滇西新生代盆地沉积特征及砂岩型铀矿成矿条件

Depositional features of Cenozoic basins and metallogenic conditions of sandstone-type uranium deposits in western Yunnan

滇西 (怒江以西 )地区分布着数十个新生代盆地 ,且多为小型山间盆地。盆地基底为花岗岩和中高级变质岩 ,铀源条件良好。各盆地面积不大 ,沉积厚度不等。沉积物组成了山区河流冲洪积相、湖沼相的灰色含煤建造 ,其物质成分与基底岩石具明显继承性。地层结构具砂、泥互层特点 ,砂岩岩性松散 ,渗透性好 ,赋存承压水 。

Tens of Cenozoic basins,mostly small-sized in tr amontane basins,are dispersely distributed in western Yunnan (west to Nujiang ri ver).The basement of these basins is composed of granite and medium-to high-me tamorphosed rocks being favorable uranium source.The area of various basins is n ot great,and the thickness of cover sediments is variable.Sediments in basins co nsist of grey coal-bearing formation composed of fluvial alluvial,proluvial fac ies,lacustrine-swamp facies.The material composition of sedimentary rocks shows inherited features of basement rocks.Cover sediments are characterized by the i ntercalation of sandstone and mudstone.Sandstones are loose,well permeable and w ater-bearing,possessing favorable conditions for the formation of epigenetic hy drogenic uranium deposit,and prospecting potential.