García Romero, Emilia

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First Name
Last Name
García Romero
Universidad Complutense de Madrid
Faculty / Institute
Ciencias Geológicas
Mineralogía y Petrología
Cristalografía y Mineralogía
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Now showing 1 - 10 of 105
  • Publication
    Spanish Bentonites: A Review and New Data on Their Geology, Mineralogy, and Crystal Chemistry
    (MDPI, 2019) García Romero, Emilia
    A review and a synthesis of the geological, mineralogical, and crystal chemical data available in the literature on active Spanish bentonitic exploitations were done, and at the same time, new data are provided from a set of representative samples from these deposits. They were located in three different areas with different geological origins: (1) Miocene sedimentary deposits from the Tajo Basin (Madrid–Toledo provinces) in the center of the Iberian Peninsula, where bentonites appear in two different units named for their colors (Green Clays and Pink Clays); (2) samples from Tamame de Sayago (Zamora province) originating from the hydrothermal alteration of granitic Variscan rocks; and 3) Miocene deposits originating from the hydrothermal alteration of volcanic or subvolcanic rocks from the Cabo de Gata volcanic area (Almería Province) in the southern part of Spain, where the three main deposits (Cortijo de Archidona, Los Trancos, and Morrón de Mateo) were studied. The bentonites from the Tajo Basin were formed mainly by trioctahedral smectites, and there were significant mineralogical differences between the Green and Pink Clays, both in terms of the contents of impurities and in terms of smectite crystallochemistry and crystallinity. The smectites from Tamame de Sayago were dioctahedral (montmorillonite–beidellite series), and they appeared with kaolinite, quartz, and mica in all possible proportions, from almost pure bentonite to kaolin. Finally, the compositions of the bentonites from the three studied deposits in Cabo de Gata were quite similar, and zeolites and plagioclases were the main impurities. The structural formulae of the smectites from Cortijo de Archidona and Los Trancos showed a continuous compositional variation in beidellite–montmorillonite, while in Morrón de Mateo, the smectites were mainly montmorillonite, although there was continuous compositional variation from Al montmorillonites to Fe–Mg-rich saponites. The variation in the smectite composition is due to the intrusion of a volcanic dome, which brings new fluids that alter the initial composition of the smectites.
  • Publication
    Trioctahedral entities in palygorskite: Near-infrared evidence for sepiolite-palygorskite polysomatism
    (Mineralogical Society of America., 2011) Stathopoulou, Elizabeth T.; Súarez Barrios, Mercedes; García Romero, Emilia; Sánchez del Río, Manuel; Kacandes, Georges H.; Gionis, Vassilis; Chryssikos, Georgios D.
    The mixed dioctahedral-trioctahedral character of Mg-rich palygorskite has been previously described by the formula yMg5 Si8 O20(OH)2(OH2)4(1–y)[xMg2Fe2(1–x)Mg2 Al2] Si8 O20(OH)2(OH2)4, where y is the trioctahedral fraction of this two-chain ribbon mineral with an experimentally determined upper limit of y 0.5 and x is the FeIII content in the M2 sites of the dioctahedral component. Ideal trioctahedral (y ¼ 1) palygorskite is elusive, although sepiolite Mg8Si12O30(OH)4(OH2)4 with a similar composition, three-chain ribbon structure and distinct XRD pattern is common. A set of 22 samples identified by XRD as palygorskite and with variable composition (0 , x , 0.7, 0 , y , 0.5) were studied to extrapolate the structure of an ideal trioctahedral (y ¼ 1) palygorskite and to compare this structure to sepiolite. Near-infrared spectroscopy was used to study the influence of octahedral composition on the structure of the TOT ribbons, H2O in the tunnels and surface silanols of palygorskite, as well as their response to loss of zeolitic H2O. All spectroscopic evidence suggests that palygorskite consists of discrete dioctahedral and trioctahedral entities. The dioctahedral entities have variable structure determined solely by x=FeIII/(Al+FeIII) and their content is proportional to (1–y). In contrast, the trioctahedral entities have fixed octahedral composition or ribbon structure and are spectroscopically identical to sepiolite. The value of d200 in palygorskite follows the regression d200 (A°)= 6.362 + 0.129 x(1–y) + 0.305y, R2 = 0.96, σ = 0.013A°. When extrapolated to y = 1,d200 is identical to sepiolite. Based on this analysis, we propose that palygorskite samples with non-zero trioctahedral character should be considered as members of a polysomatic series of sepiolite and (dioctahedral) palygorskite described by the new formula y'Mg8 Si12 O30(OH)4(OH2)4.(1–y')[x'Mg2Fe2(1–x')Mg2Al2]Si8O20(OH)2(OH2)4, with 0 < x'= x < 0.7 and 0 < y' = y/(2–y) < 0.33.
