Papers by Luis Gago-Duport
Boletín de la Sociedad Española de Mineralogía, 1991
Nature Astronomy, 2021
In situ investigations by the Mars Science Laboratory, Curiosity rover, have confirmed the presen... more In situ investigations by the Mars Science Laboratory, Curiosity rover, have confirmed the presence of an ancient lake in Gale crater for up to 10 million years. The lake was filled with sediments that eventually converted to a compacted sandstone. However, it remains unclear whether the infilling of the lake was the result of background sedimentation processes or represents punctual flooding events in a largely isolated lake. Here we used the XRD data obtained with the Chemistry and Mineralogy instrument (CheMin), on board the Curiosity rover, to characterize the degree of disorder of clay minerals in the Murray formation (MF) at Gale crater. Our analysis shows that they are structurally and compositionally related to glauconitic clays, which are a sensitive proxy of quiescent conditions in liquid bodies for extended periods of time. Such results provide evidence of long periods of extremely low sedimentation in an ancient brackish lake on Mars, signature of an aqueous regime with slow evaporation at low temperatures. More in general, the identification of lacustrine glauconitic clays on Mars provides Users may view, print, copy, and download text and data-mine the content in such documents, for the purposes of academic research, subject always to the full Conditions of use:
EN LA PRESENTE TESIS SE ABORDA EL ESTUDIO DE LA CINETICA DE NUCLEACION DEL NITRATO AMONICO A PART... more EN LA PRESENTE TESIS SE ABORDA EL ESTUDIO DE LA CINETICA DE NUCLEACION DEL NITRATO AMONICO A PARTIR DE SOLUCIONES MEDIANTE LA OBSERVACION DEL EFECTO TERMICO QUE, UNIDO AL PRODUCIDO POR EL ULTERIOR CRECIMIENTO DE LOS NUCLEOS, PRODUCE ESTE FENOMENO. DICHO EFECTO SE PONE DE MANIFIESTO EN UNA ALTERACION DE LA CURVA DE ENFRIAMIENTO EXPONENCIAL DE LA SOLUCION. CON EL OBJETO DE ESTIMAR LA VELOCIDAD DE NUCLEACION A PARTIR DE LA CURVA DE ENFRIAMIENTO SE HAN DESARROLLADO UNOS ALGORITMOS QUE PERMITEN LA MODELIZACION DEL PROCESO. SE ABORDA ASIMISMO EL PROBLEMA DE LA NUCLEACION Y CRECIMIENTO EN RELACION CON LAS TRANSICIONES POLIMORFICAS II - IV, II - III - IV. LA JUSTIFICACION DE LAS SECUENCIAS DE TRANSFORMACION SE REALIZA EN BASE A UN DIAGRAMA DE SOLUBILIDADES QUE INCLUYE TRAMOS DE "SOLUBILIDAD METAESTABLE".
With the aim of establishing the relations that exist between certain minerals, sulphides and car... more With the aim of establishing the relations that exist between certain minerals, sulphides and carbonates, in anoxic marine environments as well as to understand the factors and mechanisms that control the reactions that are necessary for their formation or dissolution, a number of laboratory experiments are carried out to simulate in detail the reactions in shallow water carbonate sediments and the sulphate reduction reactions in shallow water siliciclastic sediments in which the content and the reactivity of Fe is not a limiting factor. In the experiments a series of coupled reactions take place that cause, in the first case the dissolution of aragonite and the recristallization ofcalcite and, in the second case the formation of amorphous iron sulphides and the formation of siderite. In addition the diagenetic environments for the formation of these components, sulphides and carbonates, in the sediments of the Bay of Cadiz are explained.
Journal of Iberian Geology, 2000
La interpretacion estratigrafica de unidades que contienen glauconita requiere de una adecuada ca... more La interpretacion estratigrafica de unidades que contienen glauconita requiere de una adecuada caracterizacion del grado de evolucion, definido a partir del concepto de madurez (Amorosi, 1995). Su utilizacion es util para determinar la duracion de periodos asociados a bajas tasas de sedimentacion o para caracterizar condiciones paleoceanograficas y paleoambientales en la interfase sedimento-agua del mar. En este tipo de estudios se asume implicitamente que la glauconita actua como un sistema abierto, susceptible de continuos cambios en la estequiometria, como resultado del intercambio de cationes con el agua del mar que, a su vez, inducen reajustes estructurales. La determinacion del grado de evolucion de glauconitas esta asociada habitualmente a la presencia de determinados marcadores, algunos de tipo cualitativo como es el color o bien asociados a la variacion de alguna de sus propiedades fisicas, como es la susceptibilidad magnetica o composicionales y estructurales, como son la ...
