Electrical structure of seafloor massive sulfide deposits in South Mid-Atlantic ridge based on marine transient electromagnetic method

Abstract

The Mid-Atlantic Ridge is a typical slow spreading ridge, with great potential for the formation of seafloor massive sulfide deposits. At present, the international investigation and research on the hydrothermal activities in the Mid-Atlantic Ridge is mainly concentrated in the North Mid-Atlantic Ridge, while the research on the South Mid-Atlantic Ridge is a less. In addition, the traditional methods mainly used can only detect the surface characteristics of the deposit, and its morphology, scale and occurrence state still need to be solved. Marine transient electromagnetic method (MTEM) has become one of the emerging methods for the detection and evaluation of seafloor massive sulfide deposits because of its sensitivity to shallow conductivity. In order to study the submarine hydrothermal system in the South Atlantic, China has carried out several cruises in the South Atlantic. We have conducted a transient electromagnetic survey in the South Atlantic Ridge during cruise DY52 segment 2, using a central loop method towed by a ship. The Occam method is used for inversion. The results show that the shallow resistivity of the survey area is low, while the deep resistivity is higher. The conductivity in the shallow is distributed along the line, while the deep resistivity varies unevenly. Between points 840-880 and points 1060-1080, there are two continuous low-resistance anomalies ranging from shallow to deep, and the corresponding secondary field response is relatively strong, which is speculated to be seafloor massive sulfide deposits. The seafloor massive sulfide deposit has a tubular shape, extending down about 30 m. Which proves that the marine transient electromagnetic method can be used to locate hydrothermal sulfide ore, delineate the scope of sulfide ore, study the spatial structure of sulfide ore, etc., and finally serve the evaluation of polymetallic sulfide mineral resources.