Dating methods for travertine and siliceous sinter in geothermal systems: Progress and applications

Sinters of geothermal system are usually dominated by travertine and siliceous sinter. With rich information on multi-temporal and spatial scales, they can be used to restore paleohydrological and paleoclimatic histories, reconstruct the evolutionary process of regional hydrothermal activity, and constrain tectonic modes. Accurate dating of sinters is the basis of relevant researches. Common dating methods include radiocarbon dating (based on inorganic and organic carbon), uranium series disequilibrium dating, cosmogenic nuclide dating, optically stimulated luminescence (OSL) dating, and electron spin resonance dating. Radiocarbon dating has primarily used for the dating of hot-spring sinters in China, followed by electron spin resonance dating and uranium series disequilibrium dating, which have been applied more widely. This study systematically reviewed the basic principles, dating ranges, applicable conditions, and requirements for samples of these methods. Furthermore, the existing problems and future development directions of these methods are proposed. For travertine samples, those with high purity carbon can be dated using organic carbon-based radiocarbon and uranium series disequilibrium dating, while well-consolidated samples can also be dated using electron spin resonance method. For these samples, paleomagnetic dating worth further exploration. For siliceous sinter samples, organic carbon-based radiocarbon dating and electron spin resonance dating are more suitable, while uranium series disequilibrium and paleomagnetic dating can be tried. Additionally, cosmogenic nuclide dating, such as those using ¹⁰Be and ²⁶Al, can be used for paleosinter dating. The two main challenges of dating are sample with low purity problem (or difficult correction) and limited dating range. For the first challenge, the ion probe technique can be used to determine the isotopes of U and Th in the microscopically high-purity calcite to obtain the sample ages. To improve the representativeness of problem samples, it is necessary to measure as many uniformly distributed points as possible. These data can be used to determine the sinter ages on a million-year scale by obtaining long-half-life cosmogenic nuclides. Further development of dating methods will focuses on the research of new techniques and the quantitative correction of low-purity samples.