Fluorine contents in about 160 representative Quaternary volcanic rocks and 15 hornblende and biotite phenocrysts in a calc-alkali series in Japan have been determined by a selective ion-electrode method. Tholeiites have the lowest contents and the narrowest range (58-145 ppm), while alkali basalts have the highest contents and the widest range (301-666 ppm); high-alumina basalts have intermediate values (188-292 ppm). F contents in basalts clearly increase from east to west across the Japanese Islands, as do alkalis, P2O5, REE, U, Th and H2O. The volcanic rocks studied are divided into two groups on the basis of F: 1) with increasing % SiO2 or advancing fractionation, F contents show progressive enrichment; or 2) with increasing fractionation, F contents show rather constant values. The former is produced by fractionation of anhydrous phases from basalt to mafic andesite magmas; the latter group is derived through separation of amphibole-bearing phases from basaltic magmas at various depths from upper mantle (approx 30 km) to upper crust.-T.R.
|Title of host publication||Journal of Volcanology & Geothermal Research|
|Number of pages||15|
|Publication status||Published - 1980|
ASJC Scopus subject areas
- Earth and Planetary Sciences(all)
- Environmental Science(all)