Successive Eruption of Alkaline and Tholeiite Magmas in a Japanese Palaeozoic Geosynclinal Basalt Body with Special Reference to Rare Earth Element Features
Electron-microprobe analyses are presented for pyroxene, amphibole, and biotite from monzonite, granodiorite, and granite at Finnmarka, Norway. Compositional trends measured in biotite, present in all three rock types, and in amphibole, present in the monzonite and granodiorite, are markedly atypical and are interpreted as reflecting crystallization under progressively more oxidizing conditions. The average Fe/Fe + Mg for biotites from successively more silicic rock types changes from 0.64 → 0.35 → 0.28, and for amphiboles changes from 0.58 in the monzonite to 0.29 in the granodiorite.