Nature Astronomy, 2018
The ancient rock record for Mars has long been at odds with climate modelling. The presence of va... more The ancient rock record for Mars has long been at odds with climate modelling. The presence of valley networks, dendritic channels and deltas on ancient terrains points towards running water Reprints and permissions information is available at www.nature.com/reprints.
Journal of Geophysical Research: Planets, 2017
Geochemical models of secondary mineral precipitation on Mars generally assume semiopen systems (... more Geochemical models of secondary mineral precipitation on Mars generally assume semiopen systems (open to the atmosphere but closed at the water-sediment interface) and equilibrium conditions. However, in natural multicomponent systems, the reactive surface area of primary minerals controls the dissolution rate and affects the precipitation sequences of secondary phases, and simultaneously, the transport of dissolved species may occur through the atmosphere-water and water-sediment interfaces. Here we present a suite of geochemical models designed to analyze the formation of secondary minerals in basaltic sediments on Mars, evaluating the role of (i) reactive surface areas and (ii) the transport of ions through a basalt sediment column. We consider fully open conditions, both to the atmosphere and to the sediment, and a kinetic approach for mineral dissolution and precipitation. Our models consider a geochemical scenario constituted by a basin (i.e., a shallow lake) where supersaturation is generated by evaporation/cooling and the starting point is a solution in equilibrium with basaltic sediments. Our results show that cation removal by diffusion, along with the input of atmospheric volatiles and the influence of the reactive surface area of primary minerals, plays a central role in the evolution of the secondary mineral sequences formed. We conclude that precipitation of evaporites finds more restrictions in basaltic sediments of small grain size than in basaltic sediments of greater grain size. [Milliken et al., 2009], and to the effects of dust covering (dust creates an observational bias when analyzing Mars surface composition [Berger et al., 2016] and could even become a relevant input for the mineralogical composition of a given region [Kulowski et al., 2017], affecting equally clays, evaporites, or any other mineral on the surface of Mars).
The two classical methods, moment and graphic, used to determine grain size parameters are revise... more The two classical methods, moment and graphic, used to determine grain size parameters are revised and compared, using 282 beach, inner shelf and aeolian samples. Mean size and sorting values are similar, but skewness and kurtosis show great differences after applying the method. Furthermore, classification ranges for kurtosis and skewness obtained by moment's method have not been described. Normalisation improves kurtosis but not skewness when moment analysis is used. Separate treatment of uni modal, bimodal and polymodal distributions does not help to get better results. Consequently the graphic method should be preferably used until a sedimentary interpretation of third moment is obtained.
Geochemistry, Geophysics, Geosystems, 2015
Lithium (Li), the lightest of the alkali elements, has geochemical properties that include high a... more Lithium (Li), the lightest of the alkali elements, has geochemical properties that include high aqueous solubility (Li is the most fluid mobile element) and high relative abundance in basalt-forming minerals (values ranking between 0.2 and 12 ppm). Li isotopes are particularly subject to fractionation because the two stable isotopes of lithium-7 Li and 6 Li-have a large relative mass difference ($15%) that results in significant fractionation between water and solid phases. The extent of Li isotope fractionation during aqueous alteration of basalt depends on the dissolution rate of primary minerals-the source of Li-and on the precipitation kinetics, leading to formation of secondary phases. Consequently, a detailed analysis of Li isotopic ratios in both solution and secondary mineral lattices could provide clues about past Martian weathering conditions, including weathering extent, temperature, pH, supersaturation, and evaporation rate of the initial solutions in contact with basalt rocks. In this paper, we discuss ways in which Martian aqueous processes could have lead to Li isotope fractionation. We show that Li isotopic data obtained by future exploration of Mars could be relevant to highlighting different processes of Li isotopic fractionation in the past, and therefore to understanding basalt weathering and environmental conditions early in the planet's history.
