Chemical composition of clinopyroxenes and melt inclusions in clinopyroxenes from rocks of the Malaita Island, Ontong Java Plateau (Pacific Ocean)

The paper is based on new results of melt inclusion studies in minerals. Physicochemical and geochemical parameters of plateau basalt magmatic systems of the Siberian Platform and Ontong Java Plateau (Pacific Ocean) have been established. The studied melts are enriched in Fe. That differs them from magmatic melts of mid-ocean ridges (MOR). A comparative analysis of data on inclusions has shown a similarity of continental and oceanic plateau basalt magmatic systems. They considerably differ from those of MOR and intraplate oceanic islands. Crystallization of oceanic plateau basalts took place at lower temperatures and pressures as compared with similar rocks of the Siberian Platform. The data on inclusions evidence that the melts of the Siberian Platform and the Malaita Island underwent a serious evolution in contrast to magmas of the Nauru Basin that have more stable geochemical parameters. The most fractionated low-temperature high-Fe magmas with elevated contents of trace and rare-earth elements occur in the Malaita Island (Ontong Java Plateau) magmatic system.本研究基于矿物中熔体包裹体（melt inclusion）的最新研究成果，厘清了西伯利亚地台（Siberian Platform）与太平洋翁通爪哇高原（Ontong Java Plateau）的高原玄武岩岩浆系统的物理化学及地球化学参数。本次研究的熔体富铁，该特征使其区别于洋中脊（mid-ocean ridges, MOR）的岩浆熔体。对包裹体数据的对比分析显示，大陆高原玄武岩与大洋高原玄武岩的岩浆系统具有相似性，二者均与洋中脊及板内洋岛的岩浆系统存在显著差异。相较于西伯利亚地台的同类岩石，大洋高原玄武岩的结晶作用发生于更低的温度与压力条件下。包裹体数据表明，与地球化学参数更为稳定的瑙鲁盆地（Nauru Basin）岩浆相比，西伯利亚地台与马莱塔岛（Malaita Island）的熔体经历了显著的演化过程。分异程度最高、微量元素与稀土元素含量升高的低温富铁岩浆，产出在马莱塔岛（隶属于翁通爪哇高原（Ontong Java Plateau））的岩浆系统中。