刚果盆地钾盐矿床沉积特征及成因探讨

刚果盆地是低纬度重要的成盐盆地,主要由白垩系、新近系和第四系组成。含盐地层赋存于白垩纪地层中部,其下伏陆相碎屑岩沉积,上覆海相碎屑—碳酸盐岩沉积。盐层包括5种沉积层序,盐类矿物析出顺序是:硬石膏—石盐—光卤石—水氯镁石—溢晶石。研究区钾盐矿和石盐矿共生,钾盐矿层有20层,累计平均厚度259.61m,KCl品位大于15%。矿石类型主要为光卤石型,次为钾石盐型。矿石为滨海—泻湖相沉积蒸发岩,其沉积与大西洋裂谷的演化发展密切相关,是白垩纪裂谷发育期间,由初始浓缩沉积的富含卤化物海水运移至次级盆地进一步蒸发沉积形成。

Approach to depositional feature of potash deposits in Congo and its origin

The Congo Basin is an important salifiable basin at low latitude,mainly composed of Cretaceous System,Neogene System and Qaternary System.Saliferous strata occurs in the middle of strata of Cretaceous System,underlied by sediment of fragmental rocks in continental facies and covered by clastic-carbonate rock sediment in marine facies.Salt beds include 5 types of depositional sequence and the order of separation of saline minerals is anhydrite-halite-carnallite-bischofite-tachyhydrite.Potash and halite deposits intergrow and potash deposits have 20 layers with the accumulative total average thickness being 259.61 m and KCl grade greater than 15%.The type of the ore is primarily carnallite and secondarily sylvite.The ore is sedimentary evaporite in coast-lagoon facies with its sedimentation closely related to evolution of rift in Atlantic Ocean,which is formed by moving primarily concentrated and sedimentary halide rich seawater to a secondary basin for further evaporite deposition.