stresses. Finally, the methods and results presented in this PhD thesis are not restricted to rock salt polymineralic aggregates but are applicable to other rocks deformed predominantly by crystal-plastic processes in the Earth’s crust or mantle.
Fluid migration, rock deformation, and mineral alteration in the Earth's crust. Insights from giant quartz veins and their host rocks in the Pyrenees
(Universitat de Barcelona, 2025-04-09) González-Esvertit, Eloi; Gómez Rivas, Enrique; Canals i Sabaté, Àngels; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] The interplay between fluid migration, rock deformation, and mineral alteration processes is key to determining dynamic variations in the Earth’s crust strength, understanding changes in the physicochemical properties of rocks, and constraining the conditions responsible for the formation of ore deposits. Investigating these processes may also provide insights into the sedimentary, magmatic, and metamorphic evolution of different geological systems, helping to reconstruct regional tectono-thermal histories and tectonic plate evolution. However, bridging the gap between these phenomena is challenging due to the very different length scales (i.e., from the scale of atomic chemical changes, ca. 10^-9 m, to that of orogenic deformation, ca. 10^5 m) and timescales (i.e., from crystal dislocation glide, at ca. 10^-9 s, to ductile flow of rocks in shear zones, at ca. 10^14 s) at which their underlying processes operate. This PhD thesis aims to explore the interplay between fluid migration, rock deformation, and mineral alteration during the formation of Giant Quartz Veins (GQVs) in the Pyrenean fold-and-thrust belt, at the Iberia-Eurasia plate boundary. The fluid evolution history, GQV formation mechanisms and conditions, their geometry and distribution, as well as their relationships with host rock alteration processes, GQV ages and deformation are holistically investigated from the orogen- to the grain- scale in four representative sectors: the Canigó, Cap de Creus, Roc de Frausa, and La Cerdanya areas. This is achieved by a multidisciplinary approach that includes remote sensing analysis, fieldwork and geological mapping, structural and microstructural studies, whole-rock and mineral chemistry, mass-balance modelling, fluid inclusion microthermometry and element concentration determinations, geochronology, and crystal orientation analysis in GQVs and their host rocks, present both in basement and cover orogenic settings. Alterations of granitic rocks associated with GQVs have also inspired a literature review about our current understanding of granitic rocks, and on how granites have been defined and interpreted in the context of the major theories that have successively governed the Earth Science history. The interpretations presented in this thesis provide new insights into metasomatic and rock deformation processes, and how these are related to the formation of GQVs and the development of mylonite belts. It is suggested that GQVs are mostly formed by mineral replacement processes and that, accordingly, they form by deformation-controlled metasomatic reactions in coupled, coeval and long-lasting processes of pulses of fluid supply and shear zone activity. The results of this PhD thesis allow for a better understanding of the deformation of crustal rocks, the formation mechanisms of GQVs, and the tectono-thermal history of the Pyrenees. The thesis further challenges practices commonly used for paleotemperature and fluid provenance determinations, classical interpretations of the formation mechanisms, origin, and significance of GQVs worldwide, and assumptions that Pyrenean mylonite belts and GQVs developed during the retrograde stages of the Variscan orogeny.
Multi-isotopic tools for monitoring innovative remediation strategies in sites contaminated with halogenated organic compounds
(Universitat de Barcelona, 2025-05-16) Gil Villalba, Sergio; Rosell, Mònica; Palau Capdevila, Jordi; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] Remediation strategies for groundwater contaminated with chlorinated solvents have advanced significantly in recent decades. However, understanding the complexity of factors influencing contaminant degradation and developing robust tools to evaluate remediation effectiveness under diverse conditions remain critical challenges. This thesis focuses on the application of multi-isotopic tools for the assessment of two groundwater remediation techniques targeting volatile chlorinated hydrocarbons, specifically chlorinated ethenes (CEs) and methanes (CMs). Enhanced in situ biostimulation (EISB) using emulsified vegetable oil (EVO) as a slow-release electron donor was evaluated for CEs remediation. A combined approach, incorporating CEs carbon and chlorine compound-specific isotopic analysis (CSIA, δ13C and δ37Cl), molecular biology tools (MBT), and hydrochemical data revealed rapid reductive dechlorination (RD) of tetrachloroethene (PCE) and trichloroethene (TCE) in both microcosm experiments and a field application. This initial degradation process led to transient cis-1,2-dichloroethene (cDCE) accumulation, which was subsequently degraded to vinyl chloride (VC). Dual-element isotope slopes (ΛC-Cl), MBT results and hydrochemical parameters were consistent, confirming a successful biostimulation of the contaminated site leading to optimal conditions for reductive dechlorination of CEs, which was sustained for 12 months. However, discrepancies with previously reported ΛC-Cl values for laboratory studies using pure and mixed Dehalococcoides microbial populations suggest site-specific variation in reductive dehalogenases involved in cDCE RD, highlighting the need for tailored assessments. Once 2D-CSIA confirmed RD as the major degradation pathway in the field, and knowing that other degradative processes do not have a significant impact on the degradation of CEs, the microcosm-derived εC values and the carbon isotopic balance could be used to estimate the degradation extent of the contaminants in the field application and the extent of complete dechlorination of PCE to harmless ethene. In situ chemical oxidation (ISCO) with persulfate (PS) in an alkaline interception trench (IT) was evaluated using 2D-CSIA for the remediation of CMs and CEs, but with special focus on trichloromethane (TCM). Laboratory batch experiments revealed significant variability in TCM isotopic trends under varying environmental conditions, including pH values and the presence of CO32- ions. Under most studied conditions, PS radical-driven degradation dominated; however, alkaline hydrolysis became the main degradation process at higher pH values. While alkaline conditions seemed to favor TCM oxidation by SO4·- and OH· radicals, isotopic data suggested a shift toward reductive degradation pathways in CO32--rich environments. The results highlight the complexity underlying this remediation technique and the critical role of 2D-CSIA in thoroughly assessing TCM fate during a PS ISCO in alkaline IT systems. Additionally, the accumulation of hexachloroethane (HCA), a higher chlorinated compound than the original contaminant was observed in the batch experiments. This finding raises significant environmental concerns, as the generation of HCA as a by-product could undermine the remediation process by introducing a compound with severe ecological implications. Overall, this thesis demonstrates the potential of the application of δ13C and δ37Cl CSIA as a powerful tool for improving the understanding of contaminant transformation mechanisms under different field conditions. These findings provide key information that can support environmental consultants and contaminated site managers in selecting and optimizing remediation strategies (e.g. dosages, injection pulses) for sites contaminated with chlorinated solvents and open avenues for further research into site-specific transformation processes.
Mineral system in the mantle section of forearc ophiolites
(Universitat de Barcelona, 2025-04-09) Domínguez Carretero, Diego; Proenza Fernández, Joaquín Antonio; García Casco, Antonio; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] Ophiolitic sequences are the remnants of past oceanic lithosphere, including upper mantle and oceanic crust, that have been tectonically emplaced onto continental margins or volcanic arcs. Subduction-related ophiolites are the most common type of ophiolite formed in the so-called suprasubduction zone (SSZ). The mantle section of ophiolitic sequences is predominantly constituted by peridotites, mainly harzburgites with layers, dikes and/or sills of dunites, lherzolites, and pyroxenites. Ophiolitic peridotites are most relevant in the study of the composition of oceanic lithospheric mantle and in understanding large-scale geodynamic processes. However, ophiolitic peridotites also have a great potential at containing important economic resources of a suite of different metals, such as Cr, Ni, Co, Sc, Cu, Au, Ag, and platinum group elements (Ru, Os, Ir, Rh, Pt, Pd). In recent years, many national and international agreements have been signed to reduce, and eventually cut off, the emission of greenhouse gases, to slow the effects of climate change. However, the implementation of low-carbon energy technologies entails a considerable increase in the demand for minerals. In this regard, the mantle section of ophiolitic sequences has great potential to contribute to ease the demand of several metals catalogued as critical. The criticality of these metals lies in their essential role in modern technologies, economies, and national security, while their supply chains remain vulnerable to disruption. In this Ph.D. thesis, three different mineral systems hosted in the mantle section within the forearc region of a SSZ ophiolitic sequence are evaluated. The three studied mineral systems formed at different stages within the evolution of the intra-oceanic subduction setting, produced by the subduction of the proto-Caribbean lithosphere (inter-American Mesozoic ocean of Atlantic affinity formed after the breakup of Pangea) underneath the Caribbean lithosphere (of Pacific affinity), which generated the Cretaceous Caribbean island arc. The evaluation of the different deposits from a mineral system point of view considers all the geological processes that take place in the genesis and preservation of an ore deposit. This includes the mobilization, transport and accumulation of metals from a fertile source to an accumulation zone, together with all the processes responsible for preserving the deposit after its genesis.
