ISOTOPIC COMPOSITIONS OF BORON IN SEDIMENTS AND THEIR IMPLICATIONS

The abundance and isotopic compositions of boron in sediments from the salt lakes of Qaidam Basin, China have been determined by thermal ion ization mass spectrometry of cesium berate, The results show large var iations in the isotopic compositions of boron. The observed variations of delta(11)B, ranging from - 25.2 parts per thousand to + 26.08 part s per thousand (relative to NBS SRM 951) indicate both an enrichment a nd depletion in the lighter isotope (B-10) in the lake sediments, The lower delta(11)B values of sediments are mostly closer to the boron is otopic compositions of minerals. Such low delta(11)B values are attrib uted to the presence of berates, ulexite and other carbonate minerals in sediments of the salt lakes of Qaidam Basin.