Greinar (Vísindafélag Íslendinga) - 01.01.1976, Blaðsíða 170

TABLE 2
Modal analyses
groundmass
plag. phenocrysts
pyroxene phenocrysts
olivine phenocrysts
12 3 4
90.20 91.53 99.00 96.54
6.60 5.45 1.00 4.46
3.20 1.18
90.80
8.36
5
1.84
0.84
1. Kapelluhraun 4. Lava from volcanic fissure west of
2. Afstapahraun Núpshlíðarháls.
3. ögmundarhraun 5. Hrútagjárdyngja.
APPENDIX
The following components, Si02, A1203, Ti02, CaO, K20 and
total Fe (as Fe203) were determined by X-ray fluorescence, but FeO
with KMn04 titration, MgO with atomic absorption, Na20 with
flame photometer, and MnO and P205 with spectrophotometer.
Total H20 was determined by Penfield’s method, but H20— gravi-
metrically after heating for six hours at 105°C.
REFERENCES
1. Jakobsson, S. 1972: Chemistiy and distribution of recent basaltic rocks in
Iceland. Lithos 5. pp. 265-286.
2. Chayes, F. 1966: Alkaline and subalkaline basalts. Am. Journ. of Science.
vol. 264 pp. 128-145.
3. Irvine and Baragar 1971: A guide to the chemical classification of common
volcanic rocks. Canadian Joumal of Earth Science 8. pp. 532-548.
4. Steinþórsson, S. 1974: The oxide mineralogy, initial oxidation state and
deuteric alteration in some precambrian diabase dike swarms in Canada.
Ph.D., thesis. Princeton University.
5. Sigvaldason, G. 1969: Chemistry of basalts from the Icelandic rift zone.
Contr. Min. and Petrol. 20, pp. 357-370.
6. Sæmundsson, K. 1974: Evolution of the axial rifting zone in Northera Iceland
and the Tjöraes fracture zone. Geol. Soc. of Am. Bull. vol. 85, pp. 495-504.