Experimental modeling of the conditions for the Formation of Precambrian weathering profiles. Composition of solutions and redistribution of lanthanides

Abstract

Experimental test data of paleproterozoic granitoids leaching in oxygen and argon conditions and in various acid alkaline environments showed that active leaching and forming of solutions with total cations concentration of more than 20mg/l and K/Na>1 can only occur in an acid oxiditation environment. In humid conditions solutions with negative cerium anomaly are forming, when in arid conditions the cerium anomaly does not exist. During the formation of hypergene profiles in the Early Precambrian there was a redistribution of components between the residual material of the weathering crust and the authigenic component. The residual part of the weathering crust is combined with LREE while the authigenous component of the weathering crust got enriched with the leached components. Drained solution at the outlet of the hypergene profile has acquired ultrafresh characteristics, but a higher ratio Rb/Sr and K/Na. Refs 21. Figs 4. Tables 8.