Modelling the eruptive and pre-eruptive dynamics on Teide-Pico Viejo complex
(Universitat de Barcelona, 2024-12-19) Dorado García, Olaya; Geyer Traver, Adelina; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] The volcanic island of Tenerife (Canary Islands, Spain), the largest and most populated island of the Canarian archipelago, hosts the active Teide-Pico Viejo (T-PV) volcanic complex in its central region, known for its high explosive potential. The volcanic activity of this central complex, along with the primarily effusive activity of the island's two rift zones (Santiago and La Dorsal), poses a significant risk to the island's population. Eruptions in Tenerife are infrequent, with estimated recurrence intervals of around 100 years for effusive rift eruptions, and approximately 1,000 years for phonolitic eruptions from the central complex. Therefore, studying past eruptions is essential to understand the volcanic activity on the island. The petrological and geochemical study of eruptive products, along with geophysical data, can help us understand the internal structure of the magmatic system and the pre-eruptive processes that influence magma evolution and eruptive dynamics. Despite numerous studies conducted on the island of Tenerife, only a limited number has focused on studying the T-PV magmatic system as a whole. Furthermore, the few existing studies are outdated regarding recent advances in volcanology. Thus, the objective of this thesis is to improve our understanding of the active magmatic system in Tenerife, consolidating previous knowledge and contributing with new insights into the volcanic history, pre-eruptive conditions, and magmatic processes that have occurred on the island since the last caldera collapse (< 180 ka). Special attention has been given to phonolitic eruptions, not only because they have the highest explosive potential, but also because they exhibit the greatest compositional variety. Additionally, this study aims to investigate whether significant differences exist between central phonolitic eruptions (originating from Teide) and those from the domes (felsic flank vents) that may explain the supposed difference in eruptive dynamics (effusive vs. explosive, respectively). To conduct this research, we first reviewed both the geophysical studies carried out on Tenerife and the petrological and geochemical studies of the T-PV complex and the island's two active rifts. The main goal was to unify all previous knowledge within a common framework, thus identifying potential knowledge gaps. The results of these reviews have been compiled into two databases: i) a database of geophysical observations and interpretations, which has allowed us to synthesize all information into a series of geological cross-sections illustrating Tenerife's internal structure; and ii) a geochemical database of whole-rock analyses from the T-PV complex and the two active rifts (GeoTeRi). The latter database includes information on 561 rock samples, 540 major element analyses, 517 trace element analyses, 172 isotopic ratios, and 60 datings. The compilation of these datings, along with a review of published maps, has also enabled a reanalysis of the volcanic stratigraphy of the T-PV complex. Secondly, we have conducted new sampling of eruption products (lavas and various pyroclast types) from the central T-PV complex outcropping within the Las Cañadas Caldera and from some eruptions of the Santiago rift proximal to the central complex. Whole-rock data were obtained for all these samples, thus complementing the data in the GeoTeRi database. Additionally, mineral chemistry analyses were performed on some of the collected samples. This allowed performing a general petrological and geochemical characterization of the recent eruptions from the central complex, as well as the identification of the different compositional groups within the magmatic series. Detailed studies were then conducted on some of these samples to calculate pre-eruptive conditions and identify pre-eruptive processes. The most relevant findings obtained from the study of these new samples include: i) the identification of several pumice levels potentially related to Teide eruptions, indicating a higher explosive potential than previously thought; ii) the calculation of pre-eruptive conditions for both the explosive and effusive phases of the Pico Cabras eruption, revealing that the changes in eruptive dynamics were related to differences in temperature and volatile content within a zoned magma chamber emplaced at 1 ± 0.5 kbar; and iii) the identification of various processes that explain some of the compositional variability found in the T-PV eruptions, including self-mixing processes, magma mixing, melting and recrystallization of feldspar-rich crystal mushes, and the remobilization and assimilation of the partial melting of these mushes. Some of these conclusions were reached through the comparison with a model for predicting partition coefficients of several trace elements in feldspars, allowing for the identification of xenocryst populations, a methodology applicable to other alkaline volcanic systems. The joint interpretation of these new findings, along with pre-existing information on the volcanic system, has revealed that the shallow accumulation zones of phonolitic magmas are highly complex and that the active magmatic system in Tenerife exhibits the typical characteristics of a transcrustal magmatic system, with active crystal-rich mush zones in which the melt-rich domains are stored. Furthermore, the geochemical comparison of all studied samples has shown that there are no significant petrological or geochemical differences between Teide and the dome eruptions, indicating that the magmatic processes leading to the different compositional groups are not correlated with the emission area. Tt is therefore reasonable to assume that the pre-eruptive conditions of these compositionally similar eruptions are also alike. This observation challenges the previous hypothesis, which attributed the difference in eruptive dynamics to a variation in the storage depth between Teide and the dome eruptions. Our new hypothesis is further confirmed by the identification of pumice deposits from Teide eruptions. These findings are highly relevant for assessing volcanic hazard in Tenerife, as the explosive potential of Teide had been underestimated prior to this Thesis, highlighting the need for further studies to identify recent explosive deposits from the T-PV complex.
Salt sheet emplacement in fold-and-thrust belts: contributions from the Les Avellanes Diapir (South-Central Pyrenees)
(Universitat de Barcelona, 2024-06-21) Cofrade Rivas, Gabriel; Cantarero Abad, Irene; Gratacós Torrà, Òscar; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] This PhD Thesis presents the Les Avellanes Diapir (Serres Marginals, South-Central Pyrenees) as a field analogue of subaerial (extrusive) salt sheets in orogenic settings by understanding the emplacement mechanism, internal structure, kinematics, and timing of this diapir. To reach this main objective, this thesis has a multidisciplinary approach combining a field-based study focused on the structural, stratigraphical, sedimentological, and petrographical investigation of the diapir and its surrounding area, with an analogue modelling experiment to relate the internal deformation with the salt flow dynamics. The diapir is in a complex tectonic area where the Late Triassic to Eocene salt-decoupled cover from the Serres Marginals Thrust Sheet is deformed in a thin-skinned style, displaying imbricated synclines separated by thrusts and back-thrusts, which evolved from tight, salt-cored anticlines during early Eocene times. The diapir is bounded to the north by two sets of NW-SE and WSW-ENE extensional faults, which together with the NW and NE parts of the diapir body, are postdated by late Eocene-Oligocene conglomerates. By contrast, the diapir southern boundary exhibits its allochthonous emplacement over a syn-orogenic, late Eocene-Oligocene succession. Considering the sedimentary environments, stratigraphical architectures, and paleocurrent data, a salt sheet was sourced in the northern part of the diapir exposure and advanced southwards, downhill towards adjacent structural depocenters. The Les Avellanes Diapir exposure is formed of a caprock created by the dissolution of salt. This caprock is composed of a softer dissolution residue, named caprock matrix that embeds tabular, thick, and laterally extensive carbonate stringers from the M3 Muschelkalk facies, as well as layered mudrocks and dolerite bodies. The internal structure of the diapir body is hinted by the structural configuration of the M3 stringers, which present three structural domains: 1) in the northern domain, steeply dipping M3 stringers subparallel to the diapir walls change to a subhorizontal orientation southwards, 2) in the central domain, M3 stringers form juxtaposed stack-like sets of subhorizontal to subvertical stringers and, 3) in the southern domain, M3 stringers form imbricated, nappe-style sets parallel to the southern boundary. 4 To discuss the origin and timing of the salt sheet associated with the Les Avellanes Diapir, a cross-section spanning from the Serres Marginals thrust front to the Montsec is restored, constrained by surface data. A main salt migration episode is linked with the tectonic and sedimentary loading and the subsequent expulsion of salt forelandwards, induced by tectonic contraction during Eocene to Oligocene times. The gradual shortening of the inflated structures in the Serres Marginals Thrust Sheet during this time is related to the expulsion of the salt towards the surface. Shortening increased the salt supply overcoming the sedimentary rate, thus triggering the salt sheet advance. Although the origin of the feeder diapir is probably associated with the Pyrenean contraction during Eocene times, the existence of a pre-contractional precursor, relative to the position of the Serres Marginals Thrust Sheet, cannot be entirely ruled out. From the study of the Les Avellanes Diapir, discussions are upscaled to a more global perspective regarding the stratigraphical record of a salt sheet and the factors that control the kinematics of the allochthonous emplacement and associated internal deformation. The stratigraphical and sedimentological data are used to build a conceptual model to evaluate how the syn-kinematic stratigraphy next to an extrusive advancing salt sheet in continental orogenic settings responds to advance, stagnation and retreat phases in terms of progradation, aggradation and retrogradation of proximal vs. distal facies. Finally, by comparing the analogue experimental data with the Les Avellanes Diapir natural prototype, the kinematics of an extrusive salt sheet are associated with its internal structure, which in turn, results from salt flow dynamics. The structural configuration of the stringers is associated with the salt sheet geometry: 1) the northern domain is associated with the feeder, where the ascending flow carried steeply-dipping stringers from the diapir stem; 2) the central domain is associated with the salt sheet domain, where recumbently folded stringers are divided and rotated into juxtaposed subvertical and subhorizontal stack-like accumulations by the subhorizontal flow; and 3) the southern domain is associated with the salt sheet front, where contraction induced by the decelerating flow imbricated the stringers towards the direction of advance. Finally, viscous drag along the base of the salt sheet concentrates ductile deformation creating a shear zone, discussed with respect to the nature and deformation of the megabreccia that characterizes the base of the diapir body.
