The Tahamí and Anacona Terranes of the Colombian Andes: Missing Links between the South American and Mexican Gondwana Margins

AbstractNew zircon trace-element concentration data and U-Pb geochronology on gneisses from Colombia’s Central Cordillera at 6°N allow for the recognition of the distinct Anacona suspect terrane separate from the known Tahami terrane. These blocks underwent disparate Paleozoic and Mesozoic evolutions involving anatexis, S-type granite crystallization, and metamorphism. Orthogneisses from the Tahami terrane basement have yielded a 244 ± 2 Ma mean age (n = 15), and associated migmatitic paragneisses yielded a 237 ± 2 Ma mean age (n = 11). Zircon geochemistry and textures show that the orthogneiss age represents the time of crystallization of early melts in the orogenic cycle, whereas the paragneiss age represents the time of metamorphic recrystallization of the suite. In contrast, orthogneisses from the small Anacona terrane have yielded U-Pb ages of 479+15/−11 Ma (median, n = 7) and 443 ± 8 Ma (mean, n = 8) in magmatic zircon rims. The main xenocrystic zircon populations are 1265–995 and 1510–1495 Ma (no P...