Boron isotope geochemistry of Bangor Co Salt Lake(central Tibet):implications for boron origin and uneven mixing of lake water

Boron is an essential,widely used,micronutrient element and is abundant in salt lakes on the Qinghai-Tibet Plateau.The origin and distribution of boron brine deposits on the Qinghai-Tibet Plateau is an important foundation for B resource formation,evolution,and enrichment,which have long been the subject of debate.The boron isotope system is a sensitive geochemical tracer,making it useful for eff ectively and precisely tracking a wide range of geological processes and sources.This study investigates the major cations,[B],andδB values of samples(lake brine,river waters,and cold spring water)from the Bangor Co Lake which is a typical salt lake rich in boron in Tibet,China.There are magnitude-scale diff erences in[B]among diff erent sample types:river samples<cold spring water<<brine lakes.[B]values vary from 0.73 to~1113 mg/L.Similar to[B],theδB values of the samples exhibit magnitude-scale variations as[B],ranging from-7.35‰to+7.66‰.There are also magnitude-scale diff erences inδB among diff erent sample types.TheδB values of cold spring water are relatively low,and the values range from-1.26‰to-7.75‰.However,the river water samples and saline lakes have higher values,from 0.38‰to 4.62‰,and theδB values of river water samples are basically in the distribution range of those of Bangor Co Lake.This indicates that the sources of boron in Bangor Co Lake are mainly the recharge water with higherδB values and spring water with lowerδB values,and the boron sources and the uneven mixing of lake water are two reasons that account for the large change in theδB value of Bangor Co Lake.