Rare earth elements, Yttrium and scandium retention in Fe- and Al-hydroxysulfates (basaluminite and schwertmannite) under the hydrogeochemical conditions of the Tinto River estuary (SW Spain)
(Universitat de Barcelona, 2024-07-19) Gutierrez León, Joan; Cama i Robert, Jordi; Soler, Josep M.; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] Rare-earth elements (REEs: lanthanides, yttrium and scandium) are scarce in mining concentrations in the Earth’s crust, freshwater and seawater. In recent decades, REEs have become crucial to new technologies for computer chips (gadolinium), missile guidance systems (neodymium), nuclear reactor control rods (samarium), microwave emitters (yttrium), long-live missile batteries (promethium), electric vehicles (dysprosium) or in the glass industry (lanthanum). The need of REEs forces European manufacturing companies to invest in the exploration of alternative sources. An alternative source is the areas impacted by acid mine drainage (AMD), which display REE concentrations that are several orders of magnitude higher than those of freshwater and seawater. AMD neutralization as a result of mixing with seawater in estuaries prompts a spontaneous precipitation of Fe- and Al-oxyhydroxysulphate nanominerals (i.e., schwertmannite (Fe8O8(OH)6SO4) and basaluminite (Al4(SO4)(OH)10·5H2O), respectively), which play a significant role in the fate of Rare Earth Elements (REEs). The conditions for precipitating schwertmannite and basaluminite (pH 2.5-3.5 and 4.5, respectively) are not suitable to adsorb REEs, but when AMD mixes with the water of the estuary of Ria de Huelva (Spain), the pH increases up to between 4.5 and 8, yielding optimal conditions for REE adsorption on schwertmannite. A geochemical study of this estuarine system is needed to shed light on the REE distribution. Earlier studies focused on the adsorption of REEs onto these Fe- and Al-oxyhydroxysulphates. However, two important aspects related to the affinity of REEs for these minerals remained unsolved and are necessary to comprehensible understand the distribution of REEs in the estuarine system. The first one is to know the capacity of schwertmannite to retain adsorbed REEs at a pH between 4.5 and 7. Desorption batch experiments in the presence of sulphate were performed to study this capacity at this pH range and room temperature. The solution chemistry was analysed to obtain the REE surface constants for the surface complexation reactions. Desorption of Lu-enriched schwertmannite at different pH values was investigated with High Energy X-Ray Diffraction (HEXD) and Extended X-ray Adsorption Fine Structure (EXAFS) to characterize the molecular structure of the surface complexes involved in the desorption reaction. The results indicate (1) that REE adsorption/desorption on schwertmannite is pH dependent and, as a consequence, schwertmannite retains adsorbed REE at pH > 6, and (2) both monodentate and bidentate surface complexes are involved in the Lu-desorption reaction. The second aspect concerns the effects of an increase in pH and in ionic strength on the REE adsorption onto both nanominerals. In this study, REE adsorption onto schwertmannite and basaluminite has been studied in the pH range of 4.5-7 and ionic strength range of 0.25-0.5 M using batch experiments and EXAFS analysis to elucidate the behaviour of REEs under AMD impacted-estuarine conditions. The log KREE values calculated for the adsorption of REEs onto schwertmannite and basaluminite were implemented in a non-electrostatic surface complexation model (NEM), which indicated that REE adsorption is both pH dependent and ionic strength independent. For schwertmannite, low pH resulted in a low retention (up to 10% at pH 4.5) in a monodentate coordination whereas high pH increased the adsorbed fraction (up to 99% at pH 6.5) in a bidentate coordination. For basaluminite, the REE affinity was affected by the REE atomic number, enhancing the adsorption of heavy REEs (HREEs, up to 90% at pH 6.5) with respect to light REEs (LREEs, up to 20% at pH 6.5). The agreement between the NEM calculations and the EXAFS analysis in Gd-basaluminite suggests that monodentate binuclear and mononuclear are probable REE coordination in basaluminite, although the presence of outer sphere complexes is also likely for LREE. Thus, the thermodynamic parameters provided in this study prove useful to predict the geochemical behaviour of REEs in AMD-impacted estuarine areas. To shed light on the complex geochemistry of the overall estuarine system, a field campaign was carried out to collect samples of the estuarine sediment and water and to measure concentrations of relevant trace elements ((REEs) and metal(loid)s). This enabled to (1) better understand the elemental distribution in the sediments and water in the water-mixing area, (2) discern the elemental behaviour via mixing modeling, (3) reproduce the aqueous behaviour of REEs related to REE adsorption onto schwertmannite and basaluminite, and (4) evaluate the effect of the adjacent phosphogypsum stacks on the estuarine geochemistry.
Mecanismos de concentración de elementos críticos en la Carbonatita de Bailundo (Angola)
(Universitat de Barcelona, 2024-06-28) Castellano Calvo, Amaia; Melgarejo i Draper, Joan-Carles; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[spa] La reciente demanda e interés por los elementos críticos y en especial, por las REE’s ha impulsado en la última década diferentes trabajos relacionados con las carbonatitas. En muchos de ellos se demuestra la importancia que ejercen los procesos de alteración hidrotermal en la distribución de estos elementos. Los resultados obtenidos en esta tesis apoyan los trabajos anteriores y van más allá, demostrando que la mayor concentración de los elementos de REE´s se produce en los depósitos lateríticos por la acción de los procesos meteóricos. En este trabajo se presentan los resultados obtenidos tras el estudio del complejo carbonatítico de Bailundo. El complejo carbonatítico de Bailundo se sitúa en la parte central de Angola y está relacionado con la estructura tectónica de Lucapa, siendo uno de los complejos carbonatíticos más importantes del país, con más de 7km de diámetro y 38,5km2 de extensión. El estudio petrológico, mineralógico y textural ha permitido clasificar los litotipos de la carbonatita de Bailundo en tres grandes grupos: carbonatitas, foscoritas-nelsonitas y fenitas. Los resultados geoquímicos junto con los anteriores han permitido demostrar la actuación de sucesivos fenómenos de alteración hidrotermal y meteórica. Estos procesos de alteración han producido cambios importantes en la mineralogía original, generando rocas secundarias y depósitos lateríticos. Algunos minerales se revelan muy útiles para entender la evolución de los diferentes procesos que han tenido lugar. En el caso del pirocloro, tiene dos ventajas: a) se forma en diferentes estadios de cristalización; b) presenta diferentes posiciones de la estructura cristalina en que se acomodan diferentes elementos. Por lo tanto, el análisis químico de cada una de las generaciones de pirocloro refleja la actividad de estos elementos en el magma o fluidos que lo formaron. De esta forma, se deduce que los magmas primarios de la carbonatita fueron ricos en Na y F, depositándose a partir de ellos natrofluorpirocloro primario. En cambio, estadios más tardíos de cristalización magmática de la carbonatita o incluso hidrotermales contienen diversas generaciones de pirocloro progresivamente empobrecido en Na y F, que pueden desaparecer, generándose diversos tipos de kenopirocloro que se van enriqueciendo sucesivamente en Ca, Sr, Ba y Pb. En cambio, el pirocloro primario que se forma en rocas nelsonitas contiene altas concentraciones de HFSE en especial, en Ta y Zr, lo que reflejaría una mayor concentración de estos elementos en el magma parental de estas rocas. Por otro lado, se ha establecido, a partir del análisis sistemático de las inclusiones de fundidos atrapados en diversos minerales de cada estadio de las diferentes rocas, la coexistencia de vidrios de composiciones muy diferente: vidrio alcalino-carbonatítico-silícico, vidrio fluoro-carbonato-magnésico- alcalino, vidrio alcalino-magnésico-carbonatítico y vidrio natrocarbonatítico. Sin embargo, no se ha podido analizar ninguna inclusión de vidrio rico en carbonato cálcico. El estudio de las inclusiones ha sido útil también a la hora de reforzar la secuencia mineral obtenida a partir de datos petrográficos, a la vez que se establecía qué tipo de fundidos se daban en cada episodio de cristalización. En cuanto a la datación del complejo, los cristales de circón analizados proceden de carbonatitas y son muy pobres en U, por lo que la datación ha debido realizarse utilizando el método Pb208/Th203 y análisis La-ICP-MS de ET. De estos análisis se han obtenido dos edades medias, 88 ±3,4 (2σ) Ma y 97,7 ±1,4 (2σ) Ma, por lo que se trata de la segunda carbonatita más joven de Angola, después de Catanda. Por otro lado, los resultados isotópicos en C, O y S indican un origen mantélico y primario para los carbonatos y sulfuros analizados, así como fraccionamiento tipo Rayleigh, lo que apoya que hayan ocurrido procesos de cristalización fraccionada en el magma. No obstante, hay evidencias de reequilibrio con fluidos hidrotermales externos al sistema. Finalmente, con todos los resultados obtenidos a partir de los diferentes estudios, se ha realizado una aproximación al modelo genético del complejo carbonatítico de Bailundo.
Optimization of induced denitrification strategies in water resources contaminated by agricultural and urban sources
(Universitat de Barcelona, 2024-05-10) Alex Tiewin, Abu; Domenech Orti, Cristina; Navarro Ciurana, Dídac; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] Groundwater pollution poses a significant global environmental threat, mainly attributed to the oxidation of excess nitrogen during fertilization in aerobic conditions. The widespread occurrence of elevated nitrate levels in groundwater causes health hazards such as methemoglobinaemia in children and stomach cancer in adults and deteriorates aquatic life. Addressing this issue necessitates effective remediation strategies to preserve water quality and ensure sustainable access to clean water resources. The primary objective of this thesis is to develop cost-efficient, eco-friendly treatment methods for groundwater nitrate removal, advancing the understanding of nitrate decontamination pathways and quantifying the efficiency of nitrate removal. Chemical, isotopic, and numerical modeling tools are used to characterize nitrate attenuation to achieve this objective. Denitrification, driven by denitrifying bacteria, is the primary mechanism for groundwater nitrate attenuation. The activity of these bacteria, distributed widely in both surface and subsurface water bodies, hinges on the availability of electron donors, a crucial limiting factor for denitrification. This research explores potential low-cost electron donors like two types of wine industry residues to induce or enhance nitrate removal efficiency. Laboratory experiments, including batch and column studies, are conducted to assess their efficiency in inducing denitrification through chemical and isotopic tools. Experimental investigations revealed promising results in nitrate removal with one of the residues, showcasing the potential for field-scale applications. Isotope analysis suggested denitrification as the dominant mechanism for nitrate attenuation, with isotopic fractionation values for quantification of denitrification efficiency in future field studies. To further elucidate the complex interplay of nitrate reduction mechanisms, a conceptual and geochemical numerical model that integrates nitrate and nitrite degradation kinetics, isotopic fractionation and biomass dynamics is developed to simulate N compounds dynamics. The successful simulation of the experimental data by the models sets the stage for its potential application in real-world scenarios. Chemodenitrification can coexist with biological denitrification in iron-rich environments; consequently, this thesis also focuses on the performance of nitrite reduction by ferrous iron in laboratory batch experiments. The research examines the influence of aqueous Fe(II) and Fe(II) minerals on nitrite removal efficiency and the production of nitrous oxide (N2O), a potent greenhouse gas. Chemical and isotopic tools are used to characterize nitrite attenuation and N2O production and quantify the efficiency of nitrite reduction and N2O production. A geochemical model is developed to describe the coupled nitrite reduction-Fe(II) oxidation linked to nitrogen-nitrite isotopic fractionation. The model successfully replicates the experimental data and holds promise for application in other laboratory and field-scale chemodenitrification studies. Partially treated wastewater effluents are recognized for having elevated levels of inorganic nitrogen, primarily ammonium, easily oxidized to nitrate and other nitrogen compounds as groundwater contaminant sources. Safely using these effluents for domestic purposes and groundwater aquifer recharge necessitates ammonium nitrogen remediation. Permeable reactive barriers emerge as promising solutions to address the problem of the high levels of inorganic nitrogen in untreated and partially wastewater effluents. This research evaluates the effectiveness of permeable reactive barriers in subsurface infiltration systems, comparing scenarios with and without reactive barriers. Chemical and isotopic analyses reveal spatial and temporal dynamics of nitrogen compounds, offering valuable insights into the efficiency of nitrogen-ammonium transformation and attenuation pathways. This thesis advances our understanding of pollution remediation of nitrate and other nitrogen compounds by investigating cost-effective and eco-friendly electron donors through innovative removal methods. The research outcomes hold significant implications for environmental sustainability, offering practical solutions to mitigate nitrate pollution in water resources. The research outcomes have been disseminated through three peer-reviewed publications and presented at seven international and national conferences, fostering knowledge exchange and collaboration in the field of groundwater contaminant remediation.
