Instituto Andaluz de Ciencias de la Tierra
Recent publications
True control over the morphology of gypsum crystals formed via homogeneous precipitation from solution has rarely been reported in the literature. In this work, we have tested a large number of dissolved additives (polymers as well as small molecules) with respect to their ability to alter the typical microscopic appearance of precipitated gypsum powders, which is usually characterized by a mixture of single-crystalline needles and twinned plates. Among the many additives studied, a copolymer of vinylpyrrolidone and acrylic acid (PVP-co-PAA) was identified as powerful growth modifier for gypsum already at low concentrations. In both slow titration and rapid mixing experiments, unconventional blocky crystals with tilted stacking edges as well as pseudo-hexagonal plates could be synthesized reproducibly with the help of the copolymer. Systematic characterization revealed the dynamic mode of action of the newly identified growth modifier, which seems to stabilize a highly reactive face of gypsum and promote the formation of macrosteps. The degree of morphological control achieved in this way is unprecedented in the case of calcium sulfate and may devise entirely new concepts for additive design in the areas of plasters and cementitious materials, gypsum wallboard production and/or scale prevention.
The detrimental effects of inorganic scaling in industrial and domestic applications are often mitigated with scale inhibitors. Increasing environmental awareness and stringent regulations require developing more sustainable antiscalants. Testing of suitable candidates is often the rate-limiting step in development cycles, therefore we developed a high-throughput methodology to rapidly evaluate the antiscaling potential of new additives under different application conditions. Using this method we determined the performance of two potential green additives – a chelating agent and a threshold inhibitor – in delaying CaSO4 precipitation over a wide range of supersaturations, temperatures and salinities. The threshold inhibitor strongly delayed CaSO4 scaling, but its performance is highly dependent on the physicochemical conditions, with the appropriate application window comprising low salinities and mild temperatures. In contrast, the chelating agent showed a lower inhibiting capacity, but its performance remained relatively constant throughout the entire matrix of physicochemical conditions. Noteworthy, we also observed that at intermediate salinities the absolute induction time for CaSO4 precipitation is dramatically prolonged, offering a sustainable strategy to mitigate scaling. Overall, our method allows simultaneously benchmarking the scaling kinetics and testing the scale-inhibiting performance of additives, providing a direct route to a more rational design of antiscaling technologies.
Although most arcuate orogens are deformed as progressive arcs—curvature is acquired during shortening‐, they have been scarcely simulated by analog modeling. To investigate factors that control the growth of progressive curves in fold‐and‐thrust belts, we developed seven analog models where the backstop shape changed over time, and distinctive geometric heterogeneities were set in the detachment layer. These heterogeneities, often described in natural cases, include diapirs, thickness lateral variations (including pinch‐outs) of the viscous detachment layer as well as frontal pinch‐outs. Our results show that strain was partitioned between shortening structures showing radial transport directions, and both normal and oblique strike‐slip faults that accommodated arc‐lengthening. The location of any heterogeneity conditioned the nucleation of structures and thus, the wedge evolution and its resulting geometry. The presence of both diapirs and frontal silicone pinch‐outs favored the stagnation of the deformation front, and the subsequent wedge thickening up to reach the supercritical angle. Both diapirs and thickness lateral variations of the viscous layer localized arc‐parallel stretching. In addition, their configuration determined the amount and distribution of salients and recesses along the arcuate belt, diapirs and more frictional detachments favoring thicker wedges and less frontal propagation. The differential displacement between salients and recesses was accommodated by strongly partitioned transfer zones, localized by the boundaries between distinctive detachment domains. These results may be useful to investigate geometric and kinematic changes along natural progressive arcs such as the Gibraltar, Sulaiman and Zagros cases.
