Insight into volatile behavior at Nyamuragira volcano (D.R. Congo, Africa) through olivine-hosted melt inclusions
Head, Elisabet M.
Shaw, Alison M.
Wallace, Paul J.
Sims, Kenneth W. W.
Carn, Simon A.
MetadataShow full item record
We present new olivine-hosted melt inclusion volatile (H2O, CO2, 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 contain naturally glassy inclusions that underwent less post-entrapment modification than crystallized inclusions. Volatile concentrations of the 1986 and 2006 samples are as follows: H2O ranged from 0.6 to 1.4 wt %, CO2 from 350 to 1900 ppm, S from 1300 to 2400 ppm, Cl from 720 to 990 ppm, and F from 1500 to 2200 ppm. Based on FeOT and S data, we suggest that Nyamuragira magmas have higher fO2 (>NNO) than MORB. We estimate the total amount of sulfur dioxide (SO2) released from the 1986 (0.04 Mt) and 2006 (0.06 Mt) Nyamuragira eruptions using the petrologic method, whereby S contents in melt inclusions are scaled to erupted lava volumes. These amounts are significantly less than satellite-based SO2 emissions for the same eruptions (1986 = ∼1 Mt; 2006 = ∼2 Mt). Potential explanations for this observation are: (1) accumulation of a vapor phase within the magmatic system that is only released during eruptions, and/or (2) syn-eruptive gas release from unerupted magma.
Author Posting. © American Geophysical Union, 2011. 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 12 (2011): Q0AB11, doi:10.1029/2011GC003699.
Showing items related by title, author, creator and subject.
Nature, origin, transport and deposition of andosol parent material in south-central Chile (36-42°S) Bertrand, Sebastien; Fagel, Nathalie (2007-07)The andosols of south-central Chile (36-42°S) are developed on yellow-brown loams that cover the region with a thickness of several meters. In the literature, several hypotheses concerning the nature, origin, mode of ...
Submarine volcanic morphology of the western Galapagos based on EM300 bathymetry and MR1 side-scan sonar Glass, Jennifer B.; Fornari, Daniel J.; Hall, Hillary F.; Cougan, Allison A.; Berkenbosch, Heidi A.; Holmes, Mark L.; White, Scott M.; De La Torre, Giorgio (American Geophysical Union, 2007-03-21)A compilation of high-resolution EM300 multibeam bathymetric and existing MR1 side-scan sonar data was used to investigate the volcanic morphology of the flanks of the western Galápagos Islands. The data portray an assortment ...
Timescales of magmatic processes and eruption ages of the Nyiragongo volcanics from 238U-230Th-226Ra-210Pb disequilibria Chakrabarti, Ramananda; Sims, Kenneth W. W.; Basu, Asish R.; Reagan, Mark K.; Durieux, Jacques (2009-09-04)The silica-undersaturated Nyiragongo volcanics, located in the East African rift, have globally unique chemical compositions and unusually low viscosities, only higher than carbonatite lavas, for terrestrial silicate ...