Post-caldera volcanism of Deception Island (Antarctica): new insights from Tephra studies and Port Foster Bay volcanic deposits
(Universitat de Barcelona, 2024-04-05) Hopfenblatt, Joaquín; Geyer Traver, Adelina; Aulinas Juncà, Meritxell; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] Deception Island (South Shetland Islands) is one of the most active volcanoes in Antarctica and has experienced over 20 explosive eruptive events in recent centuries. Recent eruptions in 1967, 1969, and 1970, as well as volcanic unrest episodes in 1992, 1999, and 2014–2015, highlight the ongoing and potential future volcanic activity on the island. Despite this volcanic activity, the region has witnessed a substantial increase in scientific bases, tourist activities, and air and vessel traffic in the last decades. This surge in interest has raised concerns as the escalating infrastructure and population in the area are increasingly exposed to the risk of future eruptions. This enhanced exposure necessitates an urgent, and accurate, long-term assessment of the volcanic hazard posed by Deception Island. Previous attempts at such assessments have been limited by the incompleteness of the island’s eruptive record. The complexities of Deception Island's magmatic and volcanic evolution demand continued significant research efforts to enhance our understanding and contribute to more effective hazard assessments. This Doctoral Thesis combines diverse research lines, revealing crucial insights into the island's past, present, and potential future volcanic evolution as well as the associated impact of future eruptive events. The investigation encompasses two primary research lines: (1) the study of Port Foster's most relevant eruptive episode, focusing on the formation of the Stanley Patch volcanic edifice, and (2) the identification, compositional, and textural characterization of tephra layers sourced from Deception Island. These research lines are integral to enhance our understanding of the island's geological evolution since the caldera collapse. The combination of research lines pertaining to Port Foster and tephra studies provides significant advancements in our understanding of the post-caldera volcanic activity of Deception Island. The insights gained not only contribute to our comprehension of the island's geological evolution but also serve as a basis for accurate hazard assessments, comprehension of Deception Island’s post-caldera volcanic activity, its past and future evolution, and the potential impact of future eruptive events.
Caracterización de las mineralizaciones de Gavà: implicaciones geoarqueológicas
(Universitat de Barcelona, 2022-11-28) Díaz Acha, Yael; Melgarejo i Draper, Joan-Carles; Campeny, Marc; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[spa] El municipio de Gavà (Cataluña) ha sido históricamente rico en recursos minerales, los cuales se han explotado desde hace más de 6.000 años. En este sentido, son especialmente destacables el caso de los minerales de hierro, beneficiados durante las épocas Íbera, Romana, la Edad Media y hasta la era industrial del siglo XIX-XX, y el de la variscita (un fosfato de aluminio de color verde intenso), que se explotó intensamente durante el Neolítico. A nivel geológico, las mineralizaciones de hierro de Gavà se formaron en dos estadios diferenciados. En el primero, la circulación de fluidos hidrotermales de baja temperatura produjo la ankeritización de las calizas de las series del Devónico; mientras que, en un segundo estadio, dichos carbonatos fueron alterados por fluidos de origen supergénico durante el Plioceno y el Cuaternario, formándose depósitos de goethita y hematites. El estilo de mineralización depende en gran medida de las características del protolito reemplazado, lo cual lleva a la definición de tres estilos de mineralización: (1) el reemplazamiento supergénico de calizas masivas ankeritizadas del Prídoli; (2) el reemplazamiento de alternancias de calizas ankeritizadas con pizarras del Lochkoviense que contienen pirita diseminada; (3) el reemplazamiento de protolitos complejos, con alteración simultánea de carbonatos cabalgados por pizarras ricas en sulfuros y niveles de fosfatos. Estas últimas son las mineralizaciones de mayor tamaño y grado del área. En cuanto al conjunto de minas neolíticas de Gavà, explotadas para el beneficio de la variscita, se pueden distinguir dos zonas mineras diferenciadas: Can Tintorer, que incluye el actual Parque Arqueológico de las Minas de Gavà (PAMiG), y Les Ferreres. Este conjunto de minas constituye uno de los complejos mineros más antiguos conocidos en Europa, así como el ejemplo más antiguo de la aplicación de conceptos geológicos y mineros complejos. En estas minas se explotaba principalmente la variscita, pero también la turquesa, para la fabricación de ornamentos. Recientemente, se ha podido constatar que se excavaban algunos pozos y túneles de exploración para el beneficio de otros minerales verdosos de aspecto similar y que se han caracterizado como fases del grupo de las esmectitas o las canditas. En la zona de Les Ferreres las explotaciones son simples, mostrando una entrada única a galerías simples o rampas que alcanzan menos de 5 m de profundidad y excavadas directamente en afloramientos de fosfatos. En contraste, en la zona de Can Tintorer la presencia de abundantes vetas subverticales de variscita permitió un complejo desarrollo de galerías en diferentes niveles de explotación comunicadas por pozos y rampas, alcanzándose 15 m de profundidad. La explotación empleada por los mineros neolíticos fue mediante realce ascendente y descendente; aunque también usaron pilares y rellenos de explotaciones más antiguas para evitar el colapso de la mina. Asimismo, quizás con el fin de favorecer la estabilidad de las galerías, algunos pozos fueron cavados directamente en el duro caliche cuaternario discordante, revelando que los mineros intuyeron la existencia de la mineralización por debajo de la cubierta de caliches. La variscita de la zona de Can Tintorer reemplaza niveles de fluorapatito intercalados con pizarras negras meteorizadas de la serie del Silúrico, o bien aparece en forma de vetillas que cortan a estos materiales. Este conjunto está localmente cubierto por caliches discordantes del Cuaternario. La variscita, junto con los otros fosfatos y sulfatos encontrados en Gavà, se formó por la acción de fluidos meteóricos ácidos y oxidantes que generaron una intensa meteorización durante el Pleistoceno temprano, afectando a series de pizarras negras y fosfatos sinsedimentarios del Silúrico. La circulación de estos fluidos ácidos en niveles más profundos del perfil generó mineralizaciones similares en vetas supergénicas compuestas por fosfatos secundarios (p. ej., variscita, perhamita, crandallita, fosfosiderita) y sulfatos (p. ej., jarosita, alunita). En este estudio se ha descrito que esta mineralización supergénica está significativamente enriquecida en ciertos elementos críticos (p. ej., galio, elementos de las tierras raras, indio, cobalto y antimonio) que se movilizaron a partir de los componentes de la roca y luego se hospedaron en la estructura cristalina de los minerales supergénicos. Los procesos de meteorización y el correspondiente enriquecimiento supergénico de elementos críticos en el depósito de Gavà podrían utilizarse como ejemplo para determinar las pautas de exploración de elementos críticos en los perfiles de meteorización y los fosfatos supergénicos asociados en todo el mundo. Con el propósito de esclarecer las causas de las diferentes coloraciones de la variscita de Gavà, que pueden variar del verde musgo al verde oliva, e incluso, al verde blanquecino, se elaboró un estudio tridimensional de la distribución de las fases minerales para determinar los parámetros implicados en los colores de la variscita. Los métodos comprenden colorimetría cuantitativa, petrografía de lámina delgada en luz transmitida y reflejada, SEM-EDS, microsonda electrónica (EMPA), difracción de polvo de rayos X (XRD) y espectroscopía Raman y Mössbauer. La distribución de estos valores en las minas indica que el color no depende directamente de la profundidad. Aunque la variscita de Gavà es pobre en cromo III y vanadio III, en comparación con la variscita gema de otras localidades, las muestras de color verde intenso contienen los valores más altos de cromo III. En el caso de mezclas criptocristalinas con jarosita, fosfosiderita o goethita, la variscita tiende a adquirir una tonalidad marrón verdosa a olivácea. Si en las mezclas intervienen minerales blancos, como cuarzo, candita, crandallita o alunita, los colores de la variscita y la turquesa se vuelven más pálidos.
Isotopic characterization of precipitation and its relationship with groundwater in the Central Andes
(Universitat de Barcelona, 2022-07-19) Valdivielso Mijangos, Sonia; Vázquez Suñé, Enric; Custodio, Emilio; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] The availability of water resources is increasingly limited worldwide. Therefore, optimal and sustainable management is necessary to ensure a balance between ecosystems and human rights and activities. In the arid Central Andes, there is a great demand for water for different uses, including domestic consumption, intensive mining and, in some areas, livestock and emerging ecotourism. These human activities must respect and conserve the lagoon systems of the salt flats, on which the fauna depend. Understanding the hydrological and hydrogeological functioning of basins is essential for the optimal and sustainable management of water resources. To address this issue, the objective of this thesis is to advance the knowledge on the isotopic composition of precipitation and its relationship with groundwater in the Central Andes, particularly in the Salar de Atacama basin (Chile). This thesis contributes to the (1) understanding of the origin of precipitation in the Central Andes and reviews how it varies isotopically (δ18O and δ2H) throughout the Amazon basin and in the Central Andes between 14°S and 28°S, (2) identification of the factors that control the isotopic composition of precipitation in areas with scarce isotopic and meteorological data and estimation of the meteorological and isotopic variables of precipitation, (3) characterisation of precipitation and identification of the recharge zone of the Salar de Atacama basin using stable isotopes, and (4) quantification of the contribution of snowmelt to the recharge of the aquifer of the basin. Through an exhaustive review of the literature, precipitation in the Central Andes has been characterised. Precipitation occurs mainly during the austral summer. The masses of humidity have different origin: (1) from the North Atlantic Ocean through the Amazon basin, (2) from the South Atlantic Ocean through the Plate River basin and the Gran Chaco in summer, and (3) the Pacific Ocean in winter. The processes involved in the isotopic evolution of summer convective precipitation in the Eastern Cordillera are known. However, there is no consensus on the factors that control the isotopic variation in the Western Cordillera. To identify the processes that determine the precipitation isotopy in the Cordillera Occidental, a statistical analysis is carried out between geospatial, meteorological and isotopic variables. The result indicates that temperature is controlled by altitude and latitude, while relative humidity is controlled by latitude, and summer precipitation is controlled by altitude and latitude. The stable isotopes of precipitation are controlled by temperature, altitude, latitude, longitude, and precipitation. Finally, based on these relationships, these variables are estimated by independent models throughout the study area and three isotopic models (summer, winter and annual). The isotopic compositions of the surface water and groundwater indicate the presence of evaporation and that they are similar to each other in each subbasin, both in the Salar de Atacama and in the Altiplano-Puna. Finally, the meteoric source of the waters of the Altiplano-Puna basins is more depleted of heavy isotopes than are the waters of the peripheral subbasins of the salar. Therefore, these results show that there is no hydraulic connection between basins and that there is no significant transfer of water from the Altiplano-Puna to the peripheral aquifer of the Salar de Atacama. This thesis presents a first view of the behavior of snow in the Toconao subbasin (subbasin east of the Salar de Atacama) through physical models. The total average precipitation was 139 mm/year in 2017, of which a third was in the form of snow. In summer the snow was above 4500 m asl and it melted in 10 days. In winter, when the temperature is lower, the snow cover covered much of the basin and slowly melted for a month.
