NEW EVIDENCES ABOUT THE MIOCENIC MAGMATISM IN THE VETASCALIFORNIAMINING DISTRICT (SANTANDER MASSIF, EASTERNCORDILLERA, COLOMBIA)

Abstract

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.