Comment on "U-Pb geochronology of the Acatlan Complex and implications for the Paleozoic paleogeography and tectonic evolution of southern Mexico" by O. Talavera-Mendoza, J. Ruiz, G.E. Gehrels, D.M. Meza-Figueroa, R. Vega-Granillo and M.F. Campa-Uranga [Earth Planet. Sci. Lett. 235 (2005) 682-699]
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Talavera-Mendoza et al. [1] are to be congratulated for providing important new U-Pb geochronological constraints for the tectonothermal evolution of the Acatln Complex in southern Mexico. The new data, which provide maximum depositional age constraints on various units and intrusive ages of plutonic bodies, require a complete reevaluation of the evolution of this important assemblage of rocks and add substance to the major tectonostratigraphic revisions revealed by our own research [2,3]. We do not question the accuracy of their data, which are of high quality and consistent with our own. However, we do question whether the precision of the data is adequate to resolve the known geochronological complexities in some of these rocks, and we take issue with the interpretation they place on some of the results. Here, we offer alternative interpretations of some of their data, which, we believe, lead to a much simpler description of the tectonothermal evolution of the Acatln Complex. The tectonic model for the complex proposed by Talavera-Mendoza et al. [1, Fig. 7] differs significantly from our own largely because we disagree with three aspects of their interpretation of the data, each of which is central to resolving the complex's tectonothermal evolution. These are: (i) the timing of the megacrystic plutonism, (ii) the age of the high-grade metamorphism of the Piaxtla Group, and (iii) the provenance of its sedimentary components. Given that detailed future work will be required to determine the geologic context of the new ages, we also take issue with the authors' failure to provide detailed location information for the dated samples. 2006 Elsevier B.V. All rights reserved.
