中西太平洋海山区的岩石圈有效弹性厚度及其地质意义

中西太平洋海山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, 为探讨区内众多海山的构造成因, 以板块构造理论为指导运用弹性板挠曲理论计算了中西太平洋海山区岩石圈的有效弹性厚度.结果显示, 研究区的有效弹性厚度总体上表现为北西高南东低的趋势, 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递减的现象, 且这2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.据此推测它们是在白垩纪期间(约130~90 Ma)形成于现今法属玻利尼西亚群岛处的大规模热点群附近, 且受到了后期火山岩浆活动的改造作用. 

The Effective Elastic Thickness of Lithosphere in the Mid-West Pacific and Its Geological Significance

The Mid-West Pacific region is featured with the oldest oceanic crust, the most complicated magnetic anomaly lineation, the densest seamounts, the most peculiar geological feature and the strongest tectonic activity. To research tectonic genesis of these intraplate seamounts, this paper calculates the effective elastic thickness of the lithosphere (T_e) with the elastic plate flexure based on the plate tectonic theory in the Mid-West Pacific. As a whole, T_e slowly drops from the northwest part to the southeast part in the region. T_e of the MST is higher in the middle of the trail than that in the north and the south parts. T_e of the MPM is higher in the west part of the mountains than that in the east part. Furthermore, T_e of these two typical areas is close to that of the present French Polynesia region. Thus, these seamounts were formed by the large volcanism which was produced by several hotspots during Cretaceous in the present French Polynesia region. And then these seamounts underwent some tectonic activities.