西藏当雄错流域热泉成因机制及其对盐湖成矿物质(Li-Rb-Cs)的供给

Origin mechanism of thermal springs and their supply of minerals to the salt lake(Li-Rb-Cs)in the Tangqung Co watershed of Tibet

【研究目的】西藏当雄错地区位于当惹雍错—许如错裂谷的北部,区内的曲热白玛和扎日取生等地分布有多处热水活动,由于泉水向当雄错盐湖供给了Li和B物质,因此对其水化学特征和成因研究具有十分重要的科学意义。【研究方法】采集了6件泉水样品并进行化学组分和稳定同位素分析,计算了泉水的主要化学系数和矿物饱和指数,对泉水的化学组分进行了聚类分析。【研究结果】结果表明,曲热白玛泉水富集元素Li、B、Rb、Cs等元素。泉水受大气降水和雪水补给,具有浅循环特征。曲热白玛泉水具有较长的径流路径和更强烈的水岩相互作用,泉水中的HCO_(3)-主要来自碳酸盐岩和岩浆活动产生的CO_(2)。SiO_(2)温标计算的热储温度相对可靠,曲热白玛样品的热储温度为123.33~128.22℃。【结论】当雄错地区的热水活动受控于南北向的当惹雍错—许如错裂谷,受地壳深部的局部熔融层影响,热水与硅酸盐矿物发生了水岩作用,携带了Li、Rb、Cs等微量元素,在混入地表冷水后,还与二叠系、白垩系的碳酸盐岩发生了水岩作用,沿区内的活动断裂上升至地表最终汇入当雄错湖水。这一现象表明,西藏部分富Li、Rb盐湖的成矿物质来源可能与广泛的南北向裂谷活动有关,这些裂谷不仅提供了盐湖聚集成矿的地理空间,同时也提供了沟通深部物源和地表空间的通道。

This paper is the result of mineral exploration engineering.[Objective]The Tangqung Co area in Tibet is located in the north of Tangra Yum Co-Xuru Co rift.The presence of geothermal springs in locations like Qurebaima and Zhariqusheng has prompted the need for a comprehensive study of their hydrochemical characteristics and origin,particularly regarding their contribution of Li and Rb substances to the Tangqung Co salt lake.[Methods]This study involved the collection and analysis of six spring water samples to determine their chemical composition and stable isotopes.Various chemical coefficients and mineral saturation indices were calculated,and cluster analysis was performed on the chemical components of the springs.[Results]The findings reveal that Qurebaima spring waters exhibit enrichments in elements such as Li,B,Rb,and Cs.These springs are influenced by atmospheric rainfall and snowmelt,displaying shallow circulation characteristics.The springs'extended flow path and substantial water-rock interaction contribute to the predominance of HCO_(3)-originating from carbonate rocks and CO_(2) produced by magmatic activity.Moreover,the calculated thermal reservoir temperature based on SiO2 geothermometers falls within the range of 123.33 to 128.22℃ for Qurebaima samples.[Conclusions]Geothermal activity in the Tangqung Co area is governed by the N-S trending Tangra Yum Co-Xuru Co rift valley,wherein the geothermal water acquires Li,Rb,Cs,and other trace elements through interactions with silicate minerals.Additionally,the water-rock interaction extends to the Permian and Cretaceous carbonate rocks,ascending along active faults in the region,and ultimately mixing with water from the Tangqung Co lake.This phenomenon suggests that the formation of Li and Rb-rich salt lakes in Tibet may be associated with extensive N-S rift activities,which not only provide geographic space for the accumulation and mineralization of salt lakes but also act as conduits between deep sources and surface environments.