10Be in Geothermal Systems

Abstract

10Be is a cosmogenic radioactive isotope previously used as a dating tool or as a tracer of young surficial processes. In order to test its possible applications to geothermal systems, we studies its behavior in natural system, we studies its behavior in natural systems, including waters and their associated rocks and sediments. 10Be concentrations range from 10/3 to 10/5 atoms/g in waters, 10/4 to 10/6 atoms/g in volcanic rocks, 10/6 to 10/10 atoms/g in sediments and 10/4 to 10/10 atoms/g in hydrothermal sulfides and oxides. These concentrations can be explained by the strong pH dependence exhibited by the 10Be solubility. Above pH = 5.2 there is a very effective sorption and retention of the isotope by the fine grained surficial materials (Kd = 10/6) whereas under pH = 5.2, 10Be can stay in solution and migrate easily though the system (Kd = 10/2). In addition we observed that high salinity also enhances the solubility of 10Be. These results are only the firs stone on the way to the knowledge of the 10Be behavior in geothermal systems an they appear to be promising.