SEM and TEM evidence of mixed-layer illite-smectite formed by dissolutioncrystallization processes in continental Paleogene sequences in northwestern Argentina

In the northernmost Calchaquí Valley (Salta, Argentina), the Paleogene continental sediments show a transition from smectite, at the top, to R3 I-S (>90% illite) through R1 I-S (65–80% illite), in contrast to the remaining sectors, containing smectite up to the bottom. Samples at the base of the succession were characterized by high-quality step-scan X-ray diffraction (XRD), scanning electron microscopy (SEM) and analytical high-resolution transmission electron microscopy (HRTEM). Analysis by SEM demonstrated dissolution of primary phases (feldspars, micas and quartz) and crystallization of illite, I-S and kaolinite. As this alteration is not pervasive, an intermediate fluid/rock ratio could be inferred. The lattice-fringe images of the samples from upper parts of the sequence show abundant I1-rich areas, whereas in the lower parts of the sequence, illite packets and I3 I-S coexist and compositions evolve towards muscovite (tetrahedral-charge increase, principally compensated by Mgby-Al substitution in octahedral sites and by a slight decrease in Ca in interlayer sites). As burial temperatures were probably similar in all the samples, depth was not responsible for the illite formation at the bottom. The TEM textures suggest that illitization proceeded mainly by dissolution-crystallization. The active faults close to the northern Calchaquí Valley probably promoted the circulation of hot, deep fluids, favouring illitization

Evidence of cyclic climatic changes recorded in clay mineral assemblages from a continental Paleocene-Eocene sequence, northwestern Argentina

The continental Paleocene-Eocene sequence investigated in this study belongs to the Salta Group, deposited in an intracontinental rift, the Salta Basin (NW Argentina), that evolved from the lower Cretaceous to the middle Paleogene, and is subdivided into the Pirgua, the Balbuena and the Santa Barbara Subgroups. The Maíz Gordo Formation (200 m thick) is the middle unit of the Santa Bárbara Subgroup, deposited during late post-rift sedimentation. We studied the mineralogy of fine-grained horizons of this formation by X-ray diffraction and Scanning Electron Microscopy (SEM) in order to examine the connection between vertical changes in clay mineralogy in alluvial sediments and paleosols, and global paleoclimatic changes registered during the Paleogene. Paleosols vary from calcic vertisols in the lowermost levels, to inseptisols and gleysols in intermediate positions, to gleyed oxisols in the upper section, indicating increased chemical weathering through time. Clay mineral relative abundances vary with a general increase in kaolinite content from bottom to top. However, at one site there are significant variations in kaolinite/muscovite (Kln/Ms) that define five cycles of kaolinite abundance and Kln/Ms. that indicate cyclic patterns of paleoprecipitation and paleotemperature. These are interpreted as several short-lived hyperthermals during the Paleocene-early Eocene in the Southern Hemisphere, which correlate with well-established episodes of warmth documented from the Northern Hemisphere

Evaluación de la fisibilidad y durabilidad de pizarras de techar mediante microscopía óptica y SEM

The fissility and durability of representative samples of commercial roofing slates from ten deposits in the NW of Spain have been evaluated using transmitted and reflectedlight optical microscopy, scanning electron microscopy, chemical testing and geomechanical procedures. The dominant sulphides in the different slate samples are pyrite and pyrrhotite, the weathering potential of which can be highly variable. The dominant carbonate mineral is ankerite, which explains the low reactivity of these slates in acidic media. The minimum commercial plate thickness varies between 3.5 and 5 mm, depending on the microtexture of the rock. The methodology used in this paper is proposed in order to eliminate the subjectivity of input data that are used in current methods of evaluation and modelling of slate deposits, thus producing an improvement in the profitability of mining operations and a reduction in waste materials.Para evaluar la fisibilidad y la durabilidad de pizarras de techar comerciales, muestras representativas de diez yacimientos del NO de España han sido estudiadas mediante microscopía óptica de luz transmitida y reflejada, microscopía electrónica de barrido y ensayos tecnológicos. Los sulfuros dominantes en las diferentes pizarras estudiadas son pirita o pirrotina, por lo que la alterabilidad de estas es muy variable. La especie carbonatada dominante es ankerita, lo que explica la baja reactividad de estas pizarras en medios ácidos. El espesor comercial mínimo varía en función de la microtextura de la roca, oscilando entre 3,5 y 5 mm. Se propone el uso de la metodología desarrollada en este trabajo, con objeto de eliminar la subjetividad de los inputs de entrada utilizados en las metodologías actuales de evaluación y modelización de yacimientos, lo que incidiría en la mejora de los rendimientos de las explotaciones y en la minimización de la producción de estériles

