The Causes Of Gravity And Magnetic Anomaly In Yunyheng Basin And Its Adjacent Area

Yuncheng basin is located in the south of Shanxi Province,the south edge of the joint belt between Ordos block and Hehuai block.and it is a part of small and medium-sized basins group in Shanxi rift zone.Exploration practices and predecessors' studying results show that the hydrocarbon generation conditions of Mesozoic strata in Shanxi small and medium-sized basin group is similar to that of the present ordos basin,with more similarities,its oil conditions should be the same as residual Ordos basin.In addition,at the east of Yuncheng basin,Zhongtiao mountain block is famous for it's concentration region of polymetallic deposit in our country.Predecessors had conducted a lot of research work in this area,but the system researches on the cause of gravity and magnetic anomaly are little.By systematically gravity and magnetic data processing,transformation parameters maps had been got in this paper.Combined with drilling data,regional geologic data and predecessors' research results,through using gravity and magnetic data that had been completed in this area,this paper detailedly analyzed the characteristics of gravity and magnetic anomaly and its geological genesis,concluded the faults structure,explained the cause of local gravity and magnetic anomaly,made quantitative interpretation about gravity anomaly profile and divided the tectonic units.The results of this paper will provide gravity and magnetic basic research data for the further related researches.The main achievements and conclusions of this study are as follows:Bouguer gravity anomaly in the study area distributed zonally high and low,the trend is NE,gravity field value in different zone variety obviously,which reflects the basement ups and downs.The trend of aeromagnetic ?T is similar to the trend of bouguer gravity anomaly,and the anomly value change drastically,the extremely high value zones of magnetic anomaly are the reflection of the basic and ultrabasic magmatite.The magnetic bodies are developmental.The structure is complex,and the faults are developmental in the study area,the trends of faults structure are mainly NE and NW two groups,X shape faults structure system are shown in this area,the extension scale of NE faults is large,and the distance is long,except F6 and F7,the rest of the NW trending faults are on a smaller scale.The boundaries of tectonic units in the area are controlled by NE trending faults.The localstructures are developmental in the study area,and obviously controlled by faults,and their macro trends are in keeping with the trends of regional structure.Local high gravity are mainly centralized in the uplift zone,and caused by high density old strata as well as basic magmatic rocks.Local low gravity are mainly distributed in basins,and caused by the Cenozoic low density layer.Aside from M-3 and M-4,the local high magnetic anomaly are all distributed in uplift zones,they are mainly caused by magnetic basement uplift,medium and acidic magmatic rocks or basic magmatic rocks.The sedimentary in Yuncheng basin and Jishan-Houma basin is thick,the corresponding gravity anomaly is low,the magnetic anomaly in Jishan-Houma basin is high,low in Yuncheng basin,magnetic bodies in Jishan-Houma basin are developmental,and is not developmental in Yuncheng basin.Magnetic anomaly value is high in Emei platform,the sedimentary is thin formation,and the magnetic bodies are developmental.Magnetic bodies are developmental in Zhongtiao mountain block.The study area can be divided into 4 first-order tectonic units and 7secondary tectonic units.