Polymorphism and crystallization behaviour of triacylglycerols. From pure components to mixtures rich in oleic acid
(Universitat de Barcelona, 2022-07-15) Macridachis González, Jorge; Calvet Pallàs, Maria Teresa; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] Quality attributes of food products such as visual appearance, melting behavior, or shelf-life are strongly determined by the crystallization behavior of natural fats and oils within. In turn, this behavior depends on the polymorphism and the sort of mixing states (eutectic phase, solid solution phase, molecular compound formation) displayed by their major triacylglycerol components. Therefore, it becomes essential that studies regarding lipid crystallization cover from pure molecular components and their mixtures to real fats and oils. In connection with the above, this thesis focuses on gaining further fundamental knowledge about the polymorphism and crystalline behavior of lipid systems with varying degrees of complexity. Thus, the first stage of the research involved a study of pure triacylglycerols based on palmitic, lauric, and oleic acids (P, L, and O, respectively), which are typical of natural fats and oils such as lard and palm, olive, and coconut oils. During the second stage, binary and ternary mixtures including these triacylglycerols were examined to obtain an insight into their solid-state miscibility properties. Concretely, the mixtures were composed of a fully saturated triacylglycerol and one or two saturated-unsaturated triacylglycerols able to form a molecular compound. Despite the presumable crucial role of interactions including triacylglycerols forming molecular compound in the physical behavior of natural lipids and their blends, the phase behavior of triacylglycerol mixtures with such configuration is barely known. Finally, the third stage consisted of a more applied investigation of the crystalline and thermal properties of blends including natural fats. More specifically, binary blends of cocoa butter and shea butter stearin. Regarding the investigation of pure TAGs, calorimetric and X-ray diffraction techniques were used to examine the polymorphic occurrence and transformation behavior of PPP, LLL, OPO, and PPO during the application of dynamic thermal treatments at varying cooling and heating rates. The results showed that the polymorphic occurrence on cooling, as well as the sequence and type of transformations during heating, were influenced by the rate of the thermal treatments applied. However, it was also found that the extent of the kinetic influence depended on the intrinsic properties of triacylglycerols such as the length of the fatty acid chains or the characteristic polymorphism. The mixtures under examination during the phase behavior studies included the binary systems PPP/POP, PPP/PPO, PPP/OPO, LLL/POP, and LLL/PPO, and the ternary systems PPP/POP/OPO, PPP/POP/PPO, and LLL/POP/PPO (keeping an equimolecular ratio of POP/OPO or POP/PPO to favor molecular compound formation). Eutectic behavior with partial miscibility was observed under metastable and stable conditions. Furthermore, the results obtained for stable binary mixtures showed that the degree of miscibility was primarily influenced by the oleic acid content of the unsaturated component, as well as the differences in the size of the triacylglycerols within the mixture. From the solid-state miscibility observed in ternary systems containing LLL or PPP, it was concluded that third components may affect the mixing interactions associated with molecular compound formation. In addition, the results suggested that the ternary interactions studied may help to explain the crystallization behavior of edible lipids like palm oil and be useful in fat structuring applications. As a case study of real fat blends, combinations of cocoa butter and shea butter stearin at varying proportions were examined through calorimetric, X-ray diffraction, spectroscopic, and microscopic techniques. These made possible to characterize the effect of composition on the polymorphic crystallization and transformation properties, the melting profile, and the microstructural development. The results obtained for some of the parameters under study suggested that specific combinations might be considered for its application in chocolate-type confectionery products.
Carbon capture and storage in compressional basins: global to reservoir-scale assessments and integrated case study of the Puig-reig anticline (SE Pyrenees)
(Universitat de Barcelona, 2021-10-15) Sun, Xiaolong; Gómez Rivas, Enrique; Alcalde Martín, Juan; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] Carbon capture and storage (CCS) has been proposed as a potential technology to mitigate climate change. However, there is currently a huge gap between the global CCS deployment and that which will be ultimately required. To date, CCS deployment has been restricted to the most favourable tectonic settings, such as extensional passive margin and post-rift basins and compressional foreland basins. In addition, CCS deployment has stalled in most countries, with only limited commercial projects realised mainly in hydrocarbon-rich countries for enhanced oil recovery. This Ph.D. thesis aims to assess the potential of CCS development in compressional basins and hydrocarbon-limited regions at different scales: from a global-scale assessment to a national-scale assessment in Spain and finally, to a reservoir-scale analogue case study, focusing on the Puig-reig anticline (SE Pyrenees). Compressional settings host some of the most significant oil and gas resources in the world and will be key to the large-scale deployment of CCS. On the global scale, we present an integrated source-to-sink analysis tool that combines basin distribution, hydrocarbon resources and CO2 emissions to assess the potential of compressional basins for CCS development. This methodology allows identifying five high-priority regions for prospective CCS development in compressional basins: North America, north-western South America, south-eastern Europe, the western Middle East and western China. The results indicate that compressional basins will have to play a critical role in the future of CCS if this technology is to be implemented worldwide. Instead of developing CCS via CO2 enhanced oil recovery (CO2-EOR), hydrocarbon-limited countries need to devise alternative strategies if they intend to implement CCS in their decarbonisation strategies. On the national scale, we present a novel systematic source-to-sink assessment methodology based on a hubs and clusters approach to identify favourable regions for CCS deployment in hydrocarbon-limited countries. Throughout the evaluation of the Spanish case study, we identify 15 emission hubs from the power and the hard-to-abate sectors and priority source- to-sink clusters, based on screening and ranking processes using a multi-criteria decision-making method. North-Western and North-Eastern Spain are recognised as priority regions due to resilience provided by different types of CO2 sources and multiple geological storage structures. CCS, especially in the hard-to-abate sector, and in combination with other low-carbon energies, remains a significant contributor to the Paris Agreement’s mid-century net-zero target. This methodology can attract renewed public and political interest in viable deployment pathways of CCS in hydrocarbon-limited countries. The Ebro Foreland Basin, identified as one of the most potential areas for CCS development in Spain, is a typical hydrocarbon-limited compressional basin with low availability of geological and geophysical data required for the suitability assessment for CO2 storage. In this work, we carry out an integrated study of the Puig-reig anticline (SE Pyrenees) to be used as an outcrop analogue to explore the reservoir potential of foreland basin margin sedimentary systems. This anticline exposes continuous outcrops deposited in a proximal to medial fluvial fan system with an overall southeast downstream trend. The proximal deposits, mainly spreading in the northwest portion of the anticline, are characterised by conglomerates with minor interbedded sandstones. These are interpreted as having been deposited from unconfined flash floods and wide-shallow channel streams. The medial deposits, covering the rest of the anticline, consist of interbedded beds of conglomerates, sandstones and claystones, deposited in braided channel streams and overbanks. In order to understand the fracture distribution in the Puig-reig anticline and how it can potentially affect reservoir potential, fracture networks have been characterised using the linear scanline method, and four fracture sets (F1 to F4) have been identified in the target structure. The north limb shows low fracture intensity but large fracture length and aperture. The crest and the crest-limb transition zones present relatively high fracture intensity and variable fracture length and aperture. The south limb has low fracture intensity and small fracture length and aperture. Based on multiple linear regression analysis, we observe that fracture intensity is mainly controlled by the structural position, bedding thickness and lithological associations, with more intense fracturing in thin sandstone layers with multiple interlayers of fine deposits in the high strain zones. The fracture length mainly depends on bedding thickness and is affected by lithological associations. The fracture apertures are mainly controlled by lithofacies. An integrated analysis of structural, petrological and geochemical characteristics allows identifying five generations of calcite cements (Cc0 to Cc4) and fluid regimes in the Puig-reig anticline. Before intensive deformation, Cc0 precipitated in intergranular porosity from meteoric fluids in the phreatic zone. During the most intense phase of thrusting and folding, Cc1 precipitated in intergranular porosity, faults and F1 to F4 fracture sets from hydrothermal fluids migrated from the deep areas of the SE Pyrenees. During the late stage of fold growth, Cc2 mainly precipitated in normal and strike- slip faults in the anticline crest from the mixing between hydrothermal and meteoric fluids during the crestal collapse, or from hydrothermal fluids with shallower burial depth compared to that of Cc1. Cc3 mainly precipitated in faults and F1 and F4 fracture sets in the north-western zone of the anticline from formation fluids probably migrated through the frontal thrusts. During the continuous denudation, Cc4 precipitated in the reopened F1 to F4 fracture sets from meteoric fluids. The comparison of the Puig-reig anticline with other similar depositional and tectonic settings worldwide allows exploring the reservoir potential for CO2 storage at foreland basin margins. In the Puig-reig anticline, the proximal to medial deposits present low porosity of host rocks due to the prevailing presence of calcite cement, with limited high porosity concentrated in massive medium and coarse lithofacies in the medial fluvial fan. Sandstone lithofacies deposited from the medial fluvial fan and located in the high strain zones feature relatively high fracture intensity, which have relative high potential to be effective reservoirs. The study conducted in the Puig-reig anticline provides a conceptual model useful to understand the reservoir characteristics at the basin margins. According to this model, the reservoir potential is comprehensively controlled by sedimentology, diagenesis and deformation. The effective combination of both structure and facies can make basin margin locations potential areas for effective reservoirs, even in the presence of overall low porosity. Future work will focus on building a static reservoir model of the Puig-reig anticline based on the results obtained in the sedimentology, fracture and diagenesis studies, and finally carrying out fluid flow simulations to determine the main controls on CO2 injection and storage in such a geological setting.
