Study On The Distribution Of Basins,faults And Igneous Rocks By Gravity And Magnetic Data In The South China Sea

The South China Sea is a semi-enclosed sea to the south of the Chinese mainland and west of the Pacific Ocean.It is one of China's three largest marginal seas,and its area and water depth are the highest in the Chinese offshore.The South China Sea is one of the four major offshore oil and gas accumulation centers in the world,and it is also a key area for China's oil and gas resources exploration strategic constituency.The area has undergone multiple tectonic movements with complex evolution.A series of faults,basins,uplifts,and depressions have formed along with geological movements.The research bases on the high-precision satellite gravity data and aeromagnetic anomaly data of the South China Sea.Topographic data,thickness data of sedimentary layers,seismic sounding data,etc.were collected.In combination with geological data,a conceptual model of strata was established to optimize and constrain the anomaly separation.Using the current stable and rapid numerical calculation method,anomalies reflecting the basins,faults,and igneous rock masses were obtained.Comprehensively analyze the physical properties of rock strata in the area,study the main field source information that causes gravity and magnetic anomalies,improve the geological cognition in the area,and enrich the survey results of oil and gas resources.The anomalous separation method with abnormal stripping and regularization filtering of gravitational data was used.The Moho surface anomaly was separated and the depth of the Moho surface was inverted under the constraint of the results of seismic sounding.The residual anomaly was separated and used for boundary recognition calculation and derivative conversion.The use of low-latitude poles for magnetic anomalies and optimization of filtering anomaly separation methods.Extensively researches,collects,collates,and summarizes relevant geological data such as geological stratigraphy,rock properties,drilling data,magmatic rock activity distribution characteristics,and research results in the South China Sea and its surrounding areas.In combination with the gravity and magnetic regions and local anomaly features,the boundaries of the Mekong basin and the Bijia Basin were re-divided and 19 basin boundaries were adjusted;the depth of the Moho interface obtained provided a preliminary indication of the depth of the basin's inherited sediments on the Moho surface.The distribution of the South China Sea basin and the distribution of the crust are improved.Based on the calculation results of total gravity and tilt angles of gravity anomalies,the division of fault tectonics in the South China Sea is adjusted,and the trend of faults in the northern South China Sea has been adjusted to a large extent.Based on the gravity anomaly and magnetic anomaly and magnetic anomaly analytic signals,the volcanic rock anomalies in the South China Sea were identified and 161 magmatic rocks were newly defined.