A volcanic centre in Mexico’s Pacific continental shelf
Published:January 01, 2017
Román Alvarez, Fernando Corbo Camargo, Vsevolod V. Yutsis, Jorge A. Arzate, 2017. "A volcanic centre in Mexico’s Pacific continental shelf", Monogenetic Volcanism, K. Németh, G. Carrasco-Núñez, J. J. Aranda-Gómez, I. E. M. Smith
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On the continental platform of western Mexico, there is a young island of volcanic origin: Isla Isabel. It is the only volcanic manifestation in the region, contrasting with Islas Tres Marías, which are not volcanic. We aim at characterizing the source of the volcanic activity present in this particular location. Under Isla Isabel there is a bathymetric bulge that rises 60–80 m above the platform, and extends 20 km in the NW–SE direction and 17 km in the perpendicular direction. Isla Isabel is the only emerged portion of the bulge, extending only 1.8 km in the NW–SE direction. The island shows Plio-Pleistocene volcanic activity, including the formation of maars and the presence of mantle xenoliths. Using independent 2D modelling and 3D inversion methods for the gravity and magnetic fields, we analyse the nature of the bulge and its surroundings. A magnetotelluric station yields information about the electrical resistivity under the island, with penetration depths of approximately 20 km. The models are consistent with the presence of dense bodies of varying magnetizations that are interpreted as intrusive bodies. Results support the presence of an intrusion that locally has raised the ocean-floor topography. Volcanic activity projected from the bulge created Isla Isabel; the existence of additional, submerged volcanic centres in the area is most probable. We are inclined to identify the Isabel Bulge as a laccolith.
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The nature and origin of the small-scale volcanic systems, generally referred to as “monogenetic”, have enjoyed an elevated level of interest during the past decade. There has been recognition that their ostensibly simple volcano types are a window into the nature of explosive volcanism, landscape evolution and the processes of magma generation in the Earth’s upper mantle. In the past few years, major conferences have offered specialized technical sessions dealing with monogenetic volcanism and there have been thematic conferences, such as the IAVCEI International Maar Conference series, which have provided a focus for discussion of volcanological and geochemical aspects of small-scale basaltic volcanism. Many new aspects of monogenetic volcanism have emerged and have clearly demonstrated that this volcanism can be very complex on a fine scale. This book is a collection of papers arising from two recent Maar Conferences (the fifth in Queretaro Mexico and the sixth in Changchun, China) and serves as a snapshot of current research on monogenetic volcanism.