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Titolo:
H2O abundance in depleted to moderately enriched mid-ocean ridge magmas; Part I: Incompatible behaviour, implications for mantle storage, and origin of regional variations
Autore:
Danyushevsky, LV; Eggins, SM; Falloon, TJ; Christie, DM;
Indirizzi:
Univ Tasmania, Sch Earth Sci, Hobart, Tas 7001, Australia Univ Tasmania Hobart Tas Australia 7001 Sci, Hobart, Tas 7001, Australia Australian Natl Univ, Res Sch Earth Sci, Canberra, ACT 2601, Australia Australian Natl Univ Canberra ACT Australia 2601 rra, ACT 2601, Australia Australian Natl Univ, ARC Key Ctr Geochem Evolut & Metallogeny Continen, Dept Geol, Canberra, ACT 2601, Australia Australian Natl Univ Canberra ACT Australia 2601 rra, ACT 2601, Australia Oregon State Univ, Coll Ocean & Atmospher Sci, Corvallis, OR 97331 USA Oregon State Univ Corvallis OR USA 97331 her Sci, Corvallis, OR 97331 USA
Titolo Testata:
JOURNAL OF PETROLOGY
fascicolo: 8, volume: 41, anno: 2000,
pagine: 1329 - 1364
SICI:
0022-3530(200008)41:8<1329:HAIDTM>2.0.ZU;2-S
Fonte:
ISI
Lingua:
ENG
Soggetto:
EAST PACIFIC RISE; AUSTRALIAN-ANTARCTIC DISCORDANCE; CARBON-DIOXIDE SOLUBILITIES; SOLIDUS PERIDOTITE MELTS; MARBLE-CAKE MANTLE; PARTITION-COEFFICIENTS; BASALTIC GLASSES; LAMONT SEAMOUNT; MIDOCEAN RIDGES; ION MICROPROBE;
Keywords:
glass; geochemistry; H2O; MORB; petrology;
Tipo documento:
Article
Natura:
Periodico
Settore Disciplinare:
Physical, Chemical & Earth Sciences
Citazioni:
83
Recensione:
Indirizzi per estratti:
Indirizzo: Danyushevsky, LV Univ Tasmania, Sch Earth Sci, GPO Box 252-79, Hobart, Tas7001, Australia Univ Tasmania GPO Box 252-79 Hobart Tas Australia 7001 ia
Citazione:
L.V. Danyushevsky et al., "H2O abundance in depleted to moderately enriched mid-ocean ridge magmas; Part I: Incompatible behaviour, implications for mantle storage, and origin of regional variations", J PETROLOGY, 41(8), 2000, pp. 1329-1364

Abstract

The H2O contents and trace-element abundances are presented for two well-studied suites of mid-ocean ridge basalt (MORB) glasses from the Northern East Pacific Rise (EPR, 9-11 degrees N) and the South East Indian Ridge (SEIR, 127-129 degrees E). Exactly the same region of the glass samples has beenanalysed for these components using microbeam techniques. Our data allow examination of the fine details of H2O geochemical behaviour during MORB genesis. We demonstrate that relative H2O contents [i.e. H2O/(another incompatible element)] vary systematically with increasing (La/Sm)(N) in Morb glasses from both the EPR and SEIR. This indicates that H2O behaves like other incompatible (in peridotite mineralogies) elements during MORB petrogenesis,and is primarily controlled by solid-melt partitioning. However, the relative H2O contents of MORB glasses from the SEIR are higher than in glasses from the EPR at a given (La/SM)(N), demonstrating global variations in the H2O contents of MORB. Despite regional differences in relative H2O contents,the incompatible behaviour of H2O is similar in both studied regions. The relative incompatibility of H2O varies systematically with increasing (La/Sm)(N): in depleted MORB, H2O is similar to La whereas in EMORB, H2O is similar to Ce. Similar patterns of varying relative incompatibility (to REE) are displayed by Zr, Hf, and P. Our data are best explained if H2O is stored in the mantle in the same phase with LREE (clinopyroxene?) at sub-solidus. Regional variations in relative H2O contents in EMORB that have more radiogenic Sr, Nd and Pb isotopes might be explained by differences in the natureof enriched components recycled via subduction processes. However, when EMORB have the same radiogenic isotope compositions as NMORB within a segment, relative H2O contents in EMORB probably reflect local processes that leadto enrichment in incompatible elements. Regional differences in relative H2O contents of NMORB may reflect either initial variations in the Earth's mantle or inhomogeneities left after formation of the continental crust.

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Documento generato il 05/04/20 alle ore 22:59:59