冲绳海槽中部热液区及典型喷口区地形地貌特征

TOPOGRAPHICAL AND GEOMORPHOLOGICAL FEATURES OF THE HYDROTHERMAL FIELDS AND TYPICAL HYDROTHERMAL VENTS IN THE MID-OKINAWA TROUGH

利用最新测量的高精度深水多波束资料,对冲绳海槽中部热液活动区的地形地貌特征进行了系统的分析后发现,研究区地形情况相当复杂,起伏变化较大,总体上呈沿SW—NE向延伸的裂谷地势,裂谷水深范围约在1 500~1 800m,大量呈SW—NE向的线性海山链和裂谷、洼地地貌交错出现,分析认为其形成可能与冲绳海槽的弧后扩张作用有关。另外,通过ROV(Remotely Operated Vehicle)上获得的影像,结合浅表层沉积物和岩石样品分析发现,2处喷口地形地貌情况明显不同,Iheya North喷口区地形起伏变化大,具有较多烟囱体、丘体,周围沉积物以硫化物砂为主;Iheya Ridge则以裂隙式溢流为主,分布范围广,地形倾斜平整,少见烟囱体、丘体,底质较硬,热液沉积物分布较少。

The characteristics of topography and geomorphology of the hydrothermal fields in the MidOkinawa Trough are studied with the latest high-precision deep-water multibeam bathymetric data.Results show that the topography is complicated in the study area.There is a rift extending along SWNE direction,of which the depth of rift ranges approximately from 1 500 mto 1 800 m.A large linear seamount chain extends along SW-NE direction,with some depressions within it.The formation of topography is most likely associated with the back-arc spreading of the Okinawa Trough.In addition,the characteristics of topography and geomorphology of two typical hydrothermal vents are studied with the images obtained by ROV(Remotely Operated Vehicle),combined with the shallow sediment and rock samples.Results show that the topography of hydrothermal vent in the Iheya North area varies from place to place,with many chimneys and mounds surrounded by sulfide sand sediments,while the topography of hydrothermal vent in the Iheya Ridge area is rather smooth.Hydrothermal fluid coming from fissures spread on the hard seafloor.There are little hydrothermal sediments.