[SIT29-09] Doming induced by rapid exhumed serpentinite bodies in the subduction mélange and the associated structures: a case study of the Yuli Belt in eastern Taiwan
Keywords:Doming, Serpentinite , Exhumation, Yuli belt, Taiwan
We conducted detailed field surveys around the Serpentinite bodies within the Yuli belt in the Chingshui River area. We found that the km-scale-wide serpentinite bodies served as stronger competent rock bodies. So that the surrounding pelitic schist, which served as weaker incompetent rock units, shows bending or folding of the main cleavage set S2. Note that we tentatively called the main deformational composition layers S2 (for the sake of field investigations), which also developed a regional penetrative cleavage set. It is worth noting that the edge of the serpentinite bodies has formed a series of layers of metasomatism products, such as chlorite schist and talc schist. These serpentinite-edge-schist developed a dominant vertical cleavage, with orientations generally parallel or sub-parallel to the edge shape of the serpentinite body. We also commonly observed breccia deformation bands sub-parallel to the main cleavage in the serpentinite edge, implying strongly mechanical shearing has been occurred around the edge of serpentinite in contact with the surrounding pelitic schist.
The deforming and bending of the S2 cleavage (i.e., main composition layers and the most penetrative cleavage) of the pelitic schist surrounding the km-wide serpentinite bodies indicates that the pelitic rocks encountered the serpentinite bodies after they have already formed the S2-related structures, probably during the exhumation process rather than the subduction process? Finally, in the regional scale, the shallow dipping S2 (and S3) outside the serpentinite bodies reveal a dome-shape (or anticlinal-form shape) character, strongly suggesting a upward serpentinite bodies and unroofing process during the rapid exhumation of the eastern Central Range of Taiwan.