Zn/Pb ratios in the Archaean rocks are larger than eight and those in the Middle Proterozoic rocks are 2-4.Zn/Pb ratios in ores from some SEDEX type Pb-Zn deposits in North China are consistent with those of the basement rocks of every deposit.

• 在太古代时,岩石的Zn/Pb比值一般>8,中元古代时这一比值降低为2~4。