Geocronología del volcanismo del Cretácico Inferior en la Cordillera de la Costa (29°20'-30°S), Chile
- Diego Antonio Morata Céspedes
- Gilbert Feraud
- Gloria Arancibia
- Javier Carrillo Rosúa
- Salvador Morales Ruano
- Mauricio Enrique Belmar Urbina
- Luis Aguirre le Bert
ISSN: 0716-0208, 0717-618X
Datum der Publikation: 2008
Ausgabe: 35
Nummer: 1
Seiten: 123-145
Art: Artikel
Andere Publikationen in: Revista geológica de Chile: An international journal on andean geology
Zusammenfassung
40Ar/39Ar age data (laser and furnace step heating) on plagioclase from Lower Cretaceous volcanic sequences from the Arqueros Formation in two sections of the Coastal Range at the latitude of La Serena (=29°S) have been obtained. Due to the partial alteration of plagioclase crystals, disturbed age spectra in the furnace experiments have been observed, whereas laser heating determinations involving a much smaller quantity of grains carefully selected, could display plateau ages corresponding to pure plagioclase, as demonstrated by a constant 37Arc¡/39ArK ratio. Plateau ages of 114.1±0.5 Ma (sample ARQ99-4), 111.3±0.9 Ma (sample TC99-5a), and 91.0±0.6 Ma (sample TC99-2) were found in lava flows, and 84.3±1.3 Ma on a dyke (sample ARQ99-7). These new 40Ar/39Ar ages, together with those previously published in central Chile, allow a constriction of the extensional magmatism during the Early Cretaceous in the Coastal Range of central and north-central Chile. All these data are in accordance with a long lived Early Cretaceous Magmatic Province (119-84 Ma), that could have started with a brief and huge magmatic event, mostly developed in the central part of the Coastal Range, followed by discrete magmatic pulses at further northern latitudes.