Miocene volcanism in the central Chilean Andes (31°30′S–34°35′S)

Vergara, Marcos; Charrier, Reynaldo; Munizaga, Francisco; Rivano, Sergio; Sepulveda, P.; Thiele, Ricardo; Drake, Robert E.

doi:10.1016/0895-9811(88)90038-7

Cited by 47 publications

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“…La Formación Farellones es una sucesión casi enteramente volcánica de carácter calcoalcalino, suavemente plegada, y que aflora aproximadamente entre 32° y 35°S (Vergara et al, 1988). Alcanza un espesor de 2.400 m y consiste en lavas andesíticas a riolíticas, depósitos piroclásticos, volcanoclásticos, y escasas intercalaciones sedimentarias (Thiele, 1980;Charrier, 1981;Vergara et al, 1988).…”

Section: Marco Geológicounclassified

“…Alcanza un espesor de 2.400 m y consiste en lavas andesíticas a riolíticas, depósitos piroclásticos, volcanoclásticos, y escasas intercalaciones sedimentarias (Thiele, 1980;Charrier, 1981;Vergara et al, 1988). Su contacto con la subyacente Formación Abanico se presenta concordante y discordante según la zona de estudio considerada, en general dependiendo de la cercanía con estructuras que hayan producido plegamiento en la Formación Abanico, previo a la depositación de la Formación Farellones (Charrier et al, 2002).…”

Section: Marco Geológicounclassified

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El Cenozoico del alto río Teno, Cordillera Principal, Chile central: estratigrafía, plutonismo y su relación con estructuras profundas

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Castelli²,

Charrier

et al. 2010

AndGeo

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RESUMEN.La evolución geológica cenozoica del sector central de la Cordillera Principal a ~35ºS, se encuentra ínti-mamente relacionada con la evolución de estructuras profundas, las cuales habrían controlado, en distintas etapas de su historia, tanto la depositación de secuencias volcano-sedimentarias como el ascenso y emplazamiento de cuerpos intrusivos. Estudios estratigráficos en el entorno de estas estructuras, permiten confirmar la edad cenozoica de un conjunto de rocas piroclásticas y sedimentarias que subyacen concordantemente a lavas andesíticas de la Formación Abanico (asignada al Eoceno Tardío-Mioceno Temprano a Medio). Se determinó la existencia de cuatro fases intrusivas principales (diorita, granodiorita, pórfido riodacítico y pórfido dacítico, en ese orden de intrusión), cuyos productos afloran siguiendo una franja de orientación norte-sur. La granodiorita fue datada en 7,8±0,4 Ma (K-Ar en biotita). Pórfidos riodacíticos, considerados como facies marginales de la unidad anterior, se dataron en 7,9±0,4 Ma (K-Ar en fenocristales de plagioclasa). Se reconocieron dos estructuras de importancia regional: el Corrimiento El Fierro, y, más al oeste, se definió el Sistema de Fallas Infiernillo-Los Cipreses. En la caracterización de esta última estructura, se utilizó la modelación magnética de secciones como complemento a la información geológica. Se interpreta que el ascenso de las distintas fases intrusivas mencionadas fue controlado por el Sistema de Fallas Infiernillo-Los Cipreses. Este, al igual que el Corrimiento El Fierro, habría actuado como una falla normal de borde de cuenca durante el Eoceno Tardío-Mioceno Medio, controlando la depositación de productos volcánicos y sedimentarios de la Formación Abanico. Ambas fallas fueron reactivadas en modo inverso durante un importante episodio de contracción tectónica y de elevada presión de fluidos inducida por circulación de magmas, en el Mioceno Tardío, focalizando el ascenso de los intrusivos mencionados. ABSTRACT. The Cenozoic of the upper Teno River, Cordillera Principal, Central Chile: stratigraphy, plutonism and their relation with deep structures. The Cenozoic geologic evolution of the central part of the Cordillera Principal at ~35°S, is intimately related to the geodynamic evolution of deep crustal structures, which during different stages controlled the deposition of volcanosedimentary sequences, and the ascent and emplacement of epizonal intrusions. Newly defined stratigraphy around these structures confirms the Cenozoic age of a group of pyroclastic and sedimentary rocks, which conformably underlie andesitic lavas of the Abanico Formation (assigned to the Late Eocene-Early to Middle Miocene). Intrusive rocks correspond to four main phases (from oldest to youngest: diorite, granodiorite, rhyo-dacitic and dacitic porphyry), which occurs in a North-South trending belt. The granodiorite was dated at 7.8±0.4 Ma (K-Ar in biotite). Rhyo-dacitic porphyries, considered as a marginal lithodeme of the granodiorite, yielded 7.9±0.4 Ma (K-Ar in plagioclase ph...

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Section: Marco Geológicounclassified

El Cenozoico del alto río Teno, Cordillera Principal, Chile central: estratigrafía, plutonismo y su relación con estructuras profundas

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Castelli²,

Charrier

et al. 2010

AndGeo

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“…1). Between 33° and 34°S, the Cenozoic deposits are known as the Abanico Formation (Aguirre, 1960;Klohn, 1960) of Upper Eocene-Lower Miocene age (Vergara et al, 1999;Charrier et al, 2002) and the Farellones Formation (Klohn, 1960) of Miocene age Vergara et al, 1988). The Abanico Formation shows two parallel N-S-oriented belts, separated by the overlying Farellones Formation (Fig.…”

Section: Geological Backgroundmentioning

confidence: 99%

Prehnite-pumpellyite facies metamorphism in the Cenozoic Abanico Formation, Andes of central Chile (33°50'S): chemical and scale controls on mineral assemblages, reaction progress and the equilibrium state

