1,720,976 research outputs found
Petrological study of the Cotacachi-Cuicocha Volcanic Complex, Ecuador: understanding the eruptive dynamic and evolution of the magma
No full textEcuador is a country with 97 volcanoes, of which 13 are considered as active. Therefore, volcanic hazards are an important and concerning issue for Ecuadorians and their authorities. Most of these volcanoes are stratovolcanoes which usually present a complex and varied eruptive history. One of this, is the dormant Cotacachi volcano, which is part of the Cotacachi-Cuicocha Volcanic Complex (CCVC). This volcanic complex is located in the Western Cordillera of Ecuador and comprises, apart from the Cotacachi volcano, three satellite domes called Peribuela, Loma Negra and Muyurcu, and the Cuicocha caldera, which have four intra-caldera domes. The latest activity recorded of this volcanic complex was located on the southern flank of the Cotacachi volcano, with the growth of a fourth dome, destroyed in a caldera-forming eruption ~3.1 ka ago, and the growth of the four intra-caldera domes. In this thesis, data from a petrological study, which includes the use of an optical microscope and SEM coupled with an EDS detector, is presented, with an emphasis on the analysis of textures, chemical zonation, reaction rims in crystals and physical properties of the rocks from the CCVC. Textures such as oscillatory zoning, patchy zones, and sieve textures found in plagioclase crystals indicate kinetic effects and long-term processes within the magmatic chamber, decompression in magmas undersaturated in water, and magma mixing, respectively. Chemical zonation in pyroxene crystals shows different magma composition, and reaction rims in amphibole crystals reveal heating or decompression-induced processes that occurred during rim growth. Furthermore, the crystal population, their modal abundance, and vesicles were analyzed and related to viscosity. By considering all these data, we recognize some magmatic processes that occurred throughout the history of the CCVC, and we were able to reconstruct the magmatic history of the different eruptive phases of this volcanic complex.Ecuador es un país con 97 volcanes, de los cuales 13 se consideran activos. Por lo tanto, los peligros volcánicos son un tema importante y preocupante para los ecuatorianos y sus autoridades. La mayoría de estos volcanes son estratovolcanes que generalmente presentan una historia eruptiva compleja y variada. Uno de estos es el volcán inactivo Cotacachi, que forma parte del Complejo Volcánico Cotacachi-Cuicocha. Este complejo volcánico está localizado en la Cordillera Occidental del Ecuador y comprende, además del volcán Cotacachi, tres domos satélites llamados Peribuela, Loma Negra y Muyurcu, y la caldera Cuicocha, que tiene cuatro domos intra-caldera. La última actividad registrada de este complejo volcánico se localizó en el flanco sur del volcán Cotacachi, con el crecimiento de un cuarto domo, el cual fue parcialmente destruido durante una erupción que formó la caldera hace ~3.100 años, y el crecimiento de cuatro domos intra-caldera. En esta tesis, se presentan datos de un estudio petrográfico, que incluye el uso de un microscopio óptico y el SEM junto con un detector EDS, con énfasis en el análisis de texturas, zonación química, bordes de reacción en cristales y propiedades físicas de las rocas del Complejo Volcánico Cotacachi-Cuicocha. Texturas tales como zonación oscilatoria, zonación irregular y texturas de tamiz que se encuentran en los cristales de plagioclasa indican efectos cinéticos y procesos a largo plazo dentro de la cámara magmática, descompresión en magmas subsaturados en agua y mezcla de magma, respectivamente. La zonación química en los cristales de piroxeno muestra una composición de magma variada, y los bordes de reacción en los cristales de anfíboles revelan procesos de calentamiento o descompresión inducida que ocurrieron durante el crecimiento del borde. Además, la población de cristales, su abundancia modal y las vesículas fueron analizadas y relacionadas con la viscosidad. Al considerar todos estos datos, se reconocieron ciertos procesos magmáticos que ocurrieron a lo largo de la historia del Complejo Volcánico Cotacachi-Cuicocha, y así pudimos reconstruir la historia magmática de las diferentes fases eruptivas de este complejo volcánico.Geólogo/
