U–Pb ages, trace element content and oxygen isotope ratios of single zircons from five plagiogranite intrusions of the Troodos ophiolite were measured to determine their crystallization age and assess the importance of fractional crystallization versus crustal anatexis in their petrogenesis. The results indicate that oceanic magmatism in Troodos took place at 94 3 6 0 5 Ma, about 3 Myr earlier than previously recognized. Later hydrothermal alteration has affected most of the Troodos plagiogranitic rocks, resulting in growth of new zircon and/or partial alteration of zircon domains, causing slightly younger apparent crystallization ages. The new age inferred for seafloor spreading and ocean crust accretion in Troodos nearly overlaps that of the Semail ophiolite in Oman (95– 96 Ma), strengthening previous indications for simultaneous evolution of both ophiolites in similar tectonic settings. Average dO(Zrn) values in the Troodos plagiogranites range between 4 2 and 4 8 &. The lower values in this range are lower than those expected in equilibrium with mantlederived melt (5 3 6 0 6 &), indicating variable contribution from hydrothermally altered, deepseated oceanic crust in most of the Troodos plagiogranite intrusions. The inferred substantial involvement of crustal component is consistent with the existence of a shallow axial magma chamber, typical of fast-spreading mid-ocean ridge settings, within the Troodos slow-spreading ridge environment. This apparent contradiction may be reconciled by episodically intense magmatism within an otherwise slow, magmatically deprived spreading axis.

中文翻译：

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斜长花岗岩的起源：耦合 SIMS O 同位素比、U-Pb 测年和来自塞浦路斯 Troodos 蛇绿岩的锆石的微量元素组成

测量了来自 Troodos 蛇绿岩的 5 个斜花岗岩侵入体的单个锆石的 U-Pb 年龄、微量元素含量和氧同位素比，以确定它们的结晶年龄，并评估分级结晶与地壳贫矿在其成岩作用中的重要性。结果表明，特罗多斯的海洋岩浆活动发生在 94 3 6 0 5 Ma，比以前认识的早约 3 Myr。后期的热液蚀变影响了特罗多斯斜长花岗岩的大部分，导致新锆石的生长和/或锆石域的部分蚀变，导致表观结晶年龄略年轻。Troodos 的海底扩张和海洋地壳增生推断的新时代几乎与阿曼 Semail 蛇绿岩的时代重叠（95-96 Ma），加强了先前在类似构造环境中两种蛇绿岩同时演化的迹象。Troodos 斜长花岗岩中的平均 dO(Zrn) 值介于 4 2 和 4 8 & 之间。该范围内的较低值低于与幔源熔体平衡时的预期值 (5 3 6 0 6 &)，表明在大多数 Troodos 斜花岗岩侵入体中，热液蚀变、深部海洋地壳的贡献不同。推断的地壳成分的实质性参与与在特罗多斯缓慢扩张的海脊环境中存在一个浅轴岩浆房一致，这是快速扩张的洋中脊环境的典型特征。这种明显的矛盾可能会被一个缓慢的、缺乏岩浆作用的扩张轴内间歇性强烈的岩浆作用所调和。