An integrated zircon geochronological and geochemical investigation into the Miocene plutonic evolution of the Cyclades, Aegean Sea, Greece: Part 1: Geochronology
An integrated zircon geochronological and geochemical investigation into the Miocene plutonic evolution of the Cyclades, Aegean Sea, Greece: Part 1: Geochronology
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DOI：
10.1007/s00410-010-0504-4
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发表时间：
2010-03
影响因子：
3.5
通讯作者：
R. Bolhar;U. Ring;C. Allen
中科院分区：
文献类型：
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作者：
R. Bolhar;U. Ring;C. Allen
我们使用在希腊爱琴海基克拉泽斯群岛五个岛屿上收集的 14 个花岗岩样本中的 369 个单独的 U-Pb 锆石年龄来限制后退的希腊俯冲带上方 I 型和 S 型岩体的结晶历史。基克拉泽斯群岛的中新世岩浆活动持续了 17 Ma 至 11 Ma。 S 型花岗岩的年龄比 I 型花岗岩的年龄系统地早约 200 万年。单独考虑岩体时，锆石数据定义了从简单单峰到复杂多峰的年龄谱。 14 个调查样品中的 7 个产生了不止一种不同的锆石结晶年龄，其中一个来自米科诺斯岛的 I 型花岗闪长岩样品代表了最复杂的情况，具有三个可分辨的年龄峰值。伊卡利亚岛 S 型花岗岩的两个样本似乎具有超过 2-300 万年的结晶锆石，而对于具有多个锆石年龄群体的大多数单个样本，计算的年龄偏差为 1-150 万年。我们对年龄数据的解释反映了一段漫长的历史，包括在较深的岩石圈水平上最初部分熔融，随后在较浅的地壳水平上结晶和冷却。我们的研究证实了已发表的研究，认为岩体的形成是由于数百万年来多次岩浆脉冲的增量侵位所致。假设我们 14 个样本的多个年龄峰值确实可以量化岩浆侵位的时间跨度，我们的数据表明爱琴海岩体是在几百万年的时间内形成的。我们对 U-Pb 年龄的构造解释是，S 型花岗岩是下地壳部分熔融和混合作用的结果，可能开始于约 23 Ma。 I 型花岗岩和相关的镁铁质熔体被解释为反映了基克拉泽斯群岛约 15 Ma 开始的岩浆弧阶段。
We use 369 individual U–Pb zircon ages from 14 granitoid samples collected on five islands in the Cyclades in the Aegean Sea, Greece, for constraining the crystallisation history of I- and S-type plutons above the retreating Hellenic subduction zone. Miocene magmatism in the Cyclades extended over a time span from 17 to 11 Ma. The ages for S-type granites are systematically ~2 million years older than those for I-type granites. Considering plutons individually, the zircon data define age spectra ranging from simple and unimodal to complex and multimodal. Seven of the 14 investigated samples yield more than one distinct zircon crystallisation age, with one I-type granodiorite sample from Mykonos Island representing the most complex case with three resolvable age peaks. Two samples from S-type granites on Ikaria appear to have crystallised zircon over 2–3 million years, whereas for the majority of individual samples with multiple zircon age populations the calculated ages deviate by 1–1.5 million years. We interpret our age data to reflect a protracted history involving initial partial melting at deeper lithospheric levels, followed by crystallisation and cooling at shallower crustal levels. Our study corroborates published research arguing that pluton construction is due to incremental emplacement of multiple magma pulses over a few million years. Assuming that multiple age peaks of our 14 samples can indeed serve to quantify time spans for magmatic emplacement, our data suggest that Aegean plutons were constructed over a few million years. Our tectonic interpretation of the U–Pb ages is that the S-type granites resulted from partial melting and migmatisation of the lower crust, possibly starting at ~23 Ma. The I-type granites and associated mafic melts are interpreted to reflect the magmatic arc stage in the Cyclades starting at ~15 Ma.