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

In the El Volcan and Rodeo de los Bueyes areas, Andean Principal Cordillera (east of Santiago; 33°50'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...

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Autores principales:	Muñoz,Marcia, Aguirre,Luis, Vergara,Mario, Demant,Alain, Fuentes,Francisco, Fock,Andrés
Lenguaje:	English
Publicado:	Servicio Nacional de Geología y Minería (SERNAGEOMIN) 2010
Materias:	Abanico Formation Andes Prehnite-pumpellyite facies Cenozoic
Acceso en línea:	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062010000100003
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spelling	oai:scielo:S0718-710620100001000032010-04-14Prehnite-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 stateMuñoz,MarciaAguirre,LuisVergara,MarioDemant,AlainFuentes,FranciscoFock,Andrés Abanico Formation Andes Prehnite-pumpellyite facies Cenozoic In the El Volcan and Rodeo de los Bueyes areas, Andean Principal Cordillera (east of Santiago; 33°50'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, prehmte or prehnite+actinolite in a few samples. Chemical characteristics, such as low compositional variability of mixed-layer chlorite-smectite and actino-lite 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 CO2 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 320°C, respectively.info:eu-repo/semantics/openAccessServicio Nacional de Geología y Minería (SERNAGEOMIN)Andean geology v.37 n.1 20102010-01-01text/htmlhttp://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062010000100003en10.4067/S0718-71062010000100003
institution	Scielo Chile
collection	Scielo Chile
language	English
topic	Abanico Formation Andes Prehnite-pumpellyite facies Cenozoic
spellingShingle	Abanico Formation Andes Prehnite-pumpellyite facies Cenozoic Muñoz,Marcia Aguirre,Luis Vergara,Mario Demant,Alain Fuentes,Francisco Fock,Andrés 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
description	In the El Volcan and Rodeo de los Bueyes areas, Andean Principal Cordillera (east of Santiago; 33°50'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, prehmte or prehnite+actinolite in a few samples. Chemical characteristics, such as low compositional variability of mixed-layer chlorite-smectite and actino-lite 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 CO2 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 320°C, respectively.
author	Muñoz,Marcia Aguirre,Luis Vergara,Mario Demant,Alain Fuentes,Francisco Fock,Andrés
author_facet	Muñoz,Marcia Aguirre,Luis Vergara,Mario Demant,Alain Fuentes,Francisco Fock,Andrés
author_sort	Muñoz,Marcia
title	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
title_short	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
title_full	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
title_fullStr	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
title_full_unstemmed	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
title_sort	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
publisher	Servicio Nacional de Geología y Minería (SERNAGEOMIN)
publishDate	2010
url	http://www.scielo.cl/scielo.php?script=sci_arttext&pid=S0718-71062010000100003
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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

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