ManuscriptView metadata, citation and similar papers at core.ac.uk brought to you by CORE provided by Woods Hole Open Access Server 1 Timescales of Magmatic Processes and Eruption Ages of the Nyiragongo 2 volcanics from 238U-230Th-226Ra-210Pb disequilibria. 3 4 Ramananda Chakrabarti 1#*, Kenneth W. W. Sims2, 3, Asish R. Basu1, Mark Reagan4, 5 Jacques Durieux5 6 7 1. Department of Earth and Environmental Sciences, University of Rochester, 8 Rochester, NY-14627 9 10 2. Department of Geology and Geophysics, Woods Hole Oceanographic Institution, 11 Woods Hole, Massachusetts, MA 02543 12 13 3. Dept of Geology and Geophysics, University of Wyoming, Laramie, WY 82071 14 15 4. Department of Geoscience, University of Iowa, Iowa City, Iowa 52242 16 17 5. Deceased, formerly at Unite De Gestion Des Risques Volcaniques, UNDP / 18 UNOPS, Goma - Nord-Kivu - RD Congo 19 20 # Current address: Department of Earth and Planetary Sciences, Harvard University, 21 Cambridge, MA 02138 22 * Corresponding author - email:
[email protected] 23 24 Keywords: Silica-undersaturated volcanism, 238U-230Th-226Ra-210Pb series 25 disequilibria, Magma transport and residence time, Carbonate metasomatism, Volcanic 26 hazard assessment. 27 28 29 Abstract 30 The silica-undersaturated Nyiragongo volcanics, located in the East African rift, have 31 globally unique chemical compositions and unusually low viscosities, only higher than 32 carbonatite lavas, for terrestrial silicate magmas. We report 238U-230Th-226Ra-210Pb series 33 disequilibria in 13 recent and prehistoric lava samples from Nyiragongo including those 34 from the 2002 flank eruption and a 2003 lava lake sample. (230Th/238U) ranges from 0.90- 35 0.97 in the recent lavas and from 0.94-1.09 in the prehistoric lavas.