MRS Proceedings, 1992
A numerical model based in nucleation and growth algorithms has been designed to compute the temp... more A numerical model based in nucleation and growth algorithms has been designed to compute the temporal sequences of precipitation and phase transformation kinetics in metastable solutions of polymorphic or hydrated substances. A outline of the model is made for the particular case of crystallization of several hydrated phases from nickel nitrate solutions
MRS Proceedings, 1994
ABSTRACTLattice parameters of some different chromium-doped mullites obtained by a sol-gel route ... more ABSTRACTLattice parameters of some different chromium-doped mullites obtained by a sol-gel route and sintered at 1650° C have been determined from X-Ray Diffraction data as a function of both temperature and Cr contents. Profile refinements on the X-ray diffraction diagrams have been carried out, showing that, at temperatures between 800° and 1535° C, an anisotropic thermal expansion takes place for the a and b lattice parameters of the Cr-doped mullite. We show that this anisotropic expansion is dependent on the temperature increase and the chromium content for the different compositions of the mullite crystals.
Boletín de la Sociedad Española de Cerámica y Vidrio, 2004
En este trabajo se exponen los resultados obtenidos del seguimiento, mediante difracción de rayos... more En este trabajo se exponen los resultados obtenidos del seguimiento, mediante difracción de rayos X en cámara de alta temperatura, del comportamiento frente a la dilatación térmica de diversas mullitas (3Al 2 O 3 •2SiO 2) sol-gel dopadas con contenidos del 1, 3, 6 y 9% en peso de Cr 2 O 3. La presencia de cromo permite obtener materiales con ausencia de fase vítrea y microestructuras homogéneas, lo cual resulta de enorme interés ya que la presencia de vidrio en estos materiales supone una degradación de sus propiedades mecánicas, sobre todo en regímenes de funcionamiento a alta temperatura. Los resultados de dicho estudio revelan que la introducción de cromo en la red de mullita produce una reducción efectiva de su coeficiente lineal de expansión térmica, aunque también un aumento de la anisotropía con que dicha expansión tiene lugar. Únicamente con dopados de un 6% en peso de Cr 2 O 3 se consiguen comportamientos similares al de la mullita no dopada en cuanto a anisotropía en la dilatación de la red. Palabras clave: Expansión térmica, mullita, difracción de rayos X. High-temperature behaviour of mullites: Study by means of X-Ray Diffraction Results on thermal behaviour of several sol-gel chromium doped mullites (3Al 2 O 3 •2SiO 2 with Cr contents of 1, 3, 6 and 9 wt.% Cr 2 O 3) by means of high-temperature X-ray diffraction are exposed in this work. Chromium additions make possible to obtain glass-free materials with very homogeneous microstructures, which is highly convenient as the presence of glass in these materials provides a certain degradation on their mechanical properties, especially at high temperature operations. This study reveals that the chromium introduction in the mullite lattice promotes an effective reduction of its linear thermal expansion coefficient, although also an increase in the anisotropy with which this expansion takes place. Only with the 6 wt.% Cr 2 O 3 content the anisotropy for the lattice expansion is similar to the non-doped mullite.
Beilstein Journal of Nanotechnology, 2014
The Fenton reaction is the most widely used advanced oxidation process (AOP) for wastewater treat... more The Fenton reaction is the most widely used advanced oxidation process (AOP) for wastewater treatment. This study reports on the use of pyrite nanoparticles and microparticles as Fenton reagents for the oxidative degradation of copper phthalocyanine (CuPc) as a representative contaminant. Upon oxidative dissolution in water, pyrite (FeS2) particles can generate H2O2 at their surface while simultaneously promoting recycling of Fe3+ into Fe2+ and vice versa. Pyrite nanoparticles were synthesized by the hot injection method. The use of a high concentration of precursors gave individual nanoparticles (diameter: 20 nm) with broader crystallinity at the outer interfaces, providing a greater number of surface defects, which is advantageous for generating H2O2. Batch reactions were run to monitor the kinetics of CuPc degradation in real time and the amount of H2O2. A markedly greater degradation of CuPc was achieved with nanoparticles as compared to microparticles: at low loadings (0.08 mg/...
