Petrologic study and REE (rare earth element) characterization of dolomite samples from Jingzhu and Zhongba outcrops of the Cambrian Loushanguan Group in SE Sichuan Basin identified four types of dolomite:micritic dolomite

grain dolomite

crystalline dolomite and baroque dolomite.The analysis results of the REE characteristics show that all the 4 types have low REE content (avg.15.69ppm) and relatively high Y/Ho ratios (avg.50).The very poor correlation of REE content with Fe and Mn contents suggests a limited effect of terrigenous clastics and iron and manganese oxyhydroxide on the dolomite in the study area.Different types of dolomite vary in their total REE content readings.The micritic dolomite is rich in algae and has the highest content of REE (avg.21.06ppm).The grain dolomite (avg.13.66ppm) and crystalline dolomite (avg.13.02ppm) have similar REE content.The baroque dolomite has relatively high REE content (avg.16.28ppm)

indicating possible involvement of hydrothermal fluids.It also shows that all types of dolomite shares similar REE patterns with limestone.The average value of (Nd/Yb)

SN

in dolomite samples is 1.52

indicating they are relatively rich in LREE and depleted in HREE.All the samples show negative Eu and Ce anomalies (avg.0.79 and 0.36

respectively).Significant positive Y anomalies and positive La anomalies were also observed.All these facts indicate that the dolomite was formed by fluids of marine origin in a relatively closed diagenetic system of relatively reducing environment and low temperature.