1,720,991 research outputs found
Evolución del volcanísmo Cenozoico en la Puna Argentina
Full text linkFil: Petrinovic, Iván A. CICTERRA (CONICET-UNC); Argentina.Fil: Grosse, Pablo. CONICET y Fundación Miguel Lillo; Argentina.Fil: Guzmán, Silvina. Instituto de Bio y Geociencias del NOA (IBIGEO), UNSa, CONICET; Argentina y Instituto de Ciencias de la Tierra Jaume Almera, ICTJA-CSIC; España.Fil: Caffe, Pablo Jorge. Instituto de Ecoregiones Andinas (CONICET-UNJu) e Instituto de Geología y Minería,
Universidad Nacional de Jujuy; Argentina.Se presenta una síntesis del volcanismo ocurrido durante el Cenozoico en la región de la Puna argentina, teniendo
en cuenta los cambios en la localización, composición, edad y estilos eruptivos del volcanismo en relación a
condiciones geotectónicas variables
Neogene monogenetic volcanism from the Northern Puna region: products and eruptive styles
No full textThe Neogene mafic volcanism of the Northern Puna region in the Central Andes isrepresented by scoria cones and lava flows dispersed over a wide region (c. 9150 km2) as isolated or poorly clustered centres. Although all the products are basaltic andesites to andesites, the behaviour of these magmatic systems resembles that seen in basaltic monogenetic fields. These centreswere studied with the aim of defining the main volcanic lithofacies and evaluating the eruptive styles. The results suggest that the eruptions developed under a dry strombolian dynamic, with brief periods of lava fountaining and hydrovolcanism, the latter usually restricted to the early stagesof cone construction. Changes in eruptive style are thought to be caused by variations in both the internal (e.g. magma ascent) and external (e.g. surficial water availability) conditions. The transitions do not reflect compositional changes, as evidenced by the small chemical differences observed among the products of the studied eruptive centres. Stratigraphic analysis, in additionto a few pre-existing radiometric dates, suggests that this volcanic activity occurred during the Late Miocene to Early Pliocene. This information supports the inference that these eruptions occurred before the peak of Southern Puna mafic volcanism and that they were coeval with eruptions of some of the most important silicic calderas of the Altiplano-Puna Volcanic Complex. Thegood preservation of volcanic edifices reveals that erosion rates were extremely low, in agreement with the high aridity conditions that have prevailed in the Puna region since the Mid- to Late Miocene.Fil: Maro, Guadalupe. Universidad Nacional de Jujuy. Facultad de Ciencias Agrarias. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico CONICET - Salta. San Salvador de Jujuy; ArgentinaFil: Caffe, Pablo Jorge. Universidad Nacional de Jujuy. Facultad de Ciencias Agrarias. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico CONICET - Salta. San Salvador de Jujuy; Argentin
The Cerro Bitiche Andesitic Field: petrological diversity and implications for magmatic evolution of mafic volcanic centers from the northern Puna
Full text linkThe Cerro Bitiche Andesitic Field (CBAF) is one of the two largest mafic volcanic fields in northern Puna (22–24° S) and is spatially and temporally associated with ignimbrites erupted from some central Andean Altiplano-Puna Volcanic Complex calderas. The CBAF comprises seven scoria cones and widespread high-K calcalkaline lava flows that cover an area of 200 km2. Although all erupted rocks have a relatively narrow chemical range (56–62 % SiO2, 3–6 % MgO), there is a broad diversity of mineral compositions and textures. The least evolved lavas (∼58–61 % SiO2) are high-Mg andesites with scarce (<10 %) microphenocrysts of either olivine or orthopyroxene. The small compositional range and low phenocryst content indicate evolution controlled by low percentages (<10 %) of fractional crystallization of olivine and clinopyroxene of magmas similar to the least evolved rocks from the field, accompanied by assimilation during rapid ascent through the crust. Evolved andesites (∼62 wt% SiO2), on the other hand, are porphyritic rocks with plagioclase + orthopyroxene + biotite and ubiquitous phenocryst disequilibrium textures. These magmas were likely stored in crustal reservoirs, where they experienced convection caused by mafic magma underplating, magma mixing, and/or assimilation. Trace element and mineral compositions of CBAF lavas provide evidence for complex evolution of distinct magma batches.Fil: Maro, Guadalupe. Universidad Nacional de Jujuy. Facultad de Ciencias Agrarias. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico CONICET - Salta. San Salvador de Jujuy; ArgentinaFil: Caffe, Pablo Jorge. Universidad Nacional de Jujuy. Facultad de Ciencias Agrarias. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico CONICET - Salta. San Salvador de Jujuy; Argentin
Los xenolitos en la Puna Norte (Argentina): ¿Qué son y qué nos cuentan?
