(1. 自然資源部第一海洋研究所 自然資源部海洋地質(zhì)與成礦作用重點(diǎn)實(shí)驗(yàn)室，青島 266061；
2. 青島海洋科學(xué)與技術(shù)試點(diǎn)國(guó)家實(shí)驗(yàn)室 海洋地質(zhì)過程與環(huán)境功能實(shí)驗(yàn)室，青島 266237)
摘 要: 大西洋中脊屬于典型的慢速擴(kuò)張洋中脊，具有形成大型熱液硫化物礦床的潛力。目前，國(guó)際上對(duì)大西洋中脊熱液活動(dòng)的調(diào)查研究主要集中在北大西洋，而對(duì)于南大西洋中脊的調(diào)查和研究相對(duì)較少，且主要采用傳統(tǒng)的技術(shù)手段，只能探測(cè)到礦床的表面特征，而對(duì)其形態(tài)、規(guī)模及賦存狀態(tài)等問題無法得到準(zhǔn)確的評(píng)估。海洋瞬變電磁法對(duì)淺部高導(dǎo)體異常靈敏，這使其成為熱液硫化物資源探測(cè)和評(píng)價(jià)的新興手段之一。為了研究南大西洋海底熱液系統(tǒng)，我國(guó)在南大西洋開展了多個(gè)科考航次，其中大洋52航次在南大西洋熱液硫化物區(qū)開展了瞬變電磁勘查工作；基于Occam反演方法對(duì)數(shù)據(jù)進(jìn)行了反演。結(jié)果表明：測(cè)線區(qū)域淺部電阻率整體偏低，而深部電阻率較高且橫向變化不均勻；在840~880和1060~1080號(hào)點(diǎn)之間存在兩處由淺到深的連續(xù)低阻異常，均對(duì)應(yīng)著較強(qiáng)的二次場(chǎng)響應(yīng)，推測(cè)為熱液硫化物礦堆。該礦堆呈現(xiàn)管狀形態(tài)，向下延伸30 m左右。這證明了海洋瞬變電磁法在熱液硫化物礦的定位、圈定硫化物礦的范圍、研究硫化物礦的空間結(jié)構(gòu)等方面具有較強(qiáng)的可行性，可有效地服務(wù)于多金屬硫化物礦資源評(píng)價(jià)工作。
關(guān)鍵字: 海底熱液；多金屬硫化物；南大西洋；瞬變電磁；資源評(píng)價(jià)
（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
