Correlated Nd, Sr and Pb isotope variation in Walvis Ridge basalts and implications for the evolution of their mantle source

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doi: 10.1016/0012-821X(82)90135-2
Authors:Richardson, S. H.; Erlank, A. J.; Duncan, A. R.; Reid, D. L.
Author Affiliations:Primary:
Mass. Inst. Technol., Cent. Geoalchemy, Cambridge, MA, United States
Other:
Univ. Cape Town, South Africa
Volume Title:Earth and Planetary Science Letters
Source:Earth and Planetary Science Letters, 59(2), p.327-342. Publisher: Elsevier, Amsterdam, Netherlands. ISSN: 0012-821X
Publication Date:1982
Note:In English. 68 refs.; illus. incl. 3 anal., 1 table, sketch map
Summary:Basement intersected by three DSDP holes on the Walvis Ridge consists of submarine basalt flows and pillows with minor intercalated sediments. These holes are situated on a NNW-SSE-trending ridge block which would have closely paralleled the palaeo mid-ocean ridge. The basalts were erupted approx 70 m.y. ago, an age equivalent to that of adjacent oceanic crust in the Angola Basin. The basalt types vary from aphyric quartz tholeiites on the crest to highly plagioclase phyric olivine tholeiites on the ridge flank. These show systematic differences in incompatible trace-element and isotopic composition. The low Nd, Pb and Sr ratios of the ridge-crest basalts suggest derivation from an old Nd/Sm-, Rb/Sr- and Pb/U-enriched mantle source. The isotopic trends may be extrapolated beyond the ridge-flank basalts, with higher Nd, Pb, ratios and lower Sr ratios in the direction of increasingly Nd/Sm- , Rb/Sr- and Pb/U-depleted source compositions. Observed Zr-Ba-Nb-Y interelement relationships are inconsistent with a simple two-component model of magma mixing. In the preferred petrogenetic model, the Walvis Ridge basalts were derived by partial melting of mantle similar to an enriched MORB source which had become heterogeneous on a small scale due to the introduction of small volume melts and metasomatic fluids. [P.Br.]
Subjects:Alkaline earth metals; Basalts; Data; Deep Sea Drilling Project; Genesis; Geochemistry; Igneous rocks; Isotopes; Lava; Lead; Magmas; Mantle; Metals; Nd-144/Nd-143; Neodymium; Partial melting; Rare earths; Sr-87/Sr-86; Stable isotopes; Strontium; Upper mantle; Volcanic rocks; Atlantic Ocean; DSDP Site 525; DSDP Site 527; DSDP Site 528; IPOD; Leg 74; South Atlantic; Southeast Atlantic; Walvis Ridge; Ratios
Coordinates:S300000 S270000 E0050000 E0000000
Abstract Numbers:83M/0528
Record ID:1982057991
Copyright Information:GeoRef, Copyright 2019 American Geosciences Institute. Reference includes data from Mineralogical Abstracts, United Kingdom, Twickenham, United Kingdom
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