No full textLos xenolitos son agregados de diversos minerales que no cristalizaron directamente por el enfriamiento del magma que los hospeda, sino que representan una porción de la litósfera (manto superior y corteza) incorporado a dicho magma. Es por ello que estas inclusiones de rocas son ventanas al interior de la Tierra y permiten explorar las características del manto y la corteza en el momento de la erupción del magma y cómo éstas se han modificado en el tiempo geológico. Conocer la variación de la temperatura deformación y de la composición de las rocas con la profundidad, tanto en el espacio como en el tiempo, es esencial para la comprensión de muchos procesos geológicos.Fil: Maro, Guadalupe. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; ArgentinaFil: Caffe, Pablo Jorge. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; ArgentinaFil: Jofré, Cynthia Betina. Universidad Nacional de Jujuy. Instituto de Ecorregiones Andinas. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta. Instituto de Ecorregiones Andinas; Argentin
Petrology of the Coyaguayma ignimbrite, northern Puna of Argentina: Origin and evolution of a peraluminous high-SiO 2 rhyolite magma
Full text linkThe Coyaguayma ignimbrite is a strongly peraluminous (SP), sillimanite, garnet-bearing silicic rhyolite which erupted in the northern Puna segment of the central Andean plateau in the Upper Miocene (~11Ma), a period that was characterized by the eruption of voluminous (100s to 1000s km 3) dacitic ignimbrites of high-K calc-alkaline affinity. In this region, the SP magmatic rocks are both rare and small, but their importance is potentially much greater as rocks of this type are usually interpreted as products of crustal melting and therefore useful for addressing mantle addition vs crustal recycling in the central Andes.The phenocryst assemblage of the Coyaguayma ignimbrite comprises plagioclase (An26-18), quartz, Ba-rich and Ba-poor sanidine, minor Al-rich ferromagnesian minerals (Al T- and Al VI-rich biotite, almandine-spessartine garnet) and sillimanite, as well as accessory zircon and monazite. Textural relations suggest that the accessory and ferromagnesian phases crystallized before quartz and feldspars. Mineral equilibria suggest that crystallization of the rhyolite magma began at ~5kbar and 800°C, and continued almost isobarically to 720°C, causing the residual liquid to increase H 2O contents from ~4-5% to ~7.5% before eruption.Most major features (e.g., high SiO 2, A/CNK >1.3, low CaO, MgO, TiO 2 and FeO) and trace element patterns (low Ba, Sr, Th, LREE and Eu/Eu*; high Rb, U, Y and Nb), along with the thermobarometric constraints on magmatic P, T and water contents are consistent with an origin by mica dehydration melting of metapelitic sources (e.g., typical biotite-muscovite gneisses from the outcropping S Puna basement). However, the relatively low initial 87Sr/ 86Sr (~0.7125), and high 143Nd/ 144Nd (~0.512200) ratios invalidate a pure crustal origin. Instead, we propose contamination of calc-alkaline dacitic magmas similar to typical Puna ignimbrites by metapelite at mid-crustal settings (≥18km depth). Geochemical modeling that satisfies the chemical and isotopic data suggests mixing of 70% dacite and ~30% of metapelite partial melts, followed by extensive (70%) fractionation of plagioclase, K-feldspar, quartz and biotite, with minor magnetite and apatite from the hybrid magma. Sillimanite in the Coyaguayma rhyolite is interpreted as a restite mineral or a product of incongruent melting of the metapelite, which was preserved intact in the hybrid melt due to local equilibrium.This petrogenetic model explains most characteristics of crystal-poor SP rhyolites from the Puna plateau (e.g., Tocomar, Ramadas rhyolites) and it may be more generally applicable to occurrences of SP magmas in Andean-type continental arcs dominated by calc-alkaline magmatism.Fil: Caffe, Pablo Jorge. Universidad Nacional de Jujuy; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; ArgentinaFil: Trumbull, Robert. German Research Centre for Geosciences; AlemaniaFil: Siebel, Wolfgang. Eberhard Karls Universität Tübingen; Alemani
Tertiary mafic volcanism of the Jujuy Puna, the Cerros Negros de Jama
Full text linkLos Cerros Negros de Jama (23°29' S - 66°56' O) forman parte de un conjunto de centros eruptivos representativos del volcanismo más máfico que aconteció durante el Cenozoico en la Puna septentrional. Consisten en conos de escoria y coladas de lava edificados por erupciones explosivas estrombolianas concomitantes con erupciones efusivas. La textura afírica a microporfírica esqueletal de estas rocas, junto a una asociación mineral dominada por microfenocristales de olivina y/u ortopiroxeno, sugieren etapas cortas o inexistentes de almacenamiento en cámaras magmáticas supracorticales, así como una temperatura de los magmas superior a los 1000 °C y condiciones próximas a las de saturación en agua. La usual aparición de xenocristales de cuarzo magmático con diferentes texturas de reacción sugiere asimilación de magmas/rocas ígneas ácidos en condiciones termobáricas dispares. Un ascenso rápido y turbulento, más el sobrecalentamiento de los magmas habrían sido claves en el proceso de contaminación de los