Tectono-magmatic implications of the Jurassic volcanic and volcanoclastic record of the Santa Marta Massif (Colombia)

Abstract

The Lower-Middle Jurassic volcanic and volcanoclastic rocks of the Santa Marta Massif (SMM) record the magmatic evolution of a continental arc developed on the NW margin of Gondwana. However, the lack of a comprehensive description of these successions has made it difficult to understand the geologic processes that occurred during the onset, development, and termination of the volcanic activity. Our new U–Pb zircon ages, whole-rock geochemistry, and petrographic analyses suggest that volcanism started at ca. 191 Ma, similar to plutonic activity, likely after the slab rolled-back from a previous flat-slab subduction zone. During this initial stage, the volcanic deposits consisted of andesite-basaltic andesite and trachy-andesite rocks, of calc-alkaline to high-K calc-alkaline character and dominantly metaluminous affinity. At ca. 177–168 Ma, the geologic record included andesite-basaltic andesites, dacites and, rhyolites of high-K calc-alkaline to calc-alkaline character, and peraluminous to metaluminous affinity. Finally, before cessation, at ca. 167–163 Ma, the volcanism presented andesite-basaltic andesite, trachy-andesite, trachyte and rhyolite compositions, with dominantly high-K calc-alkaline character, and peraluminous to metaluminous affinity. The geochemical comparison with coeval volcanic units deposited in La Guajira, Middle Magdalena Valley, Perijá, and San Lucas ranges indicate a similar magmatic evolution in the north of Colombia. The causes of the cessation of magmatic activity are still unknown, however, these may be associated with the generalized extensional event that was triggered by the breakup of Pangea.