Magnetometry survey applied to geothermal exploration in Chachimbiro, northern of Ecuador
No full textGeophysical surveys are efficient ways to obtain information on subsurface structures. The magnetic method is especially useful to detect shallow structures and changes in magnetization due to several processes, such as faulting and hydrothermal alterations. Despite the richness of available geothermal resources in South America, their use for electricity production is very limited. In Ecuador, geothermal projects in Ecuador are still at very initial phases of prospection and exploration. Chachimbiro, in northern Ecuador, is one of the potential site for developing a geothermal power plant. The objective of this project is to provide complementary studies to improve the existing model. We performed high resolution magnetometry survey with ~30 m spacing between points around the drilling area to get a better understanding of the shallow structure above the reservoir, as well as two survey lines with ~5 m spacing perpendicular to local faults. We then compared our results with existing magnetotelluric and gravimetric data, which are less precise for shallow structural features. Comparison with previous works shown that faults location and low magnetic anomalies distribution of this study fits with the locations described in previous studies. Our magnetic survey was usefulness to differentiate magnetic anomalies related to topography, faulting and hydrothermal alterations. Our study thus contributes to a better knowledge of the area, needed for future drilling planning of potentially, the first geothermal power plant of the country.Los estudios geofísicos son una forma eficiente de obtener información de las estructuras bajo la superficie. El método magnético es especialmente útil para detectar estructuras poco profundas y cambios en la magnetización debido a varios procesos, tales como el fallamiento y las alteraciones hidrotermales. A pesar de la riqueza de recursos geotérmicos en América del Sur, su uso para generación de energía eléctrica es muy limitado. En Ecuador, la mayoría de los proyectos geotérmicos están en fases de prospección y exploración inicial. Chachimbiro, ubicado al norte del Ecuador, es uno de los sitios con mayor potencial a convertirse en una planta de energía geotérmica. El objetivo de este trabajo es el de realizar estudios complementarios para mejorar el modelo existente del sistema geotérmico. Para esto, realizamos un estudio magnético de alta resolución con un distanciamiento de ~30 m entre puntos, alrededor del área del pozo Chachimbiro 1, y así comprender mejor las estructuras poco profundas que están sobre el reservorio, de la misma forma se realizaron dos líneas de estudio con un distanciamiento de ~5 m entre puntos y perpendicularmente a las fallas locales. Luego se compararon estos resultados con datos magnetelúricos y gravimétricos, que son menos precisos para detectar rasgos poco profundos. La comparación con estudios previos mostro que las fallas y la distribución de anomalías magnéticas de este estudio se ajustan con lo descrito en estudios previos. Nuestro estudio magnético fue útil para diferenciar las anomalías magnéticas relacionadas con topografía, fallamiento y alteraciones hidrotermales. Además, este estudio contribuirá a tener un mejor entendimiento del área, lo que es necesario para realizar futuras perforaciones en el área, que es potencialmente la primera planta de energía geotérmica del país.Geólogo/
XRD Analysis Procedure For Clay Minerals – Application To Chachimbiro Geothermal System
