Earlier history of the ≥70-Ma-old Canary hotspot based on the temporal and geochemical evolution of the Selvagen Archipelago and neighboring seamounts in the eastern North Atlantic

Abstract

Major element, trace element and Sr–Nd–Pb isotope data, combined with 40Ar/39Ar age determinations, of volcanic rocks from the Selvagen Islands and neighboring seamounts in the eastern North Atlantic reveal the earlier history of the ≥70Ma old Canary hotspot. A basanitic to phonolitic late shield stage intrusive complex (29Ma) is exposed on Selvagem Pequena. The evolution of Selvagem Grande can be divided into three magmatic phases: a tephritic to phonolitic late shield stage intrusive complex (24–26Ma) and two rejuvenated or post-erosional stages (8–12 and 3.4Ma) consisting of alkali basalt, basanite and rare phonolite. During the early to mid-Miocene volcanic hiatus (12–24Ma), the top of the volcano was beneath sea level as evidenced by marine carbonate sediments (13–24Ma, dated through correlation of 87Sr/86Sr with the seawater Sr isotope curve). The geochemistry of the shield stage lavas indicates that they derive from plume sources, whereas the post-erosional lavas are derived from metasomatized lithospheric sources. Five sampled seamounts to the east and northeast of the islands range in composition from alkali basalt and basanite to phonolite. Samples from Dacia, Conception Bank and Lars were dated at 9, 17 and 68Ma, respectively. Geochemical data suggest that the dredged samples come from the post-erosional stage of volcanism, and therefore, the dates represent minimum ages for the seamount volcanoes. The elevation of erosional platforms formed at wave base decrease from Selvagen Grande (∼100m above sea level) to Lars seamount (∼900m below sea level), suggesting a southwest to northwest age progression and that all of these seamounts are older than the Selvagen Islands. Trace element and Sr–Nd–Pb isotopic composition of the Selvagen Islands and neighboring seamounts are consistent with their origin from the Canary plume. Interaction of the weak Canary mantle plume with a slow moving plate appears to be responsible for generating a 450-km-wide, irregular hotspot track extending 800km from the youngest Canary Island of Hierro in the southwest to Lars seamount in the northeast.