Effects of basic intrusions on REE mobility of sandstones and their geological significance: A case study from the Qianjiadian sandstone-hosted uranium deposit in the Songliao Basin

REE geochemistry of sandstones and their carbonate cements from the Upper Cretaceous Yaojia Formation in the Qianjiadian uranium deposit, southern Songliao Basin are illustrated in order to reveal effects of basic intrusions on REE mobility of sandstones and their geological significance. Compared with the sandstones far away from the diabase dikes, the sandstones near the diabase dikes are obviously depleted in REEs. ∑LREE content, ∑HREE content and ∑REE content all increase with an increase of the distance away from the diabase dikes. Carbonate cements in the sandstones comprise of dolomite, siderite, ankerite and calcite, which are successively formed from the early to late stage. In the sandstones near the diabase dikes, the dolomite and siderite are partly dissolved, and the ankerite is accumulated. ΣLREE content and ΣHREE content are both gradually decreasing in turn from the dolomite, to siderite, to ankerite, and to calcite. Dolomite content is positively correlated with ∑HREE content, siderite content is positively correlated with ∑LREE content or ∑HREE content, and ankerite content is inversely correlated with ∑LREE content. Dissolution of the dolomite and siderite and formation of the ankerite were aroused by intrusion of the diabase dikes, resulting in the sandstones near the diabase dikes being depleted in REEs. The study suggests that high-grade uranium mineralization may be attributed to the diabase dikes, REE depletion of the sandstones can be severe as a new prospecting indicator, and sandstones affected by igneous intrusions should be avoided during sampling for sandstone provenance by REEs.