Formation of the metamorphic sole of the Semail ophiolite: High-precision U-Pb dating of the preserved remnants of a subducted slab

Semail 蛇绿岩变质底的形成：俯冲板片保存遗迹的高精度 U-Pb 测年

• 批准号: 1650407
• 负责人: Matthew Rioux
• 金额: $ 23.11万
• 依托单位: University of California-Santa Barbara
• 依托单位国家: 美国
• 项目类别: Standard Grant
• 财政年份: 2017
• 资助国家: 美国
• 起止时间: 2017-04-15 至 2022-03-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1650407&HistoricalAwards=false
• 关键词: Formation; metamorphic; sole; Semail; ophiolite

Ophiolites are pieces of oceanic crust and upper mantle that have been emplaced onto the continents. The formation of ophiolites is a fundamental component of plate tectonics, potentially related to the initiation of new subduction zones. Recent application of high-precision U-Pb dating has advanced our understanding of the formation and emplacement of the Semail (Oman-United Arab Emirates) ophiolite, the largest and best studied ophiolite in the world. This project will expand on the recent work, undertaking detailed high-precision dating of metamorphic rocks persevered below the ophiolite, which likely formed at depths greater than 35 km within a subduction zone. The results will address long-standing debates regarding the origin of ophiolites, and provide new insight into how ophiolites can be used to understand modern mid-ocean ridges, subduction zones, and potentially the initiation of subduction, a critical but poorly understood tectonic process. The research will advance desired societal outcomes by graduate student training in the earth sciences, involvement of Omani students, public outreach, and fostering collaborations between scientists from the United States, the United Kingdom, Oman, and the United Arab Emirates.A thin sole of amphibolite- to granulite-facies metamorphic rocks underlies the Semail and other Tethyan ophiolites. As preserved remnants of the underthrust plate, sole exposures can be used to better understand the formation and obduction of ophiolites. Recent data from two large exposures of the metamorphic sole below the Semail ophiolite yielded surprising results, indicating that that the earliest sole metamorphism was synchronous with or pre-dated formation of the ophiolite crust and that metamorphism was diachronous along the length of the ophiolite, spanning 1.3 Ma, contrary to current models. These data, combined with existing geochemical constraints and the estimated metamorphic pressures from the sole, are best explained by formation of the ophiolite in a supra-subduction zone setting, with metamorphism of the sole rocks occurring in a subducted slab. To better understand the implications of these results to the origin of ophiolites, the project scientists will carry out high-precision isotope dilution-thermal ionization mass spectrometry (ID-TIMS) U-Pb zircon dating at exposures of the metamorphic sole throughout the Semail ophiolite. The new dataset from the sole of the ophiolite has the potential to provide transformative insight into the formation and emplacement of ophiolites, and to processes of subduction and exhumation at convergent margins.

蛇绿岩是已扩散到大陆的海洋壳和上地幔的碎片。蛇绿岩的形成是板块构造的基本组成部分，可能与新俯冲带的启动有关。高精度U-PB约会的最新应用使我们对世界上最大，最有研究的蛇绿岩（Ariota）的ophiolite（阿拉伯阿拉伯阿拉伯酋长国）Ophiolite的形成和安置的理解提高了我们的理解。该项目将扩大最近的工作，进行详细的高精度年代的变质岩石，在蛇绿岩下方坚持不懈，这可能在俯冲带内的深度大于35 km的深度形成。结果将讨论有关蛇绿岩的起源的长期辩论，并提供有关如何使用蛇绿岩来理解现代海洋山脊，俯冲带，以及俯冲的启动的新见解，这是一个关键但知之甚少的构造过程。这项研究将通过地球科学的研究生培训，阿曼族学生的参与，公共宣传以及促进美国，英国，阿曼，阿曼和阿拉伯联合阿拉伯酋长国的科学家之间的合作来提高所需的社会成果。作为保留的底板残留物，唯一暴露可用于更好地理解蛇绿岩的形成和产物。最新数据来自两次大型鞋底鞋底下方的大型鞋底鞋底，得出了令人惊讶的结果，表明最早的唯一变质性与粘泥土外壳的或预先形成或预先形成，而变形是沿着覆盖率的1.3 ma，相反，当前的模型沿着覆盖层的长度进行了重新定位。这些数据，结合现有的地球化学约束以及唯一的估计变质压力，可以通过在超染料区设置中形成蛇绿岩的形成，并在搭配板上发生的唯一岩石的变质来解释。为了更好地理解这些结果对蛇绿岩的起源的含义，该项目科学家将在整个Semail Ophiolite中对变质鞋底的暴露时进行高精度的同位素稀释 - 热电离质谱法（ID-TIMS）U-PB锆石的日期。来自蛇绿岩鞋底的新数据集具有对蛇绿岩的形成和增强的变革性见解，以及在收敛边缘处的俯冲和挖掘过程。

项目成果

The Origin of Felsic Intrusions Within the Mantle Section of the Samail Ophiolite: Geochemical Evidence for Three Distinct Mixing and Fractionation Trends

• DOI: 10.1029/2020jb020760
• 发表时间: 2021-03
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: M. Rioux;M. Benoit;I. Amri;G. Ceuleneer;J. Garber;M. Searle;Kayla Leal

One line on the map: A review of the geological history of the Semail Thrust, Oman-UAE mountains

• DOI: 10.1016/j.jsg.2022.104594
• 发表时间: 2022-05
• 期刊: Journal of Structural Geology
• 影响因子: 3.1
• 作者: M. Searle;M. Rioux;J. Garber

Petrochronology of Wadi Tayin Metamorphic Sole Metasediment, With Implications for the Thermal and Tectonic Evolution of the Samail Ophiolite (Oman/UAE)

• DOI: 10.1029/2020tc006135
• 发表时间: 2020-12-01
• 期刊: TECTONICS
• 影响因子: 4.2
• 作者: Garber, Joshua M.;Rioux, Matthew;Searle, Michael P.
• 通讯作者: Searle, Michael P.

High‐Precision U‐Pb Zircon Dating of Late Magmatism in the Samail Ophiolite: A Record of Subduction Initiation

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
• 发表时间: 2021
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Rioux, Matthew;Garber, Joshua M.;Searle, Michael;Kelemen, Peter;Miyashita, Sumio;Adachi, Yoshiko;Bowring, Samuel
• 通讯作者: Bowring, Samuel

Dating Continental Subduction Beneath the Samail Ophiolite: Garnet, Zircon, and Rutile Petrochronology of the As Sifah Eclogites, NE Oman

萨梅尔蛇绿岩下方大陆俯冲年代测定：阿曼东北部 As Sifah 榴辉岩的石榴石、锆石和金红石岩石年代学

• DOI: 10.1029/2021jb022715
• 发表时间: 2021
• 期刊: Journal of Geophysical Research: Solid Earth
• 作者: Garber, Joshua M.;Rioux, Matthew;Searle, Michael P.;Kylander‐Clark, Andrew R.;Hacker, Bradley R.;Vervoort, Jeff D.;Warren, Clare J.;Smye, Andrew J.
• 通讯作者: Smye, Andrew J.