Collaborative Research: Magma Generation in the Early Mariana Arc System Revisited

建议项目是对伊豆-博宁-马里亚纳（IBM）弧系南弧和弧后弧的始新世至中新世火山活动进行全面的地球化学和年代学研究，追踪其较早的发展。在此过程中，推荐的研究还将重新检查以前使用旧的、过时的分析技术调查过的具有良好特征的样品。本研究将考察IBM系统中火山作用性质的变化，因为它从与俯冲起始相关的“博宁质”火山作用转变为更“正常”的拉斑岩和钙钙弧火山作用，也在现代火山弧和后弧中看到。本研究还将研究在这一转变过程中地幔源性质的变化，以及它们在弧系演化过程中对构造过程的影响。以前取样的熔岩和其他火山岩将在关岛实地工作期间收集新的样品作为补充；所有这些样品将使用最新的分析技术进行主要和微量元素组成，同位素组成和地质年代（40 Ar - 39 Ar）测年分析。

Recommended project is for a comprehensive geochemical and geochronological examination of Eocene to Miocene volcanism in the southern arc and backarc of the Izu-Bonin-Marianas (IBM) arc system, tracing its older development with time. In doing so, the recommended research will also re-examine well-characterized samples that have been previously investigated using older, obsolescent anayltical techniques. This study will examine the changing nature of volcanism in the IBM system, as it transformed from "boninitic" volcanism associated with subduction initiation to the more "normal" tholeitic and cal-clkaline arc volcanism also seen today in the modern volcanic arc and backarc. This study also will examine the changing nature of the mantle sources during this transformation, as well as the implications they carry for tectonic processes during the arc system evolution. Previously sampled lavas and other volcanic rocks will be supplemented by collection of new samples during field work on Guam; all of these samples will be analyzed for major and trace elemental composition, isotopic composition, and geochronological (40 Ar - 39 Ar) dating using the latest analytical techniques.