Geochemistry of Nevado de Longaví Volcano (36.2°S): a compositionally atypical arc volcano in the Southern Volcanic Zone of the Andes
Geoquimica del volcan Nevado de Longavi (36,2°S): un volcan de arco composicionalmente atipico en la Zona Volcanica Sur de los Andes.
| dc.contributor | en-US | |
| dc.contributor | es-ES | |
| dc.creator | Sellés, Daniel | |
| dc.creator | Rodriguez, A. Carolina | |
| dc.creator | Dungan, Michael A. | |
| dc.creator | Naranjo, Jose A. | |
| dc.creator | Gardeweg, Moyra | |
| dc.date | 2010-06-29 | |
| dc.identifier | http://www.andeangeology.cl/index.php/revista1/article/view/V31n2-a08 | |
| dc.identifier | 10.5027/andgeoV31n2-a08 | |
| dc.description | The Quaternary Nevado de Longaví volcano of the Andean Southern Volcanic Zone (SVZ) has erupted magmas that range in composition from basalt to low-silica dacite, although andesites are the dominant erupted magma type. Amphibole is a common phenocryst phase in andesites throughout the volcano, and it is the dominant mafic phase in Holocene dacites and their included mafic enclaves. Compositions of magmas erupted at Longaví volcano define arrays that diverge from trends delineated by neighboring frontal-arc volcanoes. Although mafic compositions at Longaví are broadly similar to basalts at other SVZ centers, Longaví intermediate and evolved magmas have systematically lower abundances of incompatible major (K2O, P2O5) and trace elements (Rb, Zr, Nb, REE, Th, etc), as well as high Ba/Th, Sr/Y, and La/Yb ratios. Longaví volcano magmas define two differentiation series with regard to enrichments of Rb (and other incompatible elements) with increasing silica. A high-Rb series that includes the oldest units of the volcano comprises basalts to andesites dominated by anhydrous mineral assemblages with chemical compositions similar to other SVZ magmatic series. The series with low Rb, on the other hand, includes the Holocene units that evolved from basaltic andesites to dacites by means of fractional crystallization wherein amphibole and calcic plagioclase dominate the mineral assemblage. Magmas parental to low-Rb series are interpreted to be high-degree mantle melts, highly hydrous and oxidized, formed as a response to high fluid inputs into the subarc mantle. Enhanced water transport to the subarc mantle is a plausible effect of the subduction of the oceanic Mocha Fracture Zone that projects beneath Nevado de Longaví. Volcanoes located over oceanic fracture zones further south along the SVZ have erupted hornblende-bearing magmas that share some chemical similarities with Longaví volcano magmas. | en-US |
| dc.description | El estratovolcan cuaternario Nevado de Longavi de la Zona Volcanica Sur de los Andes (ZVS) ha emitido magmas de composicion basaltica a dacitica, si bien los productos predominantes son andesiticos. La anfibola es fenocristal comun en andesitas de todo el volcan, y es la fase mafica predominante en dacitas de edad holocena y en enclaves maficos coetaneos. La composicion quimica de los magmas del Nevado de Longavi define patrones que difieren de las tendencias mostradas por otros centros del frente volcanico. Si bien las lavas maficas del Nevado de Longavi son, en terminos generales, similares a otros basaltos de la ZVS, las lavas intermedias y evolucionadas exhiben valores sistematicamente bajos de elementos incompatibles, tanto mayores (K2O, P2O5) como trazas (Rb, Zr, Nb, REE, Th, etc), asi como altos valores de Ba/Th, Sr/Y y La/Yb. Dos series magmaticas se definen en base al grado de enriquecimiento en Rb (y otros elementos incompatibles) con el aumento de silice. La serie de alto Rb, que incluye a las unidades mas antiguas del volcan, pero que podria ser en parte coetanea a la serie de bajo Rb, esta conformada por basaltos a andesitas de composicion quimica proxima a otras series magmaticas de la ZVS dominadas por asociaciones minerales anhidras. La serie de bajo Rb, que incluye a las unidades holocenas del volcan, evoluciona desde andesitas basalticas a dacitas por via de cristalizacion fraccionada involucrando importantes proporciones de anfibola y plagioclasa calcica. Los magmas parentales de esta serie serian fundidos parciales de alto grado, altamente hidratados y oxidados, consecuencia de un elevado aporte de agua a la fuente astenosferica. Un elevado transporte de agua hacia el manto astenosferico probablemente resulta de la subduccion de la Zona de Fractura oceanica Mocha que se proyecta bajo el Nevado de Longavi. Otros volcanes de la ZVS situados sobre fracturas oceanicas han emitido magmas con anfibola que comparten algunas similitudes quimicas con los magmas del Nevado de Longavi. | es-ES |
| 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/V31n2-a08/615 | |
| dc.relation | http://www.andeangeology.cl/index.php/revista1/article/view/V31n2-a08/html | |
| dc.source | Andean Geology; Vol 31, No 2 (2004); 293-316 | es-ES |
| dc.source | Andean Geology; Vol 31, No 2 (2004); 293-316 | en-US |
| dc.source | 0718-7106 | |
| dc.source | 0718-7092 | |
| dc.title | Geochemistry of Nevado de Longaví Volcano (36.2°S): a compositionally atypical arc volcano in the Southern Volcanic Zone of the Andes | en-US |
| dc.title | Geoquimica del volcan Nevado de Longavi (36,2°S): un volcan de arco composicionalmente atipico en la Zona Volcanica Sur de los Andes. | es-ES |
| 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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