白龙江工程新近系甘肃群成岩环境及物质来源研究

Diagenetic environment and material source of neogene Gansu group in Bailongjiang project

白龙江引水工程位于甘肃省境内,其输水线路陇中段穿越大量新近系甘肃群软岩地层,岩性以棕红色泥质粉砂岩、钙质粉砂岩为主。在X射线衍射及主微量元素试验结果的佐证下,认为该套地层形成于大陆岛弧环境,为干旱-半干旱气候下的淡水陆相沉积盆地。成岩物质来源于上地壳,以弱-中等风化长英质、中性岩石为主,可能混入了一定量地幔物质。甘肃群(N1G)地层为典型的初次旋回沉积物,其成分成熟度较低,为近源快速堆积的产物。岩石整体胶结程度不高,工程性状差,可能对工程安全性产生不利影响。

Bailongjiang water diversion project is located in Gansu Province,and its water transmission line passes through a large number of Neogene Gansu group soft rock strata.Its lithology is mainly brownish red argillaceous siltstone and calcareous siltstone.Based on the results of X-ray diffraction and major and trace element tests,it is considered that the strata were formed in the continental island arc environment,which is a freshwater continental sedimentary basin in arid and semi-arid climate.The diagenetic material came from the upper crust,mainly weakly to moderately weathered felsic and neutral rocks,which may be mixed with a certain amount of mantle material.Gansu group(N1G)is a typical primary cycle sediment with low component maturity,which is a product of near source rapid accumulation.The overall cementation degree of rock is not high and the engineering properties are poor,which may have adverse effects on the engineering safety.