Description: Intraplate volcanism, in contrast to mid-ocean-ridge (MOR) oceanic crustal basalts, is formed by low degrees of deep mantle melting and has a unique and distinct major and trace element and isotopic composition. Intraplate magmatism can therefore significantly alter the composition of the lithosphere, but may also trigger local structural changes and fluid flow causing large-scale hydrothermal activity, which would also modify the original composition of the lithosphere. The BATHYCHEM (MSM70, Dec 2017-Febr 2018) cruise aimed to study the effect of the magmatism of the, so far poorly researched, Bathymetrists and Grimaldi Seamounts intraplate volcanic province on the Atlantic oceanic plate. The Bathymetrists Seamounts were formed on oceanic crust that has a wide range of ages from 30 to 〉100 Ma and thus has been exposed to variable degrees of seafloor alteration. This project aims at characterizing the structure, age and composition of the Bathymetrists Seamounts and adjacent areas to understand their origin and formation mechanism, which will allow a better assessment of how intraplate volcanism modifies the structure and composition of oceanic lithosphere through time. To achieve these aims the MSM70 expedition undertook high-resolution mapping and dense rock sampling of the intraplate Bathymetrists Seamount Chain and its corresponding N-bounding fracture zones; Cape Verde Ridge and Kane Gap. Hydro-acoustic models could be greatly improved to a resolution of 50 m and the position of 40 named and unnamed seamounts could be refined. The bathymetric maps reveal a complicated pattern of emplacement and indicate that most of the seamounts (62%) resemble guyots capped by carbonated platforms. A total of 65 dredge-tows recovered volcanic samples, carbonates, phosphorites, mudstones and manganese crusts and nodules. Volcanic samples from 27 seamounts revealed dense basaltic samples and vesicular volcanoclastic material of mafic origin containing pyroxenes, amphiboles and biotite.