Jökull - 01.12.1989, Síða 89

TABLEI. Major element composition of basaltic, intermediate and silicic rocks in the Loðmundarfjörður
area. The total Fe content is given as Fe203.
TAFLAI. Meginefnasamsetning nokkurra basaltískra, ísúrra og súrra hrauna úr Loðmundarfirði.
1 2 3 4 5 6 7 8 9 10 11 12 13
Si02 44.62 45.93 46.11 47.25 46.19 49.59 50.28 60.82 64.89 68.05 69.26 69.13 66.90
tío2 2.48 2.36 2.63 2.70 3.09 3.67 2.82 1.07 0.50 0.82 0.46 0.08 0.19
ai263 14.86 16.41 15.43 15.71 14.20 13.54 14.70 14.90 13.97 13.57 13.68 11.96 10.09
Fe203 14.99 15.05 15.58 14.96 15.52 15.16 14.21 10.92 7.68 4.62 3.50 1.27 1.71
MnO 0.20 0.21 0.18 0.21 0.27 0.25 0.22 0.28 0.18 0.08 0.05 0.01 0.06
MgO 9.44 7.66 7.98 6.94 5.50 4.06 4.34 1.27 0.42 0.66 0.35 0.39 1.00
CaO 9.50 10.52 9.87 10.24 9.06 8.24 8.47 4.59 2.97 2.32 1.54 0.39 1.00
NaiO 2.42 2.30 2.49 2.49 2.88 3.45 3.44 4.51 5.01 4.35 4.56 4.79 3.80
k26 0.35 0.28 0.33 0.39 0.41 1.00 0.64 1.67 2.26 3.02 3.27 3.41 2.84
P205 0.31 0.38 0.37 0.36 0.46 0.85 0.54 0.44 0.09 0.35 0.10 0.01 0.06
C02 0.90 0.81 0.54 0.58 0.10 0.04 0.05 0.09 0.21 0.38 0.33 0.24 0.14
Totals 100.07 101.91 101.51 101.83 97.68 99.85 99.71 99.56 98.18 98.22 97.10 91.68 87.79
TABLEII. CIPW norms of the geochemically analysed rocks. OT = Olivine tholeiite (samples 1-4),
QT = Quartz tholeiite (samples 5-7), IS = Icelandite (samples 8-9), D = Dacite (samples 10-11), R = Rhyolite
(samples 12-13).
TAFLAII. CIPW staðlar efnagreindra hrauna.
Hy Fo Fa 01 Mt 11 Ap Ne Qz Or Ab An Wo En Fs Di En Fs
OT 14 4.99 11.37 7.25 18.62 4.35 4.71 0.72 0.00 0.00 2.07 20.48 28.65 6.87 4.12 2.39 13.38 3.16 1.83
OT 15 10.86 6.42 5.16 11.58 4.36 4.48 0.88 0.00 0.00 1.65 19.46 33.63 6.72 3.73 2.72 13.17 6.18 4.50
OT 13 10.58 6.81 5.28 12.09 4.52 5.01 0.79 0.00 0.00 1.95 21.07 29.95 7.01 3.95 2.78 13.74 6.21 4.37
OT 14 15.27 3.19 2.69 5.88 4.34 5.13 0.83 0.00 0.00 2.30 21.07 30.54 7.48 4.08 3.13 14.69 8.69 6.62
QT 1 17.00 1.05 1.13 2.18 4.50 5.87 1.07 0.00 0.00 2.42 24.37 24.61 7.24 3.59 3.50 14.33 8.61 8.39
QT 5 15.07 0.00 0.00 0.00 4.40 6.97 1.97 0.00 2.58 5.91 29.19 18.51 7.03 3.20 3.78 14.01 6.91 8.16
QT 2 16.50 0.00 0.00 0.00 4.12 5.36 1.25 0.00 2.57 3.78 29.11 22.78 6.56 3.05 3.44 13.05 7.76 8.74
IS 18 12.58 0.00 0.00 0.00 3.17 2.03 1.02 0.00 13.48 9.87 38.16 15.48 1.85 0.43 1.53 3.81 2.74 9.84
IS 21 7.05 0.00 0.00 0.00 2.23 0.95 0.21 0.00 17.66 13.36 42.39 8.96 2.17 0.26 2.12 4.55 0.78 6.27
D 10 5.50 0.00 0.00 0.00 1.34 1.56 0.81 0.00 24.48 17.85 36.81 8.58 0.27 0.08 0.20 0.55 1.56 3.94
D 12 4.25 0.00 0.00 0.00 1.01 0.87 0.23 0.00 25.14 19.32 38.58 6.99 0.00 0.00 0.00 0.00 0.87 3.38
R 13 1.13 0.00 0.00 0.00 0.37 0.16 0.02 0.00 26.88 20.15 40.53 1.06 0.34 0.04 0.33 0.71 0.11 1.02
R 29 1.20 0.00 0.00 0.00 0.50 0.36 0.14 0.00 31.37 16.78 32.15 2.09 1.04 0.25 0.85 2.14 0.27 0.93
Its position in the vicinity of the Dyrfjöll and
Breiðavík volcanoes suggest a relationship between
all these eruption centres, which warrants further
investigation.
ACKNOWLEDGEMENTS
We express our thanks to Prof. Dr. V.
Jacobshagen (Institut fíir Allgemeine Geologie,
Freie Universitat Berlin, F.R.G.) for valuable advice
during mapping, and two anonymous reviewers for
helpful advice.
JÖKULL, No. 39, 1989 87