The Tectonic Evolution of the Azores Based on Magnetic Data

Abstract

The Azores attracted the interest of geoscientists since the beginning of the XX century. In the late 60s, when plate tectonics was established as the basic geodynamic paradigm, the peculiar morphology of the Azores Islands and the surrounding plateau, located close to the Mid-Atlantic ridge, were early interpreted as the result of the separation between the Eurasian and the North-America plates. Nevertheless, a number of particular geological features were targeted for explanation: (i) the long active fault going from Gibraltar to the Azores (now called Gloria Fault), (ii) the existence of a large but inactive fracture on the North-American plate, offset tenths of kilometres to the north with respect to Gloria Fault, (iii) the curvilinear succession of islands marked by pervasive volcanic and seismic activity, (iv) the development of a plateau, partially split by the Mid-Atlantic Ridge. These questions remained elusive for a long time, despite the large amount of geological and geophysical data available, as most of the conventional approaches were not as fruitful as expected, and new identified features raise new unknowns or revealed uncommon geological environments. Here, we present a review of the progress made in the understanding of the tectonic evolution of the Azores, mainly based on the interpretation of magnetic and morphological data and we present an updated interpretative scheme for the genesis and evolution of the Azores triple junction.