葉恩肇Yeh, En-Chao褚穎蓉Chu, Ying-Rong2019-09-052016-12-242019-09-052016http://etds.lib.ntnu.edu.tw/cgi-bin/gs32/gsweb.cgi?o=dstdcdr&s=id=%22G060244004S%22.&%22.id.&http://rportal.lib.ntnu.edu.tw:80/handle/20.500.12235/101158臺灣為一活動造山帶，受控於歐亞板塊及菲律賓海板塊的斜向聚合作用以及弧後張裂作用，使得地質構造變化多樣。為了解岩層受斷層錯動作用的變形行為，因此本研究以海岸山脈奇美村附近的奇美斷層帶作為研究區域，應用磁性礦物組構與古地磁分析方法調查奇美斷層帶，以了解奇美斷層帶的應變演化史。 奇美斷層為中新統火成岩體的都巒山層逆衝至上新統沉積岩體的八里灣層之上，為典型的岩性差異斷層；其分佈從玉里的東北方一路向東北延伸，經過秀姑巒溪的中游奇美村後，延伸至豐濱，為唯一橫貫海岸山脈之高角度逆斷層。為深入瞭解奇美斷層各分帶的變形狀態，進而推論奇美斷層應變演化史，本研究於花蓮縣秀姑巒溪中段奇美村附近野外露頭採集定向岩芯樣本，將斷層下盤區分為I至V等五個分帶，斷層上盤分為A，B與C三個分帶，進行磁性組構分析。 磁感率橢球體及磁感率異向性分析結果顯示，離奇美斷層最遠的分帶Ⅴ，其磁性組構屬Type 2的似圓盤狀橢球體，呈東西向擠壓。於分帶Ⅳ，K1開始轉為鉛直方向，屬Type 2的似圓盤狀橢球體，呈南北向擠壓，且因受到斷層作用影響，岩體應變程度增加。到分帶Ⅱ時，呈Type 2-3的似圓盤橢球體及雪茄狀橢球體，磁性線理程度明顯。分帶Ⅰ時，主要呈Type 5的似圓盤狀橢球體，且為五個分帶中應變程度最大。而分帶Ⅲ，部分應變程度較高的橢球體為奇美斷層發育後的次要斷層變形的結果。 透過遲滯曲線與溫度─磁感率實驗，得知本研究區域斷層上下盤的磁性礦物以鐵磁性物質為主，並以磁鐵礦為主要磁性礦物，進一步由遲滯曲線實驗分析結果顯示斷層上下盤樣本中磁性礦物的磁域壁大小以偽單磁域壁（PSD）為主，且磁性礦物及磁域壁並不影響磁感率橢球體的分布。 本研究磁感率異向性及磁性組構的變化顯示整個奇美村附近之奇美斷層下盤的磁性組構演化過程，受到大地構造聚合作用影響，依據Lee et al., 1991的結果指出呂宋島弧順時鐘旋轉約30度，碰撞後導致分帶Ⅴ呈東西向擠壓，而分帶Ⅳ到分帶Ⅰ以南北向擠壓為主，而後奇美斷層作用過程中，在分帶Ⅲ又產生一個次要斷層。而斷層上盤因岩性屬火成岩，磁性組構無法顯示其變形趨勢。 本研究結果顯示磁感率橢球體於奇美斷層的變化是由於斷層作用造成岩體變形的結果，此變形演化結果可以提供奇美斷層大地構造發育的新思考方向。The island of Taiwan is an active orogen resulting from the oblique collision between the Philippine Sea Plate and the Eurasian Plate, and is located at the conjunction between two subduction zones of opposite vergence that making various geological structures in Taiwan. The Coastal Range of eastern Taiwan is the accreted material composited of Luzon arcs and surrounding basins onto the Eurasian crust. To investigate the deformation pattern across the Chimei fault more precisely, this study analyzed oriented samples along the Hsiukuluan River via anisotropy of magnetic susceptibility (AMS) and paleomagnetism. It has been demonstrated that the orientation and shape of the magnetic susceptibility ellipsoid can give reliable and important information about the deformation and the tectonic history of a rock. The Chimei fault is the only major high-angle reverse fault across the entire Coastal Range and is also a typical lithology-contrast fault thrusting the volcanic Tuluanshan Formation of Miocene over the sedimentary Paliwan Formation of Pleistocene. To decipher the deformation pattern and history across the Chimei fault, this study collected oriented samples of I-V domains in the hanging wall and of A-C domains in the footwall and conduct a series of experiences. Results of AMS and magnetic susceptibility ellipsoids show that at the zone Ⅴ, AMS indicates northwest-southeast compression and belongs to the oblate ellipsoid of Type 2. K1 orientations of magnetic ellipsoids indicate N-S compression at Zone Ⅳ and the AMS is oblate ellipsoid of Type 2. AMS at Zone Ⅱ belongs to oblate and prolate ellipsoid of Type 2 -3. At Zone I, AMS belongs to oblate ellipsoid of Type 5 with the strongest strain among all domains. Magnetic susceptibility ellipsoids with strong deformation came from the deformation of secondary fault developed after the Chimei fault. Results of the hysteresis loop and temperature-function magnetic susceptibility experiment illustrate that ferromagnetic mineral is main contribution to magnetic susceptibility in the samples across the Chimei fault and furthermore magnetite is major magnetic carrier. The hysteresis loop also indicates the PSD is the main domain size of magnetite. As a result of this study, magnetic mineral and domain size do not have strong influence to the distribution of magnetic susceptibly ellipsoids. The AMS and magnetic fabric can be treated as the representative of the finite deformation. Magnetic fabric at the foot wall of Chimei fault is strongly affected by the plate convergence. The Luzon arc rotated clockwise about 30 degree by result of Lee et al., 1991 after collision that cause NW-SE compression direction of Zone Ⅴ and N-S compression direction of ZoneⅣ to ZoneⅠ. Also, it caused the rotation of bedding strike from N-S direction of Zones V to E-W direction of ZoneⅣ to ZoneⅠ. The secondary fault at Zone III developed after the formation of Chimei fault. No clear deformation trend inferred from magnetic fabrics is observed in the hanging wall due to the strong igneous rocks. This study demonstrates that AMS pattern across the Chimei fault is the consequence of finite deformation. Our results of evolution of magnetic fabrics across the Chimei fault can provide insights into understanding the tectonic development of Chimei fault.海岸山脈奇美斷層磁感率異向性變形Coastal RangeChimei FaultAnisotropy of magnetic susceptibilityDeformation