A. Sánchez-Navas

University of Granada | UGR · Department of Mineralogy and Petrology

The behavior of aragonite (CaCO3), strontianite (SrCO3 ), cerussite (PbCO3) andwitherite (BaCO3 ) at increasing pressure have been studied up to 6 GPa using density func-tional theory with plane waves. A parallelism of the orthorhombic carbonates with theclosed-packed AsNi structure is considered in our analysis, being the CO2− groups not3centered...

The Paleocene-Eocene Cerro Munro pluton, to the east of the North Patagonian Batholith (NPB), is a tonalitic intrusion emplaced as a shallow, small, sub-circular tonalite-granodiorite body hosting abundant co-magmatic mafic microgranular enclaves (MME). Besides, the intrusive body is crosscut by radial porphyritic dikes and has been related to ande...

Crystallization of a hydrous andesite within a thermal boundary layer at 500 MPa pressure is simulated experimentally using the intrinsic thermal gradient of 10 mm length capsules in a horizontally arranged piston-cylinder apparatus. Magma solidification is programmed at two distinct cooling rates, slow (0.6 °C/h) and rapid (9.6 °C/h). Bulk laser a...

Crystallization of a hydrous andesite within a thermal boundary layer at 500 MPa pressure is simulated experimentally using the intrinsic thermal gradient of 10 mm length capsules in a horizontally arranged piston-cylinder apparatus. Magma solidification is programmed at two distinct cooling rates, slow (0.6 °C/h) and rapid (9.6 °C/h). Bulk laser a...

The calcite grains forming the wall plates of the giant barnacle Austramegabalanus psittacus have a distinctive surface roughness made of variously sized crystalline nanoprotrusions covered by extremely thin amorphous pellicles. This biphase (crystalline-amorphous) structure also penetrates through the crystal’s interiors, forming a web-like struct...

Diamond is commonly regarded as an indicator of ultra-high pressure conditions in Earth System Science. This canonical view is challenged by recent data and interpretations that suggest metastable growth of diamond in low pressure environments. One such environment is serpentinisation of oceanic lithosphere, which produces highly reduced CH 4-beari...

Palaeozoic rocks in the Betic Cordillera are widespread in the Maláguide, Alpujárride and Nevado-Filábride complexes of its Internal Domain. The Malaguide stratigraphic successions record a deepening trend during the post-rift evolution of a divergent continental margin that was paleogeographically related to the Northern Paleotethys from the lates...

Glauconite must be assessed as mica-rich mica-smectite R3 interstratified mineral, with the pure end-member mica having also intrinsic K-deficient chemical characteristic (K+ ~ 0.8 a.p.f.u.). This assertion is in accordance with our XRD and HRTEM studies and chemical analyses (EPMA) of mature glauconites in Cenozoic Antarctic sediments which indica...

Magnesium (Mg) isotopes in carbonate minerals are a useful proxy for paleoclimate studies, but interpretations are often limited by an inadequate understanding of the various factors controlling Mg isotopic fractionation during carbonate formation. Previous work has studied a number of parameters including aqueous chemistry, mineralogy, temperature...

Muscovite (Ms) and phlogopite (Phl) belong to the 2:1 dioctahedral and trioctahedral layer silicates, respectively, and are the end members of Ms-Phl series minerals. This series was studied in the 2M1 polytype and modeled by the substitution of three Mg²⁺ cations in the Phl octahedral sites by two Al³⁺ and one vacancy, increasing the substitution...

Supplementary Information to López-Quirós et al. 2019. Glaucony authigenesis, maturity and alteration in the Weddell Sea: An indicator of paleoenvironmental conditions before the onset of Antarctic glaciation. Scientific Reports.

Three types of glaucony grains were identified in the late Eocene (~35.5–34.1 Ma) sediments from Ocean Drilling Program (ODP) Hole 696B in the northwestern Weddell Sea (Antarctica). The grains are K2O-rich (~7 wt%) and formed by smectite-poor interstratified ~10 Å glauconite-smectite with flaky/rosette-shaped surface nanostructures. Two glaucony ty...

We are grateful to Massonne (2019) and Yang et al. (2019) for their constructive Comments to our recent publication (Farré-de-Pablo et al., 2018). We appreciate their interest in discussing our results and interpretations, which confirm that our work is a benchmark for future research. We are pleased to have the opportunity to address in further de...

