The Yuli Belt in Taiwan: Part of the suture zone separating Eurasian and Philippine Sea plates

Abstract

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 W-to 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.

Deep learning-based earthquake catalog reveals the seismogenic structures of the 2022 Mw6.9 Chihshang earthquake

“…The buried forearc basement due to the shortening of the Luzon forearc lithosphere is shown among those lithospheric scale models of the southern LV (e.g. Malavieille and Trullenque, 2009;Shyu et al, 2011;Zhang et al, 2020;Lai et al, 2022). The deformation of the accretionary wedge forearc basin may be the key to the complex seismogenic structures beneath the CR compared to that beneath the CoR.…”

“…Chang et al, 2000) to lithospheric scale (e.g. Malavieille and Trullenque, 2009;Shyu et al, 2011;Zhang et al, 2020;Lai et al, 2022). The buried forearc basement due to the shortening of the Luzon forearc lithosphere is shown among those lithospheric scale models of the southern LV (e.g.…”

Rock properties and sediment caliber govern bedrock river morphology across the Taiwan Central Range

“…The Tananao complex is composed mainly of schists (PM 3 ), with marbles (PM 2 ) and gneisses (PM 1 ) more prevalent to the north (30). The Yuli Belt is primarily composed of schists with limited marbles, and metamorphic phase assemblages are consistent with blueschist facies metamorphism followed by rapid exhumation of oceanic crust (31). Peak temperatures recorded by Raman spectroscopy of carbonaceous materials range from <330°C for the Slate belt of the Western Central Range and southern Eastern Central Range to 350° to 550°C in the Tananao Complex and reach 550°C in the Yuli Belt (30,32).…”