The Significance of Giant Flank Collapses on Magma Ascent in the NE Rift Zone of Tenerife, Canary Islands: A Structural Modelling and Diffusion Approach

Abstract: On the volcanic ocean island Tenerife in the Canary archipelago, several giant flank collapses haveoccurred over the last one million years. The link between the lateral collapses and the resultingvolcanism in the rift zones is not fully understood and was investigated within the framework of thisproject. A field survey along the north eastern rift zone on Tenerife was performed, where dyke intrusionstructural data was collected to analyse the exact distribution of dykes in the area. To determine themagma ascent rate, diffusion analysis of major elements in olivine crystals was conducted incollaboration with ETH Zürich. Additionally, analogue gelatine model experiments were performed toimprove the understanding of the processes that reconfigure linear rift zones to triaxial or multiaxial riftzones. Injections of fluid into the gelatine ridges produced fractures which mainly were linear andfollowed the along strike direction. Position A’ in the centre of the unstable section, produced the mostdiverse injection patterns and had a roughly 30 % higher acceleration compared to position A, positionedat the border of the unstable section. From the results of the diffusion modelling of Mg in olivinephenocrysts an ascent rate of the magma was calculated to an average ascent velocity of 10.4–14.0 km/h.This is extremely fast and suggests that the Orotava collapse is strongly connected to the formation ofankaramite dykes in the area as a result of sudden decrease in the lithostatic pressure.