25-1 Petrology of Western Flanks of Miocene Volcanism in the Sierra Madre del Sur: San José del Progreso and San Jerónimo Taviche, Oaxaca

Session: Integrating metamorphism, mass transfer, and magmatism across the American Cordillera (Posters)

Poster Booth No.: 45

Presenting Author:

Yessica Carrazco-Vega

Authors:

Carrazco-Vega, Yessica Viridiana¹, Cano-Hernandez, Néstor Alfredo², Camprubí-Cano, Antoni³, González-Partida, Eduardo⁴

Abstract:

Miocene volcanic rocks from the San Jerónimo Taviche area, in the Sierra Madre del Sur of Oaxaca, are part of arc-related magmatism associated with the subduction of the Cocos plate beneath southern Mexico. This region lies within a well-recognized regional magmatic hiatus between ~28 and 24 Ma; however, post-gap magmatism has received relatively little attention, particularly in central Oaxaca, where petrographic, geochemical, and geochronological data remain limited. This study presents an integrated characterization based on field observations, petrography, and whole-rock major, trace, and rare earth element geochemistry of Miocene andesites that crop out as subvolcanic bodies and lava flows interbedded with volcano-sedimentary sequences. These rocks yield ages between ~25 and 23 Ma, allowing the timing of the final stage of the regional magmatic hiatus to be constrained and documenting the early reactivation of arc magmatism during the Early Miocene. Petrographically, the andesites are predominantly porphyritic, with plagioclase ± clinopyroxene ± orthopyroxene phenocrysts, and display a calc-alkaline affinity. Trace element patterns, characterized by enrichment in LILE and depletion in HFSE, are consistent with arc magmas and suggest a mantle source modified by subduction-related fluids. Overall, these results provide new constraints on the evolution of post-gap magmatism in the Sierra Madre del Sur.

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