The dense sampling of the dolomite from the Bandenggou outcrop of Longwangmiao Formation in the eastern Sichuan Basin was carried out with the samples selected through X-ray diffraction.The classification and genesis of the dolomite were demonstrated based on test results such as major and trace elements

rare earth elements (REEs) and carbon and oxygen isotopes.The results show that the dolomitization of the study area could be divided into two types in terms of origins.One is the micritic dolomite with low order degree

which developed in evaporating environment and was influenced by para-syngenetic Sabkha dolomitization

seepage-reflux dolomitization

and terrigenous clastic minerals.For this kind of dolomite

MgO and CaO contents are positively correlated

and Mg/Ca ratio is high in general

with low content of Sr

high content of Fe

Mn and REE+Y

and significant δEu

&

δCe negative anomalies.Additionally

the δ

13

C

&

δ

18

O values are consistent with those of the limestone deposited in coeval sea water.The other is the powder fine crystal dolomite

formed by shallow burial dolomitization

with negatively correlated MgO and CaO content

low Mg/Ca value

high content of Sr

Fe and Mn

low content of REE+Y

δEu

&

δCe negative anomalies

and the same δ

13

C value of the limestone deposited in coeval sea water.However

the value of δ

18

O is a little bit lower than that of the limestone in coeval sea water.According to the petrographic characteristics of the dolomite

we believe that the rock has undergone the syndepositional dolomitization (including Sabkha effect and reflux infiltration)superimposed by shallow burial dolomitization at later time.As a result

the values of carbon and oxygen isotopes became different through the processes.