Collaborative Research: Reconstructing the Plastic-to-Brittle Exhumation History of the Taiwan Metamorphic Core

合作研究：重建台湾变质核从塑性到脆性的折返历史

• 批准号: 1650162
• 负责人: Timothy Byrne
• 金额: $ 24.55万
• 依托单位: University of Connecticut
• 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: 2017-08-15 至 2023-07-31
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1650162&HistoricalAwards=false
• 关键词: Collaborative; Research; Reconstructing; Plastic; Brittle

Taiwan represents one of the most active tectonic environments on Earth. The island marks the collision between the Luzon volcanic arc and the passive margin of Asia and for decades the collision has motivated geodynamic models to explain the evolution of many mountain belts around the world. This collision drives deformation and active uplift of the Taiwan mountain belt. Because of the very rapid uplift and high erosion rates the metamorphic core of Taiwan is exposed in the core of Taiwan's Central Range and its eastern margin. Here, a joint team of U.S. and Taiwanese scientists and students is exploring the idea that exhumation of the metamorphic rocks is facilitated by extension rather than the collision-driven shortening model that is usually invoked. The researchers will examine the geometry of the metamorphic rocks and the movement patterns of active faults to determine the mechanisms by which the rocks are exhumed. In addition to providing new insights into mountain building processes, the project advances desired societal outcomes through participation of women and underrepresented minorities in STEM; (b) development of a diverse, globally competitive STEM workforce through undergraduate and graduate student training plus a workshop for Taiwan undergraduate students; and (c) increased partnerships through international collaboration.More specifically, the objective of this project is to document the plastic-to-brittle exhumation history of the metamorphic core of Taiwan. The metamorphic core (the Tananao schist) in the eastern Central Range is marked by characteristics that are difficult to explain in the context of a steady-state, doubly-vergent orogenic wedge; the current prevailing model. In most parts of the mountain belt, metamorphic foliations are steeply dipping, forming a regional cleavage fan that is east dipping in the west and west dipping in the east. Close to the collisional suture (Longitudinal Valley) this simple pattern breaks down and the youngest metamorphic foliation is commonly gently dipping. Moreover, most mesoscale faults observed to date in this area record normal displacement and accommodate NE-SW extension, the same extension direction as recorded in crustal earthquakes. The researchers aim to test the hypothesis that normal displacement faults and shear zones accommodate syn-collision exhumation of the metamorphic core in eastern Taiwan. This will entail systematically documenting the geometry and kinematics of the youngest metamorphic fabrics and overprinting brittle structures in the Tananao Schist, and establishing the relation between the plastic-to-brittle deformation patterns and ongoing deformation as constrained by seismotectonics and seismic tomography. The research team composed U.S. and Taiwanese scientists and graduate and undergraduate students will collect metamorphic fabric data, and oriented rock samples for petrographic and XCT analyses. Kinematic data for ductile shear zones and overprinting brittle structures, e.g., faults and joints, will also be collected. The existing catalog of earthquake focal mechanisms will be supplemented with new mechanisms generated from Taiwan Central Weather Bureau data. The results will be integrated with seismic tomography and seismotectonic constraints on active deformation to better understand the mechanisms behind exhumation of Taiwan?s metamorphic core.

