Abstract The Yap Arc was considered to have derived from the proto-Yap-Izu Bonin-Mariana arc system. It is a rare example of subduction of an oceanic plateau with short arc–trench distance and consists mainly of metamorphic rocks, which are distinct from the Izu Bonin-Mariana arc system. However, it is not known on the origin and formation time of the basement rocks of the Yap Arc. For the first time, in this study we provide the results of radiometric age-dating and whole-rock major element, trace element and Sr–Nd–Pb–Hf isotope analyses for the metamorphic basement rocks (amphibolites) of the Yap Arc. These rock samples can be classified into three groups based on their major and trace element compositions. Group 1 samples have strong depletion of LREEs and a Dupal-type isotopic signature, and they represent forearc basalts (FABs) of the nascent Yap forearc. Group 2 samples have an alkali basalt-like geochemistry and oceanic island basalts (OIBs) type trace element patterns, and they represent the basalts of the Caroline Plateau. Group 3 samples have island-arc-type negative anomalies of Nb–Ta–Zr–Hf, and they may represent the volcanic rocks of the proto-Yap Arc. These amphibolites were formed at 21 Ma according to 40Ar/39Ar amphibole dating and in situ SIMS U Pb titanite dating, and they record the timing of the collisional event between the Caroline Plateau and the proto-Yap Arc. We propose that the Yap arc has been evolving distinctly from the Izu-Bonin-Mariana Arc since this collision time. These rocks were metamorphosed and brought onto the present Yap Arc as a result of the collision between the proto-Yap Arc and the Caroline Plateau. Based on the new results of age-dating and geochemistry of this study, we propose three stages of tectonic evolution for the Yap Arc as a result of collision from the Caroline plateau: an early stage (proto-Yap Arc) of subduction of the Caroline Plate, collision of the proto-Yap Arc with the in-coming young Caroline Plateau, and rejuvenated plate subduction at the Yap Trench with limited volcanism.

中文翻译：

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雅浦海沟原雅浦岛弧/卡罗琳高原与复兴板块俯冲碰撞的地球化学和年代学证据

摘要 雅浦弧被认为源自原始雅浦-伊豆博宁-马里亚纳弧系统。它是一个罕见的大洋高原俯冲弧-海沟距离短的例子，主要由变质岩组成，不同于伊豆博宁-马里亚纳弧系统。然而，雅浦弧基岩的成因和形成时间尚不清楚。在本研究中，我们首次提供了雅浦岛弧变质基岩（角闪岩）的放射性测年和全岩主元素、微量元素和 Sr-Nd-Pb-Hf 同位素分析结果。这些岩石样品可根据其主要和微量元素组成分为三组。第 1 组样品具有强烈的 LREE 消耗和 Dupal 型同位素特征，它们代表了新生雅浦前弧的前弧玄武岩（FAB）。第 2 组样品具有类似碱性玄武岩的地球化学和海洋岛玄武岩 (OIB) 型微量元素模式，它们代表了卡罗琳高原的玄武岩。第3组样品具有岛弧型Nb-Ta-Zr-Hf负异常，可能代表原雅浦岛弧的火山岩。这些角闪岩是根据 40Ar/39Ar 角闪石测年和原位 SIMS U Pb 钛钛矿测年在 21 Ma 形成的，它们记录了卡罗琳高原和原始雅浦弧之间碰撞事件的时间。我们认为，自这次碰撞以来，雅浦弧已经与伊豆-博宁-马里亚纳弧明显不同。由于原始雅浦岛弧和卡罗琳高原之间的碰撞，这些岩石被变质并带到了现在的雅浦岛弧上。基于本研究的年龄测年和地球化学的新结果，我们提出了由卡罗林高原碰撞导致的雅浦弧的三个构造演化阶段：卡罗林俯冲早期（原雅浦弧）板块，原始雅浦弧与即将到来的年轻卡罗琳高原的碰撞，以及在雅浦海沟恢复活力的板块俯冲，火山活动有限。