Post-collisional orogen-parallel extension in the Trans-North China Orogen: Evidence from syn-kinematic pegmatite dikes
Post-collisional orogen-parallel extension in the Trans-North China Orogen: Evidence from syn-kinematic pegmatite dikes
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华北造山带碰撞后造山带平行伸展：来自同运动伟晶岩脉的证据
DOI：
10.1016/j.precamres.2021.106503
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发表时间：
2022
影响因子：
3.8
通讯作者：
Taiping Zhao
中科院分区：
文献类型：
--
作者：
Yunjian Li;Guang Zhu;Chengchuan Gu;Cheng Liu;Shuai Zhang;Taiping Zhao
造山带平行伸展在碰撞环境中很常见，但其原因仍存在争议。古元古代跨华北造山带（TNCO）提供了对造山带平行伸展过程的见解。我们提供了中国中部小秦岭地区伟晶岩脉的结构和年代学数据，以约束 TNCO 中古元古代伸展的时间和性质。伟晶岩脉大致呈东西向走向，具有不同的倾角，并且要么变形，要么未变形。在变形岩脉中通常观察到从韧性变形到脆性变形的过程，表明同步造山隆升可能是由均衡调整驱动的。变形结构表明伟晶岩岩脉的侵入与区域伸展的单相有关，从而使它们具有同运动性。岩脉的延性组构和断层滑移数据都表明，N-S（造山带平行）伸展是岩脉变形的原因。同运动伟晶岩岩脉的锆石 U-Pb 年龄将伸展时间限制在 1840 至 1781 Ma 之间，表明造山带平行伸展的持续时间约为 59 Myr。这些数据表明，该延伸晚于 TNCO 的同步碰撞缩短，该缩短发生在 1863 年至 1840 Ma 之间。 TNCO 中的造山带平行伸展、同步均衡隆升和强烈的岩浆活动与碰撞后环境中的重力塌陷模型一致。
Orogen-parallel extension is common in collisional settings, but its cause is debated. The Paleoproterozoic Trans-North China Orogen (TNCO) provides insights into the process of orogen-parallel extension. We present structural and geochronological data from pegmatite dikes in the Xiaoqinling region of central China to constrain the time and nature of Paleoproterozoic extension in the TNCO. The pegmatite dikes strike roughly E–W, have various dip angles, and are either deformed or undeformed. A progression from ductile to brittle deformation is commonly observed in the deformed dikes, suggesting synchronous orogenic uplift probably driven by isostatic adjustments. The deformation structures demonstrate that the intrusion of the pegmatite dikes was associated with a single phase of regional extension, thus making them syn-kinematic. Both ductile fabrics and fault-slip data from the dikes indicate that N–S (orogen-parallel) extension was responsible for dike deformation. Zircon U–Pb ages for the syn-kinematic pegmatite dikes constrain the time of extension to between 1840 and 1781 Ma, suggesting a duration of ∼ 59 Myr for the orogen-parallel extension. These data suggest that the extension postdated the syn-collisional shortening in the TNCO, which occurred between 1863 and 1840 Ma. The orogen-parallel extension, the synchronous isostatic uplift, and the intense magmatism in the TNCO are consistent with a gravitational collapse model in a post-collisional setting.