台湾是地球上最活跃的构造环境之一。该岛标志着吕宋岛火山弧与亚洲被动边缘之间的碰撞，几十年来，这种碰撞激发了地球动力学模型来解释世界各地许多山脉的演化。这次碰撞带动了台湾山地带的变形和主动隆起。由于快速的隆升和高侵蚀率，台湾的变质核暴露在台湾中央山脉的核心及其东缘。在这里，一个由美国和台湾科学家和学生组成的联合小组正在探索这样的想法：变质岩的折返是通过延伸而不是通常引用的碰撞驱动的缩短模型来促进的。研究人员将检查变质岩的几何形状和活动断层的运动模式，以确定岩石被挖掘的机制。除了提供对山区建设过程的新见解外，该项目还通过妇女和代表性不足的少数群体参与 STEM 来推进预期的社会成果； (b) 通过本科生和研究生培训以及为台湾本科生举办的讲习班，培养一支多元化、具有全球竞争力的 STEM 劳动力队伍； (c) 通过国际合作加强伙伴关系。更具体地说，该项目的目标是记录台湾变质核心从塑性到脆性的折返历史。中央山脉东部的变质核（塔纳瑙片岩）具有难以在稳态、双辐造山楔的背景下解释的特征；目前流行的模式。山地带大部分地区变质叶理陡倾，形成西倾东倾、东倾西倾的区域解理扇。靠近碰撞缝合线（纵谷）时，这种简单的模式就会分解，最年轻的变质叶理通常会轻轻倾斜。此外，迄今为止在该地区观察到的大多数中尺度断层都记录了正常位移并适应NE-SW延伸，与地壳地震中记录的延伸方向相同。研究人员旨在验证以下假设：正位移断层和剪切带适应台湾东部变质核的同步碰撞折返。这将需要系统地记录 Tananao 片岩中最年轻的变质织物和套印脆性结构的几何和运动学，并建立塑性到脆性变形模式与受地震构造和地震层析成像约束的持续变形之间的关系。该研究小组由美国和台湾科学家以及研究生和本科生组成，将收集变质组构数据以及定向岩石样本以进行岩相学和 XCT 分析。还将收集延性剪切带和套印脆性结构（例如断层和接缝）的运动学数据。现有的地震震源机制目录将得到台湾中央气象局数据生成的新机制的补充。结果将与地震层析成像和地震构造对活动变形的约束相结合，以更好地了解台湾变质核折返背后的机制。

项目成果

Synorogenic extension and extrusion in southern Taiwan

• DOI: 10.1016/j.tecto.2022.229562
• 发表时间: 2022-09
• 期刊: Tectonophysics
• 影响因子: 2.9
• 作者: W. Hsu;T. Byrne;Jonathan C. Lewis;Yue‐Gau Chen;P. Yeh

Helium Isotopic Signature of a Plate Boundary Suture in an Active Arc–Continent Collision

• DOI: 10.1021/acsearthspacechem.0c00038
• 发表时间: 2020-07
• 作者: Ai-Ti Chen;Y. Sano;T. Byrne;N. Takahata;Tsanyao Frank Yang;Yun-shuen Wang;Chuan‐Chou Shen

Out of sequence faulting in the backbone range, Taiwan: Implications for thickening and exhumation processes

台湾骨干范围内的无序断层：对增厚和折返过程的影响

• DOI: 10.1016/j.epsl.2022.117711
• 发表时间: 2022
• 期刊: Earth and Planetary Science Letters
• 影响因子: 5.3
• 作者: Lee, Yuan-Hsi;Byrne, Timothy B.;Lo, Wei;Wang, Shao-Jyun;Tsao, Shuh-Jong;Chen, Cheng-Hong;Yu, Han-Cheng;Tan, Xinbin;van Soest, Matthijs;Hodges, Kip
• 通讯作者: Hodges, Kip

Mantle fluids associated with crustal-scale faulting in a continental subduction setting, Taiwan

台湾大陆俯冲环境中与地壳尺度断层相关的地幔流体

• DOI: 10.1038/s41598-019-47070-2
• 发表时间: 2019
• 期刊: Scientific Reports
• 影响因子: 4.6
• 作者: Chen, Ai-Ti;Shen, Chuan-Chou;Byrne, Timothy B.;Sano, Yuji;Takahata, Naoto;Yang, Tsanyao Frank;Wang, Yunshuen
• 通讯作者: Wang, Yunshuen

A new interpretation of the metamorphic core in the Taiwan orogen: A regional-scale, left-lateral shear zone that accommodated highly oblique plate convergence in the Plio-Pleistocene

• DOI: 10.1016/j.tecto.2022.229332
• 发表时间: 2022-04-26
• 期刊: TECTONOPHYSICS
• 影响因子: 2.9
• 作者: Ho, Gong-Ruei;Byrne, Timothy B.;Chang, Chung-Pai
• 通讯作者: Chang, Chung-Pai