Exotic blocks of massive antigorite-serpentinite (antigoritite) document a deep-seated subduction channel in the Villa Clara serpentinite-matrix mélange, central Cuba. The petrological and geochemical characteristics of antigoritite allow distinguishing two types of rock: i) antigoritite and ii) dolomite-bearing antigoritite. Both types are intimately related in field exposures and represent deep peridotite infiltrated by H2O-CO2 fluid mixtures that triggered antigoritization and local carbonation. Fluid infiltration continued after antigoritization forming a vein network as a potential response to hydrofracturing that precipitated tremolitite in the veins and triggered fluid-antigoritite reaction forming blackwalls. The mineralogical and chemical zoning in the blackwalls (Atg + Chl + Tr adjacent to antigoritite and Chl + Tr adjacent to the tremolitite vein) attest for multi-step metasomatic processes during fluid-rock interaction characterized by advection of infiltrating fluid towards the blackwall and, possibly, by diffusion out of the blackwall towards the fluid-filled vein. Tentative thermodynamic modeling of the blackwall domain Atg + Chl + Tr points vein network formation at 400–500 °C and 5–10 kbar during exhumation in the subduction channel, suggesting the infiltration of deep-seated pressurized fluid that triggered hydrofracturing. The chemical compositions antigoritites, veins and blackwalls indicate a LILE- and LREE-enriched fluid evolved from the subducting plate, while SrNd isotope systematics are compatible with an external fluid composed of a mixture of fluids evolved from sediments and, probably to a lesser extent, altered oceanic crust.
Seagrass conservation is critical for mitigating climate change due to the large stocks of carbon they sequester in the seafloor. However, effective conservation and its potential to provide nature-based solutions to climate change is hindered by major uncertainties regarding seagrass extent and distribution. Here, we describe the characterization of the world's largest seagrass ecosystem , located in The Bahamas. We integrate existing spatial estimates with an updated empirical remote sensing product and perform extensive ground-truthing of seafloor with 2,542 diver surveys across remote sensing tiles. We also leverage seafloor assessments and movement data obtained from instrument-equipped tiger sharks, which have strong fidelity to seagrass ecosystems , to augment and further validate predictions. We report a consensus area of at least 66,000 km 2 and up to 92,000 km 2 of seagrass habitat across The Bahamas Banks. Sediment core analysis of stored organic carbon further confirmed the global relevance of the blue carbon stock in this ecosystem. Data from tiger sharks proved important in supporting mapping and ground-truthing remote sensing estimates. This work provides evidence of major knowledge gaps in the ocean ecosystem, the benefits in partnering with marine animals to address these gaps, and underscores support for rapid protection of oceanic carbon sinks.
The foraminiferal order Rotaliida represents one third of the extant genera of foraminifers. The shells of these organisms are extensively used to decipher characteristics of marine ecosystems and global climate events. It was shown that shell calcite of benthic Rotaliida is twinned. We extend our previous work on microstructure and texture characterization of benthic Rotaliida and investigate shell calcite organization for planktonic rotaliid species. Based on results gained from electron backscattered diffraction (EBSD) and field emission electron microscopy (FESEM) imaging of chemically etched/fixed shell surfaces we show for the planktonic species Globigerinoides sacculifer, Pulleniatina obliquiloculata, Orbulina universa (belonging to the two main planktonic, the globigerinid and globorotaliid, clades): very extensive 60°-{001}-twinning of the calcite and describe a new and specific microstructure for the twinned crystals. We address twin and crystal morphology development from nucleation within a biopolymer template (POS) to outermost shell surfaces. We demonstrate that the calcite of the investigated planktonic Rotaliida forms through competitive growth. We complement the structural knowledge gained on the clade 1 and clade 2 species with EBSD results of Globigerinita glutinata and Candeina nitida shells (clade 3 planktonic species). The latter are significantly less twinned and have a different shell calcite microstructure. We demonstrate that the calcite of all rotaliid species is twinned, however, to different degrees. We discuss for the species of the three planktonic clades characteristics of the twinned calcite and of other systematic misorientations. We address the strong functionalization of foraminiferal calcite and indicate how the twinning affects biocalcite material properties.
