Complex sentence: They are 204 Pb, 206 Pb, 207 Pb and 208 Pb and ratios: 208 Pb/207 Pb, 207 Pb/206 Pb and 206 Pb/204 Pb are measured through mass spectrometry and widely employed to express the character of certain ore deposit.
Split into simpler sentences: They are 204 Pb, 206 Pb, 207 Pb and 208 Pb. Ratios: 208 Pb/207 Pb, 207 Pb/206 Pb and 206 Pb/204 Pb are measured through mass spectrometry and widely employed to express the character of certain ore deposit.