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Evidence from Sardinian basalt geochemistry for recycling of plume heads into the Earth's mantle.
MedLine Citation:
PMID:  11130068     Owner:  NLM     Status:  PubMed-not-MEDLINE    
Up to 10 per cent of the ocean floor consists of plateaux--regions of unusually thick oceanic crust thought to be formed by the heads of mantle plumes. Given the ubiquitous presence of recycled oceanic crust in the mantle source of hotspot basalts, it follows that plateau material should also be an important mantle constituent. Here we show that the geochemistry of the Pleistocene basalts from Logudoro, Sardinia, is compatible with the remelting of ancient ocean plateau material that has been recycled into the mantle. The Sr, Nd and Hf isotope compositions of these basalts do not show the signature of pelagic sediments. The basalts' low CaO/Al2O3 and Ce/Pb ratios, their unradiogenic 206Pb and 208Pb, and their Sr, Ba, Eu and Pb excesses indicate that their mantle source contains ancient gabbros formed initially by plagioclase accumulation, typical of plateau material. Also, the high Th/U ratios of the mantle source resemble those of plume magmas. Geochemically, the Logudoro basalts resemble those from Pitcairn Island, which contain the controversial EM-1 component that has been interpreted as arising from a mantle source sprinkled with remains of pelagic sediments. We argue, instead, that the EM-1 source from these two localities is essentially free of sedimentary material, the geochemical characteristics of these lavas being better explained by the presence of recycled oceanic plateaux. The storage of plume heads in the deep mantle through time offers a convenient explanation for the persistence of chemical and mineralogical layering in the mantle.
D Gasperini; J Blichert-Toft; D Bosch; A Del Moro; P Macera; P Télouk; F Albarède
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Publication Detail:
Type:  Journal Article    
Journal Detail:
Title:  Nature     Volume:  408     ISSN:  0028-0836     ISO Abbreviation:  Nature     Publication Date:  2000 Dec 
Date Detail:
Created Date:  2000-12-20     Completed Date:  2001-01-11     Revised Date:  2003-10-31    
Medline Journal Info:
Nlm Unique ID:  0410462     Medline TA:  Nature     Country:  England    
Other Details:
Languages:  eng     Pagination:  701-4     Citation Subset:  -    
Ecole Normale Supérieure, Lyon, France.
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