Stable isotopic values of carbon (δ¹³C) and nitrogen (δ¹⁵N) were used to characterize the trophic structure and biomagnification of Cadmium (Cd), Mercury (Hg) and Selenium (Se) in a trophic web of 18 taxa namely zooplankton, crustaceans, mollusks, fishes, and Mustelus henlei shark collected off the western coast of Baja California Sur, Mexico. Isotopic results indicated interspecies variations in the trophic web structure with mean δ ¹³C values of – 20.0 ‰ (zooplankton) < − 18.2 ‰ (M. henlei) < − 14.1 ‰ (Thaisella kiosquiformis, mollusk). In general, δ¹⁵N and δ¹³C values increased from primary consumers (zooplankton) to predators, following the isotopic patterns of other trophic webs. The concentrations of Cd, Hg and Se were relatively less in most of the organisms except mollusks that presented high concentrations of Cd. The biomagnification factors of the trophic web showed biodilution of Cd (Food Web Magnification Factor, FWMFCd = 0.2), biomagnification of Hg (FWMFHg = 3.34) and Se (FWMFSe = 1.45) respectively. However, the concentrations of Se did not increase consistently from the lower trophic levels to the higher ones. This study documents the dynamics of a marine trophic structure and demonstrates that biodilution/biomagnification processes of metal contaminants are largely species specific and are closely related to physical - chemical and food web structure.
Soda lakes of the East African Rift Valley are hyperalkaline, hypersaline lakes extremely enriched in Na⁺, K⁺, Cl⁻, CO3²⁻, HCO3⁻, and SiO2. In this paper, we investigate the chemical evolution in these lakes and the production of chemical sediments by salt precipitation via evaporation. Water samples from tributary springs and three lakes (Magadi, Nasikie Engida and Natron) have been experimentally studied by in-situ X-ray diffraction during evaporation experiments to characterize the sequence of mineral precipitation. These data are complemented by ex-situ diffraction studies, chemical analyses and thermodynamic hydrochemical calculations producing detailed information on the activity of all solution species and the saturation state of all minerals potentially generated by the given composition. Major minerals precipitating from these samples are sodium carbonates/bicarbonates as well as halite. The CO3/HCO3 ratio, controlled by pH, is the main factor defining the Na‑carbonates precipitation sequence: in lake brines where CO3/HCO3 > 1, trona precipitates first whereas in hot springs, where CO3/HCO3 ≪ 1, nahcolite precipitates instead of trona, which forms later via partial dissolution of nahcolite. Precipitation of nahcolite is possible only at lower pH values (pCO2 higher than −2.7) explaining the distribution of trona and nahcolite in current lakes and the stratigraphic sequences. Later, during evaporation, thermonatrite precipitates, normally at the same time as halite, at a very high pH (>11.2) after significant depletion of HCO3⁻ due to trona precipitation. The precipitation of these soluble minerals increases the pH of the brine and is the main factor contributing to the hyperalkaline and hypersaline character of the lakes. Villiaumite, sylvite, alkaline earth carbonates, fluorapatite and silica are also predicted to precipitate, but most of them have not been observed in evaporation experiments, either because of the small amount of precipitates produced, kinetic effects delaying the nucleation of some phases, or by biologically induced effects in the lake chemistry that are not considered in our calculations. Even in these cases, the chemical composition in the corresponding ions allows for discussion on their accumulation and the eventual precipitation of these phases. The coupling of in-situ and ex-situ experiments and geochemical modelling is key to understanding the hydrogeochemical and hydroclimatic conditions of soda lakes, evaporite settings, and potentially soda oceans of early Earth and other extraterrestrial bodies.
X-ray fluorescence techniques are widespread since the half of the last century for chemical investigation on rocks, minerals, industrial products, construction materials, precious materials, environmental pollutants, metals, paints, etc. Actually, they can be used to analyse almost every kind of solids and in many cases also liquid or gelatinous substances. XRF allows to obtain chemical analyses, in elements or in oxides, expressed as percent atoms or atoms in percent weight, alternatively as oxides, stoichiometrically binding the oxygen to the dosed cation. Depending on the accuracy of the desired data and on the sample characteristics, the XRF can be used as partially destructive or as absolutely non-destructive technique; consequently, the sample required for an analysis varies from few tens of milligrams up to about 12 g, depending on the selected analytical procedure and the type of instrumentation. In the last decades, the diffusion of the ED silicon drift detectors, together with the development of very accurate and high specialised software for quantitative analysis, increased the diffusion of portable spectrometers offering new possibilities for in-situ and very rapid specimen characterizations, useful during forensic investigations, particularly on samples that cannot be removed for legal reasons or difficult to transport as being too large. The theoretical physical principles and the main components of X-ray spectrometers, in energy dispersion (ED) and wavelength dispersion (WD), are described also comparing the advantages and disadvantages of each analytical technique. Some forensic case studies are also presented.