Journal of Sol-gel Science and Technology, 1998
Size and size distribution of the semiconductor nanocrystals embedded in a dielectric matrix play... more Size and size distribution of the semiconductor nanocrystals embedded in a dielectric matrix play a dominant role in line broadening and the exciton quantum confinement level. The results show new aspects of the CdS and CdSe crystal growth as quantum dots using small angle neutron scattering techniques (SANS). Thus, the crystal growth influences the aggregation process of the silica network.
Nature Geoscience, 2011
Phyllosilicate minerals are commonly found in marine sediments on Earth 1,2. Accordingly, the pre... more Phyllosilicate minerals are commonly found in marine sediments on Earth 1,2. Accordingly, the presence of an ocean in the northern lowlands of Mars during the Noachian period would be expected to lead to the presence of abundant phyllosilicates in crust of the same age. However, mineralogical data from orbiting spectrometers show that phyllosilicates are rare in the Noachian-aged crust that is exposed in impact craters in the northern lowlands 3. In contrast, phyllosilicate minerals are abundant in the equatorial and tropical highlands 4,5 , raising doubts about the presence of an ocean. Here we use climatic and geochemical model calculations and palaeohydrological reconstructions to assess the factors that control phyllosilicate synthesis and sedimentation on early Mars. Our model results show that temperatures in an ocean confined to latitudes poleward of 30 • N would have been near freezing, which would have hindered the formation of phyllosilicate minerals in the ocean basin. In addition, the presence of cold-based glaciers surrounding the ocean would have limited the delivery of phyllosilicates from the highlands to the ocean basin. We therefore suggest that the presence of a cold, Noachian ocean could explain the paucity of phyllosilicates in the Noachian-aged crust of the northern lowlands. The most prominent geological feature on Mars is the topographic dichotomy that divides the planet into two provinces: the northern lowlands and the southern highlands. In the Noachian crust of both provinces, hydrated silicate deposits, mostly phyllosilicates, have been identified by orbiting imaging spectrometers. Hydrated silicates are indicative of aqueous conditions 3-5 , as their synthesis requires the presence of liquid water. However, an unexplained difference exists in the abundance of hydrated silicate deposits between the two provinces: whereas phyllosilicates occur widespread in the highlands in five to ten thousand locations 3,4 including depressions, valleys and impact craters 4,5 , in the Noachian crust of the lowlands they are very scarce and have been identified so far only in nine impact craters 3. Here we show that the mineralogical differences between the ancient basements of the plains and the highlands, as exposed by impact craters, are the result of distinct climatic, hydrogeological and geochemical conditions operating at different latitudes during the Noachian, including the presence of a cold glacial northern ocean. We have modelled the surface temperatures on early Mars assuming a southern supercontinent and an ocean above 30 • latitude. In this scenario, heat transport from low to high latitudes ('meridional heat transport', that is carried by atmospheric and oceanic currents on Earth 6) only occurs from atmospheric
… 2010, held 2-7 …, 2010
The occurrence of amorphous calcium carbonate (ACC), an hydrated and highly soluble form of solid... more The occurrence of amorphous calcium carbonate (ACC), an hydrated and highly soluble form of solid CaCO3, seems to be a common feature in all carbonate forming organisms such as mollusks, corals, echinoderms and crustaceans. The ubiquity of ACC in these Ca-...
Mineralogical Magazine, 2008
The kinetics of glauconite dissolution have been determined in the pH range 2—10 (T = 25°C) using... more The kinetics of glauconite dissolution have been determined in the pH range 2—10 (T = 25°C) using flow-batch reactor experiments. Besides the kinetic characteristics, the structural and textural aspects which could influence its long-term reactivity have also been characterized by means of X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), scanning electron microscopy (SEM) and BET surface area measurements. The results from these analyses showed that glauconite follows a dual dissolution pathway which is pH-dependent, being more stable at neutral or slightly alkaline pH values. Under acidic conditions, glauconite is slightly more soluble than other ubiquitous silicates present in the marine sediments. The dissolution mechanism is incongruent at very acid pH values and tends to be congruent for intermediate and neutral ones. In addition, the results from the structural analyses suggest that the dissolution is a two-step process: the first one involves...
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Papers by Luis Gago-Duport