Geophysical modelling of Isla Isabel: a volcanic island on the Mexican continental margin
Román Alvarez, Fernando Corbo Camargo, Vsevolod V. Yutsis, 2017. "Geophysical modelling of Isla Isabel: a volcanic island on the Mexican continental margin", Monogenetic Volcanism, K. Németh, G. Carrasco-Núñez, J. J. Aranda-Gómez, I. E. M. Smith
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Isla Isabel is a small island located on top of a 20 km-long bathymetric bulge, part of the continental shelf of Nayarit in the vicinity of the mouth of the Gulf of California; it is of volcanic origin with tuff cones, basaltic flows and Surtseyan-type explosion craters exposed. Geophysical surveys were carried out in order to model the geological bodies associated with the local gravity and magnetic fields. 2D and 3D models are presented, and a 1D inversion model is derived from magnetotelluric data. Analysis of the density models of the upper 1400 m suggests two growth stages for Isla Isabel in this depth range: the first one reaching 800 m in depth and the second one projecting from that depth to the surface. The corresponding magnetic susceptibility models concur with this observation. The bodies projected to the surface appear to correspond to diatremes. The 1D magnetotelluric inversion shows two conductive anomalies within the crust between 3–5 and 8–17 km, followed by a resistive substratum that coincides with the seismically derived limit of the Earth’s crust at the island’s position.
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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.