Influence of the mineralogical composition on the self-potential response to advection of KCl concentration fronts through sand

10 11 We measured the self-potential (SP) response to advective transport of KCl 12 concentration fronts through two laboratory-scale sand-bodies with different 13 mineralogical composition. In pure quartz sand, the amplitude and polarity of the SP 14 signals agreed with a previously published model. In sand containing 3 % potassic 15 feldspars and 1 % micas and clays, the shape of the SP response differed significantly: the 16 amplitude was much larger than the model prediction and a change in polarity occurred 17 after the passage of the front. Furthermore, the KCl concentration in the effluent was 18 strongly reduced. We suggest that the minor mineral phases reacted with the K ions, 19 trapping them during the front passage and releasing them later. Even though the 20 reactions involved are not fully identified to date, this study demonstrates that even small 21 amounts of chemically active mineral phases, such as micas or clays, can significantly 22 influence the SP signals. 23