西太平洋地球动力学问题与未来大洋钻探目标

Geodynamic Problems in the Western Pacific and Future Scientific Drill Targets

西太平洋区域是全球地质构造和海陆相互作用最活动的区域,经过50多年的大洋钻探研究,人们对西太平洋弧后海底扩张成因、俯冲工厂的动力学机制、地幔演化过程、发震带、热点岩浆活动、沉积古环境等都有了深入研究和分析,但是西太平洋边缘海盆具有很大的构造多样性和复杂性,仍然有很多的科学目标和科学问题有待进一步开展研究.本文详细分析了边缘海盆的大洋岩石圈演化特殊性,原位上地幔蛇纹岩化的程度,初始俯冲与初始扩张的形成机制,海台、海山、海岭、洋脊、洋隆的属性,洋中脊水热循环活动的强度及其对大洋岩石圈演化的影响,岩石圈共轭张裂与破裂模式与机制,大洋红层与异常沉积这7个方面的科学问题,并建议就流体地球化学剖面、海山岩浆剖面、穆绍海沟与加瓜海脊、Ayu海槽、卡罗琳海岭系统、Eauripik海岭、冲绳海槽、莫霍面这8个关键具体目标开展详细的地球物理刻画并提出具有全球意义的钻探建议,为今后实现中国领导的全球大洋钻探工作提供思路.

The western Pacific is the most active area in tectonics and continental-ocean interaction in the globe. After more than 50 years of oceanic drilling in the western Pacific, many topics have been studied well, such as the origin of back-arc seafloor spreading, dynamic mechanism of the subduction factory, mantle evolution process, seismogenic zone, magmatism of hotspots,and paleo-sedimentary environments. However, tectonic histories of the western Pacific marginal basins are diverse and complex.We identified seven scientific issues yet to be fully analyzed, including unique oceanic lithospheric evolution of marginal basins, insitu upper mantle serpentinization, mechanism of initial subduction and spreading, natures of submarine plateaus/seamounts/ridges/upwells/rises, intensity of hydrothermal circulation and its influence on the evolution of oceanic lithosphere, conjugate modes and mechanisms of lithospheric rifting and breakup, and oceanic red beds and abnormal sediments. We further recommended eight key drill targets, which are fluid geochemical profiling, seamount magma profiling, the Mussau trench and the Gagua ridge, the Ayu trough, the Caroline ridge system, the Eauripik rise, the Okinawa trough, and the Moho of marginal seas.Detailed geophysical investigations should be carried out on these targets before preparing drillable drilling proposals, and such efforts will help provide ideas for future ocean drilling research in the region.