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238U-230Th-226Ra-210Pb-210Po, 232Th-228Ra, and 235U-231Pa constraints on the ages and petrogenesis of Vailulu'u and Malumalu Lavas, Samoa

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dc.contributor.author Sims, Kenneth W. W.
dc.contributor.author Hart, Stanley R.
dc.contributor.author Reagan, Mark K.
dc.contributor.author Blusztajn, Jerzy S.
dc.contributor.author Staudigel, Hubert
dc.contributor.author Sohn, Robert A.
dc.contributor.author Layne, Graham D.
dc.contributor.author Ball, Lary A.
dc.contributor.author Andrews, J. E.
dc.date.accessioned 2010-04-20T14:29:31Z
dc.date.available 2010-04-20T14:29:31Z
dc.date.issued 2008-04-01
dc.identifier.citation Geochemistry Geophysics Geosystems 9 (2008): Q04003 en_US
dc.identifier.uri http://hdl.handle.net/1912/3263
dc.description Author Posting. © American Geophysical Union, 2008. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry Geophysics Geosystems 9 (2008): Q04003, doi:10.1029/2007GC001651. en_US
dc.description.abstract We report 238U-230Th-226Ra-210Pb-210Po, 232Th-228Ra and 235U-231Pa measurements for a suite of 14 geologically and geochemically well-characterized basaltic samples from the Samoan volcanoes Vailulu'u, Malumalu, and Savai'i. Maximum eruption ages based on the presence of parent-daughter disequilibria indicate that Vailulu'u is magmatically productive with young lavas (<8 Ka) resurfacing both its summit crater and lower flanks. 210Pb and 210Po measurements indicate that several flows have erupted within its summit crater in the past 100 years, with the newest observed flow being erupted in November of 2004. For lavas which have eruption ages that are demonstrably young, relative to the half-lives of 230Th, 231Pa, and 226Ra, we interpret their 238U -230Th, 235U-231Pa and 230Th - 226Ra disequilibria in terms of the magmatic processes occurring beneath the Samoan Islands. (230Th/238U) > 1 indicates that garnet is required as a residual phase in the magma sources for all these lavas. The large range of (238U/232Th) and (230Th/232Th) is attributed to long-term source variation. The Samoan basalts are all alkaline basalts and show significant 230Th and 231Pa excesses but limited variability, indicating that they have been derived by small but similar extents of melting. Their (230Th/238U), (231Pa/235U) and Sm/Nd fractionation are consistent with correlations among other ocean island basalt suites (particularly Hawaii) which show that (230Th/238U) and (231Pa/235U) of many OIBS can be explained by simple time-independent models. Interpretation of the 226Ra data requires time-dependent melting models. Both chromatographic porous flow and dynamic melting of a garnet peridotite source can adequately explain the combined U-Th-Ra and U-Pa data for these Samoan basalts. Several young samples from the Vailulu'u summit crater also exhibit significant 210Pb deficits that reflect either shallow magmatic processes or continuous magma degassing. In both cases, decadal residence times are inferred from these 210Pb deficits. The young coeval volcanism on Malumalu and Vailulu'u suggests the Samoa hot spot is currently migrating to the northeast due to dynamic interaction with the Tonga slab. en_US
dc.description.sponsorship Support for this research was provided by NSF grants EAR-9909473 (KWWS), EAR-0509891 (SRH), EAR- 0609670 (MKR) and EAR-0504362 (MKR). en_US
dc.format.mimetype application/pdf
dc.language.iso en_US en_US
dc.publisher American Geophysical Union en_US
dc.relation.uri http://dx.doi.org/10.1029/2007GC001651
dc.subject U-series disequilibria en_US
dc.subject Samoa en_US
dc.subject Eruption ages en_US
dc.title 238U-230Th-226Ra-210Pb-210Po, 232Th-228Ra, and 235U-231Pa constraints on the ages and petrogenesis of Vailulu'u and Malumalu Lavas, Samoa en_US
dc.type Article en_US
dc.identifier.doi 10.1029/2007GC001651


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