Eyjafjallajökull 2010 - Chemical composition

Chemical analysis* of rocks from the Eyjafjöll 2010 eruptions - Níels Óskarsson

Major oxides in Wt%, minor elements in mg/kg (ppm)



FIM-1         21.3.2010   Fimmvorduhals-Sample from initial crater. Coll: Thor Kjartansson
FIM-2         27.3.2010   Fimmvorduhals-Sample Hrunagil, Lava termination. Coll: SG, HN, IOB, AE
SRG 2b     15.4.2010   Eyjafjallajokull- Sample Myrdalssandur ash-layer (GPS: 63-32-023;18-27-510). Coll: S.R. Gislason
SRG 5a     27.4.2010   Eyjafjallajokull- Sample Direct fallout (GPS: 63-40-626; 19-48-602). Coll: S.R. Gislason
BO1510      *1maj-10   Eyjafjallajokull- Sample from large bomb summit Coll: Bjorn Oddson
HO7510      *7maj-10   Eyjafjallajokull- Sample Direct fallout from Fimmvorduhals. Coll: Halldor Ólafsson
PAA8510     *8maj-10   Eyjafjallajokull- Sample from large bomb summit. Coll: Patrick Allard
GSV165-3 *16maj-10  Eyjafjallajokull- Sample Direct fallout summit, Coll: Gudrun Sverrisdottir

*Average of duplicate analysis.
Method: Rock powder fluxed with lithium metaborate, dissolved in nitric/hydrochloric/oxalic - acid mixture.
Analysis made on ICP-OES simutlaneous spectrograph (Spectro CIROS)
Reference material (SRM): USGS-BHVO - USGS QLO-1.

Gas composition and flux report (pdf file)

Leaching experiment on ash from Eyjafjallajökull - Eydís Salome Eiríksdóttir and Helgi A. Alfreðsson (pdf-file)

Soluble fluoride on volcanic ash and scoria from the eruption on Fimmvörðuháls

Soluble fluoride was measured in three samples from the eruption on Fimmvörðuháls:
1. Sample from the eruption site - fine glassy scoria.
2. Ash sample from snow on the lowland (VP323 á 63.36.36,4-19.26.17,3)  - glassy ash 0.2-1 mm.
3. Similar to Sample No 2.

Results
Soluble fluoride on ash surface: mg F pr. kg ash (ppm).
1. (pH 6.45) Fluoride 92 ppm (Leached in the laboratory. Fluoride and pH of leachate measured in the laboratory).
2. (pH 5.66) Fluoride 112 ppm (Fluoride and pH measured in meltwaer).
3. (pH 5.55) Fluoride 112 ppm (Fluoride and pH measured in meltwaer).

The leachate is slightly acidic suggesting minor condensate from volcanic gases on grain surfaces. It is pointed out that the samples are coarse ash. Therefore, is has to be assumed that fluoride values will increase away from the volcano where the ash is more fine-grained and its surface are is larger.
It may be inferred that fluoride values on the Mid-southern lowlands might reach 400-500 ppm.
These values are similar to the values foun during the 1973 Heimaey eruption. Even if these values are only about one third of comparable values for Hekla ash it is there is reason to be careful and move grazing animals form ash-contaminated fields and melt-water.

Chemical composition of the Fimmvörðuháls 2010 lava
The rock was analyzed by ICP-spectrometry and turned out to be alkali-olivine basalt of the following composition:

SiO2  46,99
Al2O3  15,91
FeO  12,12
MnO  0,19
MgO  6,55
CaO  10,28
Na2O  3,11
K2O  0,71
TiO2  3,32
P2O5  0,64

The composition belongs to the alkalic rock suite (.4% Ne in the Norm) at average titanium level which is characteristic for Eyjafjöll and different form the nearby High-Ti Mýrdalsjökull/Katla system.
Euhedral plagiclase, olivine and clinopyroxene phenocrysts seem to be in equilibrium with the magma.
According to the MELTS and COMAMGAT modeling software this assemblage point towards pressures about or lower than 2 kb since olivine is not an liquidus phase at higher pressures.