Geochemical Characteristics And Geological Responses Of The Late Permian Coal Measures Mudstone In Western Guizhou

Based on the comprehensive analysis of the geological data of more than 20 wells in the western Guizhou area,this paper uses theories and methods of mineral petrology,sedimentology,sequence stratigraphy,and geochemistry to use the typical wells Y-1,Y-2,J-1,and J-2 in the late Permian area.Based on the experimental test results of the coal-measure mudstone samples of the 19 th century,the study on the geochemical characteristics and geological response of the Late Permian coal-measure mudstone in the western region of Qianxi was carried out,and the geochemical characteristics of the niobium-rich samples and ordinary mudstone samples were compared and analyzed.The provenance attributes and depositional environment were discussed,and the geological controlling factors of the enrichment of niobium in coal measure mudstone samples were discussed and analyzed.Based on the analysis of the drilling test results in the study area,the samples are divided into ordinary mudstone samples and niobium-rich samples according to the content of niobium in each sample.The geochemical characteristics of the two types of mudstone samples are summarized and compared and analyzed,and it is preliminarily considered that the samples are rich in niobium.The samples were greatly affected by volcanism and were in reducing conditions during the deposition period.The two types of mudstone samples were compared and analyzed between sequences.The overall impact of volcanic ash in the SQ1 period was the largest,followed by SQ4,and SQ2 and SQ3 were relatively the smallest.The material source analysis of the two types of mudstone samples indicates that their provenance attributes are relatively consistent.They are the Emeishan high-titanium basalt near the study area.The niobium-rich samples receive more acidic input.The vertical comparison analysis shows that the sedimentation Progress,and the influence of volcanism gradually weakened;the analysis of the depositional environment of the two types of samples using typical wells Y-2 and J-2 as examples found that there was no significant difference in the paleoclimate,redox conditions and paleo-salinity of the sedimentary water during the deposition period of the two types of samples,But the sedimentary environment of niobium-rich samples is more affected by seawater,and its sedimentary water medium conditions have greater ancient salinity and stronger reduction conditions.By analyzing the differences in the geochemical characteristics of the samples at the bottom of the sequence and the Longtan Formation,and analyzing the geological control factors for the enrichment of niobium,it is concluded that the characteristics of rhythmic volcanic activity in the Late Permian and the early Longtan Formation,while volcanic ash and terrigenous origin Different degrees of contamination by detrital materials result in coal-measure mudstones showing different geochemical characteristics.At the same time,the reduction conditions during the deposition period provide good enrichment and preservation conditions for the Nb element.By comparing the difference in element content between adjacent layers at the bottom of the J-1 well in the Late Permian,combined with previous research results,it is believed that the late Permian coal-measure niobium-rich samples were also affected by later hydrothermal fluid input,leaching and other complex geological processes.