Genesis and evolution of chromitites in ophiolite complexes from a mineralogical perspective
(Universitat de Barcelona, 2021-10-08) Farré de Pablo, Júlia; Proenza Fernández, Joaquín Antonio; González Jiménez, José María; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] The finding of a suite of unusual minerals associated to ophiolitic chromitites questions traditional model for the formation of these rocks. These findings include minerals typically considered indicators of ultra-high pressure and super-reducing conditions (i.e., diamond). Several authors proposed new genetic models for ophiolitic chromitites which involved their formation and/or evolution in the deep mantle (>410 km), opening an intense debate that is still active. This Ph.D. thesis contributes to this debate by studying four examples of ophiolitic chromitites from different geodynamic settings (fore-arc, back-arc, and supra-subduction mantle interacted with mantle plume) in order to evaluate the origin of these “exotic” minerals in ophiolitic chromitites and their possible meaning into the evolutionary history of these enigmatic rocks. The studied examples of chromitites formed in fore-arc settings include chromitite veins from Havana-Matanzas ophiolite (Cuba) and chromitite pods from Loma Las Cabirmas hill in Loma Caribe peridotite (Dominican Republic). The chromitites from Havana-Matanzas are characterized by abundant platinum-group mineral (PGM) inclusions and by being associated with orthopyroxenite in ophiolitic mantle section. Chromite studies reveal that the chromitites and orthopyroxenites formed coetaneously from Si- and Mg-rich andesitic melts with boninitic affinity originated in the fore-arc mantle of an intra-oceanic arc. The melts infiltrated the pre-existing harzburgite, dissolving olivine while precipitating orthopyroxene and chromite. The abundance of PGM is interpreted to result from the “collector” effect of chromite during the chromitite formation, which was enhanced due to the small volume of chromitites formed. The Loma Las Cabirmas chromitites display unusually high platinum-group elements (PGE) contents and hydrothermal PGE mineralizations. The study of these chromitites suggests that hydrothermal fluids infiltrated the chromitites during serpentinization of the rocks and gave place to the in situ alteration of magmatic PGM in the chromitites and the precipitation of hydrothermal Pt-rich mineralization in uvarovite- and chromian clinochlore-filled fractures, within the thermal range of 350–150 ºC. Therefore, the PGE bulk geochemistry and mineralogy of these chromitites was largely impacted by post-magmatic processes. Microdiamonds were found in situ in ophiolitic chromitites from Tehuitzingo serpentinite (Mexico), interpreted as an ophiolitic mantle section formed in a back-arc geodynamic setting. Micrometric diamonds were located within healed fractures crosscutting the chromite grains. These diamonds were associated with amorphous C bearing O-species and with a low-pressure and low-temperature mineral assemblage. Thermodynamic calculations show that the chromite from the healed fractures recrystallized at 670–510 ºC. Consequently, the diamonds are inferred to be metastable and form from C undersaturated CO2–H2O–CH4 fluids infiltrating the chromitite during serpentinization processes. The diamond formed due to the super-reducing conditions achieved within the sealed inclusions. The formation of microdiamonds in (ultra)reduced low-pressure and low-temperature environments during serpentinization challenges the idea that diamond in ophiolitic rocks constitutes an unequivocal indicator of ultra-high pressure conditions. Chromitites from the northern and central part of the Loma Caribe peridotitic belt (Dominican Republic) were studied as an example of chromitites hosted in an ophiolite with geochemical fingerprints of deep-seated plume activity. These chromitites display unusual compositions, different from other ophiolitic chromitites. Instead, the analyzed chromite grains exhibit major and trace element composition that overlaps the field of komatiitic chromite. Moreover, the composition of parental melts of these chromitites is similar to plume derived products of the Dominican Republic. Therefore, I inferred that these chromitites formed in the lithospheric mantle after parental melts derived from an enriched peridotite source influenced by the Caribbean mantle plume. Altogether, my results show the importance of differentiating features resulting from magmatic primary processes from those resulting from alteration processes. Only then it will be possible to reconstruct the genetic story and evolution of the chromitites and propose accurate models.
Fluid flow evolution in the Alpine-related basement and sedimentary cover structures in the Southern Pyrenees: an integrated structural, petrographic and geochemical approach
(Universitat de Barcelona, 2021-09-23) Muñoz López, José Daniel; Travé i Herrero, Anna; Alías López, Gemma; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] This PhD thesis examines the fracture-fluid interactions across different compressional structures affecting both Paleozoic basement and Mesozoic-Cenozoic cover lithologies in the Southern Pyrenees in order to investigate the relationships between fluid flow and deformation. The studied structures include the Estamariu thrust in the Pyrenean Axial Zone and the Sant Corneli-Bóixols anticline along the front of the Bóixols thrust sheet in the Southern-Central Pyrenees. The proposed methodology integrates field data with U-Pb dating and petrographic and geochemical (δ18O, δ13C, 87Sr/86Sr, clumped isotopes and elemental composition) analyses of vein cements, fault rocks and host rocks present in the study area. The Estamariu thrust resulted from a multistage late Paleozoic to Neogene tectonic evolution. Despite this thrust is known to be Variscan in origin, in the study area it places a Devonian pre-Variscan unit on top of a Stephano-Permian late to post-Variscan sequence, indicating that the structures within this thrust zone have to be post-Variscan. The contractional structures found at the contact between Devonian and Stephano-Permian units have been attributed to the Alpine reactivation of the Estamariu thrust. This Alpine-related deformation is consistent with the transposition of the Variscan regional foliation within the main thrust zone and with the formation of a subsidiary thrust zone in the footwall of the Estamariu thrust. Other structures found in the study area, such as extensional fractures, shear bands and normal faults, postdate the reverse structures and have been attributed to the Neogene extension. In the Sant Corneli-Bóixols anticline, the folded units involve Jurassic-mid Upper Cretaceous pre-compression and latest Cretaceous-Paleocene syn-orogenic sedimentary successions detached on Upper Triassic evaporites. Contrary to the Estamariu thrust, in the Sant Corneli- Bóixols anticline this PhD thesis provides the absolute age of deformation reporting 23 U- Pb dates measured in different sets of fracture-filling calcite cements. These U-Pb dates reveal Late Cretaceous to late Miocene age variations, which are coeval with growth strata deposition and Bóixols thrust sheet emplacement (dates from 71.2 ± 6.4 Ma to 56.9 ± 1.4 Ma), tectonic transport of the Bóixols thrust sheet above the southern Pyrenean basal thrust (dates from 55.5 ± 1.2 Ma to 27.4 ± 0.9 Ma) and post-orogenic exhumation of the Sant Corneli-Bóixols anticline (dates younger than 20.8 ± 1.2 Ma). Throughout this long-lived deformation history, the geochemical data of the successive calcite veins allow to analyze the relationships between fluid flow and deformation in the two studied domains. In the Estamariu thrust, the high 87Sr/86Sr ratios of the different calcite cements indicate the interaction between the vein-forming fluids and radiogenic Paleozoic basement rocks. The geochemical evolution from the earliest to the latest calcite cements also evidence a progressive change in the fluid regime and composition during successive compressional and extensional tectonic events. The progressive increase in precipitation temperatures, from 50 ºC to around 210 ºC, and enrichment in δ18Ofluid, from -6.4 to +12 ‰SMOW, in cements attributed to the Alpine compression to cements from the Neogene extension, is probably linked to a higher extent of fluid-rock interaction with basement rocks. By contrast, during the latest stages of the Neogene extension, the geochemistry of the youngest calcite cements evidence the percolation of cold meteoric fluids that indicates a more significant change in the fluid regime, from upward to downward fluid migration. In the Sant Corneli-Bóixols anticline, the fluid origin and the extent of fluid-rock interaction varied in the several structural positions of the fold and according to the age and nature of their stratigraphy and the involved fracture networks. This evidences a compartmentalization of the fluid system. In the core of the anticline and in the lowest part of the synorogenic sequence from the footwall of the Bóixols thrust, the similar petrographic and geochemical features between successive calcite cements and host rocks indicate a closed fluid system, leading to high extent of fluid-rock interaction. This host-rock buffered fluid was likely derived from the surrounding Lower Cretaceous and Upper Cretaceous marine carbonates, respectively. Contrarily, along large faults, such as the Bóixols thrust, which affect the entire anticline and in the fold limbs, the fluid system was open. Large faults registered the upward migration of fluids in thermal and geochemical disequilibrium with surrounding host rocks, as attested by the light δ18O values of their associated vein cements, down to -14 ‰VPDB, and the high temperature of precipitation, up to 120 ºC. The fold limbs registered the infiltration of meteoric waters, corroborated by the low Sr contents and by the δ18O and δ13C values of the vein cements, from -8 to -6 ‰VPDB and down to -10 ‰VPDB, respectively, which are typical values of meteoric carbonates. In the fault zone of the Bóixols thrust, successive fracture systems and related calcite cements highlight an episodic evolution of the thrust zone. The presence of early extensional fractures and a chaotic breccia is consistent with the formation of dilatant fracturing within a process zone (around the fault tip) during initial fault growth, whereas the formation of the latest fracture system points to hybrid shear-dilational failure during propagation of the Bóixols thrust. Similarly, the different structural and fluid flow histories in the footwall and hanging wall of the Bóixols thrust indicate a compartmentalization of the thrust zone. Clumped isotopes applied to vein cements from the footwall evidence a progressive increase in precipitation temperatures from 50 ºC to 117 ºC, approximately, and an enrichment in δ18Ofluid, from -1.8 to +5.5 ‰SMOW. This has been interpreted as a change in the fluid source from meteoric fluids to evolved meteoric fluids due to water-rock interaction at increasing depths and temperatures. Contrary to the footwall, clumped isotopes applied to vein cement from the hanging wall, which is the same cement found in the fault core, revealed temperatures around 95 ºC and δ18Ofluid up to +1.9 ‰SMOW. This has been interpreted as the migration of formation waters from the fault core and towards the hanging wall. Therefore, the Bóixols thrust likely acted as a transverse barrier, dividing the thrust zone into two separate fluid compartments, and a longitudinal drain for migration of fluids. Altogether, the maximum temperatures and δ18Ofluid, up to 120 ºC and +5.5 ‰VSMOW, obtained in the Sant Corneli-Bóixols anticline, implying 3-4 km depth and presence of formation waters, respectively, together with the 87Sr/86Sr ratios of the vein cements, within the range of values documented in the sedimentary cover, discard the transfer of fluids between the basement and the sedimentary cover in the Southern-Central Pyrenees. This indicates that the paleohydrological system in the Sant Corneli-Bóixols anticline was restricted to the Bóixols thrust sheet above the Upper Triassic detachment level. This evaporitic detachment likely acted as a lower fluid barrier, preventing the input of fluids from deeper parts of the belt, as interpreted in other areas of the Pyrenees and in other detached thrust systems as the Central Appalachians and Sierra Madre Oriental. Finally, comparing the results obtained in both studied domains with those reported in previous contributions, this study assesses the fluid flow and deformation relationships at regional scale. On the one hand, this thesis highlights a common fluid flow behavior along strike in the central-eastern part of the southern Pyrenees, where major faults acted as transfer zones for migration of fluid in thermal and geochemical disequilibrium with adjacent host rocks, whereas background fracturing recorded the presence of fluids that highly interacted with surrounding host rocks. Additionally, our data indicates that regardless of the fluid origin and the tectonic context, the fluids that have interacted with basement rocks have a higher 87Sr/86Sr ratio (> 0.710) than those that have circulated through the sedimentary cover (< 0.710). Lastly, extensional deformation structures in the eastern Pyrenees have acted as conduits for hydrothermal fluid migration in Neogene times similarly as in the northern part of the Catalan Coastal Ranges. These fluids likely interacted with basement rocks before ascending through fault zones and related fractures.