Geophysical, geochemical, and geological investigations have attributed the stable behaviour of Earth’s continents to the presence of their Archean cratonic roots. These roots are likely composed of melt-depleted, low density residual peridotite with high magnesium number (Mg#), while devolatilisation from the upper mantle during magmatic events might have made these roots more viscous and intrinsically stronger than the convecting mantle. Several conceptual dynamic and petrological models of craton formation have been proposed. Dynamic models invoke far-field shortening or mantle melting events, e.g., by mantle plumes, to create melt-depleted and thick cratons. Compositional buoyancy and rheological modifications have also been invoked to create long-lived stable cratonic lithosphere. However, these conceptual models have not been tested in a dynamically self-consistent model. In this study, we present global thermochemical models of craton formation with coupled core-mantle-crust evolution driven entirely by gravitational forces. Our results with melting and crustal production (both oceanic and continental) show that formation of cratonic roots can occur through naturally occurring lateral compression and thickening of the lithosphere in a self-consistent manner, without the need to invoke far-field tectonic forces. Plume impingements, and gravitational sliding creates thrusting of lithosphere to form thick, stable, and strong lithosphere that has a strong resemblance to the Archean cratons that we can still observe today at the Earth’s surface. These models also suggest the recycling of denser eclogitic crust by delamination and dripping processes. Within our computed parameter space, a variety of tectonic regimes are observed which also transition with time. Based on these results, we propose that a ridge-only regime or a sluggish-lid regime might have been active on Earth during the Archean Eon as they offer favourable dynamics and conditions for craton formation.
Distributions of dissolved (DOM) and suspended (POM) organic matter, and their chromophoric (CDOM) and fluorescent (FDOM) fractions, are investigated at high resolution (< 10 km) in the Cape Verde Frontal Zone (CVFZ) during fall 2017. In the epipelagic layer (< 200 m), meso- and submesoscale structures (meanders, eddies) captured by the high resolution sampling dictate the tight coupling between physical and biogeochemical parameters at the front. Remarkably, fluorescent humic-like substances show relatively high fluorescence intensities between 50 and 150 m, apparently not related to local mineralization processes. We hypothesize that it is due to the input of Sahara dust, which transports highly re-worked DOM with distinctive optical properties. In the mesopelagic layer (200-1500 m), our results suggest that DOM and POM mineralization occurs mainly during the transit of the water masses from the formation sites to the CVFZ. Therefore, most of the local mineralization seems to be due to fast-sinking POM produced in situ or imported from the Mauritanian upwelling. These local mineralization processes lead to the production of refractory CDOM, an empirical evidence of the microbial carbon pump mechanism. DOM released from these fast-sinking POM is the likely reason behind the observed columns of relatively high DOC surrounded by areas of lower concentration. DOM and POM dynamics in the CVFZ has turned out to be very complex, in parallel to the complexity of meso- and submesoscale structures present in the area. On top of this high resolution variability, the input of Sahara dust or the release of DOM from sinking particles have been hypothesized to explain the observed distributions.
The aim of this study is to analyse the concentration and determine the sources of potentially toxic elements (PTEs) in urban soils under the influence of mining activities. To this end, topsoil samples were collected in the public parks and green areas in Minas de Riotinto (a town next to one of the largest open pit mines in the world) and Aracena (a nearby town outside the area of influence of the mine). After determining the concentrations of elements of interest Cr, Co, Ni, Cu, Zn, As, and Pb— the values were compared in terms of the soil location and origin (in-situ or ex-situ), and with the background and regulatory levels for the region. The elemental concentrations in the fine fraction of the soils (particles <50 μm) were also measured. The concentrations of some PTEs (Cu, As and Pb), also found in the dust from nearby mines, were higher in the in-situ soils of Minas de Riotinto than in those of Aracena. The concentrations of PTEs in ex-situ soils of both towns were much lower than in in-situ soils, and similar between the two locations, revealing the influence of the parent material as a primary source of PTEs. However, the concentrations of As and Cu in the ex-situ soils of Minas de Riotinto were significantly higher than in those of Aracena, while a significant increase of these elements in the fine fraction was seen for both in-situ and ex-situ soils. These two elements are directly related to mining activity, implying that atmospheric deposition of dust from the mines contributes to the greater concentration of PTEs in the soils of Minas de Riotinto. Because these sources lead to soils with potentially dangerous concentrations of pollutants, they should be further studied in relation to their long-term influence on human health.
