南太平洋提基海盆地质特征及深海资源潜力

Geological Characteristics and Deep-Sea Resources Prospect in the Tiki Basin,South Pacific Ocean

深海盆地是地质矿产资源开发的战略要地,国际上对深海矿产的勘探竞争也日趋激烈。以南太平洋提基海盆为目标区,分析了海盆区的地形、地层特征和资源潜力。分析表明:(1)海盆形态受东太平海隆洋中脊扩张、土阿莫土隆起和马克萨斯断裂带、南方断裂带的构造控制,洋壳年龄在40~20 Ma之间,所获玄武岩为早渐新世形成,年龄超过29 Ma;(2)地层沉积物以钙质生物化石、黏土为主要物质组成,并含有沸石、铁锰结核、铁的氧化物等海洋自生物质;(3)沉积地层呈"三明治"式结构,初步建立了土阿莫土大洋组、南方大洋组岩石地层单位,分别代表站位顶部的远洋黏土层(以第四纪为主)、站位底部含铁含黏土的钙质超微化石软泥层(早渐新世)。站位中部地层可与赤道地区的地层对比,划归至马克萨斯大洋组(晚渐新世-上新世)。(4)站位揭示提基海盆可能大范围缺失中-晚中新世至上新世的地层,推测是由海盆沉降与海洋碳酸钙补偿深度加深引起钙质溶解而形成沉积间断。(5)海盆海底浅表的远洋黏土层中稀土元素含量高,容易勘查和开采,极具资源开发潜力。

Deep sea basins are the important potential fields for submarine mineral resources exploration.The international competition is bitterly intense on the deep sea resources expedition.Based on the deep sea drilling and bathymetry documents in the Tiki Basin,the Southern Pacific Ocean,this article analyses geomorphology and stratigraphy characteristics and discusses mineral resources potentially capability.Consequently,we obtained the results in five aspects.1）The morphology of the basin is related to the submarine expansion of East Pacific Rise and is restricted by the tectonic background between the Tuamotu Rise,Marquesas Fault and Australian Fault.The basalt age is about 29 Ma in the Early Oligocene.2）Calcareous microfossils and clay minerals are the dominatant materials in the sediment layers,where there are also marine autogenetic minerals as zeolite,ferromanganese micro-nodules and the iron-oxides.3）The stratigraphic structure is like a sandwich pattern described by lithostratigrapic unit,the Tuamotu Oceanic Formation,Marquesas Oceanic Formation and Australian Oceanic Formation.The Tuamotu Oceanic Formation is set to explain the abyssal clay layer mainly within the Quaternary in the top section of the core station.Meanwhile,the Australian Oceanic Formation is set for the calcareous ooze layer with lots of ironoxides and clay particles within the Early Oligocene in the bottom section of the core station.The middle section of the sediments in cores could be correlated to the lithostratigrapic in the Equator zone,and be long to the Marquesas Oceanic Formation within the Late Oligocene to Pliocene.4）The stratum gap that happened since middle-late stage of Middle Miocene to Pliocene may be a common phenomenon in the Tiki Basin,which could be interpreted by submarine subsidence and depth ward of the Calcium Carbonate Compensation Depth,driving the calcium organism dilution and hiatus process.5）We estimated this basin owns huge resources capability based on the reality,and that the rare earth elements content are extremely higher in the shallow layer of the submarine.