Evolution of the central Atlantic hot spots cluster in the last 100 Myr: interaction between plate tectonics, a lower mantle thermochemical instability and upper mantle secondary plumes

Thursday, 18 December 2014
Aurore Sibrant1,2, Anne Davaille2, Fernando Ornelas Marques3 and Anthony Hildenbrand1, (1)Lab. GEOPS / University Paris-Sud, Orsay Cedex, France, (2)CNRS / University Paris-Sud, Laboratoire FAST, ORSAY, France, (3)Universidade de Lisboa, Lisbon, Portugal
Born 200 Ma ago, the central Atlantic presents nowadays a large low seismic velocity anomaly in the lower mantle, a cluster of "hot" spots (Azores, Cape Verde, Madeira, Canary, Great Meteor), a mid-ocean ridge, and a triple junction located in the Azores. We carried out laboratory experiments to examine the possible links between mantle instabilities, plate boundary migration, and the
development of the volcanism on various spatial and temporal scales. Coupled with the current knowledge of these volcanic areas (tomography, tectonics and K/Ar dating), our fluid mechanics
experiments suggest that:

(1) The Azores, as Canary, Cape Verde, Madeira Islands and Great Meteor seamounts might be the surface expression of a cluster of mantle instabilities rising from the top of a large thermochemical dome located in the lower mantle. However, such secondary plumes present a strong
time-dependence 5-40 Myr time scale.

(2) These secondary instabilities could be sufficiently weak to adapt their motions to the pre-existing force
balance, and morphology and mechanical properties of the lithosphere.

Based on current knowledge and modelling, we present a scenario of the Central Atlantic area evolution in the last 100 Ma combining a triple junction and decompression melting-generated buoyant material (i.e. such in volatiles and/or
temperature) under a cooling and thickening lithosphere.