1,720,962 research outputs found
Structural control on geothermal circulation in the Cerro Tuzgle–Tocomar geothermal volcanic area (Puna plateau, Argentina)
No full text""The reconstruction of the stratigraphical–structural framework and the hydrogeology of geothermal areas is. fundamental for understanding the relationships between cap rocks, reservoir and circulation of geothermal. fluids and for planning the exploitation of the field. The Cerro Tuzgle–Tocomar geothermal volcanic area. (Puna plateau, Central Andes, NW Argentina) has a high geothermal potential. It is crossed by the active. NW–SE trans-Andean tectonic lineament known as the Calama–Olacapato–Toro (COT) fault system, which. favours a high secondary permeability testified by the presence of numerous springs.. This study presents new stratigraphic and hydrogeological data on the geothermal field, together with the. analysis from remote sensed image analysis of morphostructural evidences associated with the structural. framework and active tectonics.. Our data suggest that the main geothermal reservoir is located within or below the Pre-Palaeozoic–Ordovician. basement units, characterised by unevenly distributed secondary permeability. The reservoir is recharged by. infiltration in the ridges above 4500 m a.s.l., where basement rocks are in outcrop. Below 4500 m a.s.l., the. reservoir is covered by the low permeable Miocene–Quaternary units that allow a poor circulation of shallow. groundwater. Geothermal fluids upwell in areas with more intense fracturing, especially where main regional. structures, particularly NW–SE COT-parallel lineaments, intersect with secondary structures, such as at the. Tocomar field. Away from the main tectonic features, such as at the Cerro Tuzgle field, the less developed network. of faults and fractures allows only a moderate upwelling of geothermal fluids and a mixing between hot. and shallow cold waters.. The integration of field-based and remote-sensing analyses at the Cerro Tuzgle–Tocomar area proved to be. effective in approaching the prospection of remote geothermal fields, and in defining the conceptual model. for geothermal circulation."
The Calama-Olacapato-El Toro fault system in the Puna Plateau, Central Andes: Geodynamic implications and stratovolcanoes emplacement
No full text""The structural evolution of the Puna Plateau is characterized by the activity of both orogen-parallel and orogen-oblique faults. Understanding the possible relationship between these two structural styles, their geodynamic implications and the influence on the migration of magmas is important to get insights into the tectonic and magmatic evolution of the Central Andes. In this study, we present a structural analysis of the orogen-oblique Calama-Olacapato-El Toro fault system and the surrounding orogen-parallel thrust faults in the central-eastern Puna Plateau. Morphostructural analysis and field mapping reveal the geometry, kinematics and dynamics of the tectonic features in the studied area. We propose a three-dimensional geometrical reconstruction of the main fault planes showing their attitude and intersections at depth. The study indicates that the crust underwent simultaneous deformation along both the vertical transcurrent Calama-Olacapato-El Toro fault system and the low-angle thrust faults, and that the back-arc portion of the Calama-Olacapato-El Toro fault system developed as a transfer zone among the main N-striking thrusts. Our model considers that both orogen-parallel and orogen-oblique fault systems should be regarded as parts of the same tectonic system, accommodating crustal shortening of a thickened crust. The study suggests that the tectonic control on the magma and fluid circulation in the crust is mainly related to the geometry of the fault planes and the orientation of the stress field, with a previously unrecognized important role played by the orogen-parallel thrust faults on the emplacement of the stratovolcanoes. (C) 2013 Elsevier B.V. All rights reserved."
Paleomagnetism of Holocene lava flows from the Reykjanes Peninsula and the Tungnaá lava sequence (Iceland): implications for flow correlation and ages
No full textThe impact of Holocene eruptive events from hot spots like Iceland may have had significant global implications; thus, dating and knowledge of past eruptions chronology is important. However, at high-latitude volcanic islands, the paucity of soils severely limits14C dating, while the poor K content of basalts strongly restricts the use of K/Ar and Ar/Ar methods. Even tephrochronology, based on14C age determinations, refers to layers that rarely lie directly above lava flows to be dated. We report on the paleomagnetic dating of 25 sites from the Reykjanes Peninsula and the Tungnaá lava sequence of Iceland. The gathered paleomagnetic directions were compared with the available reference paleosecular variation curves of the Earth magnetic field to obtain the possible emplacement age intervals. To test the methodâs validity, we sampled the precisely dated Laki (1783â1784 AD) and Eldgjà (934â938 AD) lavas. The age windows obtained for these events encompass the true flow ages. For sites from the Reykjanes peninsula and the Tugnaá lava sequence, we derived multiple possible eruption events and ages. In the Reykjanes peninsula, we propose an older emplacement age (immediately following the 870 AD Iceland Settlement age) for Ogmundarhraun and Kapelluhraun lava fields. For pre-historical (older than the settlement age) Tugnaá eruptions, the method has a dating precision of 300â400 years which allows an increase of the detail in the chronostratigraphy and distribution of lavas in the Tugnaá sequence
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
Structural and morphological features of the Torre Alfina geothermal area (central Italy)
No full textVariations 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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