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WALVIS I: Ar/Ar Geochronology and Geochemistry of existing samples from the Walvis Ridge and Rio Grande Rise

Principal Investigators: Dr. Kaj Hoernle, Dr. Folkmar Hauff HoernleRundeI

The crudely linear trend and apparent age progression of the Walvis Track (Walvis aseismic volcanic ridge and Guyot Province to the SW) is commonly believed to reflect a mantle-plume-related hotspot track connecting the Etendeka Flood Basalts with Tristan and Gough Islands. The validity of the few age data and thus age progression for the Tristan/Gough hotspot track, however, are severely questioned. The plume hypothesis itself is also increasingly challenged by „The Great Plume Debate” and requires critical field tests. In addition, the Walvis Ridge is considered a type locality for the enriched mantle (EM) I endmember of intraplate basalts. Therefore we carry out an integrated Ar/Ar geochronological and geochemical study (major and trace element and Sr-Nd-Pb-Hf-O isotopes) on existing samples from the Walvis Track and Rio Grande Rise. Our sample collection includes >100 samples from 34 sites of various international cruises and from five DSDP sites. These samples will be used to test for age progressive magmatism along the Walvis Track, to evaluate changes in chemical composition through time, particularly to see if there is a geochemical zonation along this volcanic lineament, and to constrain further the ultimate origin of the EM-I mantle endmember. This study will serve as the basis for a more detailed survey along the Walvis Ridge proposed for 2010/11 with R/V Meteor.



  • Joana Rohde  -