Éditeur(s) : Université de Bretagne Occidentale
Résumé : Ce travail a été réalisé dans un esprit de géochimie comparée des éléments de transition hygromagmatophiles (Treuil, 1973) ou hygromagmaphiles, éléments traces ayant une affinité pour le liquide silicaté.

Droits : UBO
http://archimer.ifremer.fr/doc/00034/14549/11805.pdf
http://archimer.ifremer.fr/doc/00034/14549/

Éditeur(s) : HAL CCSD Elsevier
Résumé : International audience
This study presents new geochemical data on 26 mafic lavas from the Middle Atlas and Central Morocco volcanic provinces, including Miocene nephelinites and Pliocene-Quaternary (3.9-0.6Ma) nephelinites, basanites, alkali and subalkaline basalts. Most of them represent near-primary magmas, although some alkali basalts were derived from the minor fractionation of olivine and diopside phenocrysts. These evolved samples and the subalkaline basalt display higher 207Pb/204Pb and Zr/Nb ratios and lower εNd consistent with their contamination by lower crustal granulites during an open fractionation process. The progressive enrichment in incompatible elements observed from alkali basalts to nephelinites suggests their derivation from decreasing partial melting degrees of an enriched mantle source located at the garnet-spinel transition zone. The strong negative spikes observed for K in multielement patterns indicate that this source contained a residual pargasitic amphibole. We propose that partial melting occurred at around 2GPa, i.e. near the lithosphere-asthenosphere boundary beneath the Middle Atlas (60-80km).The trace element and isotopic Sr-Nd-Pb-Hf signature of the uncontaminated lavas displays a geochemical flavour intermediate between those of high μ (HIMU), "C", and enriched mantle components. It is very similar to that of abundant metasomatic amphibole- and clinopyroxene-rich lithospheric peridotites and pyroxenites carried by Middle Atlas lavas, which likely represent an analog of the source of these lavas. It is therefore not necessary to postulate the contribution of a "fresh" asthenospheric mantle to their genesis. We propose that they resulted from the partial melting of the base of a veined lithospheric mantle metasomatised during the late Cretaceous by alkaline melts from the Central Atlantic plume, the ancestor of the Canary plume. Melting was probably triggered by the flux of a hot mantle within a regional SW-NE sub-lithospheric channel, in response to either the Alboran slab retreat or edge-driven convection around the West African craton.
ISSN: 0024-4937

insu-01056523
https://hal-insu.archives-ouvertes.fr/insu-01056523
DOI : 10.1016/j.lithos.2014.07.009

Éditeur(s) : Texas A & M University, Ocean Drilling Program, College Station, TX, United States (USA)
Résumé : This chapter presents major oxide and trace element determinations of igneous whole-rock compositions from sites drilled during Leg 60 and electron microprobe mineral and glass analyses of samples from Sites 454 and 458. Interarc basin basalts from the Mariana Trough (Sites 454 and 456) are similar in all respects to depleted mid-ocean ridge basalts. Basaltic andesites and andesites from Site 458 (Mariana fore-arc region) are more depleted than mid-ocean ridge basalts and show different geochemical behavior for Zr-, Hf, and Ti when compared on an extended Coryell- Masuda plot. [NOT CONTROLLED OCR]
Initial Reports of the Deep Sea Drilling Project (Texas A & M University, Ocean Drilling Program, College Station, TX, United States (USA)), 1981 , Vol. 60 , P. 657-677

Droits : Texas A & M University, Ocean Drilling Program, College Station, TX, United States (USA)
http://archimer.ifremer.fr/doc/1981/publication-5308.pdf
http://archimer.ifremer.fr/doc/00000/5308/