Cenozoic tholeiitic volcanism in the Colbun area, Linares Precordillera, central Chile (35º35'-36ºS).
Cenozoic tholeiitic volcanism in the Colbún area, Linares Precordillera, central Chile (35º35'-36ºS)
| dc.contributor | en-US | |
| dc.contributor | es-ES | |
| dc.creator | Vergara, Mario | |
| dc.creator | Morata, Diego | |
| dc.creator | Hickey-Vargas, Rosemary | |
| dc.creator | Lopez-Escobar, Leopoldo | |
| dc.creator | Beccar, Ingrid | |
| dc.date | 2010-07-05 | |
| dc.identifier | http://www.andeangeology.cl/index.php/revista1/article/view/V26n1-a02 | |
| dc.identifier | 10.5027/andgeoV26n1-a02 | |
| dc.description | Volcanismo toleitico Terciario en el area de Colbun, Precordillera de Linares, Chile central (35º-35º36'S. En la Precordillera de Linares, Chile central (35º5'-36ºS), afloran rocas volcanicas, cuyas edades varian del Eoceno Superior al Mioceno Medio. Sobre la base de criterios estratigraficos y dataciones K-Ar y Ar-Ar, se han diferenciado dos unidades: 1- una Unidad Inferior (Eoceno Superior a Oligoceno Superior), con predominio de rocas volcanicas siliceas en la base y basicas en el nivel superior y 2- una Unidad superior (Mioceno Inferior a Medio), con basaltos afiricos y tobas soldadas rioliticas. Las caracteristicas geoquimicas de las rocas volcanicas de Colbun, tales como bajos contenidos en K2O, razones MgO/FeO altas, patrones de REE planos, abundancia normalizada con respecto al MORB cercana a la unidad para los elementos Nb a Sc, razones isotopicas iniciales de Sr relativamente bajas (0.703575-0.704028) y relativamente altas de Nd (0.512919-0.513003), son consistentes con una afinidad toleitica y con un grado de contaminacion cortical bajo en la evolucion de los magmas parentales. Las relaciones isotopicas de Pb y el enriquecimiento en algunos elementos incompatibles, tales como K, Rb, Sr y Ba, sugieren un reciclamiento de material subductado de la placa de Nazca, el cual estuvo acompanado por un adelgazamiento cortical y el desarrollo de estructuras tipo calderas. Isotopicamente, las rocas de Colbun son las mas primitivas de los Andes chilenos. Relaciones geoquimicas sugieren que estas rocas se emplazaron en un ambiente geotectonico de trasarco, intracontinental, postorogenico y extensional. Los magmas de Colbun evolucionaron, principalmente, por cristalizacion fraccional a partir de magmas primarios generados en el manto. Las semejanzas quimicas e isotopicas presentadas por estas rocas emplazadas entre el Eoceno Superior y el Mioceno Medio sugieren que las fuentes y procesos, involucrados en su genesis y evolucion, se mantuvieron relativamente constantes durante este lapso de tiempo de 20 millones de anos. | es-ES |
| dc.description | Upper Eocene to Middle Miocene volcanic rocks are found in the Colbún area, Linares Precordillera, central Chile (35º35'-36ºS). Based on stratigraphic characteristics, K-Ar and Ar-Ar dating, two different units are recognized: 1-a Lower Unit (Upper Eocene to Upper Oligocene), in which silicic volcanic rocks predominate in the lower level and basic volcanic rocks in the upper, and 2- an Upper Unit (Lower to Middle Miocene), consisting of aphanitic basalts and rhyolitic welded tuffs. Geochemical characteristics of the Colbún volcanic rocks, such as their low K, O contents, high MgO/FeO ratios, flat REE patterns, MORB normalized Nb to Sc close to unity, relatively low initial Sr isotopic ratios (0.703575-0.704028) and high initial Nd isotopic ratios (0.512919-0.513003) are all consistent with a tholeiitic affinity and a low degree of crustal involvement in the evolution of the parental magmas. Pb isotopic relationships and the enrichment of some incompatible elements such as K, Rb, Sr and Ba suggest recycling of subducting Nazca plate material. This was accompanied by crustal thinning and development of caldera type structures. The Colbún rocks are the isotopically most primitive rocks of the Chilean Andes. Geochemical relationships suggest that these rocks were emplaced in a back-arc, intracontinental, postorogenic extensional geotectonic environment. The Colbún magmas evolved mainly by closed crystal fractionation from primary magmas generated in the mantle. The chemical and isotopic similarities exhibited by rocks ranging in age from the Late Eocene to Middle Miocene suggest that the sources and processes, involved in the generation and evolution of these magmas, were more or less constant during this time span of 20 m. y. | en-US |
| dc.format | application/pdf | |
| dc.format | text/html | |
| dc.language | eng | |
| dc.publisher | Servicio Nacional de Geología y Minería | en-US |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V26n1-a02/911 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V26n1-a02/html | |
| dc.source | Andean Geology; Vol 26, No 1 (1999); 23-41 | es-ES |
| dc.source | Andean Geology; Vol 26, No 1 (1999); 23-41 | en-US |
| dc.source | 0718-7106 | |
| dc.source | 0718-7092 | |
| dc.title | Cenozoic tholeiitic volcanism in the Colbun area, Linares Precordillera, central Chile (35º35'-36ºS). | es-ES |
| dc.title | Cenozoic tholeiitic volcanism in the Colbún area, Linares Precordillera, central Chile (35º35'-36ºS) | en-US |
| dc.type | info:eu-repo/semantics/article | |
| dc.type | info:eu-repo/semantics/publishedVersion | |
| dc.type | es-ES | |
| dc.type | en-US |
This item appears in the following Collection(s)
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Andean Geology
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