南海深水海山上的新发现

Discoveries about seamounts in deep basin of South China Sea

在国家自然科学基金委重大研究计划"南海深部计划"指导下,于2013-2019年期间,分别运用载人或遥控深潜器,针对南海深海盆中的部分海山开展了4个科学探测航次,在南海首次发现了大面积的高丰度铁锰结核分布区、"南溟"古热液区和惊人的冷水珊瑚生态林。这些发现不仅为深入认识南海不同时空尺度演化的复杂过程及相互作用开辟了新的研究领域,还探索实践了中国海洋高新技术发展与前沿基础科学研究紧密结合并相互促进的高效创新研究模式。

In the South China Sea,about one tenth of the deep basin area with water depth more than 2500 m is occupied by various seamounts.Supported by the NSFC program"Deep Water in South China Sea",more than ten seamounts were explored for the first time by four dive cruises with the HOV and the ROV from 2013 to 2019,respectively.Among the achievements in these cruises,three exciting discoveries are made,including two large ferromanganese nodule fields,the fossil hydrothermal field and the extensive deep-water coral forests.The two large ferromanganese nodule fields are on two seamounts,the Jiaolong seamount of about 3500 m deep and the Taimao seamount of 1700 m in water depth,respectively.The size of a ferromanganese nodule field on the top of the Jiaolong seamount is about 500000 m^2 with a nodule coverage from 30%to 50%.Nearly all nodules are hydrogenetic in their origin.Besides the exceptionally high Th,Pb,Ce contents,the contents of potential economic valued elements Mn,Cu,Co,Ni etc.are found between open oceans and other marginal seas.The fossil hydrothermal field is named the“Nanming”,with at least 16 extinct hydrothermal mounds along a 700m long diving survey track on the top of the Longxi seamount(about 3019 m in water depth)close to the residue spreading ridge of the South China Sea.Preliminary studies show that the low-temperature hydrothermal precipitates(mainly Fe-Si-Mn-P assemblages)are of a young age from about 5200 years BP to 14300 years BP,similar to the age of the active magmatism in the area.The fascinated deep-water corals or coral forests are discovered to live extensively on the seamounts over the South China Sea,mainly at the water depth from 800m to 1800m.There are also some corals growing on seamounts as deep as in water depth from 3000 m to 3700 m.All these discoveries shed a new light for us to understand the mechanism of the South China Sea system from earth interior to exosphere in multiple scales.