Ordovician and Mesoproterozoic Zircons from the Tecomate Formation and Esperanza Granitoids, Acatlán Complex, Southern Mexico: Local Provenance in the Acatlán and Oaxacan Complexes

Abstract

Detrital zircons from the Middle Permian and older Tecomate Formation, formerly the uppermost unit of the Acatlán Complex in southern Mexico, yielded the following U-Pb, LA-ICP-MS ages: (1) a major Cambro-Ordovician population with peaks at 460 and 500 Ma; (2) a limited Neoproterozoic population (729 and 879 Ma); and (3) a major Mesoproterozoic population ranging from ~940 to 1650 Ma with peaks at ~1025 Ma and 1100-1300 Ma. The type locality of the Esperanza blastomylonitic granite yielded concordant U-Pb ages of 471 ± 6 Ma, which, along with similar granitoids in the Acatlán Complex, appears to be the source of the Cambro-Ordovician detrital zircons in the Tecomate Formation. The provenance of the Mesoproterozoic detrital zircons seems to be in the adjacent Oaxacan Complex, which has yielded ages ranging from ~1450 to 917 Ma. The Neoproterozoic detrital zircons may have been recycled from other units in the Acatlán Complex. These data are consistent with Pangea reconstructions that place the Acatlán Complex in its present location relative to the rest of Mexico.