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

建议的项目是对伊豆-小笠原-马里亚纳（IBM）弧系南部弧和弧后始新世至中新世火山活动进行全面的地球化学和地质年代学检查，追踪其随时间的较早发展。在这样做的过程中，推荐的研究还将重新检查以前使用旧的、过时的分析技术研究过的表征良好的样品。这项研究将研究IBM系统中火山活动的变化性质，因为它从与俯冲起始相关的“玻泥质”火山活动转变为今天在现代火山弧和弧后中也看到的更“正常”的拉斑玄武岩和钙碱性弧火山活动。本研究还将探讨在这一转变过程中地幔源的变化性质，以及它们在弧系演化过程中对构造过程的影响。在关岛进行实地工作期间，将收集新的样品，以补充以前对熔岩和其他火山岩进行的取样;将利用最新的分析技术分析所有这些样品的主要和微量元素组成、同位素组成和地质年代学（40 Ar - 39 Ar）测年。

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.