Italiano, F. and Nuccio, P.M. and Nakai, S. and Wakita, H. (1999) Light-noble-gas isotopic ratios in gases from Mt. Etna (Southern Italy): Implications for mantle contamination and volcanic activity. Il nuovo cimento C, 22 C (3-4). pp. 247-252. ISSN 1826-9885
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Abstract
Helium isotopic ratios in gases from Mt. Etna are in the range of 6–7 Ra (Ra = atmospheric 3He /4He ratio 1.431026), below the MORB’s typical range, and fall in the same range of those measured in xenoliths from the Northern part of Europe, where a crustal contamination of the sub-continental mantle has been recognized. Taking into account the light-noble-gas isotopic signature of gas samples coming from the Etnean area, it seems that in this area the crustal contamination played a minor role. Instead, processes that enriched the original MORB-type mantle in incompatible elements, have to be considered. The 3He /4He ratios are, thus, lowered because of 4He produced by radioactive decay of U and Th. On the other hand, helium isotopic ratios have shown wide temporal variations sometimes reaching values as high as 7.6 Ra, out of the typical Etnean range. As these unusually high ratios have been measured during phases of unrest of the volcanic activity at Mt. Etna, this apparent discrepancy in the helium isotopic ratios is considered, as the effect of fractionation processes occurred during magma uprising.
| Item Type: | Article |
|---|---|
| Additional Information: | Paper presented at the “Fourth International Conference on Rare Gas Geochemistry”, Rome, October 8-10, 1997. |
| Uncontrolled Keywords: | Structure of the crust and upper mantle; isotopic composition/chemistry; conference proceedings |
| Subjects: | 500 Scienze naturali e Matematica > 550 Scienze della Terra |
| Depositing User: | Marina Spanti |
| Date Deposited: | 18 Sep 2018 14:47 |
| Last Modified: | 18 Sep 2018 14:47 |
| URI: | http://eprints.bice.rm.cnr.it/id/eprint/13240 |
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