NUEVAS EVIDENCIAS SOBRE EL MAGMATISMO MIOCENICO EN EL DISTRITO MINERO DE VETAS-CALIFORNIA (MACIZO DE SANTANDER, CORDILLERA ORIENTAL, COLOMBIA)
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Universidad Industrial de Santander
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En el distrito Minero de Vetas-California (DMVC) afloran rocas ígneas tanto de textura porfirítica-afanítica, como de textura porfirítica-fanerítica, relacionadas con el evento magmático más reciente conocido hasta el momento para el Macizo de Santander, de edad Mioceno. Estas rocas, al parecer se confinan hacia las zonas de influencia de fallas NNW (similares en su dirección a la Falla Bucaramanga-Santa Marta) y un sistema de fallas NE. Las rocas con textura porfirítica-fanerítica y de composiciones entre cuarzo monzodioritas y granodioritas, por ahora solo han sido observadas al Éste del área de estudio, mientras que las rocas de textura porfirítica afanítica, de composiciones entre andesitas porfiríticas y riodacitas porfiríticas, son más frecuentes al Oeste. Dos tipos de rocas datadas en el presente estudio; una de variedad andesita porfirítica, localizada en el lado Oeste del área de estudio y otra de una granodiorita de textura porfirítica-fanerítica, localizada al Éste del área; arrojaron edades de 10.1±0.2 y 10.9±0.2 Ma, respectivamente (utilizando el método U-Pb en circones, mediante la técnicaLA-MC-ICPMS: laser ablation multicollector inductively coupled plasma mass spectrometry). En este sentido, y apoyados en las aún limitadas edades conocidas, se infiere que este sector del Macizo de Santander fue afectado por un pulso ígneo de por lo menos 2.5 Ma de duración. La presencia de rocas ígneas de edad Mioceno afectadas por procesos de alteración hidrotermal y con estilos de mineralización epitermal y porfirítica, y la falta de evidencias de rocas ígneas más jóvenes que 8.4 Ma, permiten sugerir que en algún(os) momento(s) de la evolución del magmatismo Miocenico, pudieron tener lugar procesos magmático-hidrotermales asociados a eventos mineralizantes en el DMVC.
Palabras clave: Distrito Minero Vetas-California (DMVC), Mioceno, Fallas, Edades U-Pb, Macizo de Santander.
In The Vetas-California Mining District (DMVC), igneous rocks with porphyritic-aphanitic and porphyriticphaneritic textures crop out, which are related to the Miocene and most recent magmatic event known for the Santander Massif. The emplacement of these rocks is apparently controlled by the intersections of NNW faults(similar in direction to the Bucaramanga-Santa Marta fault) and the NE fault systems. Porphyritic-phaneriticquartz’ monzodiorites and granodiorite rocks are confined to the eastern part of the studied area; mean while the porphyritic-aphanitic andesite and rhyodacitic rocks are confined to the western part. The two types ofigneous rocks dated in this study; a porphyritic andesite variety (located to the western part of the studied area)and a granodiorite with prophyritic-phaneritic texture (located to the eastern part); yielded ages of 10.1 ± 0.2and 10.9 ± 0.2 Ma, respectively (U-Pb method on zircons, using the LA-MC-ICPMS technique: laser ablation inductively coupled plasma multicollector mass spectrometry). These ages, together with previously published data, indicate that magmatic pulse lasted up to 2.5 Ma. The presence of Miocene igneous rocks affected by hydrothermal alteration and with epithermal and porphyry style mineralization, and the absence of igneous rocks younger than 8.4 m.y. (at least currently not known), allow to propose that during some time(s) of the Miocenic magmatic pulse,could take place magmatic-hydrothermal processes related to mineralizing events inthe DMVC. Keywords: Vetas-California Mining District, Miocene, Faults, U-Pb ages, Santander Massif.
In The Vetas-California Mining District (DMVC), igneous rocks with porphyritic-aphanitic and porphyriticphaneritic textures crop out, which are related to the Miocene and most recent magmatic event known for the Santander Massif. The emplacement of these rocks is apparently controlled by the intersections of NNW faults(similar in direction to the Bucaramanga-Santa Marta fault) and the NE fault systems. Porphyritic-phaneriticquartz’ monzodiorites and granodiorite rocks are confined to the eastern part of the studied area; mean while the porphyritic-aphanitic andesite and rhyodacitic rocks are confined to the western part. The two types ofigneous rocks dated in this study; a porphyritic andesite variety (located to the western part of the studied area)and a granodiorite with prophyritic-phaneritic texture (located to the eastern part); yielded ages of 10.1 ± 0.2and 10.9 ± 0.2 Ma, respectively (U-Pb method on zircons, using the LA-MC-ICPMS technique: laser ablation inductively coupled plasma multicollector mass spectrometry). These ages, together with previously published data, indicate that magmatic pulse lasted up to 2.5 Ma. The presence of Miocene igneous rocks affected by hydrothermal alteration and with epithermal and porphyry style mineralization, and the absence of igneous rocks younger than 8.4 m.y. (at least currently not known), allow to propose that during some time(s) of the Miocenic magmatic pulse,could take place magmatic-hydrothermal processes related to mineralizing events inthe DMVC. Keywords: Vetas-California Mining District, Miocene, Faults, U-Pb ages, Santander Massif.