Computer Science
Scientific paper
May 1995
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=1995e%26psl.132...25c&link_type=abstract
Earth and Planetary Science Letters, vol. 132, Issue 1-4, pp.25-41
Computer Science
39
Scientific paper
238 U- 230 Th- 226 Ra- 210 Pb disequilibria and ratios have been measured in a suite of prehistoric and historical lava flows from Mt. Etna. Whereas Th isotope ratios remain nearly constant during the whole period studied, 226 Ra and data allow us to distinguish two main episodes in the volcanic history. For most of the past two millenia until 1970 A.D., Ra and Ba exhibit a similar behaviour (decreasing ( ) and ratios with increasing Th contents), which is mainly controlled by plagioclase fractionation during differentiation from hawaiites to mugearites. This differentiation occurs on a short timescale ( 200 yr) and the parental hawaiitic magma seems to have maintained a constant ( ) ratio during the whole period. The 226 Ra- 230 Th data are interpreted in the context of a steady-state deep reservoir: an upper limit of 1500 yr is derived for the residence time of the magma in this reservoir, which could have a maximum volume of 150-300 km 3 , much smaller than the volume inferred from seismic studies. The present period of activity, after 1970 A.D., is characterized by the injection in the shallow plumbing system of a new basic magma enriched in Ra, K, Rb and Cs, with a higher Sr isotope ratio (0.70359 compared to 0.70340 just before 1970 A.D.). These peculiarities probably result from selective crustal contamination. Mixing of this magma with that of the pre-1970 period in the upper plumbing system explains the geochemical variability of the present lavas. 228 Ra and 210 Pb data and consideration of effusion rates suggest that the injection of the contaminated magma in the shallow plumbing system took place in 1950 A.D. The volume of this shallow system is rather small (~ 0.5 km 3 ), with a transfer and residence time of the magma of the order of a few tens of years. Finally, 226 Ra- 230 Th disequilibria provide a new method for dating prehistoric (< 8000 yr) and historical flows of unknown ages on Mt. Etna.
Condomines Michel
Michaud Valérie
Tanguy Jean-Claude
No associations
LandOfFree
Magma dynamics at Mt Etna: Constraints from U-Th-Ra-Pb radioactive disequilibria and Sr isotopes in historical lavas does not yet have a rating. At this time, there are no reviews or comments for this scientific paper.
If you have personal experience with Magma dynamics at Mt Etna: Constraints from U-Th-Ra-Pb radioactive disequilibria and Sr isotopes in historical lavas, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Magma dynamics at Mt Etna: Constraints from U-Th-Ra-Pb radioactive disequilibria and Sr isotopes in historical lavas will most certainly appreciate the feedback.
Profile ID: LFWR-SCP-O-1060259