Diverse origin and processes in the formation of diamond and other exotic minerals in ophiolitic chromitites
(Universitat de Barcelona, 2021-06-30) Pujol Solà, Núria; Proenza Fernández, Joaquín Antonio; García-Casco, Antonio; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] The discovery of ultra-high pressure (UHP), super-reduced (SuR), and continental crust-derived minerals in ophiolitic chromitites worldwide challenged the previous hypotheses for chromitite formation and motivated the proposal of complex geodynamic models involving UHP conditions of formation for the chromite or recycling of the ophiolitic rocks down to the Mantle Transition Zone (410 – 660 km depth). This thesis investigates in detail the chromitites and the associated ophiolitic rocks from the Moa-Baracoa massif, eastern Cuba, and Bou Azzer, Morocco, with emphasis on identifying the presence of exotic minerals, interpreting their formation, and understanding the related geodynamic processes. The interaction of preexisting chromitites with evolved tholeiitic melts that triggered Fe-Ti-Zr metasomatism in the Potosí chromitites (eastern Cuba) is carefully investigated here. There is evidence of coarse granular textures and strongly variable mineralogy composed of recrystallized/neoformed Fe3+-Ti-rich chromite, Ti-rich amphibole, clinopyroxene, orthopyroxene, olivine, Mg-rich ilmenite, Zr-bearing oxides and silicates, and Fe-Cu-Ni sulfides. Thorough petrographic analysis coupled with the chemical composition of the mineral phases allowed to determine the sequence of mineral formation and to propose a two-stage genetic model: 1) the crystallization of an evolved MORB liquid, via fractional crystallization, produced water-rich residual melts strongly enriched in incompatible elements, and 2) batches of this evolved melt escaped and extensively reacted and metasomatized the surrounding chromitites. U/Pb dating of baddeleyite indicates that the age of the metasomatic event (134.4 ± 14 Ma) matches the age of magmatism related to ophiolite construction in eastern Cuba. The high-Al chromitites of eastern Cuba contain exotic minerals of the three categories: diamond, oriented clinopyroxene and rutile lamellae, graphite-like amorphous carbon, moissanite, native Cu and Si, Fe-Mn alloys, zircon, corundum, and quartz. The studied diamond grains are nanometric in size, located in CH4-bearing fluid inclusions within olivine, and systematically associated with a typical serpentinization mineral assemblage composed of serpentine and magnetite. Textural-mineralogical evidences indicate that nanodiamond formed during low-pressure and low-temperature serpentinization in super-reduced microenvironments (log[fO2;MPa]=−45.3; ΔlogfO2[Iron-Magnetite]=−6.5). The other SuR minerals (moissanite, graphite-like amorphous carbon, native elements, and alloys) also formed in super-reduced CH4-rich microenvironments. On the other hand, nominally UHP phases such as the clinopyroxene lamellae formed as exsolutions after the crystallization of chromite or can represent silicate melt inclusions attached to the growing chromite grains. Oriented rutile lamellae formed after the interaction of chromitites with mafic magma. Finally, continental crust-derived minerals, such as zircon, likely represent xenocrystic material derived from the subducting slab that was entrapped by the chromitite parental melts. The investigation of the Neoproterozoic Bou Azzer chromitites (Morocco) allowed the comparison with the younger Cretaceous Cuban chromitites and other Phanerozoic and Precambrian chromitites. It was possible to determine that the Bou Azzer chromitites formed in the fore-arc setting during subduction-initiation with two stages of evolution: 1) formation of intermediate-Cr chromitites from fore-arc basalts (FAB), and 2) formation of high-Cr chromitites after boninitic melts. These chromitites host inclusions of platinum group minerals and exotic minerals. The unusual mineralogy includes oriented clinopyroxene lamellae, moissanite, native Cu, diaspore, and zircon formed after chromite crystallization and post-magmatic serpentinization processes, thus completely ruling out UHP conditions. Altogether, the results of these investigations represent the first descriptions of exotic minerals in the Cuban and Moroccan ophiolites. The corresponding discussions allowed to reject hypotheses of ultra-high pressure formation or recycling for the studied chromitites and the associated ophiolitic sequences and to ultimately provide simpler formation models for the exotic minerals. Additionally, the investigation provided definitive evidence for the formation of metastable nanodiamond, and other SuR phases, during serpentinization of the oceanic lithosphere at low-pressure and low-temperature conditions. Therefore, the presence of diamond in oceanic rocks, in particular chromitites, cannot be taken as a general indication of deep mantle recycling.
Optimization of induced denitrification strategies in polluted water bodies from agricultural sources
(Universitat de Barcelona, 2020-02-28) Margalef Marti, Rosanna; Otero Pérez, Neus; Carrey Labarta, Raúl; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[eng] The worldwide persistence of nitrate (NO -) in groundwater is worrying since this compound has been related to human illnesses and to eutrophication of aquatic ecosystems. The main sources of pollution are linked to intensive use of fertilizers and septic system leakage. Since 1991, European directives have been applied to mitigate NO - pollution by limiting N application in agricultural lands. However, due to the long residence time of N in the soil organic matter pool, the outcome of the implemented management practices can be delayed for decades. Consequently, remediation strategies must be developed and optimized. The NO3- reduction to innocuous dinitrogen gas (N2), can occur intrinsically in many environments due to the ubiquity of denitrifying microorganisms. However, the electron donor presence is usually a limiting factor in the contaminated aquifers. Hence, one feasible treatment involves inducing the denitrification by application of an external electron donor. During the implementation of bioremediation strategies, the contaminant removal can be estimated by monitoring its concentrations before and after the treatment. However, this method does not reveal the specific processes involved in the attenuation, making it challenging to focus on the improvement of the remediation approach. Isotopic analyses have proved to be a powerful tool in identifying the sources and transformation processes of groundwater contaminants. During the enzymatic NO3- reduction, the unreacted residual substrate becomes enriched in the heavy isotopes 15N and 18O, allowing to distinguish the biotic reduction from processes such as dilution with non-polluted water that could also lead to a concentration decrease without influencing the isotopic signature. The present thesis focusses on investigating the use of low-cost electron donors to promote the denitrification, and on using isotopic tools to evaluate the denitrification efficiency at field- scale. The tested materials in batch and flow-through experiments were: whey, corn stubble, wheat hay, animal compost, magnetite, siderite and olivine. Different parameters that could affect the biotic NO3- reduction efficiency were evaluated (e.g., temperature, ratio between electron donor and acceptor, harmful by-product accumulation, abiotic reactivity or coexistence of other contaminants) and the isotopic fractionation values (ε15N and ε18O) were determined for all tested conditions. At field-scale, three different polluted water bodies were studied, in which the determined ε15N and ε18O at the laboratory were applied to quantify the natural and/or induced denitrification. In a polluted aquifer in Spain, the NO3- attenuation was evaluated during a long-term induced denitrification strategy by acetic acid injections. In a polluted aquifer in Argentina, the natural NO3- attenuation was evaluated considering changes in the reactivity and isotopic fractionation due to the simultaneous presence of NO - and Cr6+. Finally, in a constructed wetland (CW) treating agricultural runoff water, the NO - attenuation was evaluated before and after application of an electron donor both in the autumn-winter and spring-summer seasons. The laboratory experiments demonstrated that magnetite nanoparticles, corn stubble, wheat hay, animal compost and whey could efficiently promote the denitrification in polluted water bodies. In these biotic experiments, the complete NO3- reduction to N2 was demonstrated by transient or negligible accumulation of other nitrogen compounds such as nitrite (NO2-), ammonium (NH +) or nitrous oxide (N O). However, the N O was found to be the end- product of the abiotic NO - reduction, which can be mediated by ferrous iron, if present. The ε15NNO3/N2 and ε18ONO3/N2 values were calculated for all the batch experiments and for the periods of the flow-through experiment that allowed complete denitrification. For the non- complete denitrification periods, the NO - isotopic characterization showed a mix of denitrified and non-denitrified water at the outflow. The isotopic characterization of NO - and N2O allowed to distinguish the biotic from the abiotic NO - reduction by ferrous iron at the laboratory-scale. A two-stage isotopic fractionation pattern was found for Cr6+, which can be reduced simultaneously to NO -. Also, the carbon compounds isotopic analysis allowed to assess the fate of the studied organic carbon materials to be used as electron donors. In the field-scale studies, the chemical and isotopic characterization allowed to trace the extent of the natural or induced denitrification and to evaluate the safety of the treatments. In a pilot plant to remediate groundwater NO3- pollution (Spain), acetic acid was injected by pulses to an alluvial aquifer for 22 months. According to the isotopic results, the induced denitrification achieved at least 50 % NO3- attenuation. The isotopic analyses also allowed to identify the reoxidation of NO2- to NO3- during the treatment and to recognize a mixture between the denitrified and partially or non-denitrified groundwater in one of the sampling points. In a polluted aquifer with both NO3- and Cr6+ (Argentina), the calculated natural attenuation was 20 % for NO3- and 60 % for Cr6+. For this calculation, the two stage trend observed for the ε53Cr was considered. The attenuation of Cr6+ in a few samples was found to be due by both reduction and dilution. In a CW treating agricultural runoff water, a slight natural NO3- attenuation was only observed when the flow was below 5.5 L/s. According to the isotopic results, after the biostimulation by stubble application, at least 60 % NO3- was removed at 16 L/s. The biostimulation treatment in autumn lasted in one month, while in spring the attenuation remained for three months.
