INAA OF ROCK SALT SAMPLES FROM A BLOCK BASIN IN EAST CHINA

17 elements including Ca, Sc, Cr, Fe, Co, Zn, Br, Rb, Sr, Ba, La, Ce, Eu, Yb, Hf, Th and U have been determined by INAA for 27 rock salt samples from Zhong Yuan oil field (geologically known as " Dong-pu seg" ) in Henan Province. The samples covering a thickness of 100 m are taken from 3000 m depth under earth surface. NaCl contents are more than 97%. The multielement concentration data have provided important information for the study of origins of the brine and the conditions of its formation. The concentrations of Br are ranging from 8.7 to 46.6 ppm, with an average of 23.5 ppm. On this basis, geologists have concluded that Dong-pu seg were formed from the sedimentation of inland salt paste.Further information on the history of geological structure may be obtained by comparing these results with trace element composition for marine facies evaporation.