No full textThis study comprises concepts about geothermal systems, their classification, exploration and exploitation with emphasis in Ecuador advance. Also, it involves principles about hydrothermal alteration and clays as descriptive clue. Besides, with the purpose to contribute to national knowledge, this research composes a laboratory procedure for clay mineral preparation to XRD analysis. It was structured by contrasting stablished methodologies but also based on conclusions empirically obtained during the experimentation in the Instituto de Investigación Geológico y Energético. The applicability of this newly procedure was remarked with the identification of five different clays in PEC1 geothermal well of Chachimbiro. Assuming they were on a stablish regime, we present two considerable advances. First, there is an illitization processes which guarantees a high increase of temperature with depth and implies the existence of argillic alteration. It allows us to suggest that the clay cap of Chachimbiro geothermal field is thicker than 340 m as other authors hold. Second, according to the temperature profile we propose a maximum temperature of 170°C until 310 meters depth and 240°C to 260°C, at greater depths than 700 meters.Esta investigación estudia sistemas geotérmicos, su clasificación, exploración y explotación con énfasis en su aplicación dentro de Ecuador. También, trabaja conceptos de alteración hidrotermal para explicar el rol de minerales arcillosos como evaluadores descriptivos. Dada la carencia de investigaciones en esta área a nivel nacional, este estudio elabora un manual de laboratorio para análisis de arcillas por DRX. Este fue elaborado comparando metodologías ya existentes y añadiendo conclusiones empíricas obtenidas durante la experimentación en el Instituto de Investigación Geológico y Energético. La aplicabilidad del procedimiento desarrollado fue comprobada con la identificación de cinco tipos de arcilla en el pozo geotérmico PEC1 de Chachimbiro. Asumiendo que las arcillas se formaron dentro de un régimen térmico estable, se presentan dos conclusiones importantes. Primero, existe un proceso de ilitización que garantiza un elevado incremento de temperatura con profundidad y sugiere alteración argílica en toda su extensión. Esto implica que la capa sello podría extenderse más que 340 metros, que es la profundidad que otros autores sostienen. Segundo, de acuerdo al perfil de temperatura obtenido, se propone una temperatura máxima de 170°C a 310 metros de profundidad y un rango de temperatura de 240 °C a 260°C a una profundidad mayor a 700 metros.GEÓLOGO/G
Thermal and morphological changes of the Volcán de Colima lava dome 2013 – 2016
No full textVolcán de Colima is one of the most active volcanoes in North America, belonging to the western sector of the Trans-Mexican Volcanic Belt. The historical eruptive activity of Colima has been characterized by a complex succession of effusive lava-dome and/or lava flow eruptions with associated block and ash flows, and explosive eruptions of varying magnitude that have produced numerous and diverse types of pyroclastic flows and tephra falls. This thesis project analyses aerial photographs and thermal images of lava domes at Volcán de Colima from 2013 to 2016 along with a study of effusion rates for a lava dome growth in 2016. Based on the morphological changes, we defined four different phases of effusive and explosive activity of the volcano during the whole period 2013-2016. It includes phases of growth, collapse and destruction of a lava dome accompanied by changes in growth processes, temperatures, and lava textures. Thermal data showed that during the period 2013-2016, the maximum observed temperatures vary from 150ºC to 500ºC. The highest temperature was recorded during the last stage of the 2016 lava dome growth, on 4th of October. Finally, effusion rates calculated for the 2016 lava dome growth indicate a maximum value of ~3.08×104 m3days-1. Growth of the 2016 lava dome was divided into four stages depending on the effusion rate, temperature, type of extruded material, and process of growth. Our results provide important information on the underlying processes of magma movement and emplacement at shallow levels, as well as an assessment of risk and hazard.El Volcán Colima es uno de los volcanes más activos en América del Norte, perteneciente al sector occidental del Cinturón Volcánico Transmexicano. La actividad eruptiva histórica de Colima se ha caracterizado por una compleja sucesión de erupciones efusivas de domos de lava y/o flujos de lava asociados a flujos de bloques y cenizas, y erupciones explosivas de diversa magnitud que han producido numerosos y