Comparative growth rate measurement of 51 lysozyme seeded crystals at various supersaturations under microgravity and in normal gravity were successfully conducted by ex-situ method in a Russian Foton-M3 recovery satellite. Growth rate of crystals both in space and on the Earth were calculated by measuring the thickness of each growth zone that was caused by the change of gravity level. It is surprising to find that growth rate under microgravity was the same as that in normal gravity or, unexpectedly, even larger by more than 20%. The experiment was conducted in the satellite in 12 days under microgravity after 6 days transportation on the ground from Nijmegen, the Netherlands, to Baikonur, Russia. 51 growth cells were kept at 20℃ after the protein solutions and the seeds were sealed. The trace of movement of 2D macro-steps on the (110) face was visualized after the flight by laser confocal microscopy. These steps were buried inside the crystals, 0-140 μm deep from the surface and so they were grown in space. The observed elongated sharp 2D steps implies that the effect of impurity was considerably reduced in space condition, compared with the rounded shape of 2D steps formed with more impurities in normal gravity. The increase in growth rate in space could be concluded due to the reduction of impurities on the surface of crystals. Several space grown crystals were examined by synchrotron X-ray topography at KEK in Tsukuba after optical observations were completed. The change of lattice perfection due to the change from normal G to μG was investigated using local rocking curve analysis (peak position, intensity, full width at half maximum) as well as X-ray topography. Clear increase of diffraction and thus better perfection were observed when the gravity changed from normal G to μG condition. However, it should be noted that perfection of the space grown crystal reached the value of the best portion of the seed crystal that was carefully prepared on the Earth. Based on these data, increased growth rate in space is conclude to be due to the reduction of impurity effects at the surface of the crystals. Better perfection might additionally increase the growth rate.
The mineral reaction pathways that yield organic compounds of increasing complexity would have required a means of protective screening against strong ultraviolet radiation for macromolecular assembly on early Earth. In this study, a bacterial chromosomal plasmid DNA was used as a model biomolecule that represents a complex polymeric nucleic acid containing genetic information. The plasmid DNA was exposed to UV radiation through a medium containing air, water, iron (Fe3+), or silica-iron rich aqueous solutions. Our results demonstrate that the plasmid DNA underwent covalent breakage in an aqueous solution when exposed to UV radiation but was shielded against damage due to the presence of iron and silica. It is demonstrated that a suspension of ca. 40 nm colloidal particles of silica gel embedded with Fe3+ ions adsorbed on silanol groups that formed nanoclusters of noncrystalline iron hydroxide is an extremely efficient shelter against intense UV radiation. The implications for our understanding of primitive Earth and Earth-like planets, moons, and asteroids are discussed. The stability of a chromosomal DNA molecule against UV radiation in the presence of iron and silica may provide support on how macromolecules endured early Earth environments and brought forth important implications on early molecular survival against UV radiation.
