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 ionization mass spectrometry of cesium borate. The results show large variations in the isotopic compositions of boron. The observed variations of δ11B, ranging from -25.2 per mille to +26.08 per mille (relative to NBS SRM 951) indicate both an enrichment and depletion in the lighter isotope (10B) in the lake sediments. The lower δ11B values of sediments are mostly closer to the boron isotopic compositions of minerals. Such low δ11B values are attributed to the presence of borates, ulexite and other carbonate minerals in sediments of the salt lakes of Qaidam Basin. (author). 27 refs., 1 tab., 1 fig