Study On The Development Characteristics And Influencing Factors Of Karsts In Xingfu Spring,Chaohu Based On Comprehensive Geophysical Methods

As an important medium for water resources,petroleum,and mineral resources,karst fissure are of great significance to study the development characteristics and influencing factors of karst fissures.This paper takes the karst fissures in the Xingfu Spring area in the northern mountainous area of Chaohu Lake as the research object.On the basis of collecting and collating geological data,a combination of site measurement,comprehensive geophysical prospecting interpretation,and theoretical analysis was used to study the development characteristics of the water conduction fracture zone in the spring area and the factors affecting the development of karst fissures.Analyzed the principles and applicable conditions of several geophysical methods,and studied the feasibility of comprehensive site investigation,the four geophysical methods of high density resistivity method,ground penetrating radar,apparent resistivity sounding,and charging method are combined to take advantage of the shortcomings.Comprehensive geophysical prospecting is carried out on the development of karst fissures in the study area,so as to reduce the multi-solution of geophysical prospecting,to achieve the purpose of improving interpretation accuracy.Based on the geophysical profile anomaly analysis and geological interpretation,the development of faults and the distribution characteristics of karst fissures in the region were studied.At the same time,taking the mountainous area in the north of Chaohu as an example,the lithologic conditions,geological tectonic conditions and groundwater activity on the development of karst fissures influences.The main research results and conclusions are as follows:(1)Using comprehensive geophysical methods to promote strengths of method and avoid weaknesses,and complement each other.Detect underground media from the angles of electric field and electromagnetic field respectively.For example,the high density resistivity method is sensitive to low-resistance bodies and has obvious responses to filled karst caves,but it has poor detection effect on small-scale caves.The high accuracy of the ground penetrating radar makes up for the high density resistivity method because of the large detection depth and the reduced resolution,and the large interpretation error of the abnormal buried depth.(2)According to comprehensive geophysical anomaly analysis and geological interpretation,it is speculated that there are five northwest-developing karst fissure channels and two fault structures or bedrock fracture zones F1 and F2,among which F1 and five fissure channels may be related to the source of Xingfu Spring.In addition,the fault F1 has a north-east trend and a north-west dip in occurrence.It developed in the limestone contact zone between the Lower Permian Qixia Formation and the Carboniferous,with relatively developed karst fissures.The F2 trend is that its trend is nearly north-south,and the occurrence is inclined to north-east,developed in the Devonian Wutong Formation.(3)The development of karst fissures in the study area is affected by stratigraphic lithology and topography.The overall terrain of the study area is high in the northeast and low in the southwest.At the same time,the lithology on the side of the Xingfu Spring in the area is mainly medium-thick limestone and dolomite limestone.The higher content of mineral components is beneficial to the formation of karst fissure channels.(4)Tectonic movement is the main controlling factor for karst development in this area.The geological structure in the northern mountainous area of Chaohu Lake is complicated.It has experienced two stages of tectonic stress compression in the Indosinian NWW-SEE direction and the Yanshanian NE-SW direction,forming a lot of fractures,folds and joint fissures,strengthening the permeability of the formation.At the same time,during the Yanshanian period,the Pacific Plate subducted and collided from southeast to northwest,causing the crust to rise and fall relatively,resulting in the uplift of the study area.Due to tectonic uplifting,the underlying limestone formation was gradually exposed to the surface due to the erosion of the cover layer,and formed under the action of dissolution and cutting of surface water such as atmospheric precipitation.