Miocene fossil hydrothermal system associated with a volcanic complex in the Andes of central Chile

Francisco Fuentes, Luis Aguirre, Mario Vergara, Leticia Valdebenito, Eugenia Fonseca

Resultado de la investigación: Article

12 Citas (Scopus)

Resumen

Cenozoic deposits in the Andes of central Chile have been affected by very low-grade burial metamorphism. At about 33°S in the Cuesta de Chacabuco area, approximately 53 km north of Santiago, two Oligocene and Miocene volcanic units form a ca. 1300-m-thick rock pile. The Miocene unit corresponds to a volcanic complex composed of two eroded stratovolcanoes. Secondary mineral assemblages in both units were studied petrographically and using X-ray diffraction and electron microprobe analyses. Most of the igneous minerals are wholly or partially preserved, and the ubiquitous secondary minerals are zeolites and mafic phyllosilicates. The alteration pattern observed is characterized by a lateral zonation in secondary mineralogy related to a lateral increase in temperature but not to stratigraphic depth. The following three zones were established, mainly based on the distribution of zeolites: zone I comprises heulandite, thomsonite, mesolite, stilbite and tri-smectite; zone II contains laumontite, yugawaralite, prehnite, epidote and chlorite; and zone III comprises wairakite, epidote, chlorite, diopside, biotite and titanite. For each zone, the following temperature ranges were estimated: zone I, 100-180 °C; zone II, 180-270 °C; and zone III, 245-310 °C. The alteration episode was characterized by a high Pfluid/Ptotal ratio (ca. 1.0), although slightly variable, a high geothermal gradient of ca. 160 °C km-1 and fluid pressures below 500 bars. Although temperature was the main control on the mineral zonation, several interrelated parameters, mainly fluid composition, porosity and permeability, were also important. Hot, near neutral to slightly alkaline pH, alkali chloride hydrothermal fluids with very low dissolved CO2 contents deposited the secondary minerals. The alteration pattern is the result of depositing fluids in outflow regions from a hydrothermal system developed inside a volcanic complex during the Miocene. The hydrothermal system has been eroded to a maximum depth of 1.7 km.

Idioma originalEnglish
Páginas (desde-hasta)139-161
Número de páginas23
PublicaciónJournal of Volcanology and Geothermal Research
Volumen138
N.º1-2
DOI
EstadoPublished - 15 nov 2004

Huella dactilar

hydrothermal systems
Chile
fossils
hydrothermal system
Minerals
volcanology
minerals
Miocene
fossil
Zeolites
Fluids
secondary mineral
zeolites
fluids
epidote
fluid pressure
Mineralogy
zonation
chlorite
biotite

ASJC Scopus subject areas

  • Geophysics
  • Geochemistry and Petrology

Citar esto

Fuentes, Francisco ; Aguirre, Luis ; Vergara, Mario ; Valdebenito, Leticia ; Fonseca, Eugenia. / Miocene fossil hydrothermal system associated with a volcanic complex in the Andes of central Chile. En: Journal of Volcanology and Geothermal Research. 2004 ; Vol. 138, N.º 1-2. pp. 139-161.
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Miocene fossil hydrothermal system associated with a volcanic complex in the Andes of central Chile. / Fuentes, Francisco; Aguirre, Luis; Vergara, Mario; Valdebenito, Leticia; Fonseca, Eugenia.

En: Journal of Volcanology and Geothermal Research, Vol. 138, N.º 1-2, 15.11.2004, p. 139-161.

