Displacement history of the Atacama fault system 25°00′S-27° 00′S, northern Chile
Displacement history of the Atacama fault system 25°00′S-27° 00′S, northern Chile
复制标题
智利北部阿塔卡马断层系25°00′S-27°00′S的位移历史
DOI：
--
复制
发表时间：
1993
期刊：
影响因子：
--
通讯作者：
J. Grocott
中科院分区：
文献类型：
--
作者：
Michael Brown;F. Diáz;J. Grocott
在智利北方安第斯山脉中部的科迪勒拉-德拉科斯塔，中生代弧形复合体被一个海沟平行的走滑断层系统--阿塔卡马断层系统切割。阿塔卡马断裂系统中的脆性断裂叠加在韧性剪切带中的陡倾面理上。在南纬25° ~ 27°之间，断裂系统的西部在早白垩世时期活动，为上角闪岩相，自下而东的倾滑韧性剪切带。在断裂系统的东部，韧性变形是类似的早白垩世的年龄，但发生在低级变质条件下的绿片岩/下角闪岩相过渡。断裂系统东部的糜棱岩是由左旋走滑位移形成的。倾滑和左旋走滑位移与岩浆弧的发育是同时代的，这意味着弧的这一部分的构造环境是张扭的。韧性变形在空间上分为与岩浆侵位有关的倾滑分量和左旋走滑分量。阿塔卡马断层系统El Salado段的脆性断层带定义了大规模的侧壁剥离构造。断层泥中的近水平滑纹、不对称性剥离和S-C型组构表明脆性变形涉及左旋走滑位移。从韧性到脆性的左行走滑位移的转变可能是由于冷却，在白垩纪中期，当岩浆弧被遗弃。
In the Cordillera de la Costa of the central Andes in northern Chile, Mesozoic arc complexes are cut by a trench-parallel strike-slip fault system: the Atacama fault system. Brittle faulting in the Atacama fault system is superposed on steeply dipping foliations in ductile shear belts. Between 25°S and 27°S, the western part of the fault system was active in Early Cretaceous time as an upper amphibolite facies, down-to-the-east, dip-slip ductile shear zone. In the eastern part of the fault system, ductile deformation is of similar Early Cretaceous age but occurred under lower-grade metamorphic conditions at the greenschist/lower amphibolite facies transition. The mylonites in the eastern part of the fault system were formed by sinistral strike-slip displacement. The dip-slip and sinistral strike-slip displacements are contemporary with the development of a magmatic arc, and they imply that the tectonic environment in this part of the arc was transtensional. The ductile deformation was partitioned spatially into a dip-slip component associated with the emplacement of magmas and a sinistral strike-slip component. Brittle fault zones in the El Salado segment of the Atacama fault system define large-scale sidewall ripout structures. Subhorizontai slickenlines, ripout asymmetry, and S-C-type fabrics in fault gouge indicate that brittle deformation involved sinistral strike-slip displacements. The transition from ductile to brittle sinistral strike-slip displacements may have occurred due to cooling, in mid-Cretaceous time, when the magmatic arc was abandoned.