Ultra High Resolution Transmission Electron Microscopy of Matrix Mineral Grains in CM Chondrites: Preaccretionary or Parent Body Aqueous Processing?

CM chondrites are highly hydrated meteorites associated with a parent asteroid that has experienced significant aqueous processing. The meteoritic evidence indicates that these non-differentiated asteroids are formed by fine-grained minerals embedded in a nanometric matrix that preserves chemical clues of the forming environment. So far there are two hypothesis to explain the presence of hydrated minerals in the content of CM chondrites: one is based on textural features in chondrule-rim boundaries [1-3], and the other ‘preaccretionary’ hypothesis proposes the incorporation of hydrated phases from the protoplanetary disk [4-6]. The highly porous structure of these chondrites is inherited from the diverse materials present in the protoplanetary disk environment. These bodies were presumably formed by low relative velocity encounters that led to the accretion of silicate-rich chondrules, refractory Ca- and Al-rich inclusions (CAIs), metal grains, and the fine-grained materials forming the matrix. Owing to the presence of significant terrestrial water in meteorite finds [7], here we have focused on two CM chondrite falls with minimal terrestrial processing: Murchison and Cold Bokkeveld. Anhydrous carbonaceous chondrite matrices are usually represented by highly chemically unequilibrated samples that contain distinguishable stellar grains. Other chondrites have experienced hydration and chemical homogeneization that reveal parent body processes. We have studied CM chondrites because these meteorites have experienced variable hydration levels [8-10]. It is important to study the textural effects of aqueous alteration in the main minerals to decipher which steps and environments promote bulk chemistry changes, and create the distinctive alteration products. It is thought that aqueous alteration has particularly played a key role in modifying primordial bulk chemistry, and homogenizing the isotopic content of fine-grained matrix materials [7, 11, 12]. Fortunately, the mineralogy produced by parent-body and terrestrial aqueous alteration processes is distinctive [5, 11]

Ancient Martian Floods in a Plausible Variable Climatic Environment as Revealed from the Sequential Growth of Allan Hills 84001 Carbonate Globules

No abstract available

Evolución cenozoica de la fosa de Garganta del Villar (Sistema Central español)

La fosa de Garganta del Villar (Sistema Central español) es una depresión tectónica subromboidal sobre zócalo cristalino, que localmente contiene depósitos cenozoicos (Paleógeno-Cuaternario). La interpretación geomorfológica, sedimentológica y de la mineralogía de arcillas, permite aportar nuevos datos sobre la evolución geodinámica durante el Cenozoico de este área del Macizo HercÍnico. Las etapas que configuran dicha evolución son correlacionables, en gran medida, con aquéllas establecidas por otros autores en la zona de contacto entre las grandes cuencas sedimentarias (Duero y Tajo) y el Sistema Central. Sin embargo, un buen registro de morfologías y depósitos cuaternarios de la fosa, han hecho posible matizar y complementar la sucesión de eventos pleistocenos de la misma, que evolucionó con cierta independencia respecto al resto del macizo montañoso

Ultra High Resolution Transmission Electron Microscopy of Matrix Mineral Grains in CM Chondrites: Preaccretionary or Parent Body Aqueous Processing?

CM chondrites are highly hydrated meteorites associated with a parent asteroid that has experienced significant aqueous processing. The meteoritic evidence indicates that these non-differentiated asteroids are formed by fine-grained minerals embedded in a nanometric matrix that preserves chemical clues of the forming environment. So far there are two hypothesis to explain the presence of hydrated minerals in the content of CM chondrites: one is based on textural features in chondrule-rim boundaries [1-3], and the other ‘preaccretionary’ hypothesis proposes the incorporation of hydrated phases from the protoplanetary disk [4-6]. The highly porous structure of these chondrites is inherited from the diverse materials present in the protoplanetary disk environment. These bodies were presumably formed by low relative velocity encounters that led to the accretion of silicate-rich chondrules, refractory Ca- and Al-rich inclusions (CAIs), metal grains, and the fine-grained materials forming the matrix. Owing to the presence of significant terrestrial water in meteorite finds [7], here we have focused on two CM chondrite falls with minimal terrestrial processing: Murchison and Cold Bokkeveld. Anhydrous carbonaceous chondrite matrices are usually represented by highly chemically unequilibrated samples that contain distinguishable stellar grains. Other chondrites have experienced hydration and chemical homogeneization that reveal parent body processes. We have studied CM chondrites because these meteorites have experienced variable hydration levels [8-10]. It is important to study the textural effects of aqueous alteration in the main minerals to decipher which steps and environments promote bulk chemistry changes, and create the distinctive alteration products. It is thought that aqueous alteration has particularly played a key role in modifying primordial bulk chemistry, and homogenizing the isotopic content of fine-grained matrix materials [7, 11, 12]. Fortunately, the mineralogy produced by parent-body and terrestrial aqueous alteration processes is distinctive [5, 11]