Evaluación de la movilidad potencial de metales en escorias industriales presentes en el subsuelo de un entorno urbano (barrio de la Almozara, Zaragoza)

Pyrite roasting wastes coming from a former industry closed in 1979 are still present at the subsoil of La Almozara neighborhood (Zaragoza, Spain). These granular wastes are mainly composed of Fe- and Fe-Ti-oxides, also having high Tl, As, Mo, Cu, Sb, Ag, Pb, and Be content that far exceed the generic reference levels. When these waste materials interact with water, they produce acid solutions with pH=3,2, resulting in a high mobilization of Cu, Zn, Cd, Mn, and Co. However, when wastes are mixed with granular construction materials, leachates showed neutral pH and chemical mobilization was much lower being only significant for Se and Mo. The results here obtained demonstrate the potential risk for hydrogeological contamination posed by the presence of these wastes in the subsoil and the high eolic dispersability of such materials. El cierre en 1979 de la Industrial Química de Zaragoza dejó los residuos industriales de tostación de piritas en el subsuelo del actual barrio de La Almozara (Zaragoza). Estos residuos, de carácter granular y constituidos por óxidos de Fe y Fe-Ti, poseen elevadas concentraciones en Tl, As, Mo, Cu, Sb, Ag, Pb y Be, que superan ampliamente los niveles genéricos de referencia. La interacción de estos residuos con agua provoca soluciones con pH=3,2, dando lugar a una movilización elevada de Cu, Zn, Cd, Mn y Co. Sin embargo, cuando estos residuos están mezclados con material granular de construcción, las soluciones resultantes de la interacción mantienen un pH neutro y la movilización elemental es muy inferior, siendo solo relevante para Se y Mo. Los resultados obtenidos demuestran el potencial riesgo de contaminación del medio hidrogeológico que supone la presencia de las escorias en el subsuelo y su alta dispersabilidad eólica

Wealth in Spain 1900–2017 a country of two lands

This study reconstructs Spain’s national wealth from 1900 to 2017. By combining new sources with existing accounts, we estimate the wealth of both private and government sectors and use a new asset-specific decomposition of the long-run accumulation of wealth. We find that, during the twentieth century, the national wealth-to-income ratio remained within a relatively narrow range—between 400% and 600%—until the housing boom of the early 2000s led to an unprecedented rise to 800% in 2007. Our results highlight the importance of land, housing capital gains and international capital flows as key elements of wealth accumulation

Implicacion de los genes uvra y reca de E. coli k 12 en la reparacion de monoaductos y entrecruzamientos inducidos en DNA plasmidico por 8-metoxipsoraleno mas luz ultravioleta A

Centro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai

Integral parametrization of the kinetics of crosslink production in plasmid DNA as a function of 8-methoxy-psoralen concentration

Centro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai

Localizacion puntual de mutaciones producidas en PBr 322 por tratamiento con 8-metoxipsoraleno mas luz ultravioleta A

Centro de Informacion y Documentacion Cientifica (CINDOC). C/Joaquin Costa, 22. 28002 Madrid. SPAIN / CINDOC - Centro de Informaciòn y Documentaciòn CientìficaSIGLEESSpai