老挝龙湖矿区泥岩层B同位素地球化学初步研究——以ZK309为例  

Boron isotope geochemical study of mudstone in Longhu mining area of Laos: A case study of ZK309

作　　者：唐启亮[1] 张西营[1] 李雯霞[1] 韩元红[2] 

机构地区：[1]中国科学院青海盐湖研究所盐湖地质与环境实验室,青海西宁810008 [2]中国科学院地质与地球物理研究所油气资源研究重点实验室,甘肃兰州730000

出　　处：《矿床地质》2016年第1期196-202,共7页Mineral Deposits

基　　金：国家自然科学基金项目(编号:40903014);中国科学院青海盐湖研究所青年引导基金联合资助

摘　　要：硼在自然界中分布较集中,平均丰度低,而且11B和10B之间质量差大,分馏效应显著,故B同位素的组成可以作为判定硼来源及沉积环境的有效指示剂和指相标志。文章对老挝龙湖钾盐矿区ZK309钻孔盐岩上覆泥岩层的B同位素地球化学及矿物学进行分析总结得出,其δ11B范围为7.44‰-11.62‰,均值8.96‰,明显介于海水的δ11B值（39.5‰）与陆相地下水的δ11B值（-3‰±5‰）之间;钻孔的矿物组成保存了一定的母岩特性,石英明显来自于陆源输入物;而石盐、硬石膏、石膏与残余卤水有关,推测在下盐段后期出现陆源淡水输入事件,使得后期盐岩层被淋滤,而泥岩层的δ11B值就是受淋滤后的残余卤水影响的结果,这也解释了蒸发岩沉积层序异常（钾石盐覆盖于光卤石之上）的沉积特征。Because boron exhibits relatively concentrated distribution in nature, has low average abundance, and the quality is different between11 B and10B, the fractionation effect is significant. Therefore, the boron isotopic composition may be used to determine the effective boron source indicator and facies. The Longhu potash mining area is one of the main potash mines in Khorat plateau of Laos, and drill hole ZK309 is the representative in the Longhu mining area. The boron isotope geochemical and mineralogical analyses of the salt rock overlying mudstone layers in this drill hole indicate that the δ11B values range from 7. 44‰ to 11. 62‰, 8. 96‰ on average,obviously betweenδ11B value of seawater（ 39. 5‰） and the terrestrial groundwater value（- 3‰ ± 5‰）, mineral composition in the drill hole preserved some characteristics of parent rocks, and quartz is sourced obviously from terrigenous materials.In addition, halite,anhydrite and gypsum are related to residual brine. It is inferred that the rock salt deposition was impacted by terrigenous water at the late stage,and the mudstones were reformed by brine after deposition. The brine might have been generated from dissolution of the underlying salt rocks by meteoric water. This could explain the abnormal sequence of salt rock deposition（ sylvite overlies carnallite）.

关 键 词：地质学 B同位素 泥岩 陆源淡水 老挝龙湖钾盐矿区 

分 类 号：P619.211[天文地球—矿床学]