Estudio de la idoneidad de un nuevo hormigón estructural fabricado con áridos ligeros reforzados con fibra de carbono sinterizados a partir de residuos

The suitability of three new lightweight aggregates containing carbon fiber residues (CAs) as components in structural lightweight concrete has been studied. Prismatic concrete specimens were prepared using these CAs as a coarse fraction. Additional specimens of normal-weight aggregate, commercial lightweight aggregate and mortar were prepared for comparison. The CA-concrete samples (CACs) have yielded compressive strength values between 35 and 55 MPa as well as low density and thermal conductivity results. Furthermore, the CACs have displayed the highest ratios of mechanical strength over density and the thermal conductivity, which means that there is a better balance between their mechanical and physical properties than in the other samples studied. These results indicate that the new CAs could have great potential for use in structural lightweight concrete, also complying with the principles of the Circular Economy.Este estudio pretende comprobar la idoneidad de unos novedosos áridos ligeros sinterizados con residuos de fibra de carbono (CAs) en la fabricación de hormigón ligero estructural. Se prepararon probetas prismáticas de hormigón, utilizando estos CAs como fracción gruesa, comparándose a su vez con probetas fabricadas con un árido convencional, un árido ligero comercial y mortero. Las muestras de hormigón con los áridos CA (en adelante CAC) han dado lugar a valores de resistencia a compresión entre 35 y 55 MPa, así como a resultados bajos de densidad y conductividad térmica, mostrando además las ratios más altas al relacionar estos tres parámetros. Esto indicaría por tanto un mejor equilibrio entre las propiedades mecánicas y físicas que los obtenidos en las otras muestras estudiadas. Estos resultados apuntan a que los nuevos CAs podrían tener un gran potencial para su uso en hormigón ligero estructural, cumpliendo además los principios de la Economía Circular

Ancient Martian Floods in a Plausible Variable Climatic Environment as Revealed from the Sequential Growth of Allan Hills 84001 Carbonate Globules

No abstract available

Tsunami vs. storm surge deposits: a review of the sedimentological and geomorphological records of extreme wave events (EWE) during the Holocene in the Gulf of Cadiz, Spain

The Gulf of Cadiz region of Spain has undergone many studies examining Holocene tsunami and storm deposists. Some of the studies aimed at determining recurrence intervals of events interpreted of tsunamigenic origin. A review of geomorphologic, sedimentary and paleontological features of these deposits suggests that only a few of them can be accurately ascribed to tsunami events; instead, most of them lack conclusive evidence of a tsunamigenci genesis and should be referred to as generated by extreme wave events (EWE

Palaeogeographical significance of clay mineral assemblages in the Permian and Triassic sediments of the SE Iberian Ranges, eastern Spain

The evolution of the palaeogeography of the SE Iberian Basin during the Permian and Triassic represents a general evolution from continental to marine environments. It has been recently studied from the sedimentological, stratigraphical, tectonic and palaeontological points of view. In spite of these results, many aspects of this palaeogeography are still a matter of discussion. In this study, clay mineralogy analysis complements previous studies representing a new aspect for understanding the evolution of the sedimentary environment and the palaeogeography of the Iberian Basin during the periods in question and thus of the palaeogeography and the location of the major high areas in the westernmost border of the Tethys sea. In spite of late diagenetic transformations the original clay mineral associations of the Permian-Triassic sediments of the SE Iberian Ranges can be reconstructed. Seventy-seven samples of siliciclastic and carbonate sediments of these ages have been studied (SEM and XRD), revealing six new aspects that help to precise the palaeogeographical interpretation of the area: (1) Two major mineral assemblages have been found: illite+ kaolinite +pyrophyllite in the continental facies and illite + chlorite + vermiculite + mixed-layer clays in the marine facies. (2) The Mg-rich clay minerals are here considered to be of marine origin. (3) Active phases of basin boundary faults are marked in the sediments by the presence of pyrophyllite, derived directly from the Palaeozoic metamorphic basement. (4) Unconformities separating major depositional sequences also separate formations with different clay mineralogy. (5) Different groups of clay minerals can be separated clearly coinciding with the different palaeogeographical stages also distinguished in the westernmost border of the Tethys sea. (6) The clay mineral associations back up the data of a previous hypothesis of a humid climate for the end of the Permian in the study area just prior to the first incursion of the Tethys sea

