New age and geochemical data from the Walvis Ridge: The temporal and spatial diversity of South Atlantic intraplate volcanism and its possible origin

• Published in: Geochimica et Cosmochimica Acta
• Main Authors: Homrighausen, Stephan, Hoernle, Kaj, Hauff, Folkmar, Wartho, Jo-Anne, van den Bogaard, Paul, Garbe-Schönberg, Dieter
• Format: Article in Journal/Newspaper
• Language: English
• Published: Elsevier 2019
• Subjects: Gough; Tristan; South Atlantic Ocean
• Online Access: https://oceanrep.geomar.de/id/eprint/44375/; https://oceanrep.geomar.de/id/eprint/44375/1/10.1016_j.gca.2018.09.002.pdf; https://oceanrep.geomar.de/id/eprint/44375/6/Homrighausen%20et%20al%20GCA_2019_Print.pdf; https://oceanrep.geomar.de/id/eprint/44375/12/AppendixA_Homrighausen%20et%20al%20GCA_2019.docx; https://oceanrep.geomar.de/id/eprint/44375/13/AppendixB_Homrighausen%20et%20al%20GCA_2019.xlsx; https://oceanrep.geomar.de/id/eprint/44375/14/AppendixC_Homrighausen%20et%20al%20GCA_2019.xlsx; https://oceanrep.geomar.de/id/eprint/44375/15/AppendixD_Homrighausen%20et%20al%20GCA_2019.xlsx; https://oceanrep.geomar.de/id/eprint/44375/16/AppendixE_Homrighausen%20et%20al%20GCA_2019.xlsx; https://oceanrep.geomar.de/id/eprint/44375/17/AppendixF_Homrighausen%20et%20al%20GCA_2019.xlsx; https://doi.org/10.1016/j.gca.2018.09.002

Highlights • New 40Ar/39Ar age and geochemical (major, trace element, Sr-Nd-Pb-Hf isotope) data are presented from the Walvis Ridge, belonging to the Tristan-Gough hotspot track in the South Atlantic. • The entire Tristan-Gough hotspot system, including Walvis Ridge, display a spatially continuous age progression. • The Gough-type component is the dominant geochemical flavor of the Tristan-Gough plume and has also been identified in the Discovery and Shona hotspot systems. • The geochemical heterogeneity in the South Atlantic DUPAL region can be reproduced by mixing of Gough-type enriched mantle with continental crust and a FOZO/PREMA-like component. • The HIMU-type alkalic lavas on the Walvis Ridge and older part of Shona hotspot track are ∼30 Ma younger in age than the EMI-type primarily tholeiitic basement lavas at a given locality. Abstract Long-lived spatial geochemical zonation of the Tristan-Gough and Discovery hotspot tracks and temporal variations from EMI-type basement to HIMU-type late-stage volcanism at the Walvis Ridge and Shona hotspot tracks point to a complex evolution and multiple source areas for the South Atlantic hotspots. Here we report 40Ar/39Ar age and geochemical (major and trace element, Sr-Nd-Pb-Hf isotope) data for samples from 16 new sites on the Walvis Ridge. This aseismic ridge is the oldest submarine expression of the Tristan-Gough mantle plume and represents the initial reference locality of the EMI end member in the South Atlantic Ocean. The EMI-type lavas display an excellent age progressive trend of ∼31 mm/a along the entire Tristan-Gough hotspot track, indicating constant plate motion over a relatively stationary melt anomaly over the last ∼115 Ma. The Gough-type EMI composition of the Tristan-Gough hotspot track is the dominant composition on the >70 Ma part of the Walvis Ridge, the Etendeka and Parana flood basalts, and along the Gough sub-track, extending from DSDP Site 525A on the SW Walvis Ridge to Gough Island, whereas Tristan-type EMI dominates on the Tristan Track, ...