Study On The Mechanism Of Self-potential And Detection Method Of Seafloor Polymetallic Sulfide Deposits

Marine polymetallic sulfide deposits are rich in various metallic element such as Cu,Zn,Au and Ag,and are important marine metal resource in the future.The self-potential method can quickly delineate the position distribution of sulfide deposits over a large area and has a unique effect on massive polymetallic sulfides buried beneath the sediment.Due to the complexities of the source of anomalies detected by SP method on seafloors,and the strict requirements of electrode characteristics and the arrangement of the observation system,the processing and interpretation of seafloor SP data was not ideal in the past.This paper mainly conducts forward modeling and inversion studies on SP data,which aids with more accurate detection of the position and boundary of sulfide deposits in hydrothermal areas.This paper mainly studies from the following aspects: Firstly,by establishing a plate model and an electric dipole source model with different buried depths or conductivity distributions in equivalent of sulfide deposits beneath the seafloor,finite difference forward modeling gives the distribution of SP,so the response can be analyzed;Secondly,current source probability density imaging and inversion of current density of the equivalent electric dipole source are used to detect the approximate positional distribution and boundary range of the seafloor sulfide deposits in the lateral and longitudinal directions,then the inversion of conductivity of the simulated SP response is carried out under the knowledge of the oxidation reduction potential gradient and the approximate boundary of the ore body to acquire more information about the types of metallic elements contained in the ore body in assistance of more detailed sulfide exploration and resource evaluation;Thirdly,discussing the choice of inversion parameters such as regularization factors,focus factors,and depth weighting matrices,since appropriate parameter values can make the model obtained by the inversion more close to the true distribution of seafloor sulfide deposits in position,boundary range and electrical characteristic distribution;Finally,in order to proof the reliability of probability density imaging and focus inversion,these two methods are used to process the SP data of polymetallic sulfide deposits hidden beneath calcareous sediment,which was acquired in Yuhuang hydrothermal area,southwest Indian Ridge.