Boron isotope geochemistry of Zigetang Co saline lake sediments,Tibetan Plateau  

作　　者：Xiaodan Wang Congqiang Liu Zhiqi Zhao Shijie Li Gangjian Wei 

机构地区：[1]State Key Laboratory of Environmental Geochemistry,Institute of Geochemistry, Chinese Academy of Sciences,Guiyang 550002, Guizhou, China [2]University of Chinese Academy of Sciences, Beijing 100049,China [3]State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China

出　　处：《Acta Geochimica》2017年第3期437-439,共3页地球化学学报（英文）

基　　金：supported by the National Basic Research Program(973 project)of China(2013CB956401);the National Natural Science Foundation of China(Grant Nos.41210004,41661144042)

摘　　要：The origin of boron in boron-rich salt lakes in the Tibetan Plateau is highly controversial.In this study,we carried out a detailed study on boron geochemistry and isotope composition of lake sediments collected in Zigetang Co,central Tibet.Evaporites had high boron concentrations of 172.3–418.6 lg/g and δ^(11)B values of-8.2%to-3.3%,suggesting a non-marine origin for the saline lake.The boron isotopic fractionation factor,a,between evaporite and brackish water(a_(evaporite–brackish))decreased systematically with depth,from 0.9942 at the top of the drill core to 0.9893 at the bottom;the linear variation between α_(evaporite–brackish)and depth reflects boron isotopic fractionation associated with progressive crystallization.The positive correlation between δ^(11)B versus[B]and δ^(11)B versus depth in the evaporite phase reflects pH and boron speciation in the solution control on the adsorption of boron,and B(OH)_3 species incorporated preferentially into Mg(OH)_2 precipitation at high pH.The origin of boron in boron-rich salt lakes in the Tibetan Plateau is highly controversial.In this study,we carried out a detailed study on boron geochemistry and isotope composition of lake sediments collected in Zigetang Co,central Tibet.Evaporites had high boron concentrations of 172.3–418.6 lg/g and δ^（11）B values of-8.2%to-3.3%,suggesting a non-marine origin for the saline lake.The boron isotopic fractionation factor,a,between evaporite and brackish water（a（evaporite–brackish））decreased systematically with depth,from 0.9942 at the top of the drill core to 0.9893 at the bottom;the linear variation between α（evaporite–brackish）and depth reflects boron isotopic fractionation associated with progressive crystallization.The positive correlation between δ^11B versus[B]and δ^11B versus depth in the evaporite phase reflects pH and boron speciation in the solution control on the adsorption of boron,and B（OH）3 species incorporated preferentially into Mg（OH）2 precipitation at high pH.

关 键 词：Boron isotopes Zigetang Co Equilibrium isotopic fractionation Boron concentration 

分 类 号：P597[天文地球—地球化学] P512.2[天文地球—地质学]