| 引用本文: | 吴昊阳,谭亮成,臧婧杰,林旭,唐慧茹,陈律凡.2026.洞穴次生碳酸盐锶同位素研究进展与展望[J].地球环境学报,17(4):1137-1146 |
| WU Haoyang,TAN Liangcheng,ZANG Jingjie,LIN Xu,TANG Huiru,CHEN Lüfan.2026.Advances and prospects in strontium isotope research of secondary carbonates in caves[J].Journal of Earth Environment,17(4):1137-1146 |
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| 洞穴次生碳酸盐锶同位素研究进展与展望 |
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吴昊阳1，2，谭亮成1，臧婧杰1，3，林旭1，2，唐慧茹1，2，陈律凡1，2
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1.中国科学院地球环境研究所 黄土科学全国重点实验室，西安 710061 ； 2.中国科学院大学，北京 100049 ；3.中国地质大学（武汉） 地球与行星科学学院，武汉 430074
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| 摘要: |
| 洞穴次生碳酸盐是重建过去气候环境变化的重要载体，锶同位素（87Sr/86Sr）因在碳酸盐溶解、迁移和沉淀过程中基本不发生明显分馏，可示踪水-岩相互作用、外源物质输入和岩溶水文过程。文章通过24个代表性洞穴系统梳理洞穴次生碳酸盐及滴水87Sr/86Sr研究进展。结果显示，已有研究站点分布于亚洲、美洲、欧洲和大洋洲，汇总的87Sr/86Sr总体范围约为0.70577—0.72500，其中Moaning Cave为0.70577—0.70689，Tamboril Cave为0.718—0.725，表明不同地质背景和Sr端元组成差异显著。洞穴Sr主要包括来自碳酸盐基岩溶解的内源Sr，以及来自土壤风化、大气粉尘、海雾飞沫等过程的外源Sr。地中海及邻近地区记录多受粉尘输入和大气环流影响，亚洲季风区记录主要与粉尘活动、区域干湿变化和岩溶水文有关，南美季风区记录则更多反映局地水文和植被-土壤过程。总体而言，87Sr/86Sr不宜被视为温度或降水量的单一指标，而应作为揭示Sr来源、迁移路径和环境过程变化的综合示踪指标。未来需扩大研究范围、高精度测试、现代洞穴监测、多指标联合和定量化研究。 |
| 关键词: 石笋 87Sr/86Sr 古气候意义 水-岩相互作用 |
| DOI：10.7515/JEE2025022 |
| CSTR：32259.14.JEE2025022 |
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| 基金项目:国家杰出青年科学基金项目（42323705）；中国科学院“西部之光-西部交叉团队”项目（xbzg-zdsys-202217） |
| 英文基金项目: |
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| Advances and prospects in strontium isotope research of secondary carbonates in caves |
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WU Haoyang1，2，TAN Liangcheng1，ZANG Jingjie1，3，LIN Xu1，2，TANG Huiru1，2，CHEN Lüfan1，2
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1.State Key Laboratory of Loess Science, Institute of Earth Environment, Chinese Academy of Sciences, Xi’an 710061 , China ；2.University of Chinese Academy of Sciences, Beijing 100049 , China ；3.School of Earth and Planetary Sciences, China University of Geosciences (Wuhan), Wuhan 430074 , China
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| Abstract: |
| Background, aim, and scope Cave secondary carbonates, especially speleothems, are widely used as archives for reconstructing past climatic and environmental changes because of their broad spatial distribution, high dating precision, and potential for high-resolution geochemical analysis. Among the available proxies, strontium isotopes ratio (87Sr/86Sr) have received increasing attention in recent decades. Unlike stable carbon and oxygen isotopes, the 87Sr/86Sr isotope ratio is generally not significantly fractionated during carbonate dissolution, transport, and precipitation. It therefore provides a valuable tracer for identifying material sources and evaluating the relative influence of water-rock interactions, soil processes, atmospheric inputs, and karst hydrological pathways. This review aims to synthesize published 87Sr/86Sr studies of cave secondary carbonates and drip waters, clarify the main geochemical processes controlling 87Sr/86Sr variations, evaluate their paleoclimatic significance in different climatic regions, and identify the major limitations and future directions of this proxy. Materials and methods This review is based on a systematic compilation and comparison of published 87Sr/86Sr data from cave systems worldwide. The reviewed materials include speleothems, bedrock, modern drip waters, soil waters, and related cave system components where available. The study sites are mainly distributed in Asia, the Americas, Europe, and Oceania, covering different climatic regimes, such as the Mediterranean region, the Asian monsoon region, the South American monsoon region, and temperate to subtropical karst settings. Information on cave locations, host geological background, sample type, reported 87Sr/86Sr range, and interpreted environmental significance was summarized to evaluate regional similarities and differences. Particular attention was paid to the distinction between internal Sr derived from carbonate bedrock or aquifer materials and external Sr supplied by soil weathering, vegetation cycling, atmospheric dust, sea salt or sea spray inputs, and other atmospheric deposits. Results The available records show that cave 87Sr/86Sr research has been conducted at least 24 representative sites worldwide. The compiled 87Sr/86Sr values of cave secondary carbonates or drip waters range approximately from 0.70577 to 0.72500, indicating large differences among geological settings and Sr-source end-members. The