Oaxaquia: A Grenvillian Crustal Fragment in Mexico. A Review and New Approaches

Abstract Grenvillian crustal fragments containing a crucial geological record for understanding the formation and breakup of the Rodinia supercontinent are scattered throughout Mexico. In this contribution, we synthesize the available geochronological and isotopic data from these inliers exposed south of the Ouachita-Marathon-Sonora suture belt and provide a review that integrates both traditional and emerging perspectives. The classical interpretation of the Mexican Grenvillian rocks relies on the model of Oaxaquia—a microcontinent composed of crustal blocks with protolith ages between ∼1.4 and 1.0 Ga, metamorphosed under granulite conditions at ∼0.99 Ga during the assembly of Rodinia. This tectonothermal event, locally known as the Zapotecan Orogeny, correlates in age with the Rigolet phase of the Grenvillian Orogeny. In its classical conception, Oaxaquia is a key palinspastic element in the global Meso- to Neoproterozoic geological framework. However, recent findings and data on Grenvillian crustal fragments in southern and southeastern Mexico renew earlier debates regarding their position within Rodinia and expand the classical concept of Oaxaquia. For instance, the proposed connection of Amazonia-Oaxaquia-Baltica during Rodinia's assembly is questioned, while the Amazonia-Oaxaquia-Laurentia relationship is re-examined. Additionally, the recognition of crustal fragments lacking evidence of the Zapotecan Orogeny and the presence of an extended non-granulitic tectonothermal event occurring between 950 and 920 Ma are discussed in terms of broadening the concept of Oaxaquia as a terrane comprising sub-provinces with different origins and tectonic histories. Lastly, we assess the potential subsurface extent of Oaxaquia beneath the surface and its tectonic implications. Based on new data, this contribution aims to expand the Oaxaquia paradigm by integrating new interpretations and hypotheses for future testing.