Muñoz

Aguirre

Vergara

et al. 2010

AndGeo

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ABSTRACT. In the El Volcán and Rodeo de los Bueyes areas, Andean Principal Cordillera (east of Santiago; 33º50'S), an Upper Oligocene-Lower Miocene volcanic series belonging to the Abanico Formation (Late Eocene-Early Miocene) is exposed. The rock successions outcropping in both areas, ca. 3,300 m total thickness, have been affected by very low-grade, non-deformative metamorphism in the prehnite-pumpellyite facies. This is represented by the widespread development of secondary mineral assemblages composed of epidote, mixed-layer chlorite-smectite, albite, quartz, white mica, and titanite. These mineral assemblages also contain pumpellyite, prehnite or prehnite+actinolite in a few samples. Chemical characteristics, such as low compositional variability of mixed-layer chlorite-smectite and actinolite independent from the metadomain where these phases are hosted, along with a high proportion of chlorite layers in the former, suggest that these phases closely represent the whole rock effective bulk composition. On the contrary, pumpellyite compositions show a higher variability and a strong metadomain control evidencing its lower equilibration kinetics and leaving only those that grow in the rock matrix as the more closely representative of a whole rock effective bulk compositional control. Mineral assemblages from both areas show evidence of having been formed during the same metamorphic event where reactions have ocurred equivalently between them. However, local differences in chemical variables controlling this process are recognizable. A higher CO 2 concentration in the fluids during the metamorphism in the El Volcán area than in the Rodeo de los Bueyes area is suggested by the scarce development of prehnite and the ubiquitous presence of calcite in the metamorphic assemblages of the former. Pressure and temperature of this metamorphic event have been roughly estimated to be lower than 2-3 kbar and 320ºC, respectively. Esto está representado en el desarrollo extensivo de arreglos de minerales secundarios formados por epidota, interestratificados de clorita-esmectita, albita, cuarzo, mica blanca, y titanita. Estos arreglos minerales contienen además pumpellyita, prehnita o prehnita+actinolita en algunas muestras. Las características químicas tales como una baja variabilidad composicional de los interestratificados de clorita-esmectita y actinolita independientemente del dominio donde se hospedan estas fases, junto con una alta proporción de capas de clorita en las primeras, sugieren que estas fases representan cercanamente la composición efectiva de la roca total. Por el contrario, la composición de las pumpellyitas muestra una mayor variabilidad y un fuerte control del metadominio donde éstas se desarrollan evidenciando una baja cinética de equilibrio y dejando sólo a aquellas desarrolladas en la matriz como formadas bajo un control composicional efectivo de la roca total. Los arreglos minerales de ambas áreas muestran evidencias de haberse formado bajo un mismo evento metamórfico bajo el cual las reacciones se ...

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“…The Miocene volcanic rocks of Farellones Formation are located in the central Chilean Andes east of the OligoceneMiocene magmatic belt and west of the Quaternary volcanic arc (Vergara et al 1988;Rivano et al 1990). Farellones Formation was probably deposited in a volcano-tectonic graben generated through a series of caldera collapses (Thiele et al 1991).…”

Section: Geological Settingmentioning

confidence: 99%

“…Nystrom et al (1993) and Vergara et al (1988Vergara et al ( , 1996 demonstrated a geochemical break between the tholeiitic (Abanico Formation) activity of the Oligocene to the calc-alkaline (Farellones Formation) activity of the Miocene. This change is interpreted as a consequence of major variations in the tectonic regime of the subducting Nazca plate under the western margin of South America.…”

Section: Introductionmentioning

confidence: 99%

A low‐grade metamorphic model for the Miocene volcanic sequences in the Andes of central Chile

Aguirre

Robinson

Bevins

et al. 2000

New Zealand Journal of Geology and Geophysics

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Calc-alkaline basic volcanic rocks in a c. 600 m thick sequence of Miocene age, the Valle Nevado stratified sequence (VNSS), have been affected by very low grade metamorphism characterised by mineral assemblages of the zeolite facies. Metastable conditions prevailed, most of the igneous minerals being wholly or partially preserved. The main metamorphic phases are mafic phyllosilicates and zeolites of calco-sodic and calcic composition. The intensity of the metamorphism was controlled by depth and by hydrothermal activity related to volcanic centres.From top to bottom of the sequence, the zeolites vary from heulandite-clinoptilolite through mordenite to laumontite, whereas the phyllosilicates show a compositional transition from tri-smectite to smectite/chlorite with up to 75% chlorite layers. Strong fluid/rock interaction took place only at flow levels with a high primary porosity and permeability as illustrated by: (a) the similarity of the REE patterns of the basaltic host flows and the secondary zeolites; G99004Received 20 January 1999; accepted 9 November 1999 and (b) the contrast in composition observed between phyllosilicates in vesicular tops as opposed to the massive (central) parts of the same flow. The thermal gradients acting during the metamorphic event were high and are estimated at 150-175°C/km. The metamorphic zonation is interpreted as the result of a rapid accumulation of considerable volumes of rock generated by volcanic centres connected with geothermal field activity and characterised in places by caldera collapse.

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Miocene volcanism in the central Chilean Andes (31°30′S–34°35′S)

Cited by 47 publications

References 18 publications

El Cenozoico del alto río Teno, Cordillera Principal, Chile central: estratigrafía, plutonismo y su relación con estructuras profundas

El Cenozoico del alto río Teno, Cordillera Principal, Chile central: estratigrafía, plutonismo y su relación con estructuras profundas

Prehnite-pumpellyite facies metamorphism in the Cenozoic Abanico Formation, Andes of central Chile (33°50'S): chemical and scale controls on mineral assemblages, reaction progress and the equilibrium state

A low‐grade metamorphic model for the Miocene volcanic sequences in the Andes of central Chile

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