老挝万象通芒矿区成盐期元素地球化学特征研究

Study of Geochemical Characteristics of Salt Deposits during Halogeneses in Tongmang Mining Area,Vientiane, Laos

中文关键词:  万象盆地  通芒矿区  钾盐沉积  元素地球化学  海相成因

英文关键词::Vientiane Basin  Tongmang mining area  Potash deposits  Element geochemistry  Marine origin

中文摘要:

      呵叻高原是世界上最大的钾盐矿床之一,老挝万象盆地是呵叻高原北部沙空那空盆地的一个次级盆地,通芒矿区则是万象盆地钾盐矿床的重要组成部分。近期,大量钾盐地质勘探工作的实施为该地区钾盐沉积的研究提供了良好条件和物质基础。研究表明,含盐地层包括上、中、下3个盐段,巨厚钾镁盐主要富集在塔贡组下盐段。盐类矿物主要包括石盐、光卤石、钾石盐、水氯镁石、溢晶石、硬石膏等,还包括一些碳酸盐和硼酸盐矿物。矿石类型以光卤石矿为主。含盐层位的Br含量、Br×10³/Cl比值在剖面上的变化指示了成盐期卤水不断蒸发浓缩,最终形成了具有重要经济价值的钾镁盐矿床。与世界其它海相及陆相钾盐矿床对比表明,通芒矿区钾盐沉积具有明显的海相特征,成盐成钾物质应该来自海水。

英文摘要:

      :The potash deposit on Khorat Plateau is among the largest ones in the world.The Vientiane Basin is one of subbasins of Sakon Nakhon Basin which is in the north of Khorat Plateau.Whereas the Tongmang mining area is an important part of Vientiane potash deposits.A large of geological explorations conducted in study area recently provided good conditions and substantial bases to study potash deposit in study area.Study results show that the salt-containing stratum comprises of three sections of upper,middle and lower unit.The voluminous K-Mg salts mainly are enriched in the lower unit.The main salt minerals include halite,carnallite,sylvite,bischofite,tachyhydrite,anhydrite,etc. Additionally minor carbonates and borates were found in these salts.The dominant ore type is the carnallitite type.The variations of bromine contents and Br×10³/Cl ratios in profile indicate that the brines have continuously been evaporated and concentrated during halogeneses and eventually formed K-Mg salt deposits with significantly economic values.Comparing with other marine or nonmarine potash deposits,the Tongmang potash deposit has an obvious marine signature.Therefore,it is concluded that these salts in study area should be derived from seawater.