Humphris, Susan E; Thompson, Geoffrey (1983): Geochemistry of rare earth elements in basalts from Walvis Ridge [dataset publication series]. PANGAEA, https://doi.org/10.1594/PANGAEA.714985, Supplement to: Humphris, SE; Thompson, G (1983): Geochemistry of rare earth elements in basalts from the Walvis Ridge: implications for its origin and evolution. Earth and Planetary Science Letters, 66, 223-242, https://doi.org/10.1016/0012-821X(83)90138-3
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Abstract:
Selected basalts from a suite of dredged and drilled samples (IPOD sites 525, 527, 528 and 530) from the Walvis Ridge have been analysed to determine their rare earth element (REE) contents in order to investigate the origin and evolution of this major structural feature in the South Atlantic Ocean. All of the samples show a high degree of light rare earth element (LREE) enrichment, quite unlike the flat or depleted patterns normally observed for normal mid-ocean ridge basalts (MORBs). Basalts from Sites 527, 528 and 530 show REE patterns characterised by an arcuate shape and relatively low (Ce/Yb)N ratios (1.46-5.22), and the ratios show a positive linear relationship to Nb content. A different trend is exhibited by the dredged basalts and the basalts from Site 525, and their REE patterns have a fairly constant slope, and higher (Ce/Yb)N ratios (4.31-8.50).
These differences are further reflected in the ratios of incompatible trace elements, which also indicate considerable variations within the groups. Mixing hyperbolae for these ratios suggest that simple magma mixing between a 'hot spot' type of magma, similar to present-day volcanics of Tristan da Cunha, and a depleted source, possibly similar to that for magmas being erupted at the Mid-Atlantic Ridge, was an important process in the origin of parts of the Walvis Ridge, as exemplified by Sites 527, 528 and 530. Site 525 and dredged basalts cannot be explained by this mixing process, and their incompatible element ratios suggest either a mantle source of a different composition or some complexity to the mixing process. In addition, the occurrence of different types of basalt at the same location suggests there is vertical zonation within the volcanic pile, with the later erupted basalts becoming more alkaline arid more enriched in incompatible elements.
The model proposed for the origin and evolution of the Walvis Ridge involves an initial stage of eruption in which the magma was essentially a mixture of enriched and depleted end-member sources, with the N-MORB component being small. The dredged basalts and Site 525, which represent either later-stage eruptives or those close to the hot spot plume, probably result from mixing of the enriched mantle source with variable amounts and variable low degrees of partial melting of the depleted mantle source. As the volcano leaves the hot spot, these late-stage eruptives continue for some time. The change from tholeiitic to alkalic volcanism is probably related either to evolution in the plumbing system and magma chamber of the individual volcano, or to changes in the depth of origin of the enriched mantle source melt, similar to processes in Hawaiian volcanoes.
Project(s):
Deep Sea Drilling Project (DSDP)
Coverage:
Median Latitude: -27.830321 * Median Longitude: 2.553535 * South-bound Latitude: -37.095000 * West-bound Longitude: -7.778300 * North-bound Latitude: -19.187700 * East-bound Longitude: 9.385800
Date/Time Start: 1980-06-10T00:00:00 * Date/Time End: 1980-07-29T00:00:00
Event(s):
74-525A * Latitude: -29.070700 * Longitude: 2.985300 * Date/Time: 1980-06-10T00:00:00 * Elevation: -2467.0 m * Penetration: 678.1 m * Recovery: 406.6 m * Location: South Atlantic/CREST * Campaign: Leg74 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 62 cores; 549.7 m cored; 6 m drilled; 74 % recovery
74-527 * Latitude: -28.041500 * Longitude: 1.763300 * Date/Time: 1980-06-28T00:00:00 * Elevation: -4428.0 m * Penetration: 384.5 m * Recovery: 243.4 m * Location: South Atlantic Ocean * Campaign: Leg74 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 43 cores; 380 m cored; 4.5 m drilled; 64.1 % recovery
74-528 * Latitude: -28.524800 * Longitude: 2.324000 * Date/Time: 1980-07-04T00:00:00 * Elevation: -3800.0 m * Penetration: 555 m * Recovery: 271.9 m * Location: South Atlantic/RIDGE * Campaign: Leg74 * Basis: Glomar Challenger * Method/Device: Drilling/drill rig (DRILL) * Comment: 47 cores; 441 m cored; 0 m drilled; 61.7 % recovery
License:
Creative Commons Attribution 3.0 Unported (CC-BY-3.0)
Size:
2 datasets
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Datasets listed in this publication series
- Humphris, SE; Thompson, G (1983): (Table 1) Major, trace and rare earth element concentrations of dredged sediments. https://doi.org/10.1594/PANGAEA.714983
- Humphris, SE; Thompson, G (1983): (Table 1) Major, trace and rare earth element concentrations of sediments from DSDP Legs 74 and 75. https://doi.org/10.1594/PANGAEA.714982