Petrochronology of Wadi Tayin Metamorphic Sole Metasediment, With Implications for the Thermal and Tectonic Evolution of the Samail Ophiolite (Oman/UAE)
Petrochronology of Wadi Tayin Metamorphic Sole Metasediment, With Implications for the Thermal and Tectonic Evolution of the Samail Ophiolite (Oman/UAE)
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DOI：
10.1029/2020tc006135
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发表时间：
2020-12-01
期刊：
影响因子：
4.2
通讯作者：
Searle, Michael P.
中科院分区：
文献类型：
--
作者：
Garber, Joshua M.;Rioux, Matthew;Searle, Michael P.
蛇绿岩变质底保存了蛇绿岩侵位的重要记录，但对其非基性部分的详细研究很少。我们提出了Samail（阿曼-阿联酋）蛇绿岩中Wadi Tayin上部单一暴露的沉积和基性抗蚀岩的新的热气压和岩石年代学数据。热力学模型表明，变质沉积石榴石的成核温度约为4kb，温度约为550℃，最终生长温度为7.5 +/- 1.2 kbar，温度为665 +/- 32℃，发生时间为93.0 +/- 0.5 Ma （Lu-Hf等时线）。锆石的106.9 +/- 2.3（碎屑岩）和98.7 +/- 1.7 ~ 94.1 +/- 1.6 Ma（变质岩）的U-Pb测年表明变质作用的开始，独居石的U-Pb测年接近97 ~ 89 Ma，表明发育或再结晶时间较长。镁铁质钛矿U-Pb年龄为92.2 +/- 1.8 Ma，记录了最早的高低等级底岩并置。这些数据和其他数据表明(i) Wadi Tayin sole保留了一个反向的变质、交代和年龄梯度；（ii）变质作用发生在上覆蛇绿岩结晶期间或之后不久（横跨大陆边缘100公里）和大陆边缘晚期的冷逆冲构造。
Ophiolite metamorphic soles preserve important records of ophiolite emplacement, but there have been few detailed investigations into their non-mafic portions. We present new thermobarometric and petrochronologic data from a metasediment and mafic restite in the upper Wadi Tayin sole exposure in the Samail (Oman-UAE) Ophiolite. Thermodynamic modeling suggests metasedimentary garnet nucleation at similar to 4 kb, similar to 550 degrees C and final growth at 7.5 +/- 1.2 kbar, 665 +/- 32 degrees C, occurring by 93.0 +/- 0.5 Ma (Lu-Hf isochron). Zircon U-Pb dates of 106.9 +/- 2.3 (detrital) and 98.7 +/- 1.7 to 94.1 +/- 1.6 Ma (metamorphic) bracket the initiation of metamorphism, and monazite U-Pb dates from similar to 97-89 Ma suggest a lengthy period of growth or recrystallization. A mafic titanite U-Pb age of 92.2 +/- 1.8 Ma records the earliest possible juxtaposition of high- and lower-grade sole rocks. These and other data suggest that (i) the Wadi Tayin sole preserves an inverted metamorphic, metasomatic, and age gradient,(ii) metasediment metamorphism occurred during, or soon after, crystallization of the overlying ophiolite (100 km across the continental margin and the late, cool underthrusting of the continental margin.