Annotated record of the detailed examination of Mn deposits from the 1993 R/V Sonne SO-84 expedition in the Atlantic Ocean, supplement to: Devey, Colin W; Ackermand, Dietrich; Binard, Nicolas; Chmarzynski, P; Franke-Bruckmaier, B; Geldmacher, Jörg; Graupner, T; Haake, F W; Haase, Karsten M; Hemond, Christophe; Krüger, O; Mühlhan, Norbert; O'Connor, John; Ott, S; Peucker-Ehrenbrink, Bernhard; Pototzki, Frank; Segl, Monika; Tichomirov, W (1993): Cruise report SO-84: The St Helena hotspot - Las Palmas-Cape Town 02.01.93-20.02.93. Berichte - Reports, Geologisch-Paläontologisches Institut und Museum, Christian-Albrechts-Universität, Kiel; 64; 1-103; ISSN 0175-9302, TIB - Technische Informationsbibliothek Universitätsbibliothek Hannover, Berichte-Reports, Geologisch-Paläontologisches Institut der Universität Kiel, 64, 103 pp

DOI

The SO-84 cruise from Las Palmas to Cape Town studied the underwater volcanism associated with the St Helena hotspot. Wide-spaced grid mapping of a region south and west of St Helena island identified three previously unknown hotspot volcanoes (which we named Josephine 16°27'S-9°W, Jade 16°13'S-7°46'W and Benjamin 16°12'S-8°31'W) and several older, probably near-ridge-generated seamounts. The newly discovered hotspot seamounts, and the previously-known seamounts of Bagration, Bonaparte and Kutuzov were mapped and sampled. Onboard geochemical studies confirm that they all show trace-element (Rb, Nb, Y, Zr, Sr) enriched, hotspot magma-type compositions. Morphological studies and the state of the samples collected from the seamounts (all have at least 1 mm-thick Mn crusts) suggest that none of the volcanoes is presently active, and that the St Helena hotspot is probably extinct at the present time. Josephine appears to be the youngest volcano, and one dredge here yielded fossil hydrothermal material (Fe-hydroxides). To test the hypothesis that the extinction of the hotspot is due to its magmas being channelled to the Mid-Atlantic Ridge, several dredges were taken on the ridge opposite St Helena. Furthermore, in the proposed influence zone of the St Helena plume head, Grattan seamount (9°44'S-12°48'W) was also sampled to examine whether its composition has been affected by the St Helena plume. During the transit from Las Palmas to St Helena, several sediment cores were taken in 3000 m water depth close to the ridge axis for palaeoclimatological work.

Identifier
DOI https://doi.org/10.1594/PANGAEA.875089
Related Identifier https://doi.org/10.2312/reports-gpi.1993.64
Related Identifier https://doi.org/10.7289/V52Z13FT
Related Identifier https://doi.org/10.7289/V53X84KN
Metadata Access https://ws.pangaea.de/oai/provider?verb=GetRecord&metadataPrefix=datacite4&identifier=oai:pangaea.de:doi:10.1594/PANGAEA.875089
Provenance
Creator Devey, Colin W; Ackermand, Dietrich; Binard, Nicolas; Chmarzynski, P; Franke-Bruckmaier, B; Geldmacher, Jörg; Graupner, T; Haake, F W; Haase, Karsten M; Hemond, Christophe; Krüger, O; Mühlhan, Norbert; O'Connor, John; Ott, S; Peucker-Ehrenbrink, Bernhard; Pototzki, Frank; Segl, Monika; Tichomirov, W
Publisher PANGAEA - Data Publisher for Earth & Environmental Science
Publication Year 1993
Rights Creative Commons Attribution 3.0 Unported
OpenAccess true
Representation
Language English
Resource Type Supplementary Dataset
Format text/tab-separated-values
Size 725 data points
Discipline Geosciences
Spatial Coverage (-25.149W, -17.153S, -5.659E, 0.601N); South Atlantic
Temporal Coverage Begin 1993-01-11T00:00:00Z
Temporal Coverage End 1993-02-12T00:00:00Z