Cerro Grande Volcano; the evolution of a Miocene stratocone in the early Trans-Mexican volcanic belt.

Abstract

Cerro Grande volcano is a well-preserved, low-angle composite volcano that evolved between 11 and 9 Ma. It represents the beginning of volcanism in the eastern sector of the early Trans-Mexican Volcanic Belt. Extensive field, stratigraphic and petrologic work revealed a complex volcanic evolution that can be summarized in six principal stages. I construction of a shield-like lava cone; II generation of unusual lithic-rich ignimbrites, apparently related to powerful eruptions that caused rapid and significant vent erosion--these eruptions could have resulted from shallow magma-water interactions; III eruption of peripheral fissural lava flows following a NNW-SSE-trending fissure system; IV period of dome growth and explosive collapse; V short period of repose followed by open-vent explosive magmatic and hydromagmatic eruptions; VI radial eruption of lava flows, related to a ring-fissural system. Geochemistry data of late Miocene volcanics show a continental arc magmatic origin, and show that crystal fractionation contributed strongly to magma differentiation. Several lava flows were erupted with a persistent NNW-SSE-trending orientation, and the entire late Miocene geologic record is affected by highly dislocated normal faults with the same orientation; this may indicate that late Miocene volcanism was under tectonic control. Finally, late Miocene volcanics, and the inception of the early Trans-Mexican Volcanic Belt, could be related to a shallow subduction angle influenced by a significant increase in the convergence rate along the Middle American Trench at about 20 Ma.

54 samples from this reference