Study Of The Gravity And Magnetic Field In Yanbian In Jilin Province

There are a series of small and medium-sized faulted-depression of the Mesozoic-Cenozoicorogenesis basins in Yanbian area.It’s potential of resource ishuge.But the region’s structure character is complex,with developed faults,processing and interpretation of gravity and magnetic data in the whole area data isblank.Therefore,based on the gravity and magnetic anomaly data,exploring forprocessing methods of technology to inverse the fracture structure and the basin’s distribution,giving data processing and interpretation scientifically,have practical significance.In this article, making the data of Yan7well and Yan D7well,three seismic profiles,an electrical profile and the physical properties of rocksin this study area as prior conditions,the gravity and air-magnetic anomaly data with1:200000scale in the researching area has been processed in the corresponding wave-number domain,obtained the corresponding objective anomalous characteristics,and as the basis of research results of predecessors,this article delineated the main faults,determined the depth of Mesozoic-Cenozoicorogenesis basement,and forecasted the rich coal and oil and gas prospecting areas.In the course of the study,in order to extract more affluent and accurate related geological information from the gravity and magnetic anomaly data,thispaper used the scheme of small subdomain filterting to the gravity anomaly byseveral times to recognize fractures,in addition,introduced Taylor series iteration downward continuation factor which is more stable in the calculate into theinversion of apparent property and density interfacement,and proved its rationality in the model experiments.In the actual data processing and interpretation work,used frequency-domain-space field interpolation formula to realize the separation of gravity and magnetic anomaly,by the apparent property inversion formula introduced the Taylor series iteration downward continuation factor,respectively calculated the apparent density and magnetism in the different depth.Used the small subdomain filterting by several times,Thetamap,Euler deconvolution technology to inverse fault’s position, and made the apparent density inversion results as a country,in combination with regional tectonic evolution history,to determine the fault location and research in their transformation relationship.According to the fracture’s position,residual gravity anomaly and regional geological survey of study area,divised the tectonic units.According to the depth of basemen t by interface inversion,outcroped rock and regional tectonic regular pattern,delineated the Dunhua,Yanji,Songjiang,Helong basin and Wangqing-Luozigou basingroups.In the paper, some data processing methods which have been made improvement and details of achievements are as follows:1.This paper used the scheme of small subdomain filterting to the gravityanomaly by several times to realize the step belt with abnormal tighter,highlight the fault’s character of exhibition.The experimental model with several cuboids determined using this inversion method to recoginze the positions of faults isin the feasibility.After doing the above treatment to the gravity anomaly in yanbian area,the results of the fracture structure feature was more evident,and theircontinuity was better,which corresponding effects with gravity and magnetic anomaly reflects tectonic characteristics,Thetamap great values,Euler deconvolution’s points marked in dense and the structural characteristics in the apparent density were good,all that indicated the recognition of the fault is a relatively good effect,then in combination with regional geological survey,and Helong-ChunYang electrical method profile,delineated the main fault zone in the research area.2.By using respectively integral iterative method and Taylor series iterationdownward continuation method into the magnetic model with sphere,comparedwith the theoretical value,expounded the Taylor series iteration method not only accurate but also faster, more suitable for the actual data processing work. On this basis,the author have given the apparent density and magnetism inversion formular which is combined with the Taylor series iteration downward continuation factor by transverse variable density layer gravity anomaly modeling formula and poisson formula.Because they has inherited the characteristics of theTaylor series iteration downward continuation,the two formulas can greatly increase the inversion depth and improve inversion precision.Used them to inversethe apparent property distribution in different depth in yanbian area,the resultsand YanJi basin Wells data and previous research results could be proved by each other,proved the accuracy of the inversion results, which provided the study of underground property distribution and division of fault zone data-support in the surveyed area.3.Based on characteristics of the gravity and magnetic field in the study area and corresponding processing results,combined with the boundary position between Angola flora and Chinese plants group in yanbian area and2D resistivityprofile which electrical structure existed significant differences in Baicaogou,determined east delay’s position of West Lamulun Drainage Basin suture line.4.According to the characteristics of gravity and magnetic field in yanbianarea,apparent property characteristics,regional geological structure characteristics ,the tectonic units of this study area could be divided into four levels:level1tectonic units,West Lamulun Drainage Basin suture line as a border distinguishes between the north China plate and the northeast landmass;Level2tectonic units is that by yichun-hunchun suture line northeast landmass is divided into Songnen plot and Xingkai plot;Level3tectonic units is that which makes respectively F1~F5faults as boundaries the whole study area can be divided into Fazhan uplift area,Dunhua depression area,Dapuchai River uplift area,ChunYang depression area,Tianqiaoling uplift area,Yanji-Wangqing depression area,Songjiang-Helong uplift area,Hunchun depression area and Duhuangzi uplift area;Level4tectonic units have the faults in the study region as boundaries to divide thewholearea into Dunhua basin,Yanji basin,Songjiang basin,and Helong basin,Wangqing-Luozigou basins,hunchun of basin and other uplift areas.5.By introducing Taylor series iteration downward continuation factor intodensity interface inversion,this paper gave a new single density interface inversion formula,the combinated model with defective spheres proved it not only cansolve large buried depth of the interface inversion problem very well,and havehigher precision in the inversion result.In this article, making the data of Yan7well and Yan D7well,three seismic profiles and the physical properties ofrocks in this study area as prior conditions,using this formula to invers Mesozoic-Cenozoicorogenesis basin’s basement buried depth in yanbian area,results andseismic profiles and several main basin of the geological material compliancedwell,explain the basal depth by inversion is accurate and reliable.Combining previous research results,in Yanji basin,dunhua basins forecasted the rich coal and oil and gas favorable prospect areas.The above gravity and magnetic data processing programs which were to reveal the structure characteristics in yanbian area,narrow the gap between the results by processing the gravity and magnetic exploration data with actual geological conditions, the character of the exhibition of the fault zone and by inversion basement depth of Mesozoic-Cenozoicorogenesis basin is accurate and reliable. The large scale in yanbian area of gravity and magnetic exploration degree is still not enough, the author believes that the study can provide importantreference to geological survey and energy exploration work in the region in future.