Jökull - 01.12.1984, Page 8

TABLE 1
Grímsvötn - Chemical analyses of the glass phase of tephra samples from eruptions 1903, 1922, 1934
and 1983. All samples with numbers prefixed with 00 are new microprobe analyses. Analyses with
prefix Bb are from Steinthórssorx (1977) and Lakagígar from Grönvold (1984).
Eruption in Grímsvötn 1983
nr. sío2 tío2 Al203 FeOt MnO MgO CaO NazO k2o p2o.
0001 50.3 2.98 12.8 14.0 0.20 5.00 9.71 2.58 0.45 0.32
0002 50.3 2.81 13.0 13.7 0.23 5.18 9.97 2.57 0.42 0.26
0003 50.5 2.87 13.0 13.5 0.22 5.18 9.97 2.57 0.43 0.33
0004 50.2 2.59 13.0 13.6 0.20 5.23 10.0 2.42 0.43 0.30
0010 50.4 2.70 13.0 13.5 0.20 5.25 10.2 2.40 0.42 0.28
0011 50.5 2.77 12.8 13.5 0.21 5.17 10.0 2.42 0.42 0.32
0012 50.1 3.18 12.6 14.0 0.23 4.85 9.53 2.50 0.46 0.36
0013 50.1 2.86 12.7 13.7 0.22 5.00 9.77 2.54 0.45 0.33
0014 50.5 3.02 12.6 14.4 0.26 4.94 9.55 2.62 0.51 0.36
0030 50.3 2.84 12.7 13.7 0.23 4.95 10.1 2.60 0.46 0.35
Eruption in Grímsvötn 1934
0006 50.0 3.02 13.0 13.5 0.20 5.18 9.98 2.70 0.43 0.30
0018 50.3 2.80 12.5 13.7 0.21 5.04 9.91 2.56 0.42 0.34
0019 50.0 2.86 12.5 13.7 0.21 5.04 9.81 2.50 0.41 0.32
0020 50.4 2.90 12.8 13.5 0.22 5.10 9.80 2.60 0.45 0.31
0024 50.0 3.14 12.9 14.3 0.27 5.12 9.83 2.64 0.53 0.38
0025 50.2 3.03 12.8 14.2 0.28 5.16 10.0 2.55 0.50 0.37
0026 50.7 3.08 12.9 14.5 0.26 5.12 10.0 2.52 0.52 0.37
0027 50.2 3.09 12.9 14.5 0.26 5.16 9.90 2.52 0.52 0.38
0028 50.2 3.07 12.7 14.4 0.22 5.13 10.0 2.57 0.52 0.39
0029 50.5 3.07 12.8 14.3 0.25 5.14 9.80 2.54 0.52 0.38
average 0024- 0029
50.3 3.08 12.8 14.4 0.26 5.14 9.92 2.56 0.52 0.38
Bb89 47.9 2.90 13.4 13.7 0.23 5.65 10.6 2.82 0.41 0.30
Eruption in Grímsvötn 1922
0007 50.3 3.14 12.9 14.1 0.20 5.22 10.2 2.55 0.40 0.30
0008 49.8 2.98 12.7 13.8 0.20 5.25 10.3 2.39 0.41 0.31
average 50.1 3.06 12.8 13.9 0.20 5.24 10.2 2.47 0.40 0.30
Bbll5 50.0 3.02 13.5 13.9 0.24 5.22 9.83 2.79 0.55 0.35
Eruption in Grímsvötn 1903
0009 49.8 2.92 13.1. 13.6 0.20 5.45 10.3 2.53 0.38 0.27
Average of analyses of glass from the Lakagígar eruption of 1783
49.1 2.96 12.7 13.7 0.22 5.32 10.1 2.61 0.47 0.36
Two single spot analyses
0025 49.3 2.23 13.5 11.6 0.21 6.41 11.7 2.14 0.35 0.28
0008 49.5 1.91 13.2 13.1 0.26 5.98 11.3 2.35 0.29 0.17
6 JÖKULL 34. ÁR