Analysis and modelling of the aeromagnetic anomalies of Gran Canaria (Canary Islands)

Abstract

In this paper we present a crustal magnetic model of the volcanic island of Gran Canaria based on aeromagnetic data. This magnetic study has made it possible to constrain the location and geometry of: (1) the mafic core of Gran Canaria, built as the result of the crystallization of magmas which rose from the mantle during the submarine and shield basaltic stages of its evolution. The most intense magnetic high, displayed over the NW part of the island likely shows the main feeding system of the shield volcano; (2) the residual syenitic shallow magma chamber which fed the salic volcanic activity in the center of the island, linked to the formation of the Tejeda caldera and to the intrusion of felsic rocks which made up a cone sheet; (3) a reversely magnetized linear intrusion located in the marine area to the NW of the island, which could be related to the magmatic source of the submarine volcanism between Gran Canaria and Tenerife. Most of these magnetic sources show a linear pattern with trends that are in close agreement with the orientations of previously identified fractures. The magmatic intrusion to the NW of the island could be related with a WSW–ENE active fault between Gran Canaria and Tenerife, while the main trend and location of the mafic core agree with a NW–SE fault suggested by geological studies. This means that these magnetic sources are the result of the ascent and intrusion of magma along regional fractures. Therefore, this study provides fresh data which demonstrate the influence of regional tectonics on the growth of Gran Canaria during its entire evolution. Finally, the spectral analysis of the magnetic anomaly map suggests that it is possible that rocks located at mantle-like depths (from the Moho to about 23 km) behave as magnetic sources, a fact that can be related with the magmatic underplating detected by other geophysical techniques.