Estudi petrogenètic del complex intermedi-màfic-ultramàfic de Susqueda (Serralada Prelitoral Catalana). Implicacions en la gènesi i evolució del plutonisme hercinià del NE de la Península Ibèrica.
(Universitat de Barcelona, 2021-03-18) Esteve i Girbés, Sergi; Enrique, P. (Pere); Alías López, Gemma; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[cat] El Complex de Susqueda constitueix el major aflorament de roques màfiques i ultramàfiques associades a granitoides hercinians de la Serralada Costanera Catalana. Des dels inicis del segle passat, les roques màfiques de Susqueda, dominades per plagiòclasi i hornblenda com a mineral màfic, i amb quars en quantitats variables, havien estat considerades de manera conjunta com a diorites. La cartografia i la descripció petrogràfica de detall realitzada en aquesta tesi ha permès determinar que el gruix del Complex està format per una amalgama de petites intrusions màfiques, principalment per bojites i quarsobojites, les quals es caracteritzen per una plagiòclasi més càlcica (An > 50) que la corresponent a les diorites. Aquestes litologies dominants estan associades a una gran diversitat de litologies menors, entre les quals destaquen roques ultramafiques com les hornblendites olivíniques. Les relacions intrusives observades suggereixen, a més a més, que les roques del Complex es van emplaçar amb posterioritat tant a les principals fases de deformació hercinianes com a les fases més tardanes. Les roques màfiques estan sovint associades a cossos de granodiorita biotítica i presenten relacions de mescla de magmes amb aquestes, amb la consegüent generació d’un variat espectre de roques híbrides de composició tonalítica. Aquestes relacions indiquen la coexistencia de magmes de composició bàsica i àcida en estat de fusió parcial i plantegen la possibilitat d’un nexe genètic entre ambdós. L’estudi de la geoquímica dels minerals de les diferents litologies posa de manifest l’afinitat gabroica de les roques màfiques i ultramàfiques del Complex, i ha permès obtenir estimacions de pressió i temperatura per a algunes d’elles. Les hornblendites olivíniques, per exemple, semblen haver-se format a pressions entre els 12 kbar i els 6 kbar i al voltant dels 1000 °C; mentre que la resta de litologies donen rangs inferiors de pressió i temperatura, des de 6 kbar i 1000 °C fins a 1 kbar i 650 °C. Les dades geoquímiques d’elements majoritaris en roca total mostren una certa dispersió composicional en el grup de les bojites, a partir de les quals es reconeixen al menys dues tendències evolutives. Aquestes tendències no es poden explicar només per cristal·lització fraccionada de magmes bàsics, sinó que suggereixen la participació de processos de mescla tant de magmes àcids i bàsics (evidenciats per les zones híbrides heterogènies) com de magmes bàsics i fraccionats cristal·lins, responsables de la formació de les hornblendites olivíniques. En general, les diferents litologies que conformen el Complex defineixen una sèrie calcoalcalina amb caràcter càlcic, amb una bona representació de l’extrem més bàsic, i suggereixen la participació del mantell en un context de marge compressiu amb subducció associada. Les dades isotòpiques, a més a més, indiquen que el mantell involucrat en la petrogènesi del Complex tenia una component marcadament radiogènica. Les bojites podrien representar petits volums de magmes que s’han segregat de cossos basàltics generats per la fusió del mantell i estancat a nivells més profunds o a la base de l’escorça. El Complex de Susqueda, situat en una posició marginal, és el testimoni dels processos petrogenètics i les complexes interaccions que van precedir (i potser també desencadenar) les intrusions principals de granodiorites i monzogranits del Batòlit Costaner Català.
El volcanismo calcoalcalino y peralcalino del suroeste de Cerdeña (Italia) y mineralizaciones asociadas
(Universitat de Barcelona, 2020-11-19) Carrazana Di Lucia, Ariana; Gimeno Torrente, Domingo; Universitat de Barcelona. Departament de Mineralogia, Petrologia i Geologia Aplicada
[spa] El volcanismo oligo-mioceno del Sulcis, SO de Cerdeña (Italia) presenta la particularidad de contener rocas peralcalinas y alcalinas de un ambiente geodinámico anorogénico posterior a la actividad orogénica relacionada con la subducción de una placa oceánica durante la migración antihoraria del bloque Sardo-Corso y la sincrónica creación de la cuenca Liguro-Provençal. La geocronología 40Ar/39Ar (feldespatos), marca el final de la actividad magmática calcoalcalina a 16.18±0.04 Ma (Burdigaliense) y el inicio del episodio anorogénico a 15.96±0.04 Ma (Langhiniense inferior). La duración del evento peralcalino fue de 350 ka según edades U-Pb en zircones. El volcanismo del Sulcis está relacionado con una caldera elíptica de 30x20 km con su eje mayor de dirección NE-SO, de tipo depresión volcano-tectónica de apertura gradual, relacionada con esfuerzos transcurrentes senestrales a través de lineamientos tectónicos regionales paralelos a la Fosa Sarda. Un modelamiento geológico 3D en el Entroterra Sulcitano permitió calcular 21 km3 de flujos ignimbríticos eruptados en un período de ~1.5 Ma. Se estima que el volumen eruptivo en todo el SO de Cerdeña se aproxima a 100 km3, constituyendo una de las mayores calderas del Mediterráneo Occidental. Importantes mineralizaciones de Mn (Fe-Ba) de origen volcánico-hidrotermal están controladas estructuralmente por la intersección de fallas radiales con el sistema de anillos de la caldera. Una cartografía detallada en San Pietro, Sant’Antioco y el Entroterra Sulcitano, permitió dividir una secuencia de ~1300 m de rocas ígneas dómicas, lávicas y piroclásticas en 7 series volcánicas con 25 unidades y 42 subunidades compuestas por andesitas, traquiandesitas, riolitas, comenditas y pantelleritas. Importantes evidencias de vulcanismo submarino se presentan en la Isla de San Pietro en un ambiente marcado por actividad magmático-hidrotermal al final de la serie riolítica media (MRH) y la serie comendítica inferior (LCO). Esta actividad tectono-magmático-hidrotermal es más importante en San Pietro, entre Macchione y Cala Fico, a lo largo de una falla E-O radial a la caldera, con un depósito tipo SEDEX proximal intercalado entre las unidades de Montagna di Capo Rosso y Matzaccara, compuesto por óxidos de Mn, jaspes y ocres que corresponden con el primer sistema mineralizado genéticamente relacionado con el colapso de la caldera, cambio en las condiciones locales del nivel del mar, reactivación de fallas que limitan horst y grabens y circulación de fluidos de origen magmáticos y marino. Este sistema hidrotermal está activo en la parte superior de la serie MRH durante ~10 ka. Un segundo sistema hidrotermal se produce con la erupción de las primeras unidades comendíticas de la serie LCO, también en un ambiente con influencia marina y mineralizaciones de Mn-Fe de tipo hidrotermal-epigenético que ocurren ~220 ka después del primer evento. Mineralizaciones menores de Mn suceden durante la erupción de la unidad Monte Ulmus en San Pietro y Sant’Antioco, y en las unidades Punta Mingosa y Post-Calasetta, principalmente asociados con zonas de blisters donde precipitan óxidos de Fe y se produce argilización y silicificación intensa. Los blisters en las unidades superiores de la secuencia indican un período de desgasificación importante de la cámara magmática en los estadios terminales del magmatismo del Sulcis. La geoquímica isotópica de elementos radiogénicos (Sr-Nd-Pb) muestra que la cuña mantélica implicada en la generación de rocas andesíticas y riolíticas del ambiente orogénico tienen mezcla de componentes DMM+EM1, mientras que los magmas peralcalinos y los previos (MRH) presentan una fuerte señal del componente EM2. El estudio comparado de elementos traza y radiogénicos (87Sr/86Sr vs. Zr/Nb) muestra un enriquecimiento en la isotopía de Sr a medida que los magmas peralcalinos evolucionan por cristalización fraccionada, esto permite trazar los aportes de magmas menos evolucionados que llegan sucesivamente, mostrando una señal mantélica de mayor profundidad, desencadenado las erupciones.

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