【作者】 赵俐红；

【导师】 金翔龙； 高金耀；

【作者基本信息】 中国科学院研究生院（海洋研究所） ， 海洋地质， 2005， 博士

【摘要】 论文以板块构造理论和热点-地幔柱理论为指导,运用弹性板挠曲计算和海山热点源追踪计算这两种地球物理方法并配以地球化学、矿物学、岩石学等方面的资料,着重研究了中西太平洋两大典型海山区麦哲伦海山链和中太平洋海山群富钴结壳生长海山的成因。研究区是太平洋板块上洋壳年龄最老、磁条带异常最复杂、海山分布最密集、地质构造最独特、构造活动最强烈的一个区域,也是太平洋中具有较高工业开采价值的富钴结壳赋存海山密集分布区。 弹性板挠曲计算结果显示,研究区的有效弹性厚度总体上表现为西高东低的趋势,西边的麦哲伦海山链表现出南北低中间高的趋势,东边的中太平洋海山群呈现出由西往东厚度逐渐递减的现象,且这两个典型区域的岩石圈有效弹性厚度与现今法属玻利尼西亚群岛处的比较接近。热点源追踪计算表明,研究区海山的热点源均位于现今法属玻利尼西亚群岛处,麦哲伦海山链的形成与西侧的几个热点关系密切,而中太平洋海山群的形成则与东侧的几个热点间的关系更为密切。 麦哲伦海山链和中太平洋海山群均属多热点成因的板内海山,由白垩纪期间位于现今法属玻利尼西亚群岛处的热点群的大规模活动生成的,尔后随着太平洋板块的北向漂移而到达目前位置的,它们在水平漂移过程中均发生了垂直方向上的升降,受到了沿途各种构造活动的改造作用变成了当前呈现出来的平顶海山状。但形成两者海山的热点不尽相同,所经历的构造活动也不完全一样,这一点也在一定程度上影响它们各自富钴结壳的分布。 海山热点源追踪给出了形成海山的热点位置而岩石圈有效弹性厚度又给出了这些海山形成的大致年代,两者的结合不仅确定了源于同一热点的海山还从理论上确定了热点型海山上富钴结壳的大致分布规律,为进一步寻找更有钴结壳资源潜力的海山提供了理论上的指导,这是本论文的创新之处和主要特色。更多还原

【Abstract】 This paper calculates the effective elastic thickness of the lithosphere (Te) with the elastic plate flexure and the position of the hotspot with the hot-spot-produced seamounts tracking methods based on the plate tectonic theory and hotspot-mantle plume theory in the central-west Pacific. And then we analyze the formation of seamounts distributed by cobalt-rich crust in central-west Pacific, especially the Magellan seamount trail (MST) and the Mid-Pacific mountains (MPM), according to these results and some information from geochemistry, oryctology and petrography. This region is much particular, which has the most complicated magnetic anomaly lineations, the densest seamounts, the most peculiar geological feature and the strongest tectonic activity. At the same time, there are many seamounts distributed by cobalt-rich crust in the region. As a whole, Te slowly drops from the west part to the east part in the region. Te of the MST is higher in the middle of the trail than that in the north and the south part. Te of the MPM is higher in the west part of the mountains than that in the east part. Furthermore, Te of these two typical areas is close to that of the present French Polynesia region. And the positions of the hotspots forming hot-spot-produced seamounts are situated on the present French Polynesian region. The formation of the MST is relative to several hotspots in the western part of the region while the MPM relate to some hotspots in the eastern part of the region. Thus, the MST and the MPM are intraplate seamounts which were produced by several hotspots. The large volcanism formed these seamounts during the Cretaceous time in the present French Polynesia. After then they slowly moved to the present position with the drifting of the Pacific plate. There were also vertical displacement for these seamounts and they changed to guyots. But the hotspots are actually different between the MST and the MPM. In addition, their tectonic activities which they suffered during the formation are not similar. These factors affected the distribution of the cobalt-rich crust in their seamount. The hot-spot-produced seamounts tracking methods present the position of the hotspots producing the seamounts and the seamount age is obtained by Te. According to these two results, we can know the seamounts originated from the same hotspots and the distribution of cobalt-rich crust in these seamounts. This can effectively help us to find the seamounts distributed by cobalt-rich crust in future.更多还原