Spatiotemporal distribution and geological controlling factors of critical metal enrichment layers in the Upper Permian coal measures in western Guizhou
The Late Permian coal measures of western Guizhou exhibit vertically superimposed critical metal element enrichment layers,yet their spatiotemporal distribution in the strata remains unclear. Understanding the spatial and temporal distribution of these critical metal-rich layers is crucial for predicting their distribution characteristics and elucidating the relationship between enrichment mineralization patterns and geological events during this period. This study analyzes the geochemical characteristics and vertical distribution of critical metal enrichment layers in these coal measures,aiming to identify the underlying geological controlling factors. The results show that the critical metal enrichment layers in the coal measures are characterized by a natural gamma-positive anomaly,low Sr/Ba ratios,elevated Rb/Sr and CIA corrvalues,and relatively high V/Ni and V/(V+Ni) ratios,indicating that they were formed in a relatively deep,anoxic environment during a period of relatively hot climate and low sea level. According to the observed vertical distribution patterns,we delineate six distinct depositional sequences for Ga-Zr-Nb-REY enrichment layers and three for Li enrichment layers. The vertical distribution consistently favors critical metal enrichment layers within coal seam roofs and floors,dirt bands,limestone interlayers,and mudstone interlayers. This consistent positioning in the sedimentary cycle suggests a shared depositional environment. The Ga-Zr-Nb-REY enrichment layers are mainly attributed to intraplate volcanic ash layers. Their vertical superposition pattern and critical metal element content are directly controlled by the pattern and intensity of intraplate volcanic activity. The paleogeographic setting influences the intensity of surface leaching,with intraplate volcanic ash layers experiencing weak or no leaching exhibiting enriched critical metal element characteristics. Weak hydrodynamic conditions are conducive to the preservation of volcanic ash,and the limited environment may be an important reason for the formation of Li-enriched layers. Hydrothermal fluidactivity is also implicated in the enrichment of Ti and Li in certain layers. The metallogenic regularity and distribution model can effectively predict the spatiotemporal distribution of critical metal element enrichment layers.
critical metalsspatiotemporal distribution patterngeological control factorsLate Permian
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