Geochemistry of rare earth elements (REE) and redox sensitive elements (RSE) of pyrometamorphic rocks, central Jordan

Supergene alteration processes have led to the enrichment of rare earth elements (REE) and reduced sensitive elements (RSE) in the Pleistocene-Holocene travertine, regolith, and the pyrometamorphic varicolored marble of central Jordan. Thirty-two representative samples were collected from open quarries and trenches and were subjected for geochemical investigations. The EDS/ICP-ES quantitative results of the rare earth elements (REE) and the reduced sensitive elements (RSE) have indicated that travertine hosts the highest values. The REE occur in the bituminous marl and the secondary fillings of the varicolored marble as vanadate, in the varicolored marble as oxides, and in the travertine and regolith as oxides and phosphates. Naturally occurring cerium oxide (CeO2) is reported for the first time in the varicolored marble as a result of combustion of the bituminous marl. Light rare earth elements (LREE) are dominated by La and Ce and are enriched as a result of its liberation and mobilization from the source rocks (phosphorite, bituminous marl, and varicolored marble) by the action of circulating alkaline hydroxide water. Cerium anomaly relates to the decrease in its solubility and oxidation of Ce3+ to Ce4+.