Search Results (3)

The Dzungaria Basin is located north of Xinjiang and is one of the largest inland basins in China. The eastern coalfields in the Dzungaria Basin contain a large amount of coal resources, and the thickness of the coal seams is significant. Therefore, the aim of this study was to classify the paleovegetation types and develop paleoclimate succession models of the extra-thick coal seams. We conducted the sampling, separation, and extraction of spores and pollen and carried out microscopic observations in the Wucaiwan mining area of the eastern coalfields in the Dzungaria Basin. The vertical vegetation succession in the thick seam (Aalenian Stage) in the study area was divided into three zones using the CONISS clustering method. The results show that the types of spore and pollen fossils belong to twenty families and forty-five genera, including twenty-three fern, twenty gymnosperm, and two bryophyte genera. The types of paleovegetation in the study area were mainly Lycopodiaceae and Selaginellaceae herb plants, Cyatheaceae, Osmundaceae, and Polypodiaceae shrub plants, and Cycadaceae and Pinaceae coniferous broad-leaved trees. The paleoclimate changed from warm–humid to humid–semi-humid and, finally, to the semi-humid–semi-dry type, all within a tropical–subtropical climate zone. The study area was divided into four paleovegetation communities: the nearshore wetland paleovegetation community, lowland cycad and Filicinae plant community, slope broad-leaved and coniferous plant mixed community, and highland coniferous tree community. This indicates that there was a climate warming event during the Middle Jurassic, which led to a large-scale lake transgression and regression in the basin. This resulted in the transfer of the coal-accumulating center from the west and southwest to the central part of the eastern coalfields in the Dzungaria Basin. Full article

A comprehensive assessment of the critical elements contained in coal is essential for understanding the geological processes that affect the enrichment of these elements, which can then be used to fully utilize coal in an economically and environmentally friendly manner. In order to understand the geology of an area and the impact of demolition rock on the formation and enrichment of trace elements, as well as rare earth elements (REE) in coals, we have presented a range of recent geochemical and mineralogical data from the k₇ coal seam in the Karaganda Formation of the Karaganda Coal Basin. The study revealed that the geochemical characteristics of coal-bearing deposits in the Karaganda Basin reflect the features of its geological evolution. Despite high tectonic activity and volcanic activity in the Paleozoic era, the specific composition of the rocks on the slopes and bases of coal-bearing valleys has determined the low potential for rare metals in the basin. It has been found that the coal in the Karaganda Basin is, in general, similar in terms of concentrations of most trace elements to the average for world coal. The main area of provenance of the trace elements was established using discriminant diagrams. It was established that the main source of the trace elements, including REEs in the basin coals, was the Tekturmas accretionary complex that represented the main upland (anticlinorium) during the coals’ formation. SEM studies identified micro-mineral forms that indicated the presence of trace elements of Zr, Ti, Se, and Fe in the samples of stratum k₇. Full article

Our aim in this study was to analyze the major and minor factors affecting the stability of a slope containing a coal seam in a goaf. Based on engineering experience, we first identified nine factors that may affect slope stability, of which we determined eight that may substantially affect slope stability through a single-factor numerical simulation analysis. Then, we arranged 27 groups of numerical simulation tests with eight factors and three levels with the orthogonal test method, and we determined the ranking of the major and minor influencing factors through a range of variance analyses. The results showed that the influence of each factor was ranked as the roadway width > coal seam position > slope gradient > coal seam thickness > coal seam internal friction angle > coal seam cohesion > coal seam dip angle. Among these, the roadway width, coal seam position, and slope gradient were the major factors affecting slope stability; coal seam thickness, coal seam internal friction angle, coal seam cohesion, and coal seam dip angle were the minor factors. In this study, we combined the goaf and slope containing the coal seam, and we couple analyzed the factors influencing the stability of the slope containing the coal seam in the goaf. Our findings provide a scientific basis for the treatment and protection of slopes containing coal seams in goafs in the future and have a practical engineering importance for the analysis of the excavation stability of road-cutting slopes in goafs. Full article