Resultado de la investigación: Article

TY - JOUR

T1 - Miocene fossil hydrothermal system associated with a volcanic complex in the Andes of central Chile

AU - Fuentes, Francisco

AU - Aguirre, Luis

AU - Vergara, Mario

AU - Valdebenito, Leticia

AU - Fonseca, Eugenia

PY - 2004/11/15

Y1 - 2004/11/15

N2 - Cenozoic deposits in the Andes of central Chile have been affected by very low-grade burial metamorphism. At about 33°S in the Cuesta de Chacabuco area, approximately 53 km north of Santiago, two Oligocene and Miocene volcanic units form a ca. 1300-m-thick rock pile. The Miocene unit corresponds to a volcanic complex composed of two eroded stratovolcanoes. Secondary mineral assemblages in both units were studied petrographically and using X-ray diffraction and electron microprobe analyses. Most of the igneous minerals are wholly or partially preserved, and the ubiquitous secondary minerals are zeolites and mafic phyllosilicates. The alteration pattern observed is characterized by a lateral zonation in secondary mineralogy related to a lateral increase in temperature but not to stratigraphic depth. The following three zones were established, mainly based on the distribution of zeolites: zone I comprises heulandite, thomsonite, mesolite, stilbite and tri-smectite; zone II contains laumontite, yugawaralite, prehnite, epidote and chlorite; and zone III comprises wairakite, epidote, chlorite, diopside, biotite and titanite. For each zone, the following temperature ranges were estimated: zone I, 100-180 °C; zone II, 180-270 °C; and zone III, 245-310 °C. The alteration episode was characterized by a high Pfluid/Ptotal ratio (ca. 1.0), although slightly variable, a high geothermal gradient of ca. 160 °C km-1 and fluid pressures below 500 bars. Although temperature was the main control on the mineral zonation, several interrelated parameters, mainly fluid composition, porosity and permeability, were also important. Hot, near neutral to slightly alkaline pH, alkali chloride hydrothermal fluids with very low dissolved CO2 contents deposited the secondary minerals. The alteration pattern is the result of depositing fluids in outflow regions from a hydrothermal system developed inside a volcanic complex during the Miocene. The hydrothermal system has been eroded to a maximum depth of 1.7 km.

AB - Cenozoic deposits in the Andes of central Chile have been affected by very low-grade burial metamorphism. At about 33°S in the Cuesta de Chacabuco area, approximately 53 km north of Santiago, two Oligocene and Miocene volcanic units form a ca. 1300-m-thick rock pile. The Miocene unit corresponds to a volcanic complex composed of two eroded stratovolcanoes. Secondary mineral assemblages in both units were studied petrographically and using X-ray diffraction and electron microprobe analyses. Most of the igneous minerals are wholly or partially preserved, and the ubiquitous secondary minerals are zeolites and mafic phyllosilicates. The alteration pattern observed is characterized by a lateral zonation in secondary mineralogy related to a lateral increase in temperature but not to stratigraphic depth. The following three zones were established, mainly based on the distribution of zeolites: zone I comprises heulandite, thomsonite, mesolite, stilbite and tri-smectite; zone II contains laumontite, yugawaralite, prehnite, epidote and chlorite; and zone III comprises wairakite, epidote, chlorite, diopside, biotite and titanite. For each zone, the following temperature ranges were estimated: zone I, 100-180 °C; zone II, 180-270 °C; and zone III, 245-310 °C. The alteration episode was characterized by a high Pfluid/Ptotal ratio (ca. 1.0), although slightly variable, a high geothermal gradient of ca. 160 °C km-1 and fluid pressures below 500 bars. Although temperature was the main control on the mineral zonation, several interrelated parameters, mainly fluid composition, porosity and permeability, were also important. Hot, near neutral to slightly alkaline pH, alkali chloride hydrothermal fluids with very low dissolved CO2 contents deposited the secondary minerals. The alteration pattern is the result of depositing fluids in outflow regions from a hydrothermal system developed inside a volcanic complex during the Miocene. The hydrothermal system has been eroded to a maximum depth of 1.7 km.

KW - Andes

KW - Chile

KW - Hydrothermal system

KW - Mafic phyllosilicates

KW - Outflows

KW - Zeolites

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M3 - Article

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JO - Journal of Volcanology and Geothermal Research

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