冲绳海槽宫古段中央地堑中的火山分布及地质意义
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摘要
采用中国科学院海洋研究所“科学1号”调查船及国家海洋局“向阳红9号”调查船,于20世纪90年代以来在冲绳海槽宫古段进行海底地形及反射地震调查,所取得的数据,首次详细展示了冲绳海槽宫古段南北长约200km区域内海底火山的形态及其空间分布特征。在本段冲绳海槽发育的中轴火山和岛弧火山,分别位于中央地堑和海槽盆地东部边缘紧靠琉球岛弧的西侧。岛弧火山连续性强,总体上自东北而西南都有分布;中轴火山不如岛弧火山的连续性强,只在崂山段、黄岛段、胶南段、莱西段、城阳段和李沧段分布。中轴火山是在中央地堑之后发育的。中轴火山的发育不仅改变了原来中央地堑的位置,也改变了原来中央地堑的形态。中央地堑的左旋雁行排列,以及其形态的改变都是由于中轴火山发育的结果。中央地堑的右旋展布以及海底火山对中央地堑的改造,标志着冲绳海槽的演化已经在拉张和沉降的基础上进入到一个更高级的演化阶段(海底扩张),在岩浆供应不太充足的条件下,海底火山活动是冲绳海槽低速扩张的一种形式,海底扩张沿中央地堑正在进行。
Based on geophysical data obtained in recent years by R/V "Science 1" of Institute of Oceanology, Chinese Academy of Sciences (IOCAS) and R/V "Xiangyanghong 9" of State Oceanic Administration (SOA) in a 200-km long zone of Miyoko Section of Okinawa Trough, the topography and distribution of central graben vol-canoes inside the trough was studied in great detail for the first time. Two volcanic chains have been clearly rec-ognized whose central axis located within the central graben and the island arc volcanic chain which located at the west side of Ryukyu Island Arc in this section. The island volcanic chain has a good continuity, but the axis vol-canic chain is sporadic comparatively. From seismic profile, we understand that the development of central axis volcanic chain is after the development of central graben and has effect on the topography and distribution of central graben. None of transform faults is found in this section, but we believe that in the low spreading cases, when there is short of magma supply, it is reasonable that the formation of new oceanic crust took the form of volcanism. So, this paper pointed out that the volcanism within the central graben is a form of new crust formation, and sea floor spreading is on going along the central graben of Okinawa Trough.
Based on geophysical data obtained in recent years by R/V "Science 1" of Institute of Oceanology, Chinese Academy of Sciences (IOCAS) and R/V "Xiangyanghong 9" of State Oceanic Administration (SOA) in a 200-km long zone of Miyoko Section of Okinawa Trough, the topography and distribution of central graben vol-canoes inside the trough was studied in great detail for the first time. Two volcanic chains have been clearly rec-ognized whose central axis located within the central graben and the island arc volcanic chain which located at the west side of Ryukyu Island Arc in this section. The island volcanic chain has a good continuity, but the axis vol-canic chain is sporadic comparatively. From seismic profile, we understand that the development of central axis volcanic chain is after the development of central graben and has effect on the topography and distribution of central graben. None of transform faults is found in this section, but we believe that in the low spreading cases, when there is short of magma supply, it is reasonable that the formation of new oceanic crust took the form of volcanism. So, this paper pointed out that the volcanism within the central graben is a form of new crust formation, and sea floor spreading is on going along the central graben of Okinawa Trough.
引文
李乃胜,1990.冲绳海槽的地质构造属性.海洋与湖沼,19(4):437—358
栾锡武,高金耀,梁瑞才等,2006.冲绳海槽宫古段中央地堑的形态与分布.地质学报,80(8):1149—1155
梁瑞才,吴金龙,刘保华等,2001.冲绳海槽中段线性磁条带异常及其构造发育.海洋学报,23(2):69—78
Choukroune P,Auvray B,Francheteau J et al,1986.Tecton-ics of the westernmost Gulf of Aden and the Gulf of Tadjoura from submersible observations.Nature,319:396—399
Herman B M,Anderson R N,Truchan M,1978.Extensional tectonics in the Okinawa Trough.AAPG.Mem,29:119—208
Kimura M,1985.Back-arc rifting in the Okinawa Trough.Marine and Petroleum Geology,2:222—240
Kimura M,Furukawa M,Izawa E et al,1991.Report on DELP1988cruises in the Okinawa Trough part7.Geologic investigation of the central rift in the middle to southern Okinawa Trough.Bull Earthquake Research,Inst Univ Tokyo,66:179—209
Kimura M,Hiroshima T,Inoue E,1969.Geological struc-ture beneath the East China Sea.Monthly MarineScience,7,45—51(in Japanese)
Sibuet J C,Letouzey J,Barbier F et al,1987.Back arc ex-tension in the Okinawa Trough.Journal of Geophysical Research,92:14041—14063
Sato T,Koresawa S,Shiozu Y et al,1994.Microseismicit of back-arc rifting in the middle Okinawa Trough.Geophysical Research Letter,21(1):13—16
Smith D K,Tivey M A,Schouten H et al,1999.Locating the spreading axis along80km of the Mid-Atlantic Ridge south of the Atlantis Transform.Mid-Atlantic ridge spreading axis,104:7599—7612
栾锡武,高金耀,梁瑞才等,2006.冲绳海槽宫古段中央地堑的形态与分布.地质学报,80(8):1149—1155
梁瑞才,吴金龙,刘保华等,2001.冲绳海槽中段线性磁条带异常及其构造发育.海洋学报,23(2):69—78
Choukroune P,Auvray B,Francheteau J et al,1986.Tecton-ics of the westernmost Gulf of Aden and the Gulf of Tadjoura from submersible observations.Nature,319:396—399
Herman B M,Anderson R N,Truchan M,1978.Extensional tectonics in the Okinawa Trough.AAPG.Mem,29:119—208
Kimura M,1985.Back-arc rifting in the Okinawa Trough.Marine and Petroleum Geology,2:222—240
Kimura M,Furukawa M,Izawa E et al,1991.Report on DELP1988cruises in the Okinawa Trough part7.Geologic investigation of the central rift in the middle to southern Okinawa Trough.Bull Earthquake Research,Inst Univ Tokyo,66:179—209
Kimura M,Hiroshima T,Inoue E,1969.Geological struc-ture beneath the East China Sea.Monthly MarineScience,7,45—51(in Japanese)
Sibuet J C,Letouzey J,Barbier F et al,1987.Back arc ex-tension in the Okinawa Trough.Journal of Geophysical Research,92:14041—14063
Sato T,Koresawa S,Shiozu Y et al,1994.Microseismicit of back-arc rifting in the middle Okinawa Trough.Geophysical Research Letter,21(1):13—16
Smith D K,Tivey M A,Schouten H et al,1999.Locating the spreading axis along80km of the Mid-Atlantic Ridge south of the Atlantis Transform.Mid-Atlantic ridge spreading axis,104:7599—7612
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