Graben type calderas: The Bolanos case, Sierra Madre Occidental, Mexico
Por:
Aguirre-Diaz, Gerardo J., Tristan-Gonzalez, Margarito, Gutierrez-Palomares, Isaac, Marti, Joan, Lopez-Martinez, Margarita, Labarthe-Hernandez, Guillermo, Nieto-Obregon, Jorge
Publicada:
1 sep 2021
Resumen:
Graben calderas are volcano-tectonic structures that use the faults of a
graben as main vents from which magma is massively erupted from a
shallow magma chamber during collapse of intra-graben blocks. These
eruptions are generally silicic and explosive and form large volume
ignimbrite sheets without a previous Plinian major depressurization
event. Graben calderas can be associated to tectonic settings ranging
from pure extension to strike-slip transtension, including complete
grabens, half-grabens or pull-apart grabens. The Sierra Madre Occidental
(SMO) in western Mexico includes several of these graben type calderas
with the corresponding large volume ignimbrite sheets that result from
fissure type eruptions along the graben's border and interior faults.
The Bolanos graben constitutes one of the best examples of these
tectonically controlled collapse calderas and is the second largest
caldera of the world after Toba caldera. It is a 90 x 25 km rectangular
caldera and the vent of the 25.37 +/- 0.36 Ma silicic Alacran
ignimbrite, with a minimum Dense Rock Equivalent volume of 2650 km(3)
(3800 km(3) rock volume). Post-collapse silicic domes were emplaced just
after the Alacran ignimbrite from 25.02 +/- 0.33 Ma to 23.94 +/- 0.33
Ma, with a total minimum lava volume of 171 km(3). Both ignimbrite and
domes account for at least 2800 km(3) rhyolitic magma output from
Bolanos graben caldera, without considering the distal deposits, and in
particular the co-ignimbrite ash-cloud deposit. We describe the
characteristics of the Bolanos graben caldera focusing on its major
products, the Alacran ignimbrite and the post-collapse dome volcanism,
providing the geological frame of the Bolanos graben area documented
with Ar-40-Ar-39 ages. We finally propose a conceptual model to explain
the dynamics of the Bolanos graben that can be applied to other similar
volcanotectonic depressions of the Sierra Madre Occidental and elsewhere
in the world with similar geological settings. (C) 2021 Elsevier B.V.
All rights reserved.
Filiaciones:
Aguirre-Diaz, Gerardo J.:
Univ Nacl Autonoma Mexico, Ctr Geociencias, Campus Juriquilla, Juriquilla 76230, Queretaro, Mexico
Tristan-Gonzalez, Margarito:
Univ Autonoma San Luis Potosi, Inst Geol, Slp, Mexico
Gutierrez-Palomares, Isaac:
Univ Nacl Autonoma Mexico, Ctr Geociencias, Campus Juriquilla, Juriquilla 76230, Queretaro, Mexico
Marti, Joan:
CSIC, Geosci Barcelona, Barcelona, Spain
Lopez-Martinez, Margarita:
CICESE, Lab Geocronol, Div Ciencias Tierra, Ensenada, Baja California, Mexico
Labarthe-Hernandez, Guillermo:
Univ Autonoma San Luis Potosi, Inst Geol, Slp, Mexico
Nieto-Obregon, Jorge:
Univ Nacl Autonoma Mexico, Fac Ingn, Mexico City, DF, Mexico
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