Deep volcanic morphology below Lanzarote, Canaries, from gravity inversion: New results for Timanfaya and implications

Abstract

The deep roots of oceanic island volcanoes are poorly known and geophysical models can help to constrain pro-cesses such as magma storage and transport before and during eruptions. Lanzarote, Canary Islands, is a volcanicisland in post-erosional phase where, in the 18th century, one of the most important historical eruptions, consid-ering duration and volume, of the Canary Islands took place in the Timanfaya area. To improve the knowledge onthe structure of Lanzarote and in Timanfaya area, we carry out a gravity determination of the subsurface anom-alous 3D density structure, using an improved quasi-automatic inversion methodology. The obtained model pre-sents a 3D morphology of anomalous density bodies. We describe the improvements of the inversionmethodology, the adjusted model and interpretative conclusions corresponding to the structure and the long-term cumulative magmatic plumbing system of the island. Three high-density sources are described as resultingin the inference of three main volcanic complexes: a large central complex (San Bartolomé) and two smallercomplexes, one in the NE and a third smaller one located in the SW close to the Timanfaya area. The outcropsof Miocene lavaflows from the center of the Island can be attributed to the top of the central intrusive model.We infer the local plumbing system for Timanfaya volcano area by means of strongly tilted successive branchesof magma departing from the SWintrusive body. The structural results show no evidence of any magma chamberbelow Timanfaya as proposed by previous works. Wealso present a comparison of the gravity results and geolog-ical observations, showing different cases of correlation in the Island. They go from a good match between thegravity anomaly and the position of the central volcanic structure, to no anomaly associated to thefissural Qua-ternary volcanic activity.