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Integrated geochemical, isotopic, and geochronological constraints from Jurassic plutonic rocks of the Central Cordillera in Colombia were used to determine the tectonic setting and long-term tectonomagmatic evolution of the Northern Andes. We examined three plutonic units with compositions that vary from diorite to granite and with U-Pb zircon crystallization ages from 165 Ma to 129 Ma. These units are interpreted as subduction-related magmas, as indicated by their K 2 O, Na 2 O contents, light to heavy rare earth element (LREE/HREE) ratios, and Pb isotope signatures. The Nd and Hf isotope compositions of these magmatic events become more juvenile (radiogenic) with time. This compositional record suggests an arc maturity trend in which partial melting of basaltic and peridotitic sources becomes more significant than radio genic subducted sediments or the ancient continental crust. Global-scale tectonic reconstructions suggest that Late Jurassic to Early Cretaceous subduction of the Farallon oceanic plate under the Andean continental margin became highly oblique. The consequence was a reduction of the fusible sedimentary budget commonly incorporated during subduction into the mantle, leaving a more refractory mantle with a more primitive compositional signature, and a major decrease in magmatic activity in the Early Cretaceous. In addition, the magmatic evolution recorded in the North Andean Jurassic arc shows that long-term source evolution and regionalscale plate-tectonic processes also play an important role in the compositional evolution and volumes of magmatic products in convergent settings.

U-Pb laser ablation inductively coupled plasma mass spectrometry ages and Hf isotopes in zircons were used to constrain the nature of two geological units representative of the basement of the Central Cordillera of Colombia. Graphite-quartz-muscovite schists from the Cajamarca Complex show inherited detrital zircons supplied mostly from Late Jurassic (ca. 167 Ma), Ediacaran (ca. 638 Ma), and Tonian (Grenvillian; ca. 1000 Ma) sources. These marine volcanosedimentary deposits form an N-trending metamorphic belt in fault contact to the east with orthogneisses and amphibolites of the Tierradentro unit. Zircon U-Pb determinations of the Tierradentro rocks-previously interpreted as Grenvillian basement slices-yielded crystallization ages between 271 and 234 Ma. Initial Hf data reveal that the Tierradentro unit shares isotopic characteristics similar to other Permo-Triassic rocks of the Central Cordillera. In contrast, inherited detrital zircons from the Jurassic metasedimentary rocks suggest that their sources are distinct from the plutonic rocks that crop out in the Central Cordillera with Jurassic crystallization ages. Large xenoliths of the Tierradentro unit within the Ibagué batholith indicate that the granodioritic magma mostly intruded a Permo-Triassic basement possibly by exploiting the Otú-Pericos fault. The Jurassic metasedimentary belt is correlated further south with a similar sequence in the Ecuadorian Andes named Salado terrane.