lowest values are reported from Moaning Cave, where 87Sr/86Sr ranges from 0.70577 to 0.70689, whereas the highest values are reported from Tamboril Cave, where 87Sr/86Sr ranges from 0.718 to 0.725. These values demonstrate that the 87Sr/86Sr signal in cave deposits is strongly controlled by source mixing rather than by a single climatic variable. In Mediterranean and adjacent regions, speleothem 87Sr/86Sr records commonly reflect changes in atmospheric dust input and regional atmospheric circulation. In the Asian monsoon region, 87Sr/86Sr variations are related to both dust activity and hydroclimatic processes, including soil weathering, infiltration pathways, and the residence time of karst water. In the South American monsoon region, existing studies indicate that 87Sr/86Sr can record local moisture conditions, vegetation-soil processes, and water-rock interaction intensity. Modern monitoring studies further show that drip water 87Sr/86Sr may inherit signals from soil water, bedrock dissolution, and overlying ecological conditions, but the relative contribution of these components differs among cave systems. Discussion The paleoclimatic interpretation of cave 87Sr/86Sr is region-specific and must be based on a clear understanding of Sr sources and transport processes. A higher 87Sr/86Sr value does not necessarily indicate either a drier or a wetter climate. Its environmental meaning depends on whether the high-ratio end-member is supplied by atmospheric dust, soil and vegetation, silicate weathering products, carbonate bedrock, or deeper groundwater. Similarly, a lower 87Sr/86Sr value may reflect enhanced carbonate bedrock dissolution, rapid infiltration of low- 87Sr/86Sr ratio waters, or reduced external input, depending on the geological and hydrological setting. Therefore, 87Sr/86Sr should be interpreted through an “end-member identification-process constraint-climate interpretation” framework. Reliable interpretation requires constraints from host rock composition, soil and vegetation cover, drip water chemistry, atmospheric dust sources, hydrological pathways, and cave monitoring data. Comparisons with δ18O, δ13C, Mg/Ca, Sr/Ca, Ba/Ca, particulate elements, and growth rates can help separate source effects from hydrological and depositional effects. Conclusions Cave secondary carbonate 87Sr/86Sr is a powerful proxy for tracing material sources and reconstructing environmental processes in karst systems. Its greatest value lies not in directly recording temperature or precipitation, but in revealing changes in Sr source contributions, water-rock interactions, dust input, soil weathering, vegetation dynamics, and hydrological connectivity. Existing studies show that the same direction of 87Sr/86Sr change may have different climatic meanings in different cave systems. This explains why some records associate higher 87Sr/86Sr values with dry and dusty conditions, whereas others link them to enhanced soil weathering or wetter hydroclimatic conditions. Thus, cave 87Sr/86Sr records should be regarded as process-sensitive proxies whose interpretation depends on regional geological background and modern cave system behavior. Recommendations and perspectives Future studies should focus on five major aspects. First, more records are needed from currently underrepresented regions, and a standardized global database of cave 87Sr/86Sr records should be established. Second, high-precision and low-consumption analytical techniques should be further developed to improve temporal resolution and reduce the sample amount required for solid carbonate 87Sr/86Sr measurements. Third, long-term modern monitoring of cave drip waters, soil waters, bedrock, atmospheric deposition, vegetation, and the cave microclimate should be strengthened to establish robust transfer functions between modern processes and fossil records. Fourth, quantitative source-apportionment models should be improved by combining 87Sr/86Sr with Sr concentrations, trace-element ratios, and independent environmental proxies. Fifth, future research should shift from qualitative interpretation to quantitative source apportionment of 87Sr/86Sr by adopting multi-end-member models, mass balance calculations, and Bayesian methods, and integrating multiple numerical models to validate geochemical results, thereby improving the reliability of paleoclimate reconstruction based on this proxy. |
| Key words: speleothems 87Sr/86Sr paleoclimate significance water-rock interaction |
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