洋底高原:了解地球内部的窗口

OCEANIC PLATEAUS:WINDOWS TO THE EARTH'S INTERIOR

洋底高原是洋壳的重要组成部分,它是分布在洋底的一种面积广大、且具有异常洋壳厚度的区域。洋底高原通常规模巨大,绝大多数喷发于大洋环境,岩石组成主要为镁铁质到超镁铁质,岩石类型主要为拉斑玄武岩。大多数洋底高原的岩石组成较为相似,而且均形成于一期或两期时间较短却大规模集中喷发的岩浆活动,目前认为是大规模的热地幔物质从地幔深部上升到岩石圈底部,由于巨大地幔柱头部(地幔羽)引起的熔融作用形成的。正是由于洋底高原与地幔柱之间具有这种十分密切的关系,因此对洋底高原的研究将成为我们了解地球内部的窗口。以ODP对翁通—爪哇和凯尔盖朗(Kerguelen)海台的研究为例,简单介绍了洋底高原的基本特征、地幔柱在其形成过程中的作用以及目前在这一领域还未解决的一些问题。

Based on the scientific results of ODP and focus on two typical examples, Ontong Java Plateau and Kerguelen Plateau, this paper summarizes the fundamental characteristics of oceanic plateaus, the role of mantle plumes in the formation of oceanic plateaus and some unresolved issues. As a major component of oceanic crust, oceanic plateaus are large regions of anomalously thick oceanic crust. Oceanic plateaus usually occupy large areas and erupt in an oceanic setting. They are composed predominantly of mafic to ultramafic rocks, and the rock types are mainly tholeiitic basalts. Most of these oceanic plateaus have homogeneous rock composition and erupted during one or two major pulses, which is attributed to melting in the large head of a starting mantle plume. Because of this close relationship between oceanic plateaus and mantle plume, oceanic plateaus has became the windows to the Earth's interior.