In terms o f major element compositions,diffe rent Proterozoic groups and formations h ave no distinct differences and on th e whole are characterized by interme diate SiO 2 contents and K 2 O /Na 2 O ratios and relatively high Fe 2 O 3? +MgO contents.是什么意思_In terms o f major element compositions,diffe rent Proterozoic groups and formations h ave no distinct differences and on th e whole are characterized by interme diate SiO 2 contents and K 2 O /Na 2 O ratios and relatively high Fe 2 O 3? +MgO contents.在線(xiàn)翻譯_英語(yǔ)_讀音_用法_例句