Person: Astilleros García-Monge, José Manuel
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First Name
José Manuel
Last Name
Astilleros García-Monge
Affiliation
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Department
Mineralogía y Petrología
Area
Cristalografía y Mineralogía
Identifiers
10 results
Search Results
Now showing 1 - 10 of 10
Item The role of sulfate in the hydrothermal replacement of aragonite single crystals by calcite(Earth and Planetary Science Letters, 2024) Forjanes Pérez, Pablo Cayetano; Astilleros García-Monge, José Manuel; Fernández Díaz, María LourdesAragonite (CaCO3) is a stable calcium carbonate phase under high pressure conditions. However, its formation in (sub)surface environments, where calcite is the stable polymorph, is widespread. Regardless of its origin, aragonite is expected to undergo transformation into calcite under moderate pressures and temperatures. However, this transformation does not always take place, which results in the presence of abundant aragonitic relics in the geological record. Traditionally, this preservation has been explained by the presence of chemical inhibitors that prevent the conversion of aragonite to calcite. While it is widely accepted that magnesium (Mg) plays a key role in the polymorphic selection of CaCO3, the influence of other ions has also been suggested. This work evaluates the effect that different concentrations of sulfate (SO42−) in the fluid has on the progress of the aragonite-to-calcite transformation at 220 °C. Our results show that, upon reaction with deionized water or sulfate-poor solutions ([SO42−]aq < 0.1 mM), aragonite single crystals are extensively replaced by calcite aggregates (crystal size > 15 µm) through an interface coupled dissolution-precipitation reaction. The replacement starts at the aragonite crystal surfaces and advances inwards thanks to the development of an extensive network of fractures. Contrarily, when the solution bears higher concentrations of sulfate ([SO42−]aq > 0.1 mM), only a thin layer of smaller crystals of calcite (< 10 µm) form on the aragonite substrates, without any further transformation taking place. We interpret that these smaller crystals exert too little crystallization pressure and fail to promote the development of a network of fractures. In the absence of this network, the aragonite-calcite transformation cannot take place. The transformation does not occur neither when the experiments are conducted with deionized water and fragments of gypsum or anhydrite together with the aragonite grains. The results of this study shed light on the influence of dissolved sulfate in the kinetics of the fluid-driven transformation of aragonite into calcite. These results are useful to understand the preservation of aragonite in a variety of current geological settings and provide valuable insights for better understanding the diagenesis of sedimentary carbonates.Item Dissolution and sorption mechanisms at the aluminosilicate and carbonate mineral-AMD (Acid Mine Drainage) interface(Applied Geochemistry, 2021) Kollias, K.; Godelitsas, Athanasios; Astilleros García-Monge, José Manuel; Ladas, S.; Lagoyannis, Anastasios; Mavromoustakos, Th.Aluminosilicate/silicate and carbonate materials (pure and industrial) interacted with natural Acid Mine Drainage (AMD) under ambient conditions for different time periods in order to elucidate the chemical processes at the aluminosilicate and carbonate mineral-AMD interface. More precisely, powdered materials were subjected to macroscopic neutralization experiments (using on-line pH-measurements, Inductively Coupled Plasma Optical Emission Spectroscopy, Powder X-ray Diffraction and Scanning Electron Microscopy with Energy Dispersive Spectroscopy), whereas interacted mm-sized single crystals were examined by means of nanoscale microscopic (in-situ Atomic Force Microscopy) and surface & bulk spectroscopic techniques (X-ray Photoelectron Spectroscopy, 12C-Rutherford Backscattering Spectroscopy, Solid-State 29Si and 27Al Magic-Angle-Spinning Nuclear Magnetic Resonance). The carbonates were proven to be more effective for neutralization of AMD, related to adequate removal of metals from the contaminated aqueous medium, but they are readily dissolved. The application of