Evidence of Amazonia With Baltica During the Assembly of Supercontinent Rodinia

Mesoproterozoic crust in the San Lucas Range (Colombia): an insight into the crustal evolution of the northern Andes

Authors:

Cuadros et al

Abstract:

The San Lucas Range (SLR) is located at the northernmost end of the Central Cordillera of Colombia and is considered part of the Chibcha Terrane, which is characterized by medium- to high-grade rocks with Late Mesoproterozoic-Early Neoproterozoic metamorphic ages. Granite-gneiss and metamafic rocks, including metamonzogabbro, amphibolite and granulite, crop out in the northern portion of the SLR, with a Lower Jurassic granodioritic batholith intruding all the above mentioned units. The geochemical features, in terms of major and trace element contents and U-Pb zircon geochronology, suggest protolith crystallization of both felsic and mafic rocks in a post-collisional setting between 1.54 and 1.50 Ga. In addition, positive ɛNd values and initial 87Sr/86Sr ratios less than 0.7045 indicate a mantle origin for this bimodal association, with TDM values between 1.7 and 1.5 Ga, suggesting a juvenile character. A correlation between the studied granitic rocks and the A-type Rio Uaupés Granitic Suite in the Rio Negro Province of the Amazonian Craton can be established, thus constraining a provenance from southern latitudes for the Chibcha Terrane, as suggested by earlier models. Metamorphic rims of zircons from both felsic and mafic rocks yielded ages between 1180 and 930 Ma, which are consistent with the ages of related metamorphic terranes in Ecuador, Venezuela, Perú, México and Central America. The latter terranes are regarded as having been part of the northwestern border of Amazonia during its collision with Baltica in the context of the Grenvillian/Sveconorwegian orogeny, which was related to the final assembly of Rodinia