Strontium Isotope Fractionation in Soils and Pedogenic Processes

The stable isotope composition of strontium (the ratio 88Sr/86Sr expressed as δ88/86Sr) showed significant fractionation in mountain soils of the Judea Highland. In order to understand this phenomenon, we studied the elemental composition and the stable and radiogenic Sr isotopic composition in soil transects conducted from semi-arid (desert fringe) to wetter (Mediterranean) climate zones. These transects were selected because the degree of soil leaching depends on the amount of precipitation and the permeability of the underlying bedrock. These soils are the pedogenic products of leaching of the accumulated desert dust and the underlying carbonate bedrocks resulting in, among others, enrichment of the residual soils in Al-clays. A clear negative correlation was found between the δ88/86Sr and Al2O3 (Al-clay content) values of the soils, the high δ88/86Sr-low Al2O3 being the dust end-member. This preliminary study demonstrates the feasibility of using stable 88Sr-86Sr isotopes as tracers of terrestrial weathering processes.