沉积硼酸盐矿物硼同位素组成特征及控制因素研究  

Characteristics and Control Factors of Boron Isotope Composition of Sedimentary Borate Minerals

作　　者：彭章旷 马云麒[1,2] 彭齐鸣 PENG Zhang-kuang;MA Yun-qi;PENG Qi-ming(Key Laboratory of Comprehensive and Highly Efficient Utilization of Salt Lake Resources,Qinghai Institute of Salt Lakes,Chinese Academy of Sciences,Xining,810008,China;Salt Lake Chemical Analyzing and Testing Center,Qinghai Institute of Salt Lakes,Chinese Academy of Sciences,Xining,810008,China;School of Earth Sciences and Resources,China University of Geosciences,Beijing,100083,China)

机构地区：[1]中国科学院青海盐湖研究所,中国科学院盐湖资源综合高效利用重点实验室,青海西宁810008 [2]中国科学院青海盐湖研究所,盐湖化学分析测试中心,青海西宁810008 [3]中国地质大学,地球科学与资源学院,北京100083

出　　处：《盐湖研究》2022年第3期112-121,共10页Journal of Salt Lake Research

基　　金：国家自然科学基金项目(No.41473117);中国科学院功能开发技术创新项目(2020g102)。

摘　　要：硼资源主要来自沉积硼酸盐矿床,其硼同位素组成携带着丰富的成矿及蚀变信息。通过室内模拟实验及统计全球沉积硼酸盐矿物δ^(11)B值,分析发现硼酸盐矿物δ^(11)B值主要受硼源、硼酸盐结构、pH值、后期蚀变及瑞利过程影响。不同试剂合成及不同盐湖产出的硼酸盐矿物δ^(11)B值存在显著差异,说明硼源是决定δ^(11)B值的第一要素。同一矿床及全球沉积硼酸盐矿物间δ^(11)B值均表现出钠硼酸盐(硼砂、三方硼砂、贫水硼砂)>钠—钙硼酸盐(钠硼解石、硼钠钙石)>镁硼酸盐(多水硼镁石、柱硼镁石、库水硼镁石)>钙硼酸盐(硬硼钙石、板硼石、白硼钙石、三斜硼钙石)>钙—镁硼酸盐(砷硼镁钙石、水方硼石),这与硼酸盐矿物中BO_(3)/BO_(4)比值及卤水pH值有关。原始沉积硼酸盐后期埋藏过程经历的蚀变反应会改变δ^(11)B值:(1)次生硼酸盐矿物δ^(11)B值比原生硼酸盐矿物低2‰~4‰,这是由于脱水反应中^(11)B倾向进入流体相;(2)次生硼酸盐矿物δ^(11)B值比原生硼酸盐矿物高0‰~1‰,这是因为瑞利过程中^(10)B优先进入固相造成后期沉积硼酸盐矿物δ^(11)B值升高0.3‰~2.5‰;(3)后期流体作用会显著改变δ^(11)B值,主要表现在硅—锶硼酸盐矿物δ^(11)B值与原生硼酸盐矿物具有显著差异。Sedimentary borate deposits provide the major boron resource,and theirδ^(11)B values carry rich mineralization and alteration information.Theδ^(11)B values of 234 major sedimentary borate minerals are collected,and some borates are synthesized by chemical reagent and collected from Qinghai-Tibet Plateau.Meanwhile,the change ofδ^(11)B values during the thermal decomposition and the precipitation of borates are studied.Theδ^(11)B values of borates synthesized by different reagents and produced in different salt lakes are significantly different,which shows that the boron source is the most important factor to effect theδ^(11)B value of borates.Theδ^(11)B values of the borates in the single deposit and the global sedimentary deposits all show Na-borates(Borax,Kernite,Tincal)>Na-Ca borate(Ulexite,Probertite)>Mg-borate(Inderite,Pinnoite,Kurnakovite)>Ca-borate(Colemanite,Pandermite,Inyoite,Meyerhofferite)>Ca-Mg borate(Terrugite,Hydroboracite)>other borates(howlite,Veatchite-A),which is related to the BO_(3)/BO_(4) ratio of borates and the pH values of brines.The primary sedimentary borates experience the alteration reaction during the burial process,and it will change theδ^(11)B value:(1)Theδ^(11)B value of secondary borates is 2‰~4‰lower than that of primary borates asδ^(11)B tends to enter the fluid phase during the dehydration reaction;(2)Theδ^(11)B value of secondary borates is 0‰~1‰higher than that of primary borates,which is caused by the preferential entry of ^(10)B into the solid phase during the Rayleigh process;(3)The reaction between primary borates and later fluid will significantly change theδ^(11)B value,and it is mainly manifested by the significant difference ofδ^(11)B value between silicon-strontium borates and the primary borates.Theδ^(11)B value of sedimentary borates are mainly affected by boron source,borate structure,pH value,post-alteration and Rayleigh process.

关 键 词：硼酸盐矿物 硼同位素 硼源 PH值 矿物结构 蚀变反应 

分 类 号：O611.7[理学—无机化学]