Effect of leaching on the crystallographic sites of trace metals associated with natural cements (site of Maqarin, Jordan): Case of Cr

This paper reports an investigation of the oxidation state of Cr in samples of natural cements formed 500 ky ago in Maqarin (Jordan). The analyses were conducted using the Scanning Microscope from the ID21 beamline at the ESRF (Grenoble-France) operated in fluorescence mode. Cr(III) and Cr(VI) maps are collected on these samples at a resolution of 1 mum. The results suggest the slow oxidation of Cr(III) to Cr(VI) upon alteration of the cements in conditions of high pH and low to intermediate oxygen fugacity.