Geochronology and geochemistry of the Parashi granitoid, NE Colombia: Tectonic implication of short-lived Early Eocene plutonism along the SE Caribbean margin

Abstract

The Parashi granitoid of northeasternmost Colombia intrudes the Upper Cretaceous to Lower Paleocene accretionary complex formed by the collision of the Caribbean arc and the continental margin of South America. This granitoid presently separated of the continental margin includes a major quartzdiorite body with andesite to dacite dikes and mafic enclaves. Zircon U–Pb LA-MC-ICP-MS and K–Ar geochronology on the quartzdiorite and the dikes suggest that crystallization extended from ca. 47 to 51 Ma. Major and trace elements are characterized by a medium-K, immature continental arc signature and high Al2O3, Na2O and Ba–Sr contents. Initial 87Sr/86Sr isotopic values range between 0.7050 and 0.7054, with 143Nd/144Nd = 0.51235–0.51253, εNd and εHf values from −0.81 to −4.40 and −4.4 and −5.2. Major and trace element ratios and isotopic modeling suggest that sedimentary and/or quartzofeldspathic crustal sources were mixed with a mafic melt input. The petrotectonic and geological constraints derived from this granitoid suggest that Parashi plutonism records an immature, oblique subduction-zone setting in which the presence of a high-temperature mantle realm and strong plate coupling associated to upper crust subduction caused the partial fusion of a previously tectonically underplated mafic crust and associated metasediments exposed in the continental margin. The limited temporal expression of this magmatism and the transition to a regional magmatic hiatus are related to a subsequent change to strongly and slow oblique tectonics in the Caribbean–South America plate interactions and the underflow of a relatively thick slab of Caribbean oceanic crust.