Publication Date:
2024-02-03
Description:
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.
Keywords:
12DS; 13DS; 14DS; 1DS; 20DS; 21DS; 22DS; 23DS; 24DS; 25DS; 26DS; 27DS; 31DS; 35DS; 37DS; 42DS; 43DS; 44DS; 47DS; 49DS; 53DS; 54DS; 55DS; 59DS; 60DS; 63DS; 64DS; 65DS; 68DS; 69DS; 71DS; 72DS; 74DS; 7DS; 83DS; Comment; Deposit type; DEPTH, sediment/rock; Description; Dredge; DRG; Event label; GIK/IfG; GIK17835-1; GIK17841-1; GIK17846-1; GIK17847-1; GIK17848-1; GIK17854-1; GIK17855-1; GIK17856-1; GIK17857-1; GIK17858-1; GIK17859-1; GIK17860-1; GIK17861-1; GIK17865-1; GIK17869-1; GIK17871-1; GIK17876-1; GIK17877-1; GIK17878-1; GIK17881-1; GIK17883-1; GIK17887-1; GIK17888-1; GIK17889-1; GIK17893-1; GIK17894-1; GIK17897-1; GIK17898-1; GIK17899-1; GIK17902-1; GIK17903-1; GIK17905-1; GIK17906-1; GIK17908-1; GIK17917-1; Identification; Institute for Geosciences, Christian Albrechts University, Kiel; NOAA and MMS Marine Minerals Geochemical Database; NOAA-MMS; Position; Quantity of deposit; Sediment type; Size; SO84; Sonne; South Atlantic; ST. HELENA HOTSPOT; Substrate type; Visual description
Type:
Dataset
Format:
text/tab-separated-values, 725 data points
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