洋底高原及其对地球系统意义研究综述

洋底高原是洋壳的重要组成部分,是广泛分布在洋底的一种面积广大、以镁铁质-超镁铁质岩石为主并且具有异常厚度洋壳的区域。由于洋底高原分布广泛,加之其形成与地幔柱之间具有十分密切的关系,因此洋底高原是研究地球深部过程的一个重要窗口。本文系统总结了洋底高原的研究成果,主要包括洋底高原的全球分布情况、基本特征(产出规模、形成时限、岩石组合、结构组成、地球化学)、鉴别标志、成因机制、地球动力学意义以及洋底高原对于地球表层系统可能产生的影响。洋底高原的地球动力学意义主要表现在5个方面,即:制约大洋俯冲;引起大洋俯冲带后撤和俯冲极性反转;促进大陆增生,构成古老大陆的重要组成部分;促使洋壳平俯冲及高原隆升;诱导板块构造体制的发生。洋底高原对于地球表层系统的影响主要表现在4个方面,即:促使全球海平面升高;造成全球变暖与"温室效应";引起大洋缺氧与黑色页岩沉积;诱使生物大灭绝与快速更迭。除此之外,本文还简单介绍了西藏中部中特提斯残余洋底高原的基本特征,初步探讨了洋底高原在中特提斯洋发育、班公-怒江缝合带演化以及青藏高原初始隆升中所起到的重要作用。

Oceanic plateau and its significances on the Earth system: A review

As important portion of oceanic crust, oceanic plateaux are geomorphic and tectonic units with large areas, extreme thicknesses and ultramafic-mafic components. Oceanic plateaux are distributed widely in oceanic plates, especially in Pacific and Indian oceans. Because of the wide distribution and genetic relationship with the mantle plume, ocenic plateaux will provide a significant window on knowledge of the geological processes in the depths of the earth. Based on a careful literature review, this paper firstly gives a comprehensive introduction on oceanic plateaux from the aspects of global distribution, basic characteristics (i.e., output size, formation time, rock composition, structure and geochemistry), genetic mechanism, and main discriminants that can be used to help the identification of oceanic plateaux in the geological record. Then we will analyze and discuss the main geodynamic implications of oceanic plateaux and the potential influences on the earth surface system. The main geodynamic implications of oceanic plateaux mainly involve five aspects, specifically including resisting subduction of oceanic plate, bringing about subduction retreat and flip, plateau accretion and continental growth, creating flat subduction of oceanic plate and continent marginal uplift, and causing the initiation of plate tectonic regime. The influences on the earth surface system largely include four aspects: bringing about global sea-level rise, causing global warming and the greenhouse effect, creating oceanic anoxia and black shale deposits, and inducing mass extinction and rapid alteration. Besides, we will introduce the basic characteristics of Meso-Tethyan oceanic plateau in central Tibet and explore its geodynamical implications for the development of the Meso-Tethys and the Bangong-Nujiang suture as well as the initial elevation of the Tibetan Plateau.