Constraints on the structure of Maio Island (Cape Verde) by a three-dimensional gravity model: imaging partially exhumed magma chambers

Abstract

SUMMARY We propose a 3‐D gravity model for the volcanic structure of the island of Maio (Cape Verde archipelago) with the objective of solving some open questions concerning the geometry and depth of the intrusive Central Igneous Complex. A gravity survey was made covering almost the entire surface of the island. The gravity data was inverted through a non‐linear 3‐D approach which provided a model constructed in a random growth process. The residual Bouguer gravity field shows a single positive anomaly presenting an elliptic shape with a NW–SE trending long axis. This Bouguer gravity anomaly is slightly off‐centred with the island but its outline is concordant with the surface exposure of the Central Igneous Complex. The gravimetric modelling shows a high‐density volume whose centre of mass is about 4500 m deep. With increasing depth, and despite the restricted gravimetric resolution, the horizontal sections of the model suggest the presence of two distinct bodies, whose relative position accounts for the elongated shape of the high positive Bouguer gravity anomaly. These bodies are interpreted as magma chambers whose coeval volcanic counterparts are no longer preserved. The orientation defined by the two bodies is similar to that of other structures known in the southern group of the Cape Verde islands, thus suggesting a possible structural control constraining the location of the plutonic intrusions.

3-D density structure and geological evolution of Stromboli volcano (Aeolian Islands, Italy) inferred from land-based and sea-surface gravity data

“…For the actual gravity measurements, the standard deviation of the recorded average response was 0.003 mGal on average and 0.023 mGal at the most. It appears thus safe to assume a total standard deviation of the accumulated data error of 0.1 mGal on all land-based data, which is in agreement with Represas et al (2012).…”

Intraplate seismicity across the Cape Verde swell: A contribution from a temporary seismic network

“…Structural data from the southern group of islands indicate the prevalence of tectonic or tectono-volcanic structures trending NW-SE, NE-SW, N-S and E-W Represas et al, 2012). Tectonovolcanic structures trending NW-SE are present in the islands of Santiago and Maio, including the alignment of volcanic edifices that shapes the island of Santiago and the alignment of plutonic intrusions in the island of Maio (Represas et al, 2012). The northwest flank of the island of Fogo presents conspicuous NW-SE scarps interpreted as a graben structure .…”

A geological record of multiple Pleistocene tsunami inundations in an oceanic island: The case of Maio, Cape Verde

“…Conglomerates (Coruja Formation) representing shoaling of the island overlie the sea floor sequence. This basement was intruded and deformed (folded and faulted) during the Palaeogene by the successive intrusion of plutons, forming the Central Igneous Complex (Represas et al ., ), comprising gabbros (essexites and pyroxenites) and syenites. Probably of the same age are some rare carbonatite dykes.…”