Cape Verde Seamounts - Cruise No. M80/3 - December 29, 2009 - February 1, 2010 - Dakar (Senegal) - Las Palmas de Gran Canaria (Spain) (English)

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The R/V METEOR cruise M80/3 was designed to obtain new insights into the origin and evolution of the Cape Verde Archipelago through geochemistry and age dating of rock from regionally occurring seamounts, and the characterization of marine ashes from prehistoric large explosive eruptions. The regional evolution cannot be understood without including seamounts in the data set because the islands reflect only a small part of the Cape Verde swell. During the cruise, nine seamounts were mapped, and six were investigated in detail using the ROV KIEL 6000 in combination with dredging. These include two of the presumably oldest volcanoes at Cape Verde, Senghor and Cabo Verde Seamounts, and the young and active Cadamosto Seamount, the Charles Darwin Volcanic Field (a volcano field at 3500-4000m depth), Nola Seamount and Sodade Seamount, which we discovered at the NW tip of the archipelago. Both Sodade Seamount and the Charles Darwin field comprise primitive alkaline rock compositions, and represent the early stages of seamount evolution. Two of the eruption centres at the Charles Darwin field originated through very unusual explosive volcanism at about 3500 m depth. 28 gravity cores ranging from 1.7 to 8.7 m in length were successfully recovered from around and across the entire archipelago. These cores contain a total of 205 mafic through felsic ash layers and probably cover a time span of about 500 ka. SIMRAD EM120 and PARASOUND were used to select sampling stations and to assess the structural geology of the region. The dominant macrofauna on the island and seamount slopes of the Cape Verde archipelago are comprised by recent and fossil cold-water corals, which are in many cases habitat forming, and include Isididae, scleractinian corals and octocorals covering various depth ranges down to about 3000 mbsl.