Alteration and elements migration of detrital zircons from the Daying uranium deposit in the Ordos Basin, China

Abstract

To study the alteration and elements migration characteristics of detrital zircon in sandstone-hosted uranium deposits, we analyzed three groups of zircon samples from the Jurassic Zhiluo Formation of the Daying uranium deposit in the northern Ordos Basin, China. One group of zircons was selected from the uranium metallogenic belt, while the other two groups were obtained from the non-metallogenic belt. According to the back-scattered electron (BSE) images and energy dispersive spectrometer (EDS) elemental maps, zircon can be divided into altered and unaltered zircon, and alteration types include oscillatory zoning alteration and rim alteration. The rare earth element (REE) pattern of unaltered zircon is characterized by positive Ce anomalies and negative Eu anomalies, similar with those of the Early Precambrian metamorphic rocks of the Khondalite Belt in the North China Craton. The results of the trace element analysis showed that REEs, uranium, and non-formula elements (e.g., Al, Fe, and Ca) are abundant in the altered area, specifically observable in the BSE images, and along with the EDS elemental maps of altered zircon in the uranium metallogenic belt, exhibited higher uranium concentrations and more developed cracks. Interaction of fluids with the radiation-damaged zircon lattice can provide a favorable conditions for fluid infiltration and element migration. The action of uranium-bearing fluids and the radiation of uranium minerals can induce zircon alteration and crack formation, which is instructive in uranium prospecting.