1,721,043 research outputs found
Provincias de Jujuy y de Salta
Get PDFFil: Blasco, Graciela. Ministerio de Economía. Subsecretaría de Minería. Servicio Geológico Minero Argentino (SEGEMAR); Argentina.Fil: Zappettini, Eduardo O. Ministerio de Economía. Subsecretaría de Minería. Servicio Geológico Minero Argentino (SEGEMAR); Argentina.Fil: Hongn, Fernando. Ministerio de Economía. Subsecretaría de Minería. Servicio Geológico Minero Argentino (SEGEMAR); Argentina
Estructura del Complejo Alcalino de Rangel (Salta, Argentina)
No full textThis work deals with the structure and emplacement of the alkaline complex of the Sierra de Rangel, a Cretaceous stock intruding in Ordovician metamorphic rocks of the Puna region at Salta, northwest Argentina. Field structures and magnetic fabrics reveal a complex structure composed by multiple sheets and feeding chanels. Both, the ascent and the lateral spreading of magma exploited old fractures in the country rocks.Fil: Vegas, Néstor. Universidad del País Vasco; EspañaFil: Hongn, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Tubía, José María. Universidad del País Vasco; EspañaFil: Menegatti, Nilda. Universidad Nacional de Salta; Argentin
Tectonic evolution of the western margin of Gondwana inferred from syntectonic emplacement of Paleozoic granitoid plutons in northwest Argentina
Get PDFThe Cerro Durazno, Brealito, and Cobres granitoid plutons belong to the eastern Ordovician magmatic belt of northwestArgentina and are associated with a network of NW- and N-striking ductile shear zones. A structural analysisof these plutons and their metamorphic host rocks was conducted to elucidate mid- to upper-crustal magmatism andtectonism at the western margin of Gondwana. Pluton emplacement took place at 480?455 Ma, toward the end ofa ca. 75-Ma-long episode of regional deformation and high-temperature metamorphism. The Cerro Durazno andBrealito plutons were probably emplaced as NE-SW-striking, vertical magma sheets that coalesced into large magmabodies under overall E-W shortening that generated SW-dipping metamorphic foliations at a later stage of plutonformation. These fabrics were superimposed to the magmatic structures in the granite plutons and to the high-grademetamorphic structures of the host rocks. At the northern pluton margins, ductile high-strain zones, notably theAgua Rosada Shear Zone north of the Cerro Durazno pluton, further localized ascent of granitoid magma. Similarly,emplacement of the Brealito and Cobres plutons is genetically related to prominent shear zones. Geometry andmetamorphic character of the shear zone network in the eastern Ordovician magmatic belt point to orogen-parallelextension and transverse shortening of the belt under variable metamorphic conditions. The width as well as protracteddeformation, high-temperature metamorphism, anatexis, and granitoid magmatism of the magmatic belt are keycharacteristics of a hot, wide orogen that evolved during the lower Paleozoic at the western margin of Gondwana.Remarkable geotectonic similarities with respect to the modern Andes point to comparable plate-tectonic conditionsat the lower Paleozoic and the Cenozoic convergent plate margins.Fil: Hongn, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Riller, Ulrich. Universität zu Berlin; Alemani
Quartz crystallographic and morphologic fabrics during folding/transposition in mylonites
Get PDFQuartz grain shape fabrics (GSF) and c-axis lattice preferred orientation (LPO) were investigated in folded quartz ribbons with variable fold geometry in low metamorphic-grade granitic mylonites from northwestern Argentina. The folds, which vary from open to isoclinal, show an asymmetric short limb–long limb geometry developed simultaneously with the quartz fabrics during progressive simple shear. GSF shows a consistent obliquity relative to the bulk shear plane throughout the folded ribbons. GSF inclination varies between 25° and 45° oblique to the shear plane, indicating that relatively small finite strain increments (γ∼1.2) are attained before the GSF regeneration. In contrast, the c-axis preferred orientation varies throughout the folded ribbons. Unfolded ribbons and long limbs of folds show a typical c-axis maximum near the shear plane pole, while short limbs of tight and isoclinal folds show a c-axis maximum nearly orthogonal to that of long limbs. This pattern of domainal LPO is maintained in thickened ribbons derived from folding and transposition. This indicates that the GSF regeneration is comparatively much faster than a cycle of folding/transposition. Conversely, the LPO regeneration is much slower. We conclude that folding/transposition is a mechanism for development of domainal quartz LPO in kinematic frameworks with dominant simple shear.Fil: Hongn, Fernando Daniel. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto Geonorte; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Hippertt, J. F. Universidade Federal de Ouro Preto; Brasi
Environmental instability in Western Tinogasta (Catamarca) during the Mid-Holocene and its relation to the regional cultural development
