Palaeozoic structures in the Xayacatlan area, Acatlan Complex, southern Mexico: Transtensional rift- and subduction-related deformation along the margin of Oaxaquia

The Xayacatlan area (eastern Mixteca terrane, southern Mexico) was previously inferred to preserve the Ordovician-Silurian thrust contact between vestiges of the Iapetus Ocean and the para-autochthon bordering Oaxaquia. Detailed remapping indicates that the rocks occur in four vertically-bounded, NS fault blocks. The latter record the following tectonothermal events that post-date Iapetus and occurred along the margins of the Rheic (1) and Pacific (2 and 3) oceans: (1) dextral transtension accompanying intrusion of an NS, tholeiitic dike swarm at ∼442 Ma; (2) penetrative, greenschist-facies deformation during the Mississippian related to extrusion of high-pressure rocks; and (3) subgreenschist-facies dextral transtension on NS faults during the generation of Middle Permian fabrics.