Magma flow in dikes from rift zones of the basaltic shield of Tenerife, Canary Islands: Implications for the emplacement of buoyant magma

Dikes of rift zones in the Miocene basaltic shield of Tenerife have been studied along several profiles in order to record overall variations in lateral and vertical magma flow direction and sense. Dikes were sampled for Anisotropy of Magnetic Susceptibility (AMS) and other flow indicators and dike propagation indicators were also recorded at each sampling site. Bulk susceptibilities suggest a predominance of ferromagnetic minerals in the AMS fabrics and most of the sampled dikes show normal fabrics. Magnetic fabrics have been classified according to clustering and imbrication shown by the maximum susceptibility axis on each dike margin, a procedure that provides rapid information on the direction and sense of magma flow.The flow of magma tends to be upward and steep beneath the volcanic centers of the basaltic shield massifs. Along the axes of rift zones and in those rift zones located across the flanks of the volcanic edifices (roughly normal to the main rifts), magma is mainly emplaced laterally and downward. The flow of magma is mostly towards the external parts of the volcanic centers of the basaltic shield massifs and indicates that magma propagated toward regions of lower topography. This interpretation agrees with magma being emplaced above the level of neutral buoyancy and with buoyancy as the driving pressure gradient. The observed flow patterns can be explained in terms of density gradients within the volcanic edifices, in which magma flow trajectories are toward less dense regions.