Recent findings of diamonds in ophiolitic peridotites and chromitites challenge our traditional notion of Earth mantle dynamics. Models attempting to explain these findings involve incorporation of diamonds into chromite near the mantle transition zone. However, the occurrence of metastable diamonds in this context has not been considered. Here, we...

Models for evaluating the terrestrial carbon cycle must take into account not only soil organic carbon, represented by a mixture of plant and animal remains, but also soil inorganic carbon, contained in minerals, mainly in calcite and dolomite. Thick soil caliches derived from weathering of mafic and ultramafic rocks must be considered as sinks for...

The pre-Alpine metamorphic history of basement rocks of the Alpine Betic-Rif orogen is still uncertain as a result of intense Miocene reworking. Reaction sequences and textures recorded in pre-Mesozoic quartz-K-feldspar-plagioclase-biotite-muscovite anatectic gneisses of the Upper Alpujarride units underwent a complex polymetamorphic history. U-Pb...

The Cerro Munro sub-volcanic intrusion is emplaced in the back-arc (400 km from the trench) as small sub-circular tonalite-granodiorite plutons with abundant radial porphyritic dikes. U-Pb zircon SHRIMP data give an age of crystallization of 57 Ma ± 1.4 Ma. It is located to the east of the North Patagonian Batholith (NPB) that shows a protracted an...

Mineral dust aerosols coming from the arid and semiarid regions of the world can aggregate and form microspherulites under special atmospheric conditions. This is the case for iberulites, formed in the atmosphere from Saharan dust intrusions into the southern Iberian Peninsula during the summer, prompting a noteworthy case of dust accretion unique...

A 3-m deep soil profile from Gran Canaria, Canary Islands, has been studied. The profile is interesting because soil development on mafic tephra produced a pattern of clay mineral and carbonate distribution. Carbonates precipitated abundantly, increasingly towards the bottom, making up 20–90 wt% of the soil. Sepiolite and calcite are dominant at th...

Kyanite is directly replaced by andalusite in quartz-plagioclase veins included within graphite-bearing micaschists of the Alpine Benamocarra Unit (Betic Cordillera, Spain). Electron back-scattered diffraction indicates that: i) precursory kyanite contains planar defects; andalusite growth was crystallographically controlled by the kyanite; and iii...

A chronostratigraphic approach was used to the study of pictorial layers from the polychrome decorations on the façade of the Palace of King Peter I (the Royal Alcázar of Seville, Spain), to identify the timeline of successive decorative interventions made over time. Stratigraphic and mineralogical studies enabled the identification of modification...

Saharan dust can travel long distances in different directions across the Atlantic and Europe, sometimes in episodes of high dust concentration. In recent years it has been discovered that Saharan dust aerosols can aggregate into large, approximately spherical particles of up to 100 μm generated within raindrops that then evaporate, so that the agg...

Weathering of basaltic tephra under arid-semiarid conditions in the Gran Canaria island (Canary Islands) produced soils containing sepiolite, palygorskite and quartz together with large amounts of calcite and calcian dolomite. There is a marked sequence of mineral abundance, with sepiolite and calcite forming in the upper soil horizons and palygors...

This research has been conducted on the architectural decoration of the facade of the Palace of King Pedro I (The Royal Alcazar of Seville, Spain). The stratigraphic study of pictorial layers has revealed numerous interventions made on the polychrome decorations that have been related to those referenced in historical documents. Mineralogical and c...

Cerussite, an orthorhombic lead carbonate mineral, has a structure and physical properties that cannot be understood merely in terms of ionic anion-cation interactions. The nature of the chemical bonding in cerussite is analyzed by means of the quantum theory of atoms in molecules (QTAIM) and the analysis of the electron localization function (ELF)...

Pegmatite dikes bearing andalusite crosscut foliation S2 in Alpujarride gneisses and schists. Post-S2 andalusite is transposed by a foliation S3, defined by fibrolite, which affects the dikes. The dikes represent highly differentiated granitic magmas with low REE and Zr contents and a positive Eu anomaly. U-Pb SHRIMP dating of magmatic zircons prov...

Discovery of Fe-carbonate precipitation in Rio Tinto, a shallow river with very acidic waters, situated in Huelva, South-western Spain, adds a new dimension to our understanding of carbonate formation. Sediment samples from this low-pH system indicate that carbonates are formed in physico-chemical conditions ranging from acid to neutral pH. Evidenc...

