龙江-肇州地区第三系可地浸砂岩铀成矿岩相古地理条件分析

通过对龙江-肇州地区第三系依安、大安、泰康组钻孔岩性、综合测井及古生物资料研究,认为依安组时期地表水流弱,沉积范围小,物源单一,主要为湖沼相的泥岩、粉砂岩沉积和部分冲泛平原相的粉砂岩、细砂岩的沉积;大安组时期地表水流加强,北部、北西部物质大量带入,沉积范围由北向南扩大,沿盆地西缘形成一条近南北向的条带状沉积,以砾岩为主的冲洪积相和以砂岩为主的冲泛平原相沉积成为主要沉积相;泰康组时期西部水流加大,沉积范围向南、向东扩大,以灰、灰绿色砂岩、粉砂岩、泥质粉砂岩为主的冲泛平原相广泛发育,成为主要沉积相,并在盆地西缘形成了以褐、黄色砾岩为主的冲洪积相沉积.依据可地浸砂岩铀矿岩相准则判别,本区的大安组冲洪积相和泰康组冲泛平原相具有发育厚层砂体的条件,是今后地浸砂岩铀找矿的有利层位.

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.