Large Rotations of Crustal Blocks in the Tjörnes Fracture Zone of Northern Iceland
Large Rotations of Crustal Blocks in the Tjörnes Fracture Zone of Northern Iceland
复制标题
冰岛北部 Tjörnes 断裂带地壳块的大旋转
作者：
A. J. Horst;J. A. Karson;R. Varga
大洋转换断层附近地壳最上部变形的解释是基于测深线形结构和震源机制，对转换构造带内的详细运动学知之甚少。Tjörnes断裂带是冰岛北部右旋转换剪切作用形成的一条宽广的形变带，部分出露在陆地上，为研究中中新世浅层地壳结构提供了机会，该地壳是由陆上扩张形成的厚洋壳。转换带内Húsavík-Flatey断层附近的熔岩和岩墙方向的明显结构弯曲已有很好的记录，但其起源仍存在争议。为了对变形带附近的变形进行评估，在扁平雅斯卡吉半岛变形带的8个构造位置的182个古地磁站点采集了熔岩和岩墙样品。在断层以南10多公里处，位置逐渐顺时针增加，平均剩磁下降，大致模拟了熔岩和岩墙方向的结构曲率。基于倾斜旋转轴的旋转估计表明，多个地壳块体明显顺时针旋转(74°±7°至96°±9°)。综合起来看，距离胡萨维克-弗拉蒂断层12公里的变形带内108个地点的所有数据都得出了55°±7°的最佳倾斜轴旋转角。古地磁数据和场关系符合修正的书架断裂模型，相对较小(约1公里宽)的独立旋转地壳块体具有可变的，在某些情况下，在距离转换断裂带10公里范围内发现了大范围的旋转。类似的地壳变形和类似的旋转量可能出现在其他海洋转换附近，那里的可及性和表面沉积可能会限制对更复杂的断层结构的记录。
The interpretation of uppermost crustal deformation near oceanic transform faults is based on bathymetric lineaments and earthquake focal mechanisms, and relatively little is known about the detailed kinematics within the transform tectonized zone. The Tjörnes Fracture Zone is a broad zone of deformation produced by right‐lateral transform shearing in north Iceland and is partly exposed on land providing the opportunity to study shallow‐level crustal structure of mid‐Miocene, thick, oceanic‐like crust formed by subaerial spreading. A pronounced structural curvature of lava and dike orientations near the Húsavík‐Flatey Fault within the transform zone is well documented, yet of controversial origin. In order to develop an assessment of deformation near the transform zone, samples of lavas and dikes were collected from 182 paleomagnetic sites within eight structural localities across the deformation zone on the Flateyjarskagi Peninsula. A progressive clockwise increase in locality mean remanence declinations over more than 10 km south of the fault broadly mimics the structural curvature of lava and dike orientations. Rotation estimates based on inclined rotation axes indicate significant clockwise rotation (74° ± 7° to 96° ± 9°) of multiple crustal blocks. When combined, all data from 108 sites within the deformed zone <12 km to the Húsavík‐Flatey Fault yield a best fit inclined axis rotation of 55° ± 7°. The paleomagnetic data and field relationships are consistent with a modified bookshelf faulting model, with relatively small (~1 km across) independently rotated crustal blocks with variable, and in some cases large‐magnitude rotations found within 10 km to the transform fault zone. Similar crustal deformation and comparable amounts of rotation may be present near other oceanic transforms, where accessibility and surficial deposits may limit documentation of more complex fault structures.
影响因子：
18.3
作者：
R. Green;R. White;T. Greenfield
通讯作者：
R. Green;R. White;T. Greenfield