西藏阿里地区泽错大型盐湖锂（硼）矿床的发现及开发利用前景

2016—2018年中国地质调查局天津地质调查中心联合西藏自治区地质矿产勘查开发局第五地质大队组建盐湖调查队伍,针对西藏羌塘盆地西段泽错盐湖开展调查评价工作,探获大型锂(硼)矿产地1处。泽错湖表水体长16.3 km,宽3.3～11.3 km,湖表面积113.8 km2。湖水深度变化较大,四周水较浅,逐渐向中间变深,最深处达44 m,湖水平均深度为24 m,湖面海拔4940 m。泽错盐湖位于藏北羌塘—三江复合板块内,矿区第四纪地层可划分为更新统湖积,全新统现代湖水,全新统冲洪积,全新统冲积和全新统湖积。湖盆可划分基岩裂隙水层、亚砂土孔隙含水层、亚黏土孔隙含水层和湖表卤水4个水文地质单元。经计算直接补充到湖盆表面的大气降水量为1.081×107m3/a,地表水补给湖水量为8.262×107m3/a,地下水补给量为2.052×107m3/a,泽错年补给水量为11.395×107m3/a左右。自然蒸发为泽错湖盆的主要排泄方式,泽错湖水年蒸发量为12.745×107m3/a,年均水量变化值为1.35×107m3/a,地表水补给湖水带入的总盐量为7.8×104t/a。泽错湖盆卤水中主要成盐元素有Cl-、Na+、SO42-、K+、CO32-、HCO3-、B2O3、Mg2+、Li+等,平均矿化度41.57 g/L,pH值为9.31,泽错湖水为高矿化度盐水,水化学类型为硫酸钠亚型。泽错盐湖LiCl平均品位为376.02 mg/L,LiCl资源量为102.68×104t,远景规模达到大型;B2O3平均品位为840 mg/L,B2O3资源量为229.38×104t,远景规模达到大型。在综合分析锂、硼资源需求、提锂技术、盐田建设、气候条件、经济价值等方面的基础上,对泽错盐湖的开发利用前景进行了展望。

The Discovery of lithium-boron large scale deposit in Zetso salt lake, Ngali District of Tibet and its prospects for development and utilization

During 2016-2018, aiming at the Zetso Salt Lake in the western of Qiangtang Basin, Tibet Autonomous Region, Tianjin Center of China Geological Survey joined The No.5 Geological Survey Party of Tibet Autonomous Region Geological and Mineral Exploration and Development Bureau to form a team to carry out the geological survey and assessment, eventually found it is a large scale brine-lithium-Boron deposit. Zetso Salt Lake, with a length of 16.3 km, width within 3.3-11.3 km, has an area of 113.8 km², also, it has a larger range in it depth, with shallow water around it but gradually becoming deeper and deeper to the middle of the lake with the deepest part of 44 m, average water depth of 24 m and the altitude of it is 4940 m. Zetso is located within the Qiangtang-Sanjiang Composite Plates. The Quaternary strata around Zetso can be divided into Pleistocene lacustrine sediments, Holocene alluviation, Holocene alluvial-diluvial, Holocene lacustrine sediments and Holocene surface brine. Lake basin can be divided into four hydrogeological units of bedrock fissure water, subsandy pore aquifer, subclayey pore aquifer and lake brine. By the authors statistics and calculation, the atmospheric precipitation adding into the Zetso directly is 1.081×10⁷ m³/a, the supplies of the surface water into it is 8.262×10⁷ m³/a, the supplies of the underground water into it is 2.052×10⁷ m³/a, as a result, the total watersupply amount per year into Zetso is about 11.395×10⁷ m³/a. Natural evaporation is the main discharge mode in Zetso lake. Its annual evaporation amount is 12.745×10⁷ m³/a, annual average amount value is 1.35×10⁷ m³/a, the total salt amount from surface water supplies into it is 7.8×10⁴ t/a. The main salt brine elements within Zetso are Cl^-, Na⁺, SO₄^2-, K⁺, CO₃^2-, HCO₃^-, B₂O₃, Mg²⁺, Li⁺, etc. The salt lake has an average salinity of 41.57 g/L, pH 9.31, therefore, the brine belongs to high salinity one and its water chemical type is due to sodium sulfate subtypes. The average grade of LiCl is 376.02 mg/L, its resources is 102.68×10⁴ t, thus, it has been proved to be a large scale brine-lithium deposit; in the meantime, the average grade of B₂O₃ is 840 mg/L, its resources is 229.38×10⁴ t, it also has been proved to be a large scale brine-boron deposit. On the foundation of the comprehensive analysis of lithium, boron resource requirements, extracting lithium technology, construction of salt field, and climatic conditions as well as economic value etc., the authors make a prospection of exploitation and utilization to Zetso salt lake in the future.