Idades U-Pb em zircões detriticos das rochas metamórficas aflorantes na faixa oeste no Maciço de Santander, Andes Colombianos

Abstract

The basement of the Santander Massif represents a Mesoproterozoic inlier, formed by younger rocks associated with the evolution of the Andes Mountains. The basement is formed by the units Bucaramanga Gnaiss, Silgará Schist, Chicamocha Schist, Orthogneiss, Filito San Pedro and others metamorphic low grade units. In the study area, outcrop the basement units Bucaramanga Gnaisse and Silgará Schist; the biotite gneiss is the main lithotype in the Bucaramanga Gneiss, amphibolites and quartzites are observed in a smaller proportion, while the Muscovite schist is the main lithotype in the Silgará Schist. The U-Pb ages observed in detrital zircon grains from two biotite gneisses (VRL-18-1; VRL-20-1), a muscovite gneiss (VRL-21-1) from Bucaramanga Gneisse, and a muscovite schist (VRL- 21–3) of the Silgará Schist, produced the following results: (1) Mesoproterozoic ages around 1000-1200 Ma interpreted as maximum deposition ages (2) ages around 861-1051 Ma probably associated with the first metamorphic event ( M1), result of the Grenvillian orogeny and (3) ages close to 540 Ma in the rocks of the Bucaramanga Gneiss, probably interpreted as a thermal event. The U-Pb ages in zircons suggest similarities with those obtained in the Amazonian craton, supporting a correlation and indicating that the Santander Massif is composed of rocks formed during the collision between eastern Laurentia and Amazonia craton, during the formation of Rodinia.