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Full-Text Articles in Physical Sciences and Mathematics
Understanding Melt Generation Beneath The Slow-Spreading Kolbeinsey Ridge Using (238)U, (230)Th, And (231)Pa Excesses, L. J. Elkins, Ken Sims, J. Prytulak, T. Elliott, N. Mattielli, J. Blichert-Toft, J. Blusztajn, N. Dunbar, C. Devey, D. F. Mertz, J. G. Schilling, M. Murrell
Understanding Melt Generation Beneath The Slow-Spreading Kolbeinsey Ridge Using (238)U, (230)Th, And (231)Pa Excesses, L. J. Elkins, Ken Sims, J. Prytulak, T. Elliott, N. Mattielli, J. Blichert-Toft, J. Blusztajn, N. Dunbar, C. Devey, D. F. Mertz, J. G. Schilling, M. Murrell
Ken Sims
To examine the petrogenesis and sources of basalts from the Kolbeinsey Ridge, one of the shallowest locations along the global ridge system, we present new measurements of Nd, Sr, Hf, and Pb isotopes and U-series disequilibria on 32 axial basalts. Young Kolbeinsey basalts (full-spreading rate = 1.8 cm/yr; 67 degrees 05'-70 degrees 26'N) display (230Th/238U) < 1 and (230Th/238U) > 1 with (230Th/238U) from 0.95 to 1.30 and have low U (11.3-65.6 ppb) and Th (33.0 ppb-2.40 ppm) concentrations. Except for characteristic isotopic enrichment near the Jan Mayen region, the otherwise depleted Kolbeinsey basalts (e. g. 87Sr/86Sr = 0.70272-0.70301, epsilon(Nd) = 8.4-10.5, epsilon(Hf) = 15.4-19.6 …
Temporal Isotope Variations In Glacial-Postglacial Lavas From Northern Iceland, E. M. Mervine, Ken Sims, J. Blichert-Toft, J. Maclennan, J. Blusztajn, K. Gronvold
Temporal Isotope Variations In Glacial-Postglacial Lavas From Northern Iceland, E. M. Mervine, Ken Sims, J. Blichert-Toft, J. Maclennan, J. Blusztajn, K. Gronvold
Ken Sims
Meeting abstract for “Temporal Isotope Variations in Glacial-Postglacial Lavas from Northern Iceland,” June 2010.
Combined U-Th/He And (40)Ar/(39)Ar Geochronology Of Post-Shield Lavas From The Mauna Kea And Kohala Volcanoes, Hawaii, S. M. Aciego, F. Jourdan, D. J. Depaolo, B. M. Kennedy, P. R. Renne, Ken Sims
Combined U-Th/He And (40)Ar/(39)Ar Geochronology Of Post-Shield Lavas From The Mauna Kea And Kohala Volcanoes, Hawaii, S. M. Aciego, F. Jourdan, D. J. Depaolo, B. M. Kennedy, P. R. Renne, Ken Sims
Ken Sims
Late Quaternary, post-shield lavas from the Mauna Kea and Kohala volcanoes on the Big Island of Hawaii have been dated using the 40Ar/39Ar and U–Th/He methods. The objective of the study is to compare the recently demonstrated U–Th/He age method, which uses basaltic olivine phenocrysts, with 40Ar/39Ar ages measured on groundmass from the same samples. As a corollary, the age data also increase the precision of the chronology of volcanism on the Big Island. For the U–Th/He ages, U, Th and He concentrations and isotopes were measured to account for U-series disequilibrium and initial He. Single analyses U–Th/He ages for …
Insight Into Volatile Behavior At Nyamuragira Volcano (D.R. Congo, Africa) Through Olivine-Hosted Melt Inclusions, E. M. Head, A. M. Shaw, P. J. Wallace, Ken Sims, S. A. Carn
Insight Into Volatile Behavior At Nyamuragira Volcano (D.R. Congo, Africa) Through Olivine-Hosted Melt Inclusions, E. M. Head, A. M. Shaw, P. J. Wallace, Ken Sims, S. A. Carn
Ken Sims
We present new olivine-hosted melt inclusion volatile (H(2)O, CO(2), S, Cl, F) and major element data from five historic eruptions of Nyamuragira volcano (1912, 1938, 1948, 1986, 2006). Host-olivine Mg#'s range from 71 to 84, with the exception of the 1912 sample (Mg# = 90). Inclusion compositions extend from alkali basalts to basanite-tephrites. Our results indicate inclusion entrapment over depths ranging from 3 to 5 km, which agree with independent estimates of magma storage depths (3-7 km) based on geophysical methods. Melt compositions derived from the 1986 and 2006 Nyamuragira tephra samples best represent pre-eruptive volatile compositions because these samples …