Structural and tectonic evolution of the Acatlán Complex, southern Mexico: Its role in the collisional history of Laurentia and Gondwana

Abstract

Correlation of deformational phases and thermal events in the Acatlán Complex permits definition of nine major tectonic events. Seven events are related to the evolution of the Iapetus and Rheic oceans. By the Early Ordovician, the Xayacatlán suite of Laurentian affinity was metamorphosed to eclogite facies and exhumed before colliding with the El Rodeo suite. From the Late Ordovician to Silurian, the Upper Ordovician Ixcamilpa suite with peri‐Gondwanan affinity was metamorphosed to blueschist facies, exhumed, and subsequently was overthrust by the Xayacatlán–El Rodeo block. Part of the Esperanza suite is an Early Silurian intra‐Iapetian continental arc that collided with and subducted beneath continental crust, generating a Silurian eclogitic event. By the Late Devonian, collision of the three high P/T suites closed the Iapetus Ocean. The resulting composite terrain was thrust over the Gondwana‐bordering Cosoltepec suite to close the Rheic Ocean. During the earliest Mississippian, the collision of the Acatlán Complex and the Oaxaca terrane uplifted and deformed the composite terrane. By the Early Permian, deposition of the Chazumba suite occurred in a pull‐apart basin. A latest Early Permian event produced thrust shear zones with N–S directed shortening. During the Middle Jurassic, plume rise caused regional doming, magmatism and amphibolite facies metamorphism. During the Late Cretaceous–Paleogene, folds and thrust faults overprint the Acatlán Complex. Most events in the Acatlán Complex correlate with events in the Appalachian chain, suggesting that the Acatlán Complex was located near the Appalachians until the Jurassic when it was displaced by the Gulf of Mexico opening.