The Boron Isotopic Composition Of Samples Of Low Boron Determination And Its Application

In this study, the methods of preparation and isotopic measurement of boron are introduced systematically and briefly. Based on this, the effect on the measurement of boron isotopic ratios have been researched further. The isotopic compositions of boron in halites from Qaidam Basin, Qinghai Province and Qianjiang, Hubei Province were measured. An isotopic fractionation of boron during evaportion of seawater was envestigated. The results showed as the following:The content of graphite as loading agent and the sequence of loading graphite and the sample to the filment affect the boron isotopic ratios. However, the boron isotopic ratio decreases with increasing in concentration of graphite. Especially, the method of adding the NBS 951+ graphite result in the lowest boron isotopic ratio.The separation of boron from halite has been studied by liu et al. In this study, the separation and purity of boron from halite have been perfected further and expand its application. The boron isotopic ratios of halite from Qaidam , Qinghai province and Qianjiang, Hubei Province have been determinated, and the results shows that halite in Qaidam basin belong to the non-marine evaporation minerals, the stong evaporation and the high Ca concentration make the fluid inclusions of boron and the δ¹1B value in halite increse. The δ¹1B value in halite from Qianjiang, Hubei Province decrease with increasing the depth of the sample. It indicae that the enviroment have been becoming drier and drier along with the time. But the hilate beonging to whether marine or not non-marine evaporation minerals is not elear based on the δ¹1B value and more data required to determine for its formation enviroment.The experiment is a real static evaporation of seawater using a specialquartz instrument. The boron concentration of the condensate decrease with increasing pH value of the seawater. It indicate that B(OH)₃ is main component in the evaporation. The B(OH)₃/B(OH₄)^- ratio in evaporation is higher than that in seawater which indicate the "B is enriched in evaporation.The δ¹1B value of rain from the Xining and Nanhai is lower than that of the evaporation of the seawater. The result shows that these rain were great affectedby the land enviroment.