麦哲伦海山区玄武岩化学成分的时空分布及其形成的深部动力学机制

大洋板内岩浆作用在成因上通常被认为与地幔柱有关。西太平洋海山的空间分布广、年龄分布杂乱，很难用经典的地幔柱理论来解释。由于采样难度大，西太平洋大多数海山都缺乏足够的研究，我们甚至对其岩石成因和演化过程都知之甚少。而厘清这些海山的岩石成因以及揭示其化学成分的时间和空间分布规律，对探讨其形成的深部动力学机制至关重要。我国多个大洋航次在西太平洋麦哲伦海山区10座海山取到了大量宝贵的玄武岩样品，为研究西太平洋海山的成因提供了理想契机。本项目拟对已从中国大洋样品馆申请到的72个麦哲伦海山区玄武岩样品进行主量和微量元素及Sr-Nd-Pb-Hf-Os同位素分析，结合橄榄石斑晶的元素组成特征和氧同位素数据，识别其源区岩性组成，厘清其岩石成因，揭示其化学成分的时空分布规律，来探讨其形成的深部动力学机制。

Oceanic intraplate volcanoes are generally accepted to be originating from deep, relatively stationary mantle plumes. The different groups of seamounts comprising the West Pacific Seamount Province (WPSP) do not form narrow, linear and clearly age progressive chains of volcanoes, suggesting that their origin cannot be accounted for solely by the mantle plume hypothesis. Due to the difficulty of sampling, the majority of the seamounts from the WPSP have not been well studied, and we even know little about their magmatic evolution and petrogenesis. Deciphering their petrogenesis and delineating the temporal-spatial distribution of geochemical compositions of seamount basalts from the WPSP are critical to understanding their geodynamical processes. Ten seamounts in the Magellan Seamount Area of the WPSP were densely sampled during Chinese Dayang Yihao and Xiangyanghong 04 and 09 cruises, and 72 basaltic samples were successfully obtained. These samples provide an excellent opportunity to study the origin of the Magellan seamounts. This proposal plans to analyze the major and trace element and Sr-Nd-Pb-Hf-Os isotope compositions together with element and oxygen isotope data of olivine phenocrysts, to identify the mantle source lithology of the Magellan Seamount Area and to investigate their petrogenesis. Based on these results, we can delineate the temporal-spatial variation of basalts from the Magellan Seamount Area and discuss the geodynamical process of the formation of the Magellan Seamount Area which will shed light on the origin of the other groups of seamounts in the WPSP.