NEW F(O-2)-BAROMETERS FOR QUENCHED GLASSE S OF VARIOUS PETROCHEMICAL SERIES

Empirical oxygen barometers like lagf(O2) = alog(Fe3+/Fe2+)(L) + b/T Sigma d(i)X(i) are proposed for melts of the tholeiitic, subalkaline, and alkaline petrochemical series. Their application provides improve d logf(O2) computation accuracy by 20-30%. Redox conditions of oceanic basalt crystallization were estimated using the barometers proposed. It is established that previously reported values of oxygen fugacity w ere underestimated by 0.55 log unit, on average.