mismos en curso a la superficie. Las rocas volcánicas de Jama tienen composición andesítica basáltica a andesítica/traquiandesítica y pertenecen a la serie calcoalcalina con alto K. Sus características geoquímicas son típicas de ambientes de arco continental, con empobrecimiento en Nb, Ta y P y relaciones La/Ta > 30 y Ba/Nb > 25. En diagramas de variación de elementos mayores y trazas se distinguen dos grupos de rocas con diferentes patrones evolutivos. Las concentraciones variables de algunos componentes para grados evolutivos intermedios, sugiere niveles de incompatibilidad disímiles de esos elementos por diferenciación de los magmas a distintas profundidades desde uno o dos precursores primarios.The Cerros Negros de Jama (23°29' S - 66°56' W) monogenetic volcanoes belong to a group of eruptive centers that are representative of the most mafic magmatism in the northern Puna during the Cenozoic. They comprise scoria cones and associated lava flows erupted during coeval strombolian and effusive volcanic activity. Aphyric to microporphyritic skeletal textures and microphenocryst assemblages dominated by olivine and/or orthopyroxene suggest inexistent or short residence times in supracrustal magma chambers, as well as magma temperatures higher than 1000º C and near to water saturation conditions. The frequent occurrence of magmatic quartz xenocrysts with different degrees of reaction suggests assimilation of silicic magmas/igneous rocks under variable P-T conditions. A combination of large ascent rates and strong turbulence, together with an overheating of the magmas would have been crucial for this in-route contamination process. The Jama volcanic rocks are basaltic andesites and andesites to trachyandesites which belong to the high-K calcalkaline series. The observed geochemical signature is typical of continental arc magmas, showing negative anomalies of Nb, Ta and P, La/Ta > 30 and Ba/Nb > 25. Two main groups of rocks with different evolution patterns can be distinguished from major and trace element diagrams. Different concentrations of some elements at intermediate degrees of evolution point to variable degrees of incompatibility for them, which in turn may have been caused by magma evolution at different depths from the same or different primary magmas.Fil: Maro, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta; Argentina. Universidad Nacional de Jujuy. Instituto de Geología Minera; ArgentinaFil: Caffe, Pablo Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta; Argentina. Universidad Nacional de Jujuy. Instituto de Geología Minera; Argentin
Tertiary mafic volcanism of the Jujuy Puna, the Cerros Negros de Jama
Full text linkLos Cerros Negros de Jama (23°29' S - 66°56' O) forman parte de un conjunto de centros eruptivos representativos del volcanismo más máfico que aconteció durante el Cenozoico en la Puna septentrional. Consisten en conos de escoria y coladas de lava edificados por erupciones explosivas estrombolianas concomitantes con erupciones efusivas. La textura afírica a microporfírica esqueletal de estas rocas, junto a una asociación mineral dominada por microfenocristales de olivina y/u ortopiroxeno, sugieren etapas cortas o inexistentes de almacenamiento en cámaras magmáticas supracorticales, así como una temperatura de los magmas superior a los 1000 °C y condiciones próximas a las de saturación en agua. La usual aparición de xenocristales de cuarzo magmático con diferentes texturas de reacción sugiere asimilación de magmas/rocas ígneas ácidos en condiciones termobáricas dispares. Un ascenso rápido y turbulento, más el sobrecalentamiento de los magmas habrían sido claves en el proceso de contaminación de los mismos en curso a la superficie. Las rocas volcánicas de Jama tienen composición andesítica basáltica a andesítica/traquiandesítica y pertenecen a la serie calcoalcalina con alto K. Sus características geoquímicas son típicas de ambientes de arco continental, con empobrecimiento en Nb, Ta y P y relaciones La/Ta > 30 y Ba/Nb > 25. En diagramas de variación de elementos mayores y trazas se distinguen dos grupos de rocas con diferentes patrones evolutivos. Las concentraciones variables de algunos componentes para grados evolutivos intermedios, sugiere niveles de incompatibilidad disímiles de esos elementos por diferenciación de los magmas a distintas profundidades desde uno o dos precursores primarios.The Cerros Negros de Jama (23°29' S - 66°56' W) monogenetic volcanoes belong to a group of eruptive centers that are representative of the most mafic magmatism in the northern Puna during the Cenozoic. They comprise scoria cones and associated lava flows erupted during coeval strombolian and effusive volcanic activity. Aphyric to microporphyritic skeletal textures and microphenocryst assemblages dominated by olivine and/or orthopyroxene suggest inexistent or short residence times in supracrustal magma chambers, as well as magma temperatures higher than 1000º C and near to water saturation conditions. The frequent occurrence of magmatic quartz xenocrysts with different degrees of reaction suggests assimilation of silicic magmas/igneous rocks under variable P-T conditions. A combination of large ascent rates and strong turbulence, together with an overheating of the magmas would have been crucial for this in-route contamination process. The Jama volcanic rocks are basaltic andesites and andesites to trachyandesites which belong to the high-K calcalkaline series. The observed geochemical signature is typical of continental arc magmas, showing negative anomalies of Nb, Ta and P, La/Ta > 30 and Ba/Nb > 25. Two main groups of rocks with different evolution patterns can be distinguished from major and trace element diagrams. Different concentrations of some elements at intermediate degrees of evolution point to variable degrees of incompatibility for them, which in turn may have been caused by magma evolution at different depths from the same or different primary magmas.Fil: Maro, Guadalupe. