腾格里沙漠地区砂质管状物的发现及其地质意义

砂质管状物,浅褐色,管状,致密,硬脆,中空,内孔贯通。长度3.4～18.1cm,外径1.55～3.5cm,内径0.6～1.9 cm,壁厚1～11mm。随着长度由长到短,外径、内径及壁厚均逐渐变小。管内孔壁上时有白色微晶方解石薄膜,或有管孔被白色微晶方解石半堵塞。有的管子上有与主孔相通的小孔,小孔与管壁垂直、呈30°交角或近于相切。按砂粒粒度,管子分为粗砂型和细砂型两种,其中粗砂型管子暗色砂粒含量略多。砂粒成分主要为硅质,胶结物主要为微晶方解石,孔隙式胶结。说明在地表砂层之下存在弱承压碳酸盐型咸水,这种水的上涌、渗透作用及沙漠特有干旱、风力等条件,是其主要成因。显示古腾格里湖在干涸过程中,湖水经历了"碳酸盐型→硫酸盐型→氯化物型"的浓缩过程。如果在古代砂岩中发现相同或类似的管状物,可进一步推断,该砂岩形成环境为古沙漠、有在同一套地层中存在蒸发盐矿产的可能。

DISCOVERY OF SANDY PIPE-SHAPE MINERALS AT TENGERY DESERT DISTRICT AND ITS GEOLOGICAL SIGNIFICANCES

The characters of sandy beige pipe-shape minerals are massive,hard,middle-hollow,and endoporus transfixion,with the length of 3.4～18.1cm and the outside diameter of 1.55～3.5cm,inside diameter of 0.6～1.9 cm,the wall thickness of 1～11mm.The wall thickness of outside and inside diameter sdwindle away with the length getting shotter.Some white microlite calcite membrane sometimes occurs at the bore wall in the tube or jam in it.Some small bores communicated with the tube upright or tangency the wall with 30°.There are two types of tubes,fine sand tubes and coarce sands with more dark silicone sand and microlite calcite cement,all of which shows that there is weak bearing carbonate salt water under ground layer formed by some conditions of the water emerge,osmosis and the drought,winder power.The Tengger lake water suffered carbonate-sulfade-chloride process.We could conclude that the sandstone were formed in ancient desert conditions if same or similar tube-shape minerals were found in ancient sandstone,and will find the evaporation minerals in the same stratum.