Iron oxide precipitate in seepage of groundwater from a landslide slip zone

Orange precipitate was collected at the mouth of groundwater drainage tubes from the Kumanashi Landslide slip zone in Toyama prefecture, Northwest Japan. Data from XRF, X-ray diffraction, and Mossbauer spectroscopy determined the precipitate as hydrous ferric oxide (HFO) bearing multi-elements such as phosphorous, silica, calcium, etc. The occurrence of HFO may indicate an oxidation of ferrous iron in the percolated groundwater from the slip zone. Moreover, the precipitate iron should be mobilized with groundwater circulation from the slip zone, whose reducing condition was determined by the iron speciation on the same type of landslide profiles within the study area in previous studies. The HFO precipitate may be considered as a secondary reliable indicator to locate the seepage of a slip zone on surface, especially for a landslide newly investigated under wet-warm climate.