Sources, enrichment mechanisms, and resource effects of rare metal elements-enriched geothermal springs in Xizang, China

IF 6 2区 地球科学 Q1 GEOSCIENCES, MULTIDISCIPLINARY
Fei Xue, Hongbing Tan, Xiying Zhang, Jinbao Su
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引用次数: 0

Abstract

Rare metals such as lithium (Li), rubidium (Rb), and cesium (Cs) are strategically crucial mineral resources for the development of emerging industries in China. Ensuring a stable long-term supply of these resources is essential. The geothermal systems in Xizang, China are well-developed, with a wide distribution of various types. Most high-temperature geothermal systems in Xizang are exceptionally enriched in rare metal elements (RMEs) and have the potential to become a new source of rare metals to secure China’s strategic mineral resource supply in the future. A close relationship also exists between the geothermal system and the special salt lake resources on the Tibetan Plateau. Geothermal springs thus play a key role in the migration and enrichment of RMEs from deep to shallow parts of the crust, in the transition between endogenous and exogenous mineralization, and source-to-sink processes. However, the mechanisms of element enrichment and evolution in these springs have not been systematically discussed, and many theoretical issues remain to be investigated. Based on summarizing and analyzing previous research, this study employs hydrochemical and isotopic geochemistry methods to investigate typical geothermal springs across Xizang and explore the anomalous enrichment mechanism of RMEs, and the resource effects of geothermal springs. Comprehensive analysis shows that the total dissolved solids (TDS) and hydrochemical types of geothermal springs are similar to those of major geothermal fields worldwide, but the Tibetan springs are abnormally rich in Li (averaging 5.48 mg/L), Rb (averaging 0.75 mg/L), and Cs (averaging 3.58 mg/L), which are hundreds to thousands of times more concentrated than natural waters. The distribution of these enriched geothermal springs is controlled by the Yarlung Zangbo suture zone and the extended N-S trending rifts, especially in the intersection zone of the two, where the geothermal springs are the most enriched. Based on the spatial distribution, isotopic, and elemental geochemistry, the RMEs enriched in Tibetan geothermal springs are mainly derived from the magmatic-hydrothermal fluids generated by the partial melting of the subducted Indian plate under the Eurasian continent. These fluids not only maintain geothermal activities as a heat source but also participate in the material cycle of the geothermal spring as a material source. Against the background of regional crustal enrichment in RMEs, incompatible elements such as Li, Rb, and Cs are gradually enriched in magmatic-hydrothermal processes including partial melting in the source, magmatic differentiation, and hydrothermal fluid exsolution, and some ore-forming elements are further extracted from surrounding rocks through deep high-temperature water-rock interactions. Eventually, an eruption occurs, and these fluids move to the surface to form a geothermal spring rich in RMEs. With the drainage of geothermal springs, the RMEs are continuously transported to the lake basin by surface runoff and continue to concentrate and evolve into salt lake brines under an extremely arid climate environment, constituting an endogenous source and exogenous accumulation salt lake metallogenic model. This comprehensive explanation of the sources, migration, enrichment mechanisms, and resource effects of geothermal springs will deepen the understanding of rare metal mineralization processes, and aid in the advancement of theoretical models for key rare metal mineral resources in various geological bodies of the Tibetan Plateau, significantly expanding exploration scopes and accurately assessing the resource potential of RMEs.

中国西藏稀有金属元素富集地热泉的来源、富集机制和资源效应
锂(Li)、铷(Rb)和铯(Cs)等稀有金属是对中国新兴产业发展具有战略意义的重要矿产资源。确保这些资源的长期稳定供应至关重要。中国西藏的地热系统十分发达,各种类型分布广泛。西藏大部分高温地热系统的稀有金属元素(RMEs)含量特别丰富,有望成为未来保障中国战略性矿产资源供应的稀有金属新来源。地热系统与青藏高原特殊的盐湖资源之间也存在着密切的关系。因此,地热泉在稀有金属从地壳深部向浅部的迁移和富集、内源成矿和外源成矿的过渡以及源-汇过程中发挥着关键作用。然而,这些泉水中元素富集和演化的机制尚未得到系统讨论,许多理论问题仍有待研究。本研究在总结分析前人研究的基础上,采用水化学和同位素地球化学方法对西藏各地典型地热泉进行了研究,探讨了RMEs的异常富集机制和地热泉的资源效应。综合分析表明,地热泉的总溶解固体(TDS)和水化学类型与世界主要地热田相似,但西藏地热泉的锂元素(平均5.48毫克/升)、铷元素(平均0.75毫克/升)和铯元素(平均3.58毫克/升)异常富集,是天然水的数百倍至数千倍。这些富集地热泉的分布受雅鲁藏布江缝合带和延伸的 N-S 向断裂带的控制,尤其是在两者的交汇地带,地热泉的富集程度最高。从空间分布、同位素和元素地球化学角度看,西藏地热泉富集的熔岩热液主要来源于欧亚大陆下俯冲的印度板块部分融化产生的岩浆热液。这些流体不仅作为热源维持地热活动,还作为物质源参与地热泉的物质循环。在区域地壳富集 RME 的背景下,Li、Rb 和 Cs 等不相容元素在岩浆-热液过程中逐渐富集,包括源头部分熔融、岩浆分异和热液外溶,一些成矿元素通过深层高温水-岩石相互作用进一步从周围岩石中提取。最终,火山喷发,这些流体流向地表,形成富含 RME 的地热泉。随着地热泉水的排泄,RMEs 被地表径流源源不断地输送到湖盆中,在极度干旱的气候环境下不断富集演化成盐湖卤水,构成了内源外积的盐湖成矿模式。通过对地热泉的来源、迁移、富集机制和资源效应的全面解释,将加深对稀有金属成矿过程的认识,有助于推进青藏高原各类地质体中关键稀有金属矿产资源理论模型的建立,极大地拓展勘查范围,准确评估稀有金属矿产的资源潜力。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
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来源期刊
Science China Earth Sciences
Science China Earth Sciences GEOSCIENCES, MULTIDISCIPLINARY-
CiteScore
9.60
自引率
5.30%
发文量
135
审稿时长
3-8 weeks
期刊介绍: Science China Earth Sciences, an academic journal cosponsored by the Chinese Academy of Sciences and the National Natural Science Foundation of China, and published by Science China Press, is committed to publishing high-quality, original results in both basic and applied research.
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