Abstract

BARBOZA-GUDINO, José Rafael; RAMIREZ-FERNANDEZ, Juan Alonso; TORRES-SANCHEZ, Sonia Alejandra  and  VALENCIA, Víctor A.. Geochronology of detrital zircons from several sites of the Granjeno Schist in Northeastern Mexico. Bol. Soc. Geol. Mex [online]. 2011, vol.63, n.2, pp.201-216. ISSN 1405-3322.

In northeastern Mexico, the Granjeno Schist crops out in the core of some of the Sierra Madre Oriental fold structures, such as the Huizachal-Peregrina Anticlinorium or the Miquihuana, Bustamante (both in Tamaulipas) and Aramberri (Nuevo León) uplifts. Field work and petrographic analysis of samples from selected localities, have allowed the recognition of different lithofacies, metamorphic grade and deformational style, as well as stratigraphic relationships. Although detrital zircon geochronology of all different clastic protoliths revealed mainly Grenville (1250-920 Ma) and Panafrican (730-530 Ma) provenance ages, differences in the maximum depositional ages, ranging from Neoproterozoic to Silurian and probably Devonian times, should be noticed. Minor zircon populations of Proterozoic and Paleozoic ages apparently correlate with less studied tectonomagmatic events in Mexico, as the Ordovician-Silurian magmatism. This study supports the idea that the origin of the Granjeno Schist is closely related to Grenville and Panafrican blocks from northwestern Gondwana. Our data, due to a lack of provenances from the southwestern portion of the North American craton, disagree with a sinistral displacement of a part of Mexico along several hundreds of kilometers in Late Jurassic time, as previously proposed by the Mojave-Sonora megashear hypothesis. Granjeno Schist metamorphism during the late Paleozoic could be related to a subduction process along the Pangea western margin (Granjeno-Acatlán Belt), after the Laurentia and Gondwana collision (Sonora-Oucahita-Marathon Belt). This correlates well with the Permo-Triassic magmatic arc in eastern Mexico, which is clearly a product of the same subduction during its high angle stage, following deformation and metamorphism produced by the initial low angle stage.

Keywords : metamorphic Paleozoic; northeastern Mexico; U-Pb geochronology; provenance.

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