Timing, Kinematics, and Displacement of the Taltal Fault System, Northern Chile: Implications for the Cretaceous Tectonic Evolution of the Andean Margin
Timing, Kinematics, and Displacement of the Taltal Fault System, Northern Chile: Implications for the Cretaceous Tectonic Evolution of the Andean Margin
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DOI：
10.1029/2019tc005832
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发表时间：
2020-02
期刊：
影响因子：
4.2
通讯作者：
S. Mavor;J. Singleton;R. Gomila;G. Heuser;N. Seymour;S. Williams;G. Arancibia;S. Johnston;A. Kylander‐Clark;D. Stockli
中科院分区：
文献类型：
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作者：
S. Mavor;J. Singleton;R. Gomila;G. Heuser;N. Seymour;S. Williams;G. Arancibia;S. Johnston;A. Kylander‐Clark;D. Stockli
广泛的西北走向断层系统构成了智利北部沿海科迪勒拉山脉的主要构造特征，但关于这些结构的时间和运动学的基本问题仍然存在。我们提出了新的地质测绘和地质年代学，为了解塔尔塔尔断层系统（TFS）的结构演化和构造意义提供了见解。 TFS 取代了早白垩世弧平行阿塔卡马断层系统 (AFS)，在约 15 公里宽的区域内累积偏移量约为 10.6 公里。脆性断层数据表明，TFS 垂直于陡峭的 NE 倾斜，平均左旋滑移矢量从 NW 倾斜 11°，与东西向缩短相兼容。两个早白垩世晚期的岩脉切割了 AFS，但又被 TFS 断层切割，TFS 线上的同运动方解石得出的 U-Pb 方解石年代为 114.1 ± 7.0 Ma。这些数据表明，AFS 被废弃，TFS 在约 114-107 Ma 之间开始变形（重新），在 Tropezón（约 110 Ma）和 Librillo（106-101 Ma）深成杂岩侵入后继续滑移。沿着塔尔塔尔主断层的约 146 Ma 流纹岩脉的侵位和断层核心中的 141 ± 11 Ma 方解石矿化表明，前体结构影响了晚侏罗世/早白垩世的岩浆侵位和流体流动，支持了 TFS 重新激活了长期继承的地壳弱点的假设。早白垩世，在岩浆弧迁移之前不久，TFS 上的弧平行剪切转变为滑移，并且东西向缩短，并记录了智利边缘俯冲动力学的变化。
An extensive system of NW striking faults constitutes a major tectonic feature of the Coastal Cordillera in northern Chile, but fundamental questions remain about timing and kinematics of these structures. We present new geologic mapping and geochronology that provide insight into the structural evolution and tectonic significance of the Taltal fault system (TFS). The TFS displaces the Early Cretaceous arc‐parallel Atacama fault system (AFS) with ~10.6 km cumulative offset across a ~15 km wide zone. Brittle fault data demonstrate that the TFS is vertical to steeply NE dipping with an average sinistral slip vector plunging 11° from the NW, compatible with E‐W shortening. Two late Early Cretaceous dikes cut the AFS but are cut by TFS faults, and synkinematic calcite on a TFS strand yielded a U‐Pb calcite date of 114.1 ± 7.0 Ma. These data demonstrate that the AFS was abandoned and deformation (re) initiated on the TFS between ~114–107 Ma, with continued slip after intrusion of the Tropezón (~110 Ma) and Librillo (106–101 Ma) plutonic complexes. Emplacement of a ~146 Ma rhyolite dike along the main Taltal fault and 141 ± 11 Ma calcite mineralization in the fault core suggests that a precursor structure influenced magma emplacement and fluid flow in the Late Jurassic/Early Cretaceous, supporting the hypothesis that the TFS reactivated long‐lived inherited crustal weaknesses. The Early Cretaceous shift from arc‐parallel shear to slip on the TFS and E‐W shortening shortly preceded migration of the magmatic arc and records a change in the Chilean margin subduction dynamics.