Measurements of rare earth elements

value of

87

Sr/

86

Sr

and fluid inclusion

had been carried out on facture-filling minerals(such as calcite

fluorite and barite) in Tazhong area.Results show that the

87

Sr/

86

Sr va-lues of all the filling minerals(0.708 89-0.710 36) and formation water are higher than that of the whole-rock samples of fracture-carbonate rock and sea water in the same period

and the homogenization temperature of fluid inclusion is about 20℃ higher than that of the highest temperature ever experienced by the Upper Ordovician

signaling the presence of hydrothermal fluid and a high concentration of

87

Sr.The hydrothermal fluid with high

87

Sr/

86

Sr value is most likely derived from the Cambrian or pre-Cambrian clastic rocks.Its Eu

2+

and Sr

2+

are of similar origin

resulting in a positive Eu anomaly and a good linear relationship between Eu and Sr in the fracture fillings.It induced TSR and generated HSS and pyrite.Consequently

the process led to the replacement of barite by calcite.The presence of fracture-filling

87

Sr-rich fluorite with relatively low temperature and low salinity as indicates that beside the influence of hydrothermal fluid

the area might also be affected by fresh water and basin fluid of low temperature.