Paleo-environmental constraints on uranium mineralization in the Ordos Basin: Evidence from the color zoning of U-bearing rock series

Color zoning of strata of Mesozoic continental basins in North China is closely correlated with the sedimentary environments of sandstone-type uranium deposits. Systematic research has been conducted on the colors of U-bearing rock series within the Ordos Basin by using data of several ten thousands...
Ausführliche Beschreibung

Color zoning of strata of Mesozoic continental basins in North China is closely correlated with the sedimentary environments of sandstone-type uranium deposits. Systematic research has been conducted on the colors of U-bearing rock series within the Ordos Basin by using data of several ten thousands of drill holes from coal and oil fields. Taking an ore cluster as the unit, well-tie sections of deposit areas were compiled to analyze the vertical and lateral spatial variations in different color zones of rocks. Taking the basin as the unit, two typical well-tie sections in the central-northern basin were compiled in order to summarize the rock color zoning laws of U-bearing rock series within ore clusters and the entire basin. Lithogeochemical characteristics of different color zones in deposit areas and ore barren areas were studied. Especially, variations in trace elements in different color zones and the paleo-sedimentary environments they reflect were discussed. Within the Ordos Basin, from the basin margin to the center and from the U ore clusters to the ore barren areas, colors of the Zhiluo Formation U-bearing rock series generally display vertical zoning (i.e., from up downwards, red–green–gray [grayish black]) and show no lateral zoning characteristics. U ore beds mostly occur in the lower part of the green zone and the upper part of the gray zone. This conclusion differs greatly from the understanding on rock color zoning related to classic interlayer-oxidation-zone metallogenic theory. Hence, a correct understanding on color zoning of U-bearing rock series within the Ordos Basin is of great significance not only to U mineralization exploration but also to research on sandstone-type U mineralization theory. Ausführliche Beschreibung