Abstract:

Several uranium anomalies in Yan'an Formation, Unit V, have been found in the north-east margin of Ordos Basin, which are important for building the prospective uranium reserve base. According to sedimentology, the depositional system of Unit V, Yan'an Formation, has been reconstructed, it is revealed that there is braided stream system in the northwest of study area, and meandering stream system develops in the southeast. According to successfully extracting and graphing of uranium anomalies, the self-center uranium anomalies and their close relationship with meandering stream systems have been observed. The uranium anomaly always develops in the distributary and turning place of meandering stream system, and is related with thin sand area (whose sand thickness and sand ratio are less than 30 meters and 40% respectively), thicker coal, fine lithology, but the highest value of uranium anomaly exists in middle sandstone.

Key words: depositional system, uranium anomaly, Unit V, Yan'an Formation, the north-east margin of Ordos Basin