EDTA and hydrochloric acid effects on mercury accumulation by Lupinus albus

The efficiency of white lupine (Lupinus albus) to uptake and accumulate mercury from a soil polluted by mining activities was assessed in a pot experiment with chemically assisted phytoextraction. The mobilizing agents tested were ethylenediaminetetracetic acid (EDTA) and hydrochloric acid (HCl). Two doses of each amendment were used (0.5 and 1.0 g of amendment per kg of soil), and unamended pots were used as a control. Addition of HCl to the soil did not negatively affect plant biomass, while the use of EDTA led to a significant decrease in plant growth when compared to that found for non-treated pots, with plants visually showing symptoms of toxicity. The addition of hydrochloric acid increased root, shoot and total plant Hg uptake of white lupine by 3.7 times, 3.1 times and 3.5 times, respectively, in relation to non-amended plants. The greatest efficiency was obtained for the highest HCl dose. EDTA led to higher concentrations of total plant Hg than that found with the control, but, due to the aforementioned decrease in plant biomass, the Hg phytoextraction yield was not significantly increased. These results were attributed to the capability of both amendments to form stable Hg complexes. The concentration of Hg in the water of the soil pores after the phytoextraction experiment was very low for all treatments, showing that risks derived from metal leaching could be partially avoided by using doses and chemicals suitable to the concentration of metal in the soil and plant performance.La eficiencia del altramuz blanco ( Lupinus albus) para absorber y acumular mercurio de un suelo contaminado por actividades mineras se evaluó en un experimento en macetas con fitoextracción asistida químicamente. Los agentes movilizadores probados fueron ácido etilendiaminotetracético (EDTA) y ácido clorhídrico (HCl). Se utilizaron dos dosis de cada enmienda (0,5 y 1,0 g de enmienda por kg de suelo) y se utilizaron macetas sin enmendar como control. La adición de HCl al suelo no afectó negativamente la biomasa vegetal, mientras que el uso de EDTA condujo a una disminución significativa en el crecimiento de las plantas en comparación con el encontrado en macetas no tratadas, con plantas que mostraban visualmente síntomas de toxicidad. La adición de ácido clorhídrico aumentó la absorción de Hg de la raíz, los brotes y la planta total de altramuz blanco en 3,7, 3,1 y 3,5 veces, respectivamente, en relación con las plantas no modificadas. La mayor eficiencia se obtuvo para la dosis más alta de HCl. El EDTA dio lugar a concentraciones de Hg total de la planta más altas que las encontradas con el control, pero, debido a la disminución mencionada anteriormente en la biomasa de la planta, el rendimiento de la fitoextracción de Hg no aumentó significativamente. Estos resultados se atribuyeron a la capacidad de ambas enmiendas para formar complejos de Hg estables. La concentración de Hg en el agua de los poros del suelo después del experimento de fitoextracción fue muy baja para todos los tratamientos, lo que demuestra que los riesgos derivados de la lixiviación de metales podrían evitarse parcialmente mediante el uso de dosis y productos químicos adecuados para la concentración de metal en el suelo y el rendimiento de la planta. . el rendimiento de la fitoextracción de Hg no aumentó significativamente. Estos resultados se atribuyeron a la capacidad de ambas enmiendas para formar complejos de Hg estables. La concentración de Hg en el agua de los poros del suelo después del experimento de fitoextracción fue muy baja para todos los tratamientos, lo que demuestra que los riesgos derivados de la lixiviación de metales podrían evitarse parcialmente mediante el uso de dosis y productos químicos adecuados para la concentración de metal en el suelo y el rendimiento de la planta. . el rendimiento de la fitoextracción de Hg no aumentó significativamente. Estos resultados se atribuyeron a la capacidad de ambas enmiendas para formar complejos de Hg estables. La concentración de Hg en el agua de los poros del suelo después del experimento de fitoextracción fue muy baja para todos los tratamientos, lo que demuestra que los riesgos derivados de la lixiviación de metales podrían evitarse parcialmente mediante el uso de dosis y productos químicos adecuados para la concentración de metal en el suelo y el rendimiento de la planta.

El abadengo de Sahagún : (contribución al estudio del feudalismo en España)

Precede al tit.: Real Academia de la HistoriaCopia digital. Valladolid : Junta de Castilla y León. Consejería de Cultura y Turismo, 2009-201