Field relationships and new U-Pb geochronology data indicate a temporal link among the diverse high-K mafic-intermediate magmas of the Ossa-Morena Zone (OMZ). Ages of ca. 338-335 Ma for the Vale de Maceiras gabbro and the Campo Maior microdiorite and quartz-diorite indicate that plutonism took place during Variscan extensional D2 deformation event in the OMZ. The syn-tectonic nature of the Vale de Maceiras pluton is attested by the orientation of intrusive contacts, magmatic foliation, and growth of contact metamorphic minerals in relation to Variscan extensional D2 foliation. The Campo Maior microdiorite, quartz-diorite, and orthomigmatites are temporally linked to high-temperature mylonitic gneisses formed simultaneously with the Variscan extensional D2 deformation event. The geochemical features of the Vale de Maceiras and Campo Maior mafic-intermediate rocks show an affinity with the sanukitoid series. This finding suggests that the observed geochemical variability, from tholeiitic to calc-alkaline and sanukitoid, in the Visean OMZ plutonic rocks (ca. 349-335 Ma) may have been inherited from partially melted mantle domains that were previously contaminated by crustal melts during subduction. Supplementary material at
High‐resolution microstructural analysis of porphyroblast inclusion trails integrated with Sm‐Nd garnet geochronology has provided new insight into the tectonic history of the Betic‐Rif orogen. Three principal age groups of porphyroblasts are demonstrated with distinctly oriented inclusion‐trails. Inclusion‐trail curvature axes or “FIA” (Foliation Inflexion/Intersection Axes) are shown to represent “fossilized” crenulation axes from which a succession of different crustal shortening directions can be deduced. The regional consistency of microstructural orientations and their geometric relationship with multiple sets of macroscopic folds reveal the composite character of the Gibraltar Arc formed by a superposition of different folding directions and associated lineations. Bulk‐garnet ages of 35–22 Ma obtained from five micaschist samples of the Alpujarride‐Sebtide complex (ASC) and of 35–13 Ma from four micaschists of the Nevado‐Filabride complex (NFC) allow to deduce NNE‐SSW directed shortening in the Late Eocene changing to NW‐SE shortening in the early Oligocene, alternating with suborthogonal NE‐SW shortening during the Miocene. These directions can be related to a major swing in the direction of relative Africa‐Iberia plate‐motion known from kinematic modeling of magnetic seafloor anomalies, and subsequent dynamic interference between plate convergence and suborthogonal “tectonic escape” of the Alboran Domain. Coupled to previously established P‐T‐t paths, the new garnet ages support a common tectono‐metamorphic evolution of the ASC and NFC as laterally equivalent orogenic domains until, in the Miocene, the second became re‐buried under the first.
The Hamutenha intrusion (Huíla province, SW Angola) is a 3-km-long elongated magmatic body defined by a set of two intrusive units. The northern unit is formed by alternating bands of dunites and olivine gabbros, while the southern unit is composed of amphibole diorites. The Hamutenha body is hosted by the Paleoproterozoic Epupa Complex in the Angolan Shield, SW margin of the Congo Craton. A mineralogical, petrological and geochemical study of the Hamutenha intrusion has been performed. The constrained compositional features of the parental melt suggest interaction of tholeiitic magmas with a significant enrichment in Fe and Ti. Although disseminated Fe–Ni–Cu-(Co) secondary sulphides are observed, both the crustal contamination parameters and generally low bulk-rock metals contents indicate that these elements were most likely previously extracted from the parental melt. U–Pb zircon dating of amphibole diorite samples from the southern unit yields a date of 1844 ± 14 Ma. These data suggest that the emplacement of these rocks was previous to the KC emplacement and it was probably related to the Paleoproterozoic Epupa Complex magmatism.
The endocochleate coleoid cephalopod Spirula spirula, the only present-day representative of the order Spirulida, secretes a coiled shell consisting of a series of chambers divided by septa and connected by a siphuncle. It is the shell closest to those of Recent and extinct ectochleate cephalopods: nautiloids, ammonoids. Therefore, its study may help to understand which characters remained unchanged or became transformed during the evolution of endocochleates. We have carried out detailed observations on the different structures composing the Spirula shell, with the aim of reconstructing their morphology, distribution, and mutual relationships. Alongside this, we also review the previous profuse terminology. Taking into account the additional information provided by growth lines and crystal orientations, we propose mechanisms for the secretion of the shell structures. All these mechanisms are integrated in a consistent way into a general model of chamber formation. The periostracum is secreted within a distinct periostracal groove. The outer shell layer is secreted externally to the periostracum by the soft tissues lining the shell externally. The inner shell layer is produced by the shell wall mantle, whereas the septa and the siphuncle are made periodically by a differentiated septal/siphuncular mantle. The most adoral septal mantle edge changes from secreting septal to inner shell wall material to produce the mural flap. The adapical ridge is formed by passive precipitates from cameral fluid residues trapped by surface tension, whereas the fibrous prismatic deposits of the connecting ring are biominerals produced remotely within mantle secretions. Homologies with Nautilus and Sepia are discussed.
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25 members
José Alberto Padrón-Navarta
  • Petrology Geochemistry and Geochronology
Francisco José Lobo
  • Marine Geoscience
Carmen Rodriguez
  • PGG - Petrology, Geochemistry and Geochronology (CSIC-IACT, Granada)
Menchu Comas
  • Marine Geosciences
Armilla, Spain