Study offers new insights on tectonic-magmatic history of Mexican volcanic complexes

A study published in the April issue of "Journal of South American Earth Sciences” presents new insights on the tectono-magmatic history of Los Tuxtlas, in comparison to other similar volcanic complexes in the eastern Trans-Mexican Volcanic Belt.

Researchers Sergio Rodríguez-Elizarrarás, Wendy Morales-Barrera of University of Wisconsin Milwaukee, Valerie Pompa-Mera of the National Autonomous University of Mexico, Claus Siebe, Jeff Benowitz of University of Alaska-Fairbanks, Paul W. Layer, Rufino Lozano-Santacruz and Patricia Girón conducted the study on the Los Tuxtlas Volcanic Complex, in the south of the Veracruz state of Mexico. 

The abstract of the research paper describes the Los Tuxtlas Volcanic Complex as an isolated massif surrounded by two large alluvial plains formed by the Papaloapan and Coatzacoalcos Rivers. The complex includes the active volcano San Martín Tuxtla. The ages, distribution, morphology and geochemistry of the volcanic vents and lavas offer an excellent opportunity to understand the tectono-magmatic history of the area.

The researchers used different techniques, such as geomorphological, geochemical, petrographical, and 40Ar/39Ar data, to understand the volcanic activity in the region. The geological map, the 40Ar/39Ar dating, and the geochemistry data indicate a northwest-to-southeast migration of the volcanic activity of the four stratovolcanoes that have created the Sierra de Santa Marta. 

Petrography and chemistry of rocks suggest the subalkaline rocks of the three magmatic stages were fed by subduction activity of the Cocos Plate, while the alkaline suite is likely associated with asthenosphere upwelling and slab edge melting facilitated by a slab tear of the south Cocos plate evolved since the Early Miocene.

The researchers propose three different stages of volcanic activity for Los Tuxtlas, including the older Montepío-El Vigía (7 million to 1.4 million years ago), the intermediate Santa Marta (1 million to 500,000 years ago), and the younger San Martín Tuxtla (50,000 years ago to the present). The study primarily focuses on the stratovolcanoes of the Sierra de Santa Marta, formed by at least four major NW-SE aligned volcanic edifices.

The authors of the study argue that their research provides new insights into the tectono-magmatic history of Los Tuxtlas and will help in better understanding the geological processes that occur in the eastern Trans-Mexican Volcanic Belt.