aluminosilicate/silicates showed that the removal of metals is considerably lower, and the pH stabilized at lower values, but they are more resistant. The investigation of interacted zeolite and calcite crystals revealed changes to the macrotopography, microtopography and nanotopography of surfaces. It was indicated that coupled dissolution and sorption (surface precipitation/co-precipitation, nucleation/crystal growth, adsorption or even absorption-including solid-state diffusion) phenomena occur simultaneously. Based on the experimental results, two generalized models -in nano(molecular)-scale- can be suggested regarding interaction of AMD with aluminosilicate and carbonate mineral surfaces.Item Cinética de disolución de superficies (𝟏𝟎𝟏̅𝟒) de calcita en presencia de diferentes sales de Cu2+ disueltas en agua(Macla, 2023) Pérez Garrido, Carlos; Astilleros García-Monge, José Manuel; Fernández Díaz, María LourdesLas interacciones de polimorfos del carbonato cálcico (CaCO3), principalmente calcita y aragonito, con soluciones acuosas que contienen metales contaminantes tiene un gran interés medioambiental ya que las superficies de estas fases minerales tienen la capacidad de secuestrar de forma eficaz dichos contaminantes mediante procesos acoplados de disolución-precipitación y/o adsorción (Godelitsas et al., 2003; Prieto et al., 2003). Este estudio pretende, por un lado, valuar los cambios producidos sobre las superficies de calcita en contacto con soluciones acuosas ricas en Cu2+ de diferente concentración, y por otro, estudiar la posible influencia en esos cambios de los aniones que pueden acompañar a este catión, para lo que se han utilizado soluciones de tres sales diferentes CuCl2·2H2O, CuSO4·5H2O y Cu(NO3)2·H2O.- Project number: 231
Item Creación de una Colección Multimedia de Minerales al Microscopio Petrográfico: Un Aspecto Central en la Formación en Geociencias(2023) Pérez Garrido, Carlos; García Rivas, Javier; Forjanes Pérez, Pablo Cayetano; Luque del Villar, Francisco Javier; Fernández Díaz, María Lourdes; Astilleros García-Monge, José Manuel; Yesares Ortiz, María Dolores; Carmona Tijerín, Victor; Esteban Ruiz, Paula; Fernández Riveras, Camila Isabel; García Herrador, Miguel; Sánchez Acosta, Rubén; Garrido Sánchez, AzaelEste Proyecto Innova Docente tiene como objetivo realizar una labor apenas desarrollada hasta ahora: la digitalización de muestras de minerales transparentes de la colección de las asignaturas “Mineralogía I” de GG y “Cristalografía y Mineralogía” de GIG del Departamento de Mineralogía y Petrología de la UCM. A través de la digitalización de las muestras (fotos y vídeos) se busca crear un repositorio (accesible a través de la página web del departamento y material para el Campus Virtual de las asignaturas implicadas) en el que los estudiantes puedan consultar fácilmente las propiedades ópticas de los minerales vistos en prácticas, incluyendo sus cambios en función de las diferentes orientaciones. Este repositorio multimedia pretende marcar una clara diferencia con otros repositorios de otras universidades, en los cuáles únicamente se dispone de fotografías, las cuales por si solas no permiten observar claramente muchas de las características distintivas en minerales anisótropos. Consideramos que la digitalización de estas colecciones serán de gran ayuda para el adecuado aprendizaje y estudio de las diferentes asignaturas que utilizan la microscopía de luz transmitida, ya que la accesibilidad a este tipo de microscopios por parte de los alumnos fuera de la universidad es nula o muy limitada. Además, estos materiales serán esenciales en caso de suspensión de la actividad presencial o como apoyo a las actividades realizadas por los alumnos en el aula. También se pretende involucrar a estudiantes de las asignaturas en cuestión en el desarrollo de este Proyecto, tanto los incluidos en la convocatoria como otros alumnos de la asignatura que, a posteriori, quieran sumarse a la tarea. Item The Formation of Barite and Celestite through the Replacement of Gypsum(Minerals, 2020) Forjanes Pérez, Pablo Cayetano; Astilleros García-Monge, José Manuel; Fernández Díaz, María LourdesBarite (BaSO4) and celestite (SrSO4) are the end-members of a nearly ideal solid solution. Most of the exploitable deposits