Experience of Stadial Analysis for Investigating Ultramicrocrystalline Rock (The Case of Structureless Phosphorites of the Okino-Hubsugul Basin)

Any sedimentary rock is a complex natural formation, which was formed under the influence of many processes. One of the aims of lithologists is the occurrence and study of these processes, which is necessary for targeted searches for mineral resources associated with sedimentary rock. Analysis of order of mineral crystallization (stadial analysis) is the most successful method to solve the problems. That analysis is a brunch in lithology science aimed at reconstructing the geological history of rock. The step-by-step analysis includes methods of prospecting, optical and electronic microscopy, and diagnostics of the material composition of minerals. However, the researcher receives basic information about the processes of rock formation through microscopic observations of the features of minerals: Their shapes, sizes, composition, interrelations, as well as structural and textural features. In the course of such observations, "indicator components" of rock are established with obvious signs of duration and conditions of its formation: Sedimentary "indicator components" (biogenic detritus, allothigenic fragments, tufogenic material), dia- A nd katagenetic (nodule concretions and other varieties), metagenetic "indicator components" (crystalloblasts etc.). Further analysis of the secondary alterations in the mentioned components and their minerals allows us to make series of consistent mineral formation and, thereby, reconstruct main stages and conditions of rock formation. This, in turn, provides the key to understanding the regional geological processes that took place in sedimentary basins. © 2020 Published under licence by IOP Publishing Ltd.