PETROGRÁFIA, GEOQUÍMICA Y EDAD DE LA GRANODIORITA DE FARALLONES Y LAS ROCAS VOLCÁNICAS ASOCIADAS.
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Universidad Industrial de Santander
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La Granodiorita de Farallones se localiza en el flanco occidental de la Cordillera Occidental de Colombia, está conformada por tonalitas, granodioritas, cuarzodioritas, monzodioritas, cuarzomonzodioritas, dioritas, gabros y cuarzomonzonitas. El contenido de sílice en las rocas varía entre 67,76 y 52,07%, el cuerpo no es homogéneo y se encuentran rocas alcalinas en el sur del cuerpo y subalcalinas en el sector norte del plutón, son rocas ricas en K2O que van desde series calcoalcalinas de medio K hasta la serie shoshonitica, metaluminosas, pero en los bordes del cuerpo son peraluminosas por la contaminación de sedimentos.
La Granodiorita de Farallones corresponde a magmas medianamente evolucionados con empobrecimiento de tierras raras pesadas con respecto a las livianas, que corresponde a un plutón formado en un ambiente de arco. La edad de la Granodiorita de Farallones en hornblenda por método K/Ar de 11± 2 Ma (Calle et al., 1980a) y dos en Arboleda et al. (2009) por el método Ar/Ar de 11.9 y 9.8± 0.2, corresponden al Mioceno Tardío. Esta unidad intruye las Areniscas, limolitas y lodolitas de Urrao, y a su vez son intruidas por las Brecha diatrémica de Farallones.
Palabras clave: Granodiorita de Farallones, Cordillera Occidental, Brecha diatrémica de Farallones
The Farallones Granodiorite is located on the western flank of the Cordillera Occidental of Colombia, is formed by tonalite, granodiorite, quarz diorite, monzodiorite, quarz monzodiorite, diorite, gabbro and quarz monzonite. The content of silica in the rocks varies between 67.76 and 52,07%, the body is not homogeneous and there are alkaline rocks in the southern part of the body and subalcalines in the northern sector of the pluton. There are rich rocks K2O ranging from medium K to shoshonitic series, they are metaluminous but near the edges of the pluton they are peraluminous due to contamination by sediments. The Farallones Granodiorite correspond to midly evolved magmas with impoverishment of HREE8 respect to LREE, that correspond to a pluton formed in an arc enviroment. The age of the Farallones Granodiorite in hornblende for the method K/Ar 11± 2 Ma (Calle et al., 1980a) and two in Arboleda et al. (2009) by the method Ar/Ar 11.9 and 9. 8± 0.2, which correspond to the Late Miocene. This geological unit intrudes the Sandstones, siltstones and mudstones of Penderisco, and in turn, it is intruded by the diatremic brecchas of Farallones. Keywords: Farallones Granodiorite, Cordillera Occidental of Colombia, Farallones diatremic breccia
The Farallones Granodiorite is located on the western flank of the Cordillera Occidental of Colombia, is formed by tonalite, granodiorite, quarz diorite, monzodiorite, quarz monzodiorite, diorite, gabbro and quarz monzonite. The content of silica in the rocks varies between 67.76 and 52,07%, the body is not homogeneous and there are alkaline rocks in the southern part of the body and subalcalines in the northern sector of the pluton. There are rich rocks K2O ranging from medium K to shoshonitic series, they are metaluminous but near the edges of the pluton they are peraluminous due to contamination by sediments. The Farallones Granodiorite correspond to midly evolved magmas with impoverishment of HREE8 respect to LREE, that correspond to a pluton formed in an arc enviroment. The age of the Farallones Granodiorite in hornblende for the method K/Ar 11± 2 Ma (Calle et al., 1980a) and two in Arboleda et al. (2009) by the method Ar/Ar 11.9 and 9. 8± 0.2, which correspond to the Late Miocene. This geological unit intrudes the Sandstones, siltstones and mudstones of Penderisco, and in turn, it is intruded by the diatremic brecchas of Farallones. Keywords: Farallones Granodiorite, Cordillera Occidental of Colombia, Farallones diatremic breccia