Carolina Munoz-Saez Adam M. Hudson Linda V. Godfrey Jay M. Thompson Lauren Sankovitch 2025 <p><span>Continental hydrothermal systems are critical avenues for the crustal transport of heat and mass captured for geothermal energy and mineral exploration. Thus, understanding their temporal evolution and longevity is important for resource characterization. Deposits of microlaminated siliceous sinter, common surface expressions of high temperature reservoirs (&gt; 170 °C), have the potential to trace hydrothermal histories. Geothermal reservoirs are often located within uranium-bearing silicic volcanic rock where subsurface fluid-rock interactions extract U into hydrothermal fluids. U incorporated in the surface sinter deposit has the potential to provide a U—</span><span>Th disequilibrium dating option. We focus on samples from El Tatio geyser field in the Altiplano of northern Chile, the largest geothermal system in the Andes. Our resulting&nbsp;</span>²³⁰<span>Th/U ages, along with the water and deposit elemental compositions, suggest concentrations of U and Th vary predictably along the sinter apron. While distal facies containing the highest U concentrations (&gt; 50 μg/g) are least affected by detrital Th corrections, they can display suspected open-system behavior. In contrast, more medial facies, where bacterial mats and other porous textures are co</span>mmonly concentrated, have only trace amounts of U (&lt; 0.1 μg/g), which leads to unreliable or geologically improbable dates. Proximal facies tend to date most consistently. By comparing existing&nbsp;¹⁴C ages with&nbsp;²³⁰Th/U results,&nbsp;²³⁰Th/U ages tend to be younger than the&nbsp;¹⁴C ages, supporting the presence of a&nbsp;¹⁴C-dead carbon influence. New data confirm that the onset of geothermal activity at El Tatio goes back to the late Pleistocene.</p> application/pdf 10.1016/j.jvolgeores.2025.108324 en Elsevier Applying U-Th disequilbrium for dating siliceous sinters article