Dykes, faults and palaeostresses in the Teno and Anaga massifs of Tenerife (Canary Islands)

A structural field study was made of 578 sheet intrusions (mostly dykes) and 153 (mostly normal) faults dissecting the Anaga and Teno massifs, where a complex volcanic succession of Tertiary age (the 'Old Basaltic Series) representing the shield-building stage of Tenerife (Canary Islands) crops out, Many of the: intrusions, mostly sub-vertical mafic dykes, are emplaced by multiple magma injections, with cumulative thicknesses mostly less than 2 m. Dyke tips are exposed rind preserved for 12% of the dykes. Three differently oriented sets of dykes exist in the Anaga massif (NNW-SSE, NNE-SSW. E-W), whereas there is only one main set in Teno, trending NNW-SSE. Dyke swarms and other structural features having similar orientations also exist in other Canary Islands. A minimum value of the horizontal component of extension induced by dykes is computed using a step of 5 degrees of azimuth, accounting also for the dip of dykes. The cumulative crustal dilation is at least 300 m (similar to4%) in Anaga and 270 m (similar to6%) in Teno; the maximum extension peaks at N75 degrees in Anaga and N60 degrees in Teno, indicating a general prevailing extension in direction ENE-WSW. Most of the measured faults are normal and strike NNW-SSE. Computation of palaeostresses from inversion of fault-slip data sets suggests the existence of a polyphase brittle deformation due to an extensional stress field with the minimum compressive principal axes trending NE-SW and WNW-ESE. (C) 2000 Elsevier Science B.V. All rights reserved.