Jökull - 01.12.1979, Page 61

TABLE 1.
Major element compositions of the main extrusive rock-types of Iceland.
THOLEIITIC SERIES TRANSITIONAL ALKALIC SERIES ALKALIC SERIES
1. 2. 3. 4. 5. 6. 7. 8. 9. 10. 11.
Si02: 46.21 49.30 60.59 73.23 47.08 47.08 60.52 73.60 46.56 48.46 58.64
TiOz: 0.41 2.28 1.25 0.35 2.33 4.63 1.10 0.20 2.02 3.00 1.41
A1203: 13.69 13.51 15.07 12.25 12.25 12.71 14.98 12.04 15.93 16.40 17.12
Fe^Oj: 1.37 2.34 2.31 3.46 2.46 4.24 2.02 1.26 1.61 3.27 1.93
FeO: 7.16 12.23 5.73 0.81 9.40 11.23 6.89 1.87 10.32 10.10 6.42
MnO: 0.15 0.24 0.19 0.11 0.19 0.22 0.20 0.07 0.20 0.26 0.26
MgO: 18.15 6.34 1.73 0.13 11.70 5.06 1.44 0.05 9.00 3.82 1.16
CaO: 10.99 10.71 4.94 1.87 11.40 9.91 4.69 0.38 10.51 7.71 4.92
Na^O: 1.32 2.46 4.29 4.37 2.13 3.08 4.71 5.74 3.21 5.11 5.02
KjO: 0.01 0.24 1.59 2.53 0.43 0.72 1.68 4.51 0.51 1.19 2.57
P205: 0.02 0.21 0.43 0.02 0.26 0.57 0.45 0.01 0.26 0.62 0.52
H20: 0.19 0.21 1.84 0.25 0.34 0.31 0.59 0.18 0.02 0.06 n.d.
Sum: 99.67 100.07 99.96 99.38 99.97 99.76 99.27 99.91 100.15 100.00 99.97
THOLEIITIC SERIES:
1: Oceanite (picrite basalt), Vatnsheidi lava shield, Reykjanes-Langjökull zone, Postglacial. Phenocrysts of
chromite, olivine and plagioclase (Jakobsson et al. 1978).
2: Tholeiite, Grindavík fissure lava, Reykjanes-Langjökull zone, Postglacial. Phenocrysts of olivine, plagioclase and
augite Qakobsson et al. 1978).
3: Icelandite, Thingmúli central volcano, E-Iceland, Tertiary. Phenocrysts of plagioclase, olivine, ferroaugite and
hypersthene (Carmichael 1964).
4: Rhyolite, Jörundur dome, Krafla central volcano, northern volcanic zone, Upper Pleistocene. Phenocrysts of
plagioclase, olivine, ferroaugite, magnetite and pigeonite (Wetzel et al. 1978).
TRANSITIONAL ALKALIC SERIES:
5: Ankaramite, Eyjafjöll central volcano, eastern volcanic zone, Upper Pleistocene (intrusive?). Phenocrysts of
olivine, diopsidic augite, plagioclase and magnetite (Steinthórsson 1964).
6: Transitional alkali basalt, Eldgjá lava, eastern volcanic zone, Postglacial. Phenocrysts of magnetite,
plagioclase, olivine and augite (Jakobsson 1979).
7: Transitional andesite, prehistoric Hekla lava, eastern volcanic zone. Phenocrysts of magnetite, plagioclase, olivine,
augite and apatite (Jakobsson 1979).
8: Comenditic rhyolite, Hrafntinnusker tholoid, eastern volcanic zone, Postglacial. Aphyric obsidian (Bailey &
Macdonald 1970).
ALKALIC SERIES:
9: Alkali olivine basalt, 1964 Surtsey lava, Vestmannaeyjar. Phenocrysts of picotite, olivine and plagioclase, (Tilley
etal. 1967).
10: Hawaiite, 1973 Eldfell lava, Vestmannaeyjar. Phenocrysts of plagioclase, olivine, magnetite and, kaersutite and
hornblende (on nodules) (Jakobsson et al. 1973).
11: Benmoreite, Setberg alkalic suite, Snaefellsnes, Upper Pleistocene. Phenocrysts of plagioclase, olivine, augite and
magnetite (Sigurdsson 1970).
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