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Late Pleistocene rhyolitic explosive volcanism at Los Azufres Volcanic Field, central Mexico

2012; Geological Society of America; Linguagem: Inglês

10.1130/2012.0025(04)

José Luis Arce, José Luis Macías, E. Rangel, Paul W. Layer, Víctor Hugo Garduño‐Monroy, Ricardo Saucedo, Felipe Ramos Garcia, Renato Castro, Héctor Pérez-Esquivias,

Geology and Paleoclimatology Research

Abstract Los Azufres Volcanic Field hosts the second most important geothermal field of Mexico, with a production of 188 MW of electricity. Based on fieldwork and new geochronological data (14C and 40Ar/39Ar) we define that activity at Los Azufres Volcanic Field started some 1.5 Ma with the emission of basaltic to rhyolitic lavas, and pyroclastic material. The late Pleistocene explosive activity in the southwest sector (Guangoche volcano area) of Los Azufres occurred in a narrow period of time between >31 and <26 ka. The pyroclastic stratigraphy of the S, SW, and W sectors is represented by diverse deposits of dacitic and rhyolitic composition, including a debris avalanche deposit related to a sector collapse of San Andrés volcano, several pyroclastic sequences associated with plateau forming lavas, and Guangoche volcano. Guangoche volcano was the focus of late Pleistocene eruptive activity with two Plin-ian and one subplinian events that deposited pumice-rich falls and pyroclastic flows and surges. These deposits are informally named the White Pumice (29 ka), which originated from a 23-km-high eruptive column and the ejection of 1.7 km3 of tephra that covered an area of at least 223 km2 with a mass discharge rate of 9 × 107 kg/s; the Ochre Pumice fall (<26 ka), deposited from a 16-km-high eruptive column involving 1.3 km3 of tephra at a mass discharge rate of 1.9 × 107 kg/s; and the Multilayered fallout (<<26 ka) that resulted from an 11-km-high eruptive column with 1 km3 of tephra at a mass discharge rate of 4.6 × 106 kg/s. The complete late Pleistocene stratigraphy suggests that explosive events at Los Azufres Volcanic Field have been intense. They are the subject of ongoing investigations to better understand this kind of large magnitude eruptions.