The Magmatic Evolution Between the Late Paleozoic and Triassic of the Las Delicias Terrane, Coahuila, Mexico.

In northeastern Mexico, within the Coahuila Block, lies the Las Delicias Terrane, where a Triassic plutonic body previously referenced as the Acatita intrusive suite is exposed. This suite has been interpreted within a post-orogenic collapse context and is observed emplaced in a deformed volcanosedimentary sequence of the Las Delicias Formation. Associated with both units are some questions about the transition and magmatic diversity, as well as the petrogenetic evolution of the suite. To address these questions, cartographic, geochemical, isotopic, petrographic, and geochronological analyses were conducted.

Our results suggest that the Las Delicias Formation is primarily composed of volcaniclastic deposits, rhyolites, and andesite-dacite rocks from the Carboniferous-Permian (327–270 Ma). On the other hand, the Acatita intrusive suite (223–211 Ma) consists of granodiorites, tonalites, and quartz monzodiorites, including hornblende-rich gabbroic and dioritic enclaves. Zircon Hf analyses from both units reveal variation during the magmatic transition, potentially representing different stages in the evolution of Pangea.

The geochemical signatures of the suite exhibit a typical arc pattern. However, a depletion in HREE, significant negative anomalies in Nb and Hf, and Sr enrichment are observed. These patterns, in conjunction with the disequilibrium textures observed in the petrographic analysis, suggest a simultaneous process involving mixing, assimilation and fractional crystallization, which defines the compositional variation of the intrusive suite.