ANALYSES OF LITHOFACIES AND PALEOGEOGRAPHIC CONDITIONS OF TERTIARY FOR IN-SITU LEACHABLE SANDSTONE URANIUM IN LONGJIANG-ZHAOZHOU AREA

By analyzing drill-hole lithology, comprehensive log and paleontology of the Tertiary formations in Longjiang-Zhaozhou area, the paper focuses on the lithofacies and paleogeographic features of Yi'an, Da'an and Taikang formations of Tertiary. The conclusions are as follows.
(1)Due to a weak surface water power of Yi'an period, the sediment range was limited, with single material source. The major precipitation facies were mudstone and siltstone of limnetic facies and siltstone and fine sandstone of alluvial-flood plain facies.
(2)During Da'an period, numerous materials were brought from the northern and northwestern parts of sedimentary basin by strong surface water power. Sedimentary range expanded from north to south. A north-south extending banded deposition formed along the west margin of the basin. Alluvial-proluvial conglomerate and alluvial-flood plain facies sandstone and siltstone were principal facies.
(3)As for Taikang period, stronger water flow from the west broadened the sedimentary range to east and south. Grey and greyish green sandstone, siltstone and pelitic siltstone of alluvial-flood plain facies were developed widely and became chief facies. Brown and yellow conglomerate of alluvial-proluvial facies was developed along the westem margin of the basin.
(4)According to the lithofaces criterion of in-situ leachable sandstone, Da'an and Taikang formations are ideal layers for in-situ leachable sandstone uranium deposit, because thick sandstone bodies are developed in Da'an alluvial-proluvial facies and Taikang alluvial-flood plain facies, and more, interlayer oxidation has been found in sandstone of Taikang formation.