diversos tipos de flujos piroclásticos y caídas de tefra . Este proyecto de tesis analiza fotografías aéreas e imágenes térmicas de domos de lava en el Volcán de Colima de 2013 a 2016, junto con un estudio de las tasas de efusión para el crecimiento de un domo de lava en 2016. En base a los cambios morfológicos, definimos cuatro fases diferentes de actividad efusiva y explosiva del volcán durante todo el período de 2013 a 2016. Incluye fases de crecimiento, colapso y destrucción de un domo de lava acompañado de cambios en los procesos de crecimiento, temperaturas y texturas de lava. Los datos térmicos mostraron que durante el período 2013-2016, las temperaturas máximas observadas varían de 150ºC a 500ºC. La temperatura más alta se registró durante la última etapa del crecimiento del domo de lava de 2016, el 4 de octubre. Finalmente, las tasas de efusión calculadas para el crecimiento del domo de lava de 2016 indican un valor máximo de ~ 3.08 × 104 m3 día-1. El crecimiento del domo de lava de 2016 se dividió en cuatro etapas según la velocidad de efusión, la temperatura, el tipo de material extruido y el proceso de crecimiento. Nuestros resultados proporcionan información importante sobre los procesos subyacentes del movimiento y el emplazamiento del magma a niveles poco profundos, así como una evaluación de riesgos y peligros.Geólogo/
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Trace element transport by volcanic gases at Vulcano (Sicily, Italy) – Speciation, deposition and fluxes
Full text linkThe geochemistry of trace elements in volcanic gas emissions at Vulcano (Sicily, Italy) was investigated. Trace element concentrations in 94–412 °C fumarole gases span over 10 orders of magnitude, from ∼0.01 pmol/mol to ∼300 μmol/mol, with some metalloids (B, Si) being the most abundant, followed by alkali, alkaline earth, and certain transition metals, and rare earth elements typically displaying the lowest concentrations. Thermodynamic modeling predicts most trace elements to be transported as chloride, hydroxide, and mixed hydroxy-chloro gas species (LiCl, KCl, NaCl, RbCl and CsCl, Be(OH)2, Mg(OH)2, MgCl2, CaCl2, SrCl2, CaCl(OH), TiOCl2, VOCl, VOCl2, VOCl3, NbOCl3, Cr(OH)3, CrCl3, Fe(OH)2, FeCl2 Co(OH)2, CoCl2, Ni(OH)2 to NiCl2, Cd(OH)2, CdCl2, Re(OH)3, ReCl3, ZnCl2, AgCl, WO2(OH)2, Al(OH)3, Si(OH)4, B(OH)4, TlO, GaCl3, SbCl, MnCl2, CuCl). Sulfide, hydrate, and elemental gas species are also important for some elements (Cd, AuS, Hg, PbS2, BiS, Bi, AsS, As2S3, TeS, SeH, SeS). However, for many trace elements, speciation remains uncertain or unknown due to a lack of thermodynamic data. Upon cooling and decompression of the volcanic gas, most trace elements are predicted to reach gas-solid equilibrium, resulting in the formation of secondary minerals. At high temperatures (∼700–1000 °C), the mineral assemblage forming is dominated by quartz, Ca-Na-K feldspars, and Mg-pyroxene, containing minor concentrations of other alkali and alkaline earth metals. Further cooling and decompression leads to the formation of minerals including magnetite, pyrite, chalcocite, and chalcopyrite together with other less abundant oxides (V, Cr, Ga, W, and Sn) and sulfides (Zn, Pb, Ni, Co, Cd, Mo, Ag, As, and Bi), and eventually a range of sulfates and sulfosalts (Li, K, Na, Rb, Cs, Be, Mg, Ca, Sr, Bi, Mn, Fe, Zn, Pb, and Sn) at the lowest temperatures (∼100–300 °C). For most trace elements, fumarole emission concentrations reflect higher gas-solid equilibrium temperatures than those observed during sampling, suggesting gas-solid equilibria at high temperatures followed by incomplete re-equilibration upon further cooling near the surface. Trace element fluxes span over eight orders of magnitude, ranging from >100 kg/day to ∼1·10−6 kg/day. Silica, Al, and B consistently exhibit the highest fluxes, followed by alkali and alkaline earth metals, various transition metals and metalloids, with rare earth elements and actinides displaying the lowest fluxes. Generally, the trace element fluxes are lower compared to neighboring Stromboli and Etna, except for Pb, Bi, B, As, Sb, and Te
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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