Geochemistry of rare earth elements in basalts from the Walvis Ridge; implications for its origin and evolution

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doi: 10.1016/0012-821X(83)90138-3
Author(s): Humphris, Susan E.; Thompson, Geoffrey
Author Affiliation(s): Primary:
Woods Hole Oceanogr. Inst., Dep. Chem., Woods Hole, MA, United States
Volume Title: Earth and Planetary Science Letters
Source: Earth and Planetary Science Letters, Vol.66, p.223-242. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X CODEN: EPSLA2
Note: In English. 41 refs.; illus. incl. 19 anal., 3 tables, sketch map
Summary: Selected basalts from a suite of dredged and drilled samples (IPOD sites 525, 527, 528 and 530) from this ridge were analysed for REE in order to investigate the origin and evolution of this major structural feature in the S Atlantic Ocean. All samples show a high degree of LREE enrichment, quite unlike the flat or depleted patterns normally observed for MORB. Basalts from sites 527, 528 and 530 show REE patterns of arcuate shape and low (Ce/Yb)N ratios (1.46-5.22). These ratios show a positive linear relationship to Nb content. The dredged basalts and basalts from site 525 have REE patterns with a fairly constant slope and higher (Ce/Yb)N ratios (4.31-8.50). The ratios of incompatible trace elements also indicate considerable variations within the groups. Hyperbolic ratios suggest that simple magma mixing between a 'hot spot' type of magma and a depleted source was an important process in parts of the Walvis Ridge. Site 525 and dredged basalts cannot be explained by this mixing process. The model proposed for the origin and evolution of this ridge involves an initial stage of eruption in which the magma was a mixture of enriched and depleted end-member sources. 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.
Year of Publication: 1983
Research Program: DSDP Deep Sea Drilling Project
IPOD International Phase of Ocean Drilling
Key Words: 02 Geochemistry; Aseismic ridges; Atlantic Ocean; Basalts; DSDP Site 525; DSDP Site 527; DSDP Site 528; DSDP Site 530; Data; Deep Sea Drilling Project; Genesis; Geochemistry; IPOD; Igneous rocks; Leg 74; Leg 75; Magmas; Metals; Plate tectonics; Rare earths; Rio Grande Rise; South Atlantic; Southeast Atlantic; Trace elements; Volcanic rocks; Walvis Ridge
Coordinates: S310000 S300000 W0350000 W0360000
S290500 S280000 E0030000 E0010000
Record ID: 1984024937
Copyright Information: GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom