High‐Precision U‐Pb Zircon Dating of Late Magmatism in the Samail Ophiolite: A Record of Subduction Initiation
High‐Precision U‐Pb Zircon Dating of Late Magmatism in the Samail Ophiolite: A Record of Subduction Initiation
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萨迈伊蛇绿岩晚期岩浆活动的高精密 U-Pb 锆石定年：俯冲起始记录
DOI：
10.1029/2020jb020758
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
Bowring, Samuel
中科院分区：
文献类型：
--
作者：
Rioux, Matthew;Garber, Joshua M.;Searle, Michael;Kelemen, Peter;Miyashita, Sumio;Adachi, Yoshiko;Bowring, Samuel
了解蛇绿岩形成的构造环境是必要的，以确定它们如何用于研究海洋扩张和俯冲带过程。在这里，我们提出了高精度的U-Pb锆石年龄和Sm-Nd同位素数据，从两个晚岩浆系列在阿曼和阿拉伯联合酋长国（阿联酋）的Samail蛇绿岩，这限制了其构造发展。蛇绿岩中的火山岩记录了从MORB样V1熔岩到俯冲相关V2熔岩的发展过程。与V2岩浆活动有关的深成岩的206 Pb/238 U年龄为95.557 ± 0.063-95.289 ± 0.067Ma。第二个晚期岩浆系列由长英质岩脉和岩床组成，间歇性地侵入上地幔，并归因于俯冲板片的熔融。阿曼的脉岩年龄介于95.201 ± 0.032 ~ 94.95 ± 0.10 Ma之间，εNd（t）= −5.05 ~ −1.63。单一脉岩的εNd（t）值较高，为7.35，年龄为95.478 ± 0.032Ma。阿联酋的类似侵入体更年轻，范围为94.119 ± 0.057至90.998 ± 0.052 Ma。新的和现有的资料表明，俯冲开始时蛇绿岩形成的时间轴为：（1）初始单一变质作用发生在≥ 96.2Ma，（2）地壳形成主要是通过减压相关的V1岩浆作用发生在96.1 ~ 95.6Ma，（3）V2岩浆作用发生在95.6 ~ 95.2Ma，与H2O-熔融地幔有关;（4）95.2 ~ 95.0Ma的板状长英质岩脉侵入。岩浆活动的时间进程与地球动力学模型预测的俯冲开始的时间尺度相似，并在伊豆-小笠原-马里亚纳前弧中观察到。
Understanding the tectonic setting in which ophiolites form is necessary to determine how they can be used to study ocean spreading and subduction zone processes. Here, we present high‐precision U‐Pb zircon dates and Sm‐Nd isotopic data from two late magmatic series in the Samail ophiolite in Oman and the United Arab Emirates (UAE), which constrain its tectonic development. Volcanic rocks in the ophiolite record a progression from MORB‐like V1 lavas to subduction‐related V2 lavas. Plutonic rocks related to V2 magmatism yielded206Pb/238U dates of 95.557 ± 0.063–95.289 ± 0.067 Ma. A second late magmatic series consists of felsic dikes and sills that intermittently intrude the upper mantle and are attributed to melting of a subducting slab. These dikes in Oman range from 95.201 ± 0.032 to 94.95 ± 0.10 Ma, with εNd(t) = −5.05 to −1.63. A single dike, attributed to V2 magmatism, has a higher εNd(t) = 7.35 and a date of 95.478 ± 0.032 Ma. Similar intrusions in the UAE are younger, ranging from 94.119 ± 0.057 to 90.998 ± 0.052 Ma. Our new and existing data indicate the following timeline of ophiolite formation during subduction initiation: (1) Initial sole metamorphism at ≥96.2 Ma; (2) Formation of the crust through primarily decompression‐related V1 magmatism from 96.1 to 95.6 Ma; (3) V2 magmatism related to H2O‐fluxed mantle melting from 95.6 to 95.2 Ma; and (4) Intrusion of slab‐derived felsic dikes from 95.2 to 95.0 Ma. The temporal progression of magmatism is similar to the timescales of subduction initiation predicted by geodynamic models and observed in the Izu‐Bonin‐Mariana forearc.
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DOI：
10.1029/2020jb020760
发表时间：
2021-03
期刊：
Journal of Geophysical Research: Solid Earth
影响因子：
--
作者：
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通讯作者：
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发表时间：
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影响因子：
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DOI：
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发表时间：
2017
期刊：
影响因子：
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