Collaorative Research: Magma Generation and Tectonics in the Early Mariana Arc System Revisited

建议的项目是对伊祖-博宁-马里亚纳斯(IBM)弧系南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研究，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、过时的分析技术调查过的具有良好特征的样本。这项研究将考察IBM系统中火山作用性质的变化，因为它从与俯冲启动有关的“邦尼质”火山作用转变为更“正常”的拉斑玄武岩和钙碱性弧火山作用，今天在现代火山弧和弧后也看到了这种火山作用。这项研究还将研究在这种转变过程中地幔来源的性质变化，以及它们对弧系演化过程中的构造过程的影响。以前采集的熔岩和其他火山岩样品将在关岛实地工作期间收集新的样品加以补充；所有这些样品都将利用最新的分析技术分析主要和微量元素组成、同位素组成和地质年代学(40Ar-39Ar)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.