The crystal-growth features of cerussite and hydrocerussite formed by two different chemical reactions are studied. With respect to the former, acid-vapour oxidation and latter carbonation of metallic lead produced a nanocrystalline precipitate for the lead carbonates. In the latter, cerussite and hydrocerusite are precipitated after mixing two mot...

The crystal growth features of andalusite and the transformation of andalusite to kyanite allow recognition of pre-Alpine and Alpine tectonometamorphic histories in the metapelites of the Alpujarride Complex. Two types of mineral segregations occur in relation to the andalusite → kyanite transformation. One type of segregation consists of a mantle...

Two strains of moderately halophilic bacteria were grown in aerobic culture experiments containing gel medium to determine the Sr partition coefficient between dolomite and the medium from which it precipitates at 15 to 45 °C. The results demonstrate that Sr incorporation in dolomite does occur not by the substitution of Ca, but rather by Mg. They...

Although diverse microbial metabolisms are known to induce the precipitation of carbonate minerals, the mechanisms involved in the bacterial mediation, in particular nucleation, are still debated. The study of aragonite precipitation by Chromohalobacter marismortui during the early stages (3-7 days) of culture experiments, and its relation to bacte...

Crystal-growth features of the foliated aragonite from two species of the rare monoplacophoran molluscs have been analyzed. The crystals have unique morphologies. They are very thin along the c axis and elongated along the a axis, and their arrangement varies depending on the species. Surface energy minimization in the crystal arrangement observed...

The pigments, binders and execution techniques used by the Nasrids (1238–1492) to polychrome carpentry in the Hall of the Mexuar Palace at the Alhambra (Granada, Spain) were studied using optical microscopy, scanning electron microscopy with EDX analysis, selective staining techniques and gas chromatography – mass spectrometry. This pioneering inve...

Spherulites composed of aragonite, magnesian calcite, and calcian-magnesian (-manganoan) kutnahorite-type carbonates were precipitated by two halophilic bacterial strains in porous solid as well as liquid media at high salinity. Although Mg and Ca are geochemically similar elements, Ca is preferentially incorporated into aragonite structures in liq...

Manual para alumnos de titulaciones experimentales que proporciona una visión práctica e intuitiva de la estadística descriptiva y el cálculo de probabilidades, campos básicos y fundamentales de la ciencia estadística

Extant monoplacophorans (Tryblidiida, Mollusca) have traditionally been reported as having an internal nacreous layer, thus representing the ancestral molluscan condition. The examination of this layer in three species of Neopilinidae (Rokopella euglypta, Veleropilina zografi, and Micropilina arntzi) reveals that only V. zografi secretes an interna...

Garnet growth in high-pressure, mafic garnet granulites formed by dehydration melting of hornblende-gabbronorite protoliths in the Jijal complex (Kohistan palaeo-island arc complex, north Pakistan) was investigated through a microstructural EBSD-SEM and HRTEM study. Composite samples preserve a sharp transition in which the low-pressure precursor i...

Changes in color of Upper Jurassic glauconite of the Georgiev Formation, in the West Siberian Basin, in Russia, are related to changes in physicochemical conditions that caused glauconite maturation and alteration, driven by regional paleoenvironmental evolution. Maturation produces dark green (bluish) glauconite formed from Fe-rich smectite by inc...

This study examines textural inhomogeneity and variable chemical composition of Upper Jurassic glaucony in relation to small-scale synsedimentary and postsedimentary authigenic processes controlled by the palaeonvironmental and palaeogeographical context. Four glaucony types with complex textural and compositional features have been recognized in c...

This paper investigates the thermal and irradiation-dependent dehydration and kinetics occurring in Na2SO4.10H2O (mirabilite) and MgSO4.7H2O (epsomite) at room conditions by using powder X-ray thermodiffraction. An improved version of a first optically stimulated X-ray diffractometer prototype was used. Specific software for the thermodiffraction s...

Manual en seis capítulos dedicado a la inferencia estadística. Se tratan en sus páginas temas como la estimación puntual, la estimación por intervalos, el contraste por hipótesis, los contrastes no paramétricos y la varianza.

Upper Jurassic phosphate stromatolites of the Almola Sierra (Southern Spain) encrust macrofossils and hardgrounds, and form oncoids included within pelagic, condensed fossiliferous limestones. Their accretion was determined by bacterially mediated precipitation of phosphate, by the trapping and binding of fine siliciclastics and pelagic biomicrite...

