Significance of K-Ar dating of very low-grade metamorphism in Triassic-Jurassic pelites from the Coastal Range of central Chile Belmar, Mauricio Morata, Diego Munizaga, Francisco Pérez de Arce, Carlos Morales, Salvador Carrillo Rosúa, Francisco Javier Pelites Pelitas K-Ar dating Datación K-Ar Very low-grade metamorphism Metamorfismo de muy bajo grado Costal Range Cordillera de la Costa Central Chile Chile central El artículo original ha sido publicado por la Mineralogical Society disponible en: http://www.minersoc.org/pages/e_journals/clay.html 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. 2011-01-21T07:53:49Z 2011-01-21T07:53:49Z 2004 journal article 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 0009-8558 http://hdl.handle.net/10481/7315 eng http://creativecommons.org/licenses/by-nc-nd/3.0/ open access Creative Commons Attribution-NonCommercial-NoDerivs 3.0 License Mineralogical Society