Geological conditions of coal measures metal enrichment in Linxing block, eastern margin of Ordos Basin

Abstract This study systematically elucidates the multi-scale coupled control system of the metal element enrichment mechanism in coal-bearing strata, revealing its dynamic interaction controlled by structural sedimentation fluid dynamics. Given that traditional geochemical research methods are limited by the spatial limitations of discrete well point data, it is difficult to effectively characterize the collaborative control mechanism of regional-scale structural evolution, sedimentary filling, and groundwater circulation. Therefore, this study innovatively establishes a multidimensional data integration analysis paradigm that integrates geochemical feature interpretation, logging parameter inversion, and seismic attribute analysis. Firstly, based on the experimental geochemical characterization of the Shiqianfeng Formation- Benxi Formation coal sample system, key geochemical indicators such as total organic carbon (TOC) content, sulfur(S) content, vitrinite reflectance parameters, concentration distribution of major and trace elements, and rare earth elements (REE) were quantitatively obtained. By calculating the enrichment coefficient, it was identified that elements such as Zr, Cr, Ni, and Hf exhibit significant enrichment characteristics in the coal measures of the study area. Secondly, the comprehensive facies analysis method integrating logging facies classification, seismic attribute inversion, and sedimentary evolution quantitatively constrains the multi-period paleoenvironmental evolution sequence. The study reveals that delta channel sand bodies play a key controlling role in the migration path of metal elements through three-dimensional spatial stacking patterns. The reconstruction results of the sedimentary environment indicate that the Taiyuan Formation coal measures were formed in a tidal-controlled delta tidal flat composite sedimentary system with significant interaction between sea and land. Its strong reducing diagenetic environment has a decisive control over the initial enrichment of metal elements. In terms of structural dynamics research, the regional tectonic evolution model was systematically reconstructed through erosion calculation, burial history restoration, and structural equilibrium profile technology. Research has confirmed that the accompanying hydrothermal activity events in the Zijinshan rock mass lead to differential uplift of the strata, and the resulting fault network provides advantageous channels for hydrothermal migration, promoting secondary enrichment of metal elements along the fault system in coal measures. The final study elucidated the overall process control mechanism of the groundwater circulation system for the activation, migration, phase transformation, and targeted enrichment of coal-bearing metal elements. Through the analysis of the occurrence state of the chromium(Cr) element and the study of source tracing, combined with the coupling analysis of structure, sedimentation fluid dynamics, the genetic relationship between the source of ore-forming materials and the composition of erosion source areas has been revealed. The joint control model of structure sedimentation groundwater established by the research provides a new theoretical framework and technical support for the study of key metal enrichment mechanisms in coal measures.