Very low-grade metamorphism in volcanic rocks of Formación Ventana, San Martín de los Andes, Neuquén, Argentina
Paleocene-Eocene volcanic rocks of the Formación Ventana, near San Martín de los Andes, have been affected by very low-grade regional metamorphism under zeolite, prehnite-pumpellyite and transitional to greenschists facies conditions. The mineral assemblages commonly observed are: smectite-iddingsit...
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| Autores principales: | , |
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| Formato: | JOUR |
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| Acceso en línea: | http://hdl.handle.net/20.500.12110/paper_07160208_v23_n2_p187_DeVattuonePonti |
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| Sumario: | Paleocene-Eocene volcanic rocks of the Formación Ventana, near San Martín de los Andes, have been affected by very low-grade regional metamorphism under zeolite, prehnite-pumpellyite and transitional to greenschists facies conditions. The mineral assemblages commonly observed are: smectite-iddingsite-serpentine; smectite-heulandite-mordenite; wairakite-laumontite-albite; wairakite-laumontite-pumpellyite-epidote; pumpellyite-smectite-epidote-titanite: prehnite-hematite-interstratified smectite/chlorite-titanite; interstratified smectite/chlorite-epidote-actinolite-titanite-albite-quartz. Metamorphism took place under oxidizing conditions (high fO2) in the fluid fase, indicated by the stable existence of hematite, epidote (pistacite) and pumpellyite. Four progressive metamorphic zones have been established and according to the mineral assemblages, the maximum temperature could have reached 300°C and the pressures 2 kbar. Those zones are: A- smectite-heulandite: B- wairakite-laumontite; C- prehnite-pumpellyite: D- epidote-actinolite. The diagnostic minerals: heulandite, laumontite, wairakite, prehnite, pumpellyite, epidote and actinolite suggest that the metamorphic evolution took place in an area characterized by the presence of shallow igneous intrusions. |
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