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 
投稿时间:2020-12-21  修订日期:2021-02-28
DOI:10.12119/j.yhyj.202203013
中文关键词:  硼酸盐矿物  硼同位素  硼源  pH值  矿物结构  蚀变反应
英文关键词:Borates  δ11B value  Boron source  pH value  Borate structure  Alteration reaction
基金项目: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)
作者单位
彭章旷 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
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
中国地质大学,地球科学与资源学院,北京 100083 
马云麒 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
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 
彭齐鸣 中国地质大学,地球科学与资源学院,北京 100083 
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中文摘要:
      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δ11B值,分析发现硼酸盐矿物δ11B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δ11B值存在显著差异,说明硼源是决定δ11B值的第一要素。同一矿床及全球沉积硼酸盐矿物间δ11B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BO3/BO4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δ11B值:(1)次生硼酸盐矿物δ11B值比原生硼酸盐矿物低2‰~4‰,这是由于脱水反应中11B倾向进入流体相;(2)次生硼酸盐矿物δ11B值比原生硼酸盐矿物高0‰~1‰,这是因为瑞利过程中10B优先进入固相造成后期沉积硼酸盐矿物δ11B值升高0.3‰~2.5‰;(3)后期流体作用会显著改变δ11B值,主要表现在硅—锶硼酸盐矿物δ11B值与原生硼酸盐矿物具有显著差异。
英文摘要:
      Sedimentary borate deposits provide the major boron resource,and their δ11B values carry rich mineralization and alteration information.The δ11B 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 of δ11B values during the thermal decomposition and the precipitation of borates are studied.The δ11B 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 the δ11B value of borates.The δ11B 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 BO3/BO4 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 the δ11B value:(1) The δ11B value of secondary borates is 2‰~4‰ lower than that of primary borates as δ11B tends to enter the fluid phase during the dehydration reaction;(2) The δ11B value of secondary borates is 0‰~1‰ higher than that of primary borates,which is caused by the preferential entry of 10B into the solid phase during the Rayleigh process;(3) The reaction between primary borates and later fluid will significantly change the δ11B value,and it is mainly manifested by the significant difference of δ11B value between silicon-strontium borates and the primary borates.The δ11B value of sedimentary borates are mainly affected by boron source,borate structure,pH value,post-alteration and Rayleigh process.
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