of celestite occur associated with evaporitic sediments which consist of gypsum (CaSO4·2H2O) or anhydrite (CaSO4). Barite, despite having a broader geological distribution is rarely present in these deposits. In this work, we present an experimental study of the interaction between gypsum crystals and aqueous solutions that bear Sr or Ba. This interaction leads to the development of dissolution-crystallization reactions that result in the pseudomorphic replacement of the gypsum crystals by aggregates of celestite or barite, respectively. The monitoring of both replacement reactions shows that they take place at very different rates. Millimeter-sized gypsum crystals in contact with a 0.5 M SrCl2 solution are completely replaced by celestite aggregates in less than 1 day. In contrast, only a thin barite rim replaces gypsum after seven days of interaction of the latter with a 0.5 M BaCl2 solution. We interpret that this marked difference in the kinetics of the two replacement reactions relates the different orientational relationship that exists between the crystals of the two replacing phases and the gypsum substrate. This influence is further modulated by the specific crystal habit of each secondary phase. Thus, the formation of a thin oriented layer of platy barite crystals effectively armors the gypsum surface and prevents its interaction with the Ba-bearing solution, thereby strongly hindering the progress of the replacement reaction. In contrast, the random orientation of celestite crystals with respect to gypsum guarantees that a significant volume of porosity contained in the celestite layer is interconnected, facilitating the continuous communication between the gypsum surface and the fluid phase and guaranteeing the progress of the gypsum-by-celestite replacement.Item Aproximación experimental a la formación de yacimientos de celestina: El efecto del bario(Macla, 2022) Forjanes Pérez, Pablo Cayetano; Astilleros García-Monge, José Manuel; Fernández Díaz, María LourdesItem xperimental burial diagenesis of aragonitic biocarbonates: from organic matter loss to abiogenic calcite formation(Biogeosciences, 2022) Forjanes Pérez, Pablo Cayetano; Roda, María Simonet; Greiner, Martina; Griesshaber, Erika; Lagos, Nelson A.; Veintemillas Verdaguer, Sabino; Astilleros García-Monge, José Manuel; Fernández Díaz, María Lourdes; Schmahl, Wolfgang W.Carbonate biological hard tissues are valuable archives of environmental information. However, this information can be blurred or even completely lost as hard tissues undergo diagenetic alteration. This is more likely to occur in aragonitic skeletons because bioaragonite often transforms into calcite during diagenesis. For reliably using aragonitic skeletons as geochemical proxies, it is necessary to understand in depth the diagenetic alteration processes that they undergo. Several works have recently investigated the hydrothermal alteration of aragonitic hard tissues during short-term experiments at high temperatures (T > 160 ∘C). In this study, we conduct long-term (4 and 6 months) hydrothermal alteration experiments at 80 ∘C using burial-like fluids. We document and evaluate the changes undergone by the outer and inner layers of the shell of the bivalve Arctica islandica, the prismatic and nacreous layers of the hard tissue of the gastropod Haliotis ovina, and the skeleton of the coral Porites sp. combining a variety of analytical tools (X-ray diffraction, thermogravimetry analysis, laser confocal microscopy, scanning electron microscopy, electron backscatter diffraction and atomic force microscopy). We demonstrate that this approach is the most adequate to trace subtle, diagenetic-alteration-related changes in aragonitic biocarbonate structural hard materials. Furthermore, we unveil that the diagenetic alteration of aragonitic biological hard tissues is a complex multi-step process where major changes occur even at the low temperature used in this study, well before any aragonite into calcite transformation takes place. Alteration starts with biopolymer decomposition and concomitant generation of secondary porosity. These processes are followed by abiogenic aragonite precipitation that partially or totally obliterates the secondary porosity. Only subsequently does the transformation