Numerical modelling of stable isotope (2H and 18O) transport in a hydro-geothermal system: model development and implementation to the Guide Basin, China

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Jiang, Zhenjiao; Mallants, Dirk


2019-02-01


Journal Article


Journal of Hydrology


569


93-105


The groundwater tracers, deuterium (2H or D) and oxygen-18 (18O), are widely used to determine groundwater recharge origin, rate and temperature. Quantitative methods able to interpret δD and δ18O mobility in the subsurface, especially under high pressure and temperature conditions, remain the focus of ongoing research. Here we demonstrate a new numerical model coupled with TOUGH2 to describe the evolution of δD and δ18O in groundwater induced by advection, dispersion, water-rock interaction, and fractionation due to the changes of water phase and density. The new model is tested by modelling the groundwater flow, temperature, fluid density and isotopic composition in a faulted, geothermal system in the Guide Basin, China. We found that the density-driven flow induced by temperature variations can lead to isotope fractionation between low- and high-density water. In addition, the density-driven flow creates multiple flow systems in the fault damage zone, increasing the complexity of the spatiotemporal isotope distribution. The results indicate that, under scenarios where a density contrast occurs, such as in geothermal systems, the relationship between δD and δ18O in recharge water and discharging groundwater can only be fully understood if the coupled processes of fluid flow, heat transport and isotope fractionation in the subsurface are accounted for.


Elsevier


stable isotopes, geothermal system, numerical simulation, density-driven flow


Hydrogeology


EP185373


Journal article - Refereed


English


Jiang, Zhenjiao; Mallants, Dirk. Numerical modelling of stable isotope (2H and 18O) transport in a hydro-geothermal system: model development and implementation to the Guide Basin, China. Journal of Hydrology. 2019; 569:93-105.http://hdl.handle.net/102.100.100/86052?index=1



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