Abstract:

Stable isotopic method can be used effectively in the diagenetic research of deep water carbonate rocks.According to the oxygen and carbon isotopic compositions of the Early Palaeozoic deep water carbonate rocks developed along the southeastern marginal slop of the Middle Yangtze carbonate platform,some diagenetic environments and diagenetic mechanisms are as fallowe:1)the δ¹⁸O values of nodules of Lower Ordovician nodular limestone are always more positive than those of matrix,suggesting that the prototype of the modular limestone was the product of solution and cementation occurred repeatedly on the sea floor;2)the Lower Cambrian massive dolomite with relatively concentric values of δ¹⁸O and δ¹³C was the product of high density brine replaced dolomitizatin,whereas the lower Ordovician massive dolomite with high negative δ¹⁸O value was formed by the deep burial dolomitization;3)Burial recrystallization altered strongly the Lower Ordovician carbonate rocks,and made them to have the same high negative δ¹⁸O values.

Key words: stable isotope, deep-water carbonate rock, diagenesis, Middle Yangtze Platform, Early Paleozoic