226 Ra-excess during the 1631-1944 activity period of Mt. Vesuvius (Italy): a model of alpha recoil enrichment in a metasomatized mantle and implications on the current state of the magmatic system (Articolo in rivista)

Type
Label
  • 226 Ra-excess during the 1631-1944 activity period of Mt. Vesuvius (Italy): a model of alpha recoil enrichment in a metasomatized mantle and implications on the current state of the magmatic system (Articolo in rivista) (literal)
Anno
  • 2004-01-01T00:00:00+01:00 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#doi
  • 10.1016/S0016-7037(03)00236-9 (literal)
Alternative label
  • Voltaggio M., Branca M., Tedesco D., Tuccimei P., Di Pietro L. (2004)
    226 Ra-excess during the 1631-1944 activity period of Mt. Vesuvius (Italy): a model of alpha recoil enrichment in a metasomatized mantle and implications on the current state of the magmatic system
    in Geochimica et cosmochimica acta
    (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#autori
  • Voltaggio M., Branca M., Tedesco D., Tuccimei P., Di Pietro L. (literal)
Pagina inizio
  • 167 (literal)
Pagina fine
  • 181 (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroVolume
  • 68 (literal)
Rivista
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#numeroFascicolo
  • 1 (literal)
Note
  • Scopu (literal)
  • ISI Web of Science (WOS) (literal)
Http://www.cnr.it/ontology/cnr/pubblicazioni.owl#affiliazioni
  • Voltaggio Mario (Istituto di Geologia ambientale e geoingegneria) Marilì Branca (Istituto di Geologia ambientale e geoingegneria) Tedesco Dario ( Dipartimento di Scienze ambientali,Università Napoli 2) Tuccimei Paola( Dipartimento di Scienze Geologiche, Università Roma Tre) Di Pietro Laura (Dipartimento di Scienze della Terra, Università La Sapienza) (literal)
Titolo
  • 226 Ra-excess during the 1631-1944 activity period of Mt. Vesuvius (Italy): a model of alpha recoil enrichment in a metasomatized mantle and implications on the current state of the magmatic system (literal)
Abstract
  • Abstract--The origin of the 226Ra-excess during the last cycle of Vesuvius activity was investigated by high-resolution ?-spectrometry, TIMS and EDXRF. Lavas display high initial 226Ra-excess (500 -1000%),similar (230Th/232Th) activity ratios(0.87- 0.91) and most samples show significant 238U-excess. During the period 1631-1944 the initial absolute 226Ra-excess reached the highest values (19 - 44 dpm g-?1) recorded for earth volcanoes. Crystal fractionation and particularly leucite floating did not cause the 226Ra-excess in spite of the high226Ra activity (21- 85 dpm g-?1) in leucite. The presence of phlogopite in the mantle source, documented by field and petrological evidences on local mantle-derived xenoliths, rules out that equilibrium partial melting can be responsible for the 226Ra-excess. This primary feature may be explained by a multistage process involving metasomatic mantle fluids (MMFs) flowing through a mantle wedge where U is concentrated as U-accessory minerals deposited along microfractures. Fluids, passing through the mantle wedge, are supplied of226Ra,230Th and 234U by ?-decay recoil of parent nuclides from U-enriched microfractures. This model calculates that the ascent time of fluids through the mantle wedge was ? 12 ka. Successively MMFs mixed with mantle-derived melts, giving rise to2 26Ra-enriched magmas, which entered the Vesuvius plumbing system less than 7 ka. Crystal fractionation did not affect extensively the initial 226Ra/Ba ratio,which varied in the 1631-1944 period according to a pattern reflecting periodic inputs of 226Ra-enriched magma, variable reservoir volumes and residence times in magmatic chamber(s). The temporal trend of the reservoir volumes, extrapolated to the present time, indicates a volume of magma of ? 0.021 km3, stored most probably in a shallow chamber. (literal)
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