  • Publication
    FTIR spectroscopic study of palygorskite: Influence of the composition of the octahedral sheet
    (Elsevier, 2006) Súarez Barrios, Mercedes; García Romero, Emilia
    The influence of chemical composition to position and intensity of the absorption bands observed in the FTIR spectra of palygorskite has been studied by a detailed comparative study of six samples. Palygorskites studied have high purity and different chemical composition. At one extreme, there are two samples that correspond to Mg-rich palygorskites, at the other extreme a sample with a composition very close to the theoretical formula of this mineral, and there are three further samples whose structural formulae lie between these extremes. The position of the bands identified in the FTIR spectra of the palygorskites studied is similar for all samples, but there are some differences in their intensity, which are significant. Analysing these intensities, valuable information about the distribution of cations along the octahedral sheet has been obtained. Isomorphic substitution in octahedral sheet occurs only in M2 position. Al, and Fe may occupy M2 position whereas Mg can occupy all possible sites: M1, M2 and M3.
  • Publication
    An arid phase in the Internal Dinarides during the early to middle Miocene: Inferences from Mg-clays in the Pranjani Basin (Serbia)
    (Elsevier, 2021-01-15) Andrić-Tomašević, N.; Simic, Vladimir; Mandic, O.; Životić, D.; Suárez, M.; García Romero, Emilia
    Lacustrine strata record long-term variations in climatic and tectonic perturbations during orogen evolution. Here we use the sedimentological record of the early to middle Miocene intramontane lacustrine Pranjani Basin (Serbia) to study tectonic and climatic variations during the evolution of the Dinaridic orogen. Our study focuses on a Mg-clay-bearing succession that belongs to the second depositional cycle. A detailed sedimentological, mineralogical and geochemical study shows that the investigated Mg-clays bearing succession consists of an alternation of smectite- (± analcime or sepiolite), dolomite-sepiolite and sepiolite layers. We interpret this high-order cyclicity to have been driven by variable water availability, i.e. by the interplay between runoff, groundwater influx and evaporation. Furthermore, we relate these pulses in water variability to wet and dry intervals under semi-arid to arid climatic conditions. Dry intervals produced a negative water balance promoting the deposition of sepiolite - and dolomite - dominated facies. Wet intervals and a positive water balance stimulated higher terrestrial input and thus favored the deposition of smectite-dominated facies. Our new data combined with a review of previous studies reveal longer-term basin-wide lake level and chemistry fluctuations, which we relate to closed and open lake phases. We suggest that these phases can be explained by alternating humid and arid phases superimposed on tectonically induced uplift and subsidence. The arid phases led to lake shrinking and deposition of an evaporite-bearing succession. During the intervening humid phase, the lake expanded. In contrast to the lakes formed in the external part of the Dinarides, the lakes that existed in its internal part contain evaporite-bearing successions, indicating that this arid phase was regionally extensive and possibly orographically controlled.