Get PDFThe survey of natural profiles comprising thin interspersed volcanic and peat banks along different ecological zones and altitudinal levels in western Tinogasta (Catamarca Province, Argentina) provides an insight into the natural environmental conditions for the past human activities in these areas. The geological analysis integrated to the archaeological data allows the proposal of climatic fluctuations, explosive volcanism and, probably recurrent, seismic activity influencing the low and null occupation intensity of the highlands and lowlands, respectively, during the Mid-Holocene (8000-4000BP). These conditions generated unstable environments that prevented the continuous and sustained occupation of the ecological zone of the Chaschuil Valley highlands (3500-4000masl), and hindered the occupation of the lowlands in the mesothermal valleys of the Fiambalá region (1400-2400masl). The products of explosive volcanism caused changes in topography which, along with other factors, had different impacts on the productive populations occupying the region since the first century AD.Fil: Ratto, Norma Rosa. Universidad de Buenos Aires. Facultad de Filosofía y Letras. Museo Etnográfico "Juan B. Ambrosetti"; ArgentinaFil: Montero Lopez, Maria Carolina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Hongn, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; Argentin
The Cobres Plutonic Complex, eastern Puna (NW Argentina): Petrological and structural constraints for Lower Paleozoic magmatism
Get PDFThe southern portion of the Cobres Range is studied with an interdisciplinary, petrological–geochemical and structural-cartographic approach. The Cobres Plutonic Complex (CPC) consists of two main plutons, a granodiorite and a monzogranite, as well as small bodies of gabbros, acidic dikes, and episyenite bands. Their mineralogy and geochemistry suggest a comagmatic character for both plutons, which are strongly peraluminous and define a typical calc–alkaline trend. Harker diagrams indicate a fractionated crystallization trend. The REEs have similar patterns for enclaves, granodiorites, monzogranites, aplites, and acidic dikes, also similar to those from the upper crust rocks. Gabbros included in the CPC show geochemical signatures compatible with the mantle. The CPC is syntectonic, though the granodioritic and monzogranitic plutons represent different stages in the tectomagmatic history of the region. The geology of the CPC and its regional framework show characteristics—thermal anomalies, alternation of contractional and extensional deformational events, magmatic rocks with crustal and mantle affiliations, and contemporaneous extensional basins—that indicate intrusion of the CPC in an extensional accretionary orogen.Fil: Kirschbaum, Alicia Matilde. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Hongn, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Menegatti, N.. Universidad Nacional de Salta. Facultad de Ciencias Naturales; Argentin
Structure of the La Paya pluton (Sierra de Cachi, Argentina)
Get PDFEl granito de La Paya se localiza en la Sierra de Cachi (Salta,Argentina),que pertenece a la Cordillera Oriental de Los Andes. Los nuevos datos estructurales y cartográficos disponibles, combinados con el estudio de lafábrica magnética del granito, ponen de manifiesto que: 1) El plutón es uncuerpo laminar, de unos 400 metros de espesor, que dibuja un pliegue antiforme,2) su techo corresponde a una zona de cizalla dúctil plegada. Las observacionesde campo y microestructurales indican un emplazamiento sincinemáticodel plutón, asociado al funcionamiento de una zona de cizalla extensionalque se plegó durante un episodio posterior compresivo.The La Paya granite is located in the Sierra de Cachi (Salta, Argentina) and belongs to the Eastern Cordillera of the Andean belt. New structural and cartographic data combined with the study of the magnetic fabric of the granite indicate that: 1) the pluton is a sheeted body, about 400 metres thick, that outlines an antiformal fold, 2) its roof is coincident with a folded ductile shear zone. Moreover, field and microstructural observations point to a syn-kinematic emplacement of the pluton linked to an extensional shear zone that was folded by a subsequent compressional eventFil: Vegas, Néstor. Universidad del Pais Vasco; EspañaFil: Hongn, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Salta. Instituto de Bio y Geociencias del Noroeste Argentino; ArgentinaFil: Aranguren, Aitor. Universidad del Pais Vasco; EspañaFil: Tubía, José María. Universidad del Pais Vasco; Españ
Comments on "Kinematic variations across Eastern Cordillera at 24°S (Central Andes): Tectonic and magmatic implications" by Acocella, et al. [Tectonophysics 434 (2007) 81-92]
Get PDFThe interpretation of Acocella et al. about (i) westward increase of strike-slip motion, (ii) strain partitioning, (iii) symmetry of the Central Andes, as well as (iv) the interpreted cause for the occurrence of magmatic centres behind the arc, from the Late Miocene onward, is largely speculative and contains major flaws. We demonstrate all above, that successive phases of deformation from Middle Eocene to Quaternary in the edge of the Puna-Eastern Cordillera, as well as the occurrence of arc/intraplate signatures in the magmatic centres of the Eastern Cordillera, result in complex geological framework which requires more detailed and intensive work in order to achieve sustainable interpretations.Fil: Petrinovic, Ivan Alejandro. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Hongn, Fernando Daniel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: del Papa, Cecilia Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Bio y Geociencias del NOA. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Museo de Ciencias Naturales. Instituto de Bio y Geociencias del NOA; ArgentinaFil: Caffe, Pablo Jorge. Universidad Nacional de Jujuy; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe 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
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