The Yuli Belt in Taiwan: Part of the suture zone separating Eurasian and Philippine Sea plates
The Yuli Belt in Taiwan: Part of the suture zone separating Eurasian and Philippine Sea plates
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DOI：
10.3319/tao.2020.06.28.01
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发表时间：
2020
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影响因子：
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通讯作者：
Yiqiong Zhang;Chin-Ho Tsai;N. Froitzheim;K. Ustaszewski
中科院分区：
文献类型：
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作者：
Yiqiong Zhang;Chin-Ho Tsai;N. Froitzheim;K. Ustaszewski
玉里带出露于台湾造山带东部的后楔中，它含有一个不均匀的蓝片岩相岩石单元。然而，尽管有新的地质年代学数据，有关其古地理起源的问题仍然存在争议。这在很大程度上是因为对尉犁带与相邻单元构造接触的构造几何学和运动学认识不正确。本文介绍了新的构造数据，从野外工作沿沿着几条河流断面的玉里带，我们联合收割机与出版的数据到一个新的构造模型。野外工作和显微构造分析表明，尉犁带经历了三个变形阶段。根据横截面和现有P-T-t数据的回顾，我们怀疑蓝片岩相单元可能在第一变形阶段D1期间沿沿着逆冲断层侵位在绿片岩相变质沉积单元之上。这个组合后来被逆冲在欧亚衍生的Tailuko带沿着寿丰断裂在D2，建议由W-倾伏拉伸线理断层平行面。D3产生了E-渐倾褶皱，轴面W-NW倾斜，再折叠早期叶理以及D1推覆接触。我们怀疑这种E向褶皱可能与沿沿着寿丰断层观察到的顶E向逆冲作用有关，涉及其从最初的E向倾斜到目前的W向倾斜接触的重新定向。玉里带的蓝片岩相变质单元可能代表了中中新世南海洋壳地幔的一个碎片。因此，它可以被认为是欧亚板块和菲律宾海板块之间缝合线的一部分。文章历史：接收于2019年8月16日修订于2020年6月25日接受于2020年6月28日
The Yuli Belt exposed in the retro-wedge of the eastern part of the Taiwan orogen hosts slivers of a heterogeneous unit of blueschist-facies rocks. However, the question pertaining to its palaeogeographic provenance is still debated despite new geochronological data. This is largely because the structural geometries and kinematics of the Yuli Belt’s tectonic contacts with its adjacent units are improperly understood. This paper presents new structural data from field work along several river transects in the Yuli Belt, which we combine with published data into a new tectonic model. Fieldwork and microstructural analyses indicate three deformation phases in the Yuli Belt. Based on cross sections and a review of available P-T-t data, we suspect that blueschist-facies units could have been emplaced on top of greenschist-facies metasedimentary units along a thrust during a first deformation phase D1. This assembly was later thrust over the Eurasian-derived Tailuko Belt along the Shoufeng Fault during D2, as suggested by W-plunging stretching lineations on fault-parallel foliation planes. D3 produced E-vergent folds with Wto NW-dipping axial planes, refolding earlier foliations as well as the D1 nappe contact. We suspect that this E-vergent folding could be related to top-E backthrusting observed along the Shoufeng Fault, involving its reorientation from an initially E-dipping to a presently W-dipping contact. The blueschist-facies metamorphic unit of the Yuli Belt likely represents a mid-Miocene fragment of oceanic crust and mantle issued in the South China Sea. It could hence be considered as part of the suture between the Eurasian and the Philippine Sea plates. Article history: Received 16 August 2019 Revised 25 June 2020 Accepted 28 June 2020