Resumo

CORREA-MARTINEZ, Ana María; RODRIGUEZ, Gabriel; ARANGO, María Isabel  e  ZAPATA-GARCIA, Gilberto. Petrography, geochemistry and U-Pb geochronology of volcanic and pyroclastic rocks of the Noreán Formation in the NW of the Santander Massif, Colombia. bol.geol. [online]. 2019, vol.41, n.1, pp.29-54. ISSN 0120-0283.  https://doi.org/10.18273/revbol.v41n1-2019002.

The volcanic and pyroclastic rocks of the Norean Formation located to the NW of the Santander Massif, are composed by lavas that range from andesitic to rhyolitic, together with glass, lithic and crystal tuffs. Mainly andesitic dikes and hypabyssal bodies are also present. Geochemically, the volcanic and pyroclastic rocks exhibit chemical similarities, belong to the calc-alkaline series and have negative anomalies of Nb, P and Ti and a positive anomaly of Pb, suggesting a subduction-related genesis. LA-ICP-MS U-Pb zircon geochronology resulted in ages of 192.4 ± 2.2 Ma in a basaltic andesite, 184.9 ± 2.0 Ma in an andesitic lava and 175.9 ± 1.1 Ma in a rhyolitic lava, indicating the occurrence of volcanic events in this section of the Noreán Formation from the Lower to the Middle Jurassic. Zircon inheritance suggests that the volcanic arc was emplaced in a Meso-Neoproterozoic basement. The Noreán Formation represents a continental arc magmatism, and can be correlated with the Saldaña Formation and the Pitalito Volcanites of the Upper Magdalena Valley, with Jurassic volcanic units of the Sierra Nevada de Santa Marta and with La Quinta Formation in the Serranía de Perijá.

Palavras-chave : Middle-Lower Jurassic; U-Pb geochronology; volcano-sedimentary rocks; Middle Magdalena Valley; San Lucas Ridge.

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