Magmatic evolution of an oceanic island arc – The New Hebrides case

大洋岛弧的岩浆演化及其对俯冲起始的潜在影响最近受到了广泛关注，IODP在Izu-Bonin-Mariana（IBM）弧、弧前和弧后的350、351和352号考察队致力于测试现有模型。因此，大多数关于俯冲起始的想法都是基于IBM弧，但这些想法是否也可以应用于其他海洋岛弧尚不清楚。新赫布里底群岛岛弧（NHIA）是地球上最年轻的岛弧之一，是在约1500万年前翁东爪哇高原碰撞后，俯冲板块极性反转后俯冲开始形成的。ODP的第134航段在新赫布里底群岛弧前和弧后钻取了7个岩心，长度达1100米，并回收了岩浆岩样品以及中中新世的火山灰层。我们建议重新分析该ODP航段的岩石样品以及其他来自潜水和疏浚巡航的分析不佳的海底样品，以便将NHIA的岩浆演化与IBM进行比较。此外，我们建议采样的中央NHIA建立老岛弧地壳的岩浆演化到20马。新的数据集还将提供对NHIA在大约2 Ma前发生的d 'Entrecasteaux岛弧俯冲之后的岩浆演化的见解。我们提出的项目对全球了解俯冲过程和上地幔中相关的岩浆形成具有重要意义。

The magmatic evolution of oceanic island arcs and their potential implications for subduction initiation received much attention recently with the IODP expeditions 350, 351, and 352 in the Izu-Bonin-Mariana (IBM) arc, forearc and rear-arc dedicated to test existing models. Most of the ideas on subduction initiation are thus based on the IBM arc but it is unknown whether these can be applied also to other oceanic island arcs. The New Hebrides island arc (NHIA) is one of the youngest arcs on Earth and formed by subduction initiation following polarity reversal of the subducting plate after the collision of the Ontong Java Plateau some 15 million years ago. Leg 134 of the ODP drilled seven cores with lengths of up to 1100 m in the New Hebrides forearc and backarc and recovered magmatic rocks samples as well as ash layers ranging to the Mid-Miocene. We suggest to re-analyse the rock samples from this ODP Leg as well as other poorly analysed submarine samples from dive and dredge cruises in order to compare the magmatic evolution of the NHIA to the IBM. Additionally, we propose sampling of the central NHIA to establish the magmatic evolution of the old island arc crust to 20 Ma. The new data set will also provide insights into the magma evolution of the NHIA following the subduction of the d’Entrecasteaux island arc that occurred some 2 Ma ago. Our proposed project has important implications for the global understanding of subduction processes and the associated magma formation in the upper mantle.