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta; Argentina. Universidad Nacional de Jujuy. Instituto de Geología Minera; ArgentinaFil: Caffe, Pablo Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta; Argentina. Universidad Nacional de Jujuy. Instituto de Geología Minera; Argentin
New paleomagnetic data from the northern Puna and western Cordillera Oriental, Argentina: A new insight on the timing of rotational deformation
Full text linkAlong the Central Andes a pattern of vertical axis tectonic rotations has been paleomagnetically identified. The rotations are clockwise in southern Bolivia, northern Chile and northwestern Argentina. Various models have been proposed to explain the geodynamic evolution of the Central Andes, but the driving mechanism of these rotations remains controversial. Constraining the spatial variability and the timing of the rotations may contribute to a better understanding of their origin. Our results complement information from previous studies, improving the knowledge of tectonic rotations in the region of the northern Argentine Puna and western Cordillera Oriental. In the San Juan de Oro basin (SJOB), 132 cores were drilled from the middle Miocene Tiomayo Formation in the zone of Tiomayo-Santa Ana (22°30′S-66°30′W), and from the ∼17 Ma Casa Colorada dacite dome complex. Another 114 cores were collected from middle Miocene dacitic dome centers emplaced in the zone of Laguna de Pozuelos basin (22°30′S-66°00′W). The results of our paleomagnetic study suggest that the sampled zones underwent very low, statistically insignificant rotation since middle Miocene. However, a tendency for low magnitude rotation appears when observing our data together with paleomagnetic results from coeval rocks in neighbouring areas. If so, this low rotation could be related to middle Miocene thrust activity in the central and eastern parts of the Cordillera Oriental. The combined analysis of paleomagnetic and structural data illustrates the probable, direct relationship between timing of significant rotations and timing of local deformation in the sourthern Central Andes.Fil: Prezzi, Claudia Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires; Argentina. Christian Albrechts Universität; AlemaniaFil: Caffe, Pablo Jorge. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro de Investigaciones y Transferencia de Jujuy. Universidad Nacional de Jujuy. Centro de Investigaciones y Transferencia de Jujuy; ArgentinaFil: Somoza, Ruben. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Departamento de Geología. Instituto de Geofísica "Daniel Valencio"; Argentin
La Candelaria Ridge (NW Argentina) as a natural lab for the exploration of the geothermal system of Rosario de La Frontera: Methods and preliminary results
Full text linkWithin the scientific framework recently proposed by C.U.I.A. (Consorzio Universitario Italiano per l’Argentina) for the development of applied researches on the Argentina territory, several research groups, belonging to selected Italian and Argentina Universities, converged in the last year on the research line devoted to the “Sustainable development of future towns”. This contribution focuses on the preliminary results achieved by this collaboration among the Universities of Camerino, Jujuy, Roma Tre, Salta, Sapienza. The project focuses on the application of robust methodologies and the development of new ones to explore the geothermal potential of the area of Rosario de La Frontera (NW Argentina) located at the northern edge of La Candelaria Ridge, one of positively inverted structures cropping out between the provinces of Salta and Tucuman. It belongs to the Santa Barbara System of the Andes retro-wedge...Fil: Maffucci, R.. Università Roma Tre III; ItaliaFil: Caffe, Pablo Jorge. Universidad Nacional de Jujuy. Instituto de Geología Minera; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta; ArgentinaFil: Corrado, Sveva. Università Roma Tre III; ItaliaFil: Invernizzi, Ciro. Università degli Studi di Camerino; ItaliaFil: Giordano, G.. Università Roma Tre III; ItaliaFil: Pierantoni, Pablo. Università degli Studi di Camerino; ItaliaFil: Viramonte, Jose Maria. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Salta; Argentina. Universidad Nacional de Salta. Facultad de Ciencias Naturales. Instituto Geonorte; Argentin
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]
Full text linkThe 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
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