(1. 自然资源部第一海洋研究所 自然资源部海洋地质与成矿作用重点实验室，青岛 266061；
2. 青岛海洋科学与技术试点国家实验室 海洋地质过程与环境功能实验室，青岛 266237)
摘 要: 大西洋中脊属于典型的慢速扩张洋中脊，具有形成大型热液硫化物矿床的潜力。目前，国际上对大西洋中脊热液活动的调查研究主要集中在北大西洋，而对于南大西洋中脊的调查和研究相对较少，且主要采用传统的技术手段，只能探测到矿床的表面特征，而对其形态、规模及赋存状态等问题无法得到准确的评估。海洋瞬变电磁法对浅部高导体异常灵敏，这使其成为热液硫化物资源探测和评价的新兴手段之一。为了研究南大西洋海底热液系统，我国在南大西洋开展了多个科考航次，其中大洋52航次在南大西洋热液硫化物区开展了瞬变电磁勘查工作；基于Occam反演方法对数据进行了反演。结果表明：测线区域浅部电阻率整体偏低，而深部电阻率较高且横向变化不均匀；在840~880和1060~1080号点之间存在两处由浅到深的连续低阻异常，均对应着较强的二次场响应，推测为热液硫化物矿堆。该矿堆呈现管状形态，向下延伸30 m左右。这证明了海洋瞬变电磁法在热液硫化物矿的定位、圈定硫化物矿的范围、研究硫化物矿的空间结构等方面具有较强的可行性，可有效地服务于多金属硫化物矿资源评价工作。
关键字: 海底热液；多金属硫化物；南大西洋；瞬变电磁；资源评价
（1. Key Laboratory of Marine Geology and Metallogeny, First Institute of Oceanography, Ministry of Natural Resources, Qingdao 266061, China;
2. Laboratory for Marine Geology, Pilot National Laboratory for Marine Science and Technology(Qingdao), Qingdao 266237, China）
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.
Key words: submarine hydrothermal; seafloor massive sulfide deposit; South Mid-Atlantic; transient electromagnetic method; resource assessment
