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CARACTERISTICAS DEL PLUTONISMO MIOCENO SUPERIOR EN EL SEGMENTO NORTE DE LA CORDILLERA OCCIDENTAL E IMPLICACIONES TECTONICAS EN EL MODELO GEOLÓGICO DEL NOROCCIDENTE COLOMBIANO

2012; National University of Colombia; Issue: 31 Linguagem: Inglês

2357-3740

G Gabriel Rodríguez, G Gilberto Zapata,

Geological and Tectonic Studies in Latin America

In the north segment of Colombia's Cordillera Occidental, at the north of Itsmina's folded belt and the fault of San Juan's river located between Tatama Hill and Farallones del Citara, outcrop a group of plutons that intrude Santa Cecilia - La Equis - Batolito de Mande Complex (Choco - Panama arc), Canasgordas Complex and El Boton's Basalts (El Boton's arc). They are intrusive bodies outcropping from Pueblo Rico (Risaralda) until Dabeiba (Antioquia). Plutons's composition belong to a group of gabro-monzodiorite-monzonite-sienite, with facies in some bodies of the group conformed by cuarzodiorite, cuarzomonzodiorite. In addition, only Farallones's Monzodiorite has signs classified as tonalites and granodiorites The chemical composition of the intrusive bodies is similar to El Boton's Basalts. These belong to the shoshonitic group with a high concentration of alkali rocks (Na2O + K2O > 5 wt%), high proportions K2O/ Na2O (> 0,6 a los 50% wt de SiO2, >1,0 a los 55% wt de SiO2), low TiO2 (<1,3 % wt), high but changeable Al2O3 (14-19 %wt). Only few bodies such as San Juan's river diorite and small bodies of gabbro placed in Santa Cecilia-La Equis Complex have affinity with calco-alkaline's group. Rare earths and its trace elements behavior is due to rocks created by an arc formed by subduction. Plutons's ages Ar-Ar and K-Ar, show values between 9 and 12 million years (Tortonian- Serravallian age). They are similar to El Boton's Basalts and Combia formation. The formation of volcanic arc El Boton and all its associated plutons was originated in the margin of the blocks conformed by Santa Cecilia- La Equis- Batolito de Mande complex and Canasgordas Complex; suggesting that the Choco-Panama Arc was already bonded from the Miocene.