A chemical definition of fractionation stages as a basis for comparison of Hawaiian, Hebridean and other basic lavas

摘要: Abstract Accepting that crystal fractionation of basic magma leads to simultaneous increases in the iron ratios ( Fe .. + Mn Mg ) and albite normative molecular anorthite ), a graphical plotting these two ratios, one against other, provides method denning successive stages fractionation. By averaging analyses falling different for main types basalt, Plateau Tholeiitic, better chemical definition is obtained composition Alkaline Tholeiitic series which they give rise. Preliminary basalts from other regions indicates at comparable stages, some are relatively rich SiO2 can be grouped as tholeiitic others poor have alkaline basalt characteristics, while yet intermediate features. Comparison averages fraotionatipn also shows minor differences believed characteristic particular regions.