The ability of Chromohalobacter marismortui to precipitate carbonate and phosphate minerals has been demonstrated for the first time. Mineral precipitation in both solid and liquid media at different salts concentrations and different magnesium/calcium ratios occurred whereas crystal formation was not observed in the control. The precipitated miner...

Octahedrally-coordinated Cr(3+) possesses peculiar spectral features which made easy to identify it in minerals, even in minor amounts. Chromium has been studied in uvarovite and fuchsite by optical and EPR spectra. Optical, EPR, FT-infrared and EPMA studies have also let to determine the presence of Fe(3+) and Ti(3+) and fluid inclusions within uv...

Mullite (Mul) formation after high-T muscovite (Ms) breakdown has been studied in phyllosilicate-rich bricks. At T ≥ 900 °C Ms dehydroxylation is followed by partial melting that triggers the nucleation and growth of Mul acicular crystals. An analytical electron microscopy study reveals that the Mul is a 3:2-type with a [6](Al1.686Ti0.031Fe0.159Mg0...

At Mazarron, SE Spain, dacitic lavas of the Neogene Volcanic Province contain numerous xenocrysts and xenoliths with abundant andalusite that displays variable degrees of transformation to both fibrolite and coarse sillimanite. At the onset of replacement, andalusite dissolves along grain boundaries and (110) cleavage planes, probably assisted by f...

Upper Jurassic phosphatic stromatolites associated with condensed pelagic sediments in Alpine-Mediterranean paleomargins mainly consist of microbially precipitated francolite, a low crystallinity carbonate fluorapatite. SEM images of microbial phosphate laminae show highly porous colloform textures formed by dense accumulations of micrometre-size s...

The alteration process of a subvolcanic rock with calcic plagioclase, pyroxene, and olivine as major components was investigated by X-ray diffraction (XRD) and analytical and transmission electron microscopy (TEM/AEM). Experimental interaction with 1 M NaOH solution led to the formation of dioctahedral beidellite to Fe-rich montmorillonite after 1...

A natural example of sequential kinetics for the muscovite dehydration reaction in highly deformed mylonitic gneisses is analyzed. Studied textures consist of deformed pegmatitic muscovite crystals surrounded by fibrolitic sillimanite tightly intergrown with biotite and with potassium feldspar in the pressure shadows. Potassium feldspar, andalusite...

Authigenic clays in close textural relation to carbonate fluorapatite within finely laminated phosphate stromatolites of Upper Jurassic age have been studied using scanning electron microscopy (SEM), transmission electron microscopy (TEM) and analytical electron microscopy (AEM). Stromatolite laminae consist of hexagonal prisms of francolite (sizes...

The white mica crystallinity index has been analyzed as a function of the following parameters: 1) the domain size, 2) lattice distortion, and 3) the presence of other phyllosilicates overlapping the 10 Å XRD peak, particularly I/S mixed-layer. A direct relationship between size and peak width, without subtraction of the lattice distortion contribu...

Muscovite from anatectic leucogneisses of the Torrox gneiss complex (Betic alpine belt, southern Spain) has an unusually wide range in composition. A continuous compositional trend of decreasing Si, Fe, Mg and Ti and increasing Al, Na and K was formed by primary and recrystallized matrix muscovite grains. The textures and compositional features ass...

TEM analysis of microstructures and mechanisms related to alteration and deformation in igneous biotites was carried out on plagioclase-rich dykes from the ultrabasic Ronda massif. Compositional data for biotite and chlorite are used to establish the mass transfer of the alteration reaction. Deformation microstructures reveal that, at low-temperatu...

Copper-zinc, cyanide-sensitive superoxide dismutase (Cu-Zn-SOD) was detected in homogenates of Moniezia expansa. The enzyme was purified by a sequence of multiple differential centrifugations, ammonium sulphate precipitation, ion-exchange and G-75 Sephadex column chromatography. The final enzyme preparation had a specific activity of 623.00 +/- 9.9...

1. Three SOD isoenzymes obtained from purified extracts of Ascaris suum were characterized. 2. The physico-chemical characteristics studied were: optimum pH, methods of preservation of enzymatic activity, molecular weight, and the u.v. and visible light absorption spectra. 3. The optimum pH for the Cu, Zn SOD I and II was 10.2 and 10.1 for the Mn S...