Significance of K-Ar dating of very low-grade metamorphism in Triassic-Jurassic pelites from the Coastal Range of central Chile
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AutorBelmar, Mauricio; Morata, Diego; Munizaga, Francisco; Pérez de Arce, Carlos; Morales, Salvador; Carrillo-Rosúa, Javier
PelitesPelitasK-Ar datingDatación K-ArVery low-grade metamorphismMetamorfismo de muy bajo gradoCostal RangeCordillera de la CostaCentral ChileChile central
Belmar, M., Morata, D., Munizaga, F., De Arce, C. P., Morales, S., & Carrillo, F. J. (2004). Significance of K-ar dating of very low-grade metamorphism in triassic-jurassic pelites from the coastal range of central chile. Clay Minerals, 39(2), 151-162. doi:10.1180/0009855043920127
PatrocinadorDepartamento de Mineralogía y Petrología
K-Ar isotopic dating of very low-grade metamorphism affecting Triassic-Jurassic rocks in the Coastal Range of central Chile was carried out on whole rocks and their <2 mm size fractions. In the study area, a regional-burial low-grade metamorphism at anchizone conditions (T ≤ 190ºC) and low-pressure conditions (P ≥1.3 kbar) has been described. Observed temperatures are related to a contact metamorphism produced by nearby Jurassic intrusions, with a P-T estimate at the immediate contact zone of ~650-690ºC and 4 kbar. The whole-rock K-Ar age of 174?5 Ma is interpreted as belonging to the contact metamorphism due to the intrusion of Jurassic plutons (165±5 Ma to 175±5 Ma). A time-interval of ~20 Ma between the diagenesis (206 Ma) and the anchizonal very low-grade metamorphism (181-184 Ma) is obtained, and a rate of subsidence of ~120 m/Ma is proposed for these Triassic-Jurassic basins. A thermal influence on the burial, very low-grade, regional metamorphism is invoked.