Catalogo Articoli (Spogli Riviste)

OPAC HELP

Titolo:
Depletion events, nature of metasomatizing agent and timing of enrichment processes in lithospheric mantle xenoliths from the Veneto Volcanic Province
Autore:
Beccaluva, L; Bonadiman, C; Coltorti, M; Salvini, L; Siena, F;
Indirizzi:
Univ Ferrara, Inst Mineral, I-44100 Ferrara, Italy Univ Ferrara Ferrara Italy I-44100 Inst Mineral, I-44100 Ferrara, Italy
Titolo Testata:
JOURNAL OF PETROLOGY
fascicolo: 1, volume: 42, anno: 2001,
pagine: 173 - 187
SICI:
0022-3530(200101)42:1<173:DENOMA>2.0.ZU;2-6
Fonte:
ISI
Lingua:
ENG
Soggetto:
OCEANIC UPPER-MANTLE; EARTHS UPPER-MANTLE; PERIDOTITE XENOLITHS; CANARY-ISLANDS; CARBONATITE METASOMATISM; SILICATE MELTS; LA PALMA; ULTRAMAFIC XENOLITHS; ABYSSAL PERIDOTITES; WESTERN VICTORIA;
Keywords:
mantle xenoliths; metasomatic melts; trace elements; clino-pyroxenes; glasses;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
56
Recensione:
Indirizzi per estratti:
Indirizzo: Beccaluva, L Univ Ferrara, Inst Mineral, Corso Ercole I Este 32, I-44100 Ferrara, Italy Univ Ferrara Corso Ercole I Este 32 Ferrara Italy I-44100 ly
Citazione:
L. Beccaluva et al., "Depletion events, nature of metasomatizing agent and timing of enrichment processes in lithospheric mantle xenoliths from the Veneto Volcanic Province", J PETROLOGY, 42(1), 2001, pp. 173-187

Abstract

Mantle xenoliths included in the alkaline basic lavas from the Paleogene Veneto Volcanic Province (VVP) consist of predominant spinel lherozlites (21-6% clinopyroxene) and minor spinel harzburgites (4 2% clinopyroxene), mainly protogranular textured. Most of the xenoliths show superimposed texturalevidence of metasomatic processes, consisting of reaction patches and spongy clinopyroxenes, variably associated with glass and secondary olivine, clinopyroxene, spinel and feldspar. Whole-rock and mineral major and trace element data indicate a complex history of depletion and enrichment processesundergone by the continental lithospheric mantle beneath a within-plate region. Protogranular-textured clinopyroxenes from lherzolites show heavy rare earth element (HREE) contents similar to 10 times chondrite and strong light REE (LREE) depletion [(La/Yb)(N) = 0.002-0.025)], whereas those in harzburgites vary from slightly LREE depleted to LREE enriched [(La/Yb)(N) = 0.64 4.00], with much lower HREE contents (similar to 3 times chondrite). Most HREE patterns can be reproduced by a simple fractional melting model and extraction of similar to 5-22% basic melts, starting from the most fertile VVP spinel lherzolite. The anomalously low HREE contents of clinopyroxenes in a single lherzolite sample, however require more complex processes possibly involving multistage melting of garnet- to spinel-bearing sources, or diffusion-controlled melt-peridotite interactions. The slightly LREE-depleted to LREE-enriched patterns of protogranular-textured clinopyroxenes in harzburgites and spongy clinopyroxenes in lherzolites [(La/Yb)(N) = 0.27-5.67]can be accounted for by metasomatic enrichment events. Major and trace element mass balance calculations were successfully carried out to quantitatively model the metasomatic parageneses by the addition of 1 6% of Na-alkaline basic melt/s. Magmatic analogues of the modelled metasomatizing agent/s occur in the South Alpine domain as late Cretaceous lamprophyric dykes, as well as VVP alkaline basic lavas. An estimate of timing of the enrichment processes was achieved by a REE inward diffusion model in primary and spongy clinopyroxenes, assuming LREE-enriched secondary clinopyroxenes as the boundary surface composition. Model calculations imply a complete chemical rehomogenization of a 1 mm crystal in a time span of 4.8 16 kyr. Consequently, the observed REE zoning of clinopyroxenes, together with the presence of glassy patches, indicates that the most recent metasomatic processes occurredshortly before the entrainment of mantle xenoliths by the host lavas.

ASDD Area Sistemi Dipartimentali e Documentali, Università di Bologna, Catalogo delle riviste ed altri periodici
Documento generato il 12/07/20 alle ore 13:23:05