  • Publication
    Ni-sepiolita en depósitos de lateritas de República Dominicana: variaciones composicionales
    (Sociedad Española de Mineralogía, 2009-09) García Romero, Emilia; Suárez Barrios, Mercedes; Tauler, Esperanza; Proenza, Joaquín; Lewis , John F.; Longo, Francisco
  • Publication
    Análisis de los minerales de la arcilla y sus procesos genéticos en las formaciones arcillosas de la Cuenca del Tajo.
    (Consejo Superior de Investigaciones Científicas, Museo Nacional de Ciencias Naturales, 1997) Domínguez Díez, M.C.; Brell, J.M.; Doval, Mercedes; García Romero, Emilia
    Se han estudiado seis sondeos, realizados en la cuenca neógena del Tajo, con el fin de conocer los procesos genéticos de los materiales arcillosos de la cuenca. Estos sondeos cortan facies correspondientes a distintos ambientes deposicionales. La evolución observada puede relacionarse con dos etapas distintas de sedimentación. La primera corresponde a la sedimentación de la Unidad de Yesos; la asociación de minerales de arcilla en esta unidad está constituida principalmente por illita, menores contenidos de esmectita, interestratificados I/Sm, Cl/Sm, Glauconita/Sm, palygorskita y clorita. El origen de esta asociación es en parte detrítica y en parte neoformada; los aportes detríticos corresponden a illita y esmectita, mientras que los minerales neoformados son principalmente illita e interestratificados, clorita y palygorskita. Esta etapa se caracteriza por la existencia de procesos de illitización. En la segunda etapa de sedimentación (Unidad de Arcillas Verdes), se observa un incremento de los aportes detríticos y una evolución hacia condiciones de menor salinidad. El ambiente de formación de esta unidad se encuentra enriquecido en magnesio y los minerales de la arcilla más característicos de las facies que componen dicha unidad son las esmectitas magnésicas (saponita y estevensita) y, en menor proporción, los interestratificados Cl/Sm. Esta asociación mineralógica se origina por la reacción entre las partículas detríticas arcillosas y los cationes del medio.
  • Publication
    Electron microscopic study of the illite– smectite transformation in the bentonites from Cerro del Aguila (Toledo, Spain)
    (Mineralogical Society / Blackwell Scientific publications, 1998) Santiago Buey, Cristina de; Súarez Barrios, Mercedes; García Romero, Emilia; Domínguez Díaz, M.C.; Doval, Mercedes
    A mineralogical and microstructural study of bentonites from ‘Cerro del Aguila’ located in the Tagus Basin (Toledo, Spain) was carried out using XRD, SEM and TEM observations and chemical data obtained by TEM-EDX. The bentonites are mainly composed of trioctahedral smectite with a unit-cell formula (Si3.76Al0.24)(Al0.44Fe3+ 0.26Mg1.81)Ca0.05K0.19O10(OH)2 and small amounts of illite. The relationships between illite and smectite particles observed by SEM and TEM allowed the study of the weathering process of illite to form smectite through possible intermediate stages. The transformation begins as an exfoliation normal to the stacking direction and develops by opening of the interlayer spacing, the replacement of K+ by hydrated interlayer cations and slight reorganization of the 2:1 layer structure. The so-called solid-state transformation process then proceeds by further dissolution and the formation of a colloidal phase acting as raw material in the growth of new phyllosilicates such as smectite.
