87

Sr/

86

Sr ratio of dolomite is an important indicator for identifying source and characteristics of fluids related to formation and evolution of dolomite.Meanwhile

the ratio has been widely used in study of seawater

87

Sr/

86

Sr ratio evolution of fossil seawater and strontium isotope stratigraphy.Thus

the existence and degree of influence of dolomitization on the

87

Sr/

86

Sr ratio is crucial to understand the geologic significances of

87

Sr/

86

Sr ratio of dolomite.However

no systematic research of this issue has been published.The Geshan section in Yixing County of Lower Yangtze region has excellent outcrops of carbonates including limestone

dolomitic limestone

calcite dolomite and dolomite

providing a chance to study the geochemical behaviors of strontium during dolomitization.In this study

we systematically analyzed the Sr contents and

87

Sr/

86

Sr ratios of these carbonates.The Sr contents of these carbonates decrease significantly with enhancing dolomitization degree

from 1358μg/g of limestone to 94μg/g of dolomite

while the

87

Sr/

86

Sr ratios increase from 0.708019 to 0.708182.An analysis of the relevant published data shows that the evolution feature of Sr is common to some degree

indicating that it may be attributed to the habitual behaviors of Sr during dolomitization.As Ca is replaced by Mg during dolomitization

the isomorphous Sr is lost simultaneously

leading to the lowering Sr content.In addition

lighter

86

Sr emigrates from the process due to the constrint of mass effect

resulting in higher

87

Sr/

86

Sr ratio.Therefore

the influences of dolomitization on

87

Sr/

86

Sr ratio must be considered when identifying the source of dolomitization fluids

establishing the

87

Sr/

86

Sr evolution curve of fossil seawater and analyzing the age of dolomite

so as to obtain correct understandings.