昆阳磷矿位于滇池西南部,为探讨该磷矿的成矿物质来源及其沉积环境,从岩相学和元素地球化学两方面对磷矿石展开了研究。研究结果显示,磷块岩矿石的主要矿物成分为胶磷矿,矿体w(P 2 O 5)平均含量为26.16%,磷块岩P 2 O 5含量由地表向地下沿倾向逐渐降低,酸不溶物含量逐渐增加,在垂直剖面上,矿区中部P 2 O 5含量相对上部和下部要高。矿石结构由下至上为砾屑结构、粒屑-鲕状结构、粒屑-粉晶结构,反映了磷块岩沉积时水动力条件由高能向低能过渡。磷块岩中发育的粒序层理、潮汐层理、火焰状构造等说明其是在强海流、强风浪的冲刷簸选过程中形成,随后,水动力条件减弱,富集成矿。综合研究表明,本区磷矿床磷的初始物质来源是富磷的陆源碎屑物和富磷质的海洋生物,其沉积环境主要为浅海浪基面以上的陆缘坻、台地、浅海盆地等。 相似文献
Weathered rockfill materials, characterized by a mixture of soil matrix and rock aggregates, are widely distributed in mountainous areas. These soils are frequently used for subgrade or riprap in engineering practice, and the mobilized shear strength is crucial for analyzing the displacement and stability of these geo-structures. A series of direct shear tests are performed on a gap-graded soil with a full range of coarse fraction. The behavior of gap-graded soils is analyzed, and a simple model is proposed for the evolution of mobilized stress ratio during direct shearing process based on mixture theory. The change of inter-aggregate configuration is incorporated by introducing a structure variable which increases with coarse fraction and decreases approximately linearly with the overall horizontal shear strain in double logarithmic plot. It reasonably reflects a gradually transformation from a matrix-sustained structure into an aggregate-sustained one with the increase of coarse fraction. The model has four parameters, and at least two direct shear tests need to be done for the calibration. Validation of the model is done by using the test data in this work and those from the literature.