  • Publication
    Ni-sepiolite-falcondoite in garnierite mineralization from the Falcondo Ni-laterite deposit, Dominican Republic
    (Mineralogical Society, 2009) Tauler, Esperança; Proenza, Joaquín A.; Galí Medina, Salvador; Lewis , John F.; Labrador Carrasco, Manuel; García Romero, Emilia; Súarez Barrios, Mercedes; Longo, Francisco; Bloise, Giovanni
    New chemical and structural data on sepiolite-falcondoite in garnierite veins from the Falcondo Ni-laterite deposits, central Dominican Republic, are reported. Samples of Ni-sepiolitefalcondoite vary in colour from whitish green to green depending on the NiO content (wt.%) and the amount of silica present. The texture is normally schistose and friable but samples with considerable quartz and/or amorphous silica are compact and hard. Back-scattered electron images indicate that the samples are composed of at least three generations of Ni-sepiolite-falcondoite. The extreme refined cell parameters for Ni-sepiolite-falcondoite vary from 13.400(2), 27.006(4), 5.273(1) A˚ to 13.340(3), 27.001(6), 5.267(1) A˚ (space group Pncn). As the Ni content increases there is a small reduction in the a parameter. Chemical compositions determined by electron probe microanalysis cover a large interval of the Ni-sepiolite-falcondoite solid solution (Fal3 and Fal77). Individual samples show a considerable range in composition with the widest range determined in one sample from 4.63 to 22.40 wt.% NiO.
  • Publication
    Génesis de arcillas magnésicas en la cuenca de Madrid: interrogantes planteados
    (Instituto Geológico y Minero de España, 2004) García Romero, Emilia
    La cuenca de Madrid es excepcionalmente rica en arcillas magnésicas (sepiolita, paligorskita, saponita y estevensita), las cuales para formarse requieren elevada actividad de silicio y magn esio, a la vez que pH alcalinos, siendo típicas de medios aridos o semiáridos. En este trabaio se revisa la composición de las potenciales áreas fuente que hayan podido aportar a la cuenca durante el Mioceno el magnesio necesario para la formación de dichas arcillas, ya que parece difícil que las rocas del entomo, ácidas y pobres en dicho elemento, hayan dado lugar a concentraciones anómalas de arcillas como las mencionadas. El estudio de dichas áreas fuente y la contrastación de los datos paleoclimáticos que se deducen de la fauna fósil descarta la extrema aridez como forma de enriquecimiento en magnesio del medio deposicional; también se hace una comparación con otros lugares del mundo en los que aparecen arcillas semeiantes, formadas en lagos salinos alcalinos, siendo la característica común a todos ellos la existencia de materiales volcánicos como fuente del magnesio y del silicio. Aunque no existen evidencias de vulcanismo o de hidrotermalismo en la cuenca de Madrid durante el Mioceno, los datos mineralógicos apuntan en este sentido para explicar dichas anomalias
  • Publication
    Clay mineral genesis and chemical evolution in the Miocene sediments of Somosaguas, Madrid Basin, Spain
    (Blackwell Scientific publications, 2007) Fesharaki, Omid; García Romero, Emilia; Cuevas González, Jaime; López Martínez, Nieves
    A mineralogical and microtextural study of Somosaguas Miocene deposits, located in the Madrid Basin (western Madrid, Spain), was carried out using X-ray diffraction, scanning electron microscopy, transmission electron microscopy and optical microscopy, whereas crystal chemistry data were obtained by analytical electron microscopy-transmission electron microscopy and electron icroprobe analysis. Four stratigraphic sections were studied, compising detrital rocks representing intermediate and distal facies from alluvial fan deposits. The predominant source area of these sediments was the granitic rocks of the Spanish Central System with a lesser contribution of metamorphic rocks. Clayey arkoses are the most abundant rocks of these sections, typical of granite alteration under warm, semi-arid climates. The mineralogy is characterized by phyllosilicates, followed by feldspars and quartz. The data obtained reveal mineral mixtures of detrital (quartz, feldspars, kaolinite, micas and chlorite), transformed (illite and beidellite) and neoformed (montmorillonite) origin. Clay minerals resulted from interactions between detrital minerals and meteoric waters. Two trends of degradation of micas are detected. The first shows a transition from muscovites and dioctahedral illites, to beidellites. The other trend is defined by the biotite degradation to beidellites with different layer charge and octahedral Fe content. Montmorillonites were neoformed from the hydrolysis and weathering of primary minerals (feldspars and muscovite). Magnesian clay minerals such as sepiolite, palygorskite and trioctahedral smectites, extremely abundant in the centre of the basin, were not detected in Somosaguas sediments.