of the aragonite into calcite occur. The kinetics of the alteration process is highly dependent on primary microstructural features of the aragonitic biomineral. While the skeleton of Porites sp. remains virtually unaltered for the entire duration of the conducted experiments, Haliotis ovina nacre undergoes extensive abiogenic aragonite precipitation. The outer and inner shell layers of Arctica islandica are significantly affected by aragonite transformation into calcite. This transformation is extensive for the prismatic shell layer of Haliotis ovina. Our results suggest that the majority of aragonitic fossil archives are overprinted, even those free of clear diagenetic alteration signs. This finding may have major implications for the use of these archives as geochemical proxies.Item Epitactic growth of celestite on anhydrite: substrate induced twinning and morphological evolution of aggregates(CrystEngComm, 2020) Forjanes Pérez, Pablo Cayetano; Gómez Barreiro, Juan; Morales, Juan; Astilleros García-Monge, José Manuel; Fernández Díaz, María LourdesEpitactic crystal growth plays a main role in the development of mineral processes and in the synthesis of advanced materials. Celestite (SrSO4) forms epitactic overgrowths on anhydrite (CaSO4) (100), (010) and (001) surfaces upon interacting with Sr-bearing aqueous solutions. Two populations of differently oriented celestite crystals related by symmetry operators of substrate are identified on (001)Anh and (100)Anh anhydrite substrates by SEM observations and synchrotron X-ray diffraction analysis. Substrate-induced twins arise after the coalescence of individuals belonging to these populations. Progressing growth results in a marked morphological evolution of epitactic celestite, whose crystals undergo sustained branching and loss of co-orientation that result in the formation of sheaf-like aggregates, on (100)Anh, and swan-like aggregates, on (001)Anh. We relate this evolution to celestite growth in a Ca-rich environment due to continued anhydrite dissolution and incorporation of small amounts of Ca into celestite structure. This incorporation would induce lattice strain which would be released through the formation of dislocations. The regular arrangement of these dislocations in small-angle boundaries would result in progressive splitting, driving the evolution from celestite single crystals to aggregates. Sharp compositional gradients in the boundary layer could explain the anisotropic development that leads to the formation of the swan-like celestites.Item Formation of Strontianite and Witherite Cohesive Layers on Calcite Surfaces for Building Stone Conservation(Crystal growth & design, 2022) Forjanes Pérez, Pablo Cayetano; Pérez Garrido, Carlos; Álvarez Lloret, Pedr; Astilleros García-Monge, José Manuel; Fernández Díaz, María LourdesThe formation of micrometric-thick mineral cohesive layers is a novel method to prevent the deterioration of historical buildings. Here, we study the formation of thin, cohesive, pseudomorphic shells of strontianite (SrCO3) and witherite (BaCO3) on the surface of calcite (CaCO3) single crystals reacted with aqueous solutions bearing Sr2+ and Ba2+, respectively. The reaction front moves inward from the calcite–solution interface through a dissolution–crystallization reaction, which stops before the strontianite and witherite shells are barely 40 thick. These shells consist of elongated crystallites that grow oriented on the calcite substrate, with which they share very small contact areas. The calcite–strontianite and −witherite epitaxies are mono-dimensional and involve a parallelism between (101̅4)Cal||(021)Str/Wth. Strontianite and witherite cohesive layers remain strongly attached to the calcite substrates, which appear crack-free even after 2 years of reaction time. The formation of thin, cohesive, and durable replacement layers of strontianite and witherite may provide a long-lasting protection for calcitic marbles and limestones used as building stones in cultural heritage.Item Formación de Estroncianita y Witherita a través del Reemplazamiento de Cristales de Calcita(Macla, 2021) Forjanes Pérez, Pablo Cayetano; Pérez Garrido, Carlos; Álvarez Lloret, Pedro; Astilleros García-Monge, José Manuel; Fernández Díaz, María Lourdes