In active volcanic arcs such as the Andean volcanic mountain belt, magmatically sourced fluids are channeled through the brittle crust by faults and fracture networks. In the Andes, volcanoes, geothermal springs, and major mineral deposits have a spatial and genetic relationship with NNE trending, margin‐parallel faults and margin‐oblique, NW trending Andean Transverse Faults (ATF). The Tinguiririca and Planchon‐Peteroa volcanoes in the Andean Southern Volcanic Zone (SVZ) demonstrate this relationship, as their spatially associated thermal springs show strike alignment to the NNE oriented El Fierro Thrust Fault System. We constrain the fault system architecture and its interaction with volcanically sourced hydrothermal fluids using a combined magnetotelluric (MT) and seismic survey that was deployed for 20 months. High‐conductivity zones are located along the axis of the active volcanic chain, delineating fluids and/or melt. A distinct WNW trending cluster of seismicity correlates with resistivity contrasts, considered to be a reactivated ATF. Seismicity occurs below 4 km, suggesting activity is limited to basement rocks, and the cessation of seismicity at 9 km delineates the local brittle‐ductile transition. As seismicity is not seen west of the El Fierro fault, we hypothesize that this structure plays a key role in compartmentalizing magmatically derived hydrothermal fluids to the east, where the fault zone acts as a barrier to cross‐fault fluid migration and channels fault‐parallel fluid flow to the surface from depth. Increases in fluid pressure above hydrostatic may facilitate reactivation. This site‐specific case study provides the first three‐dimensional seismic and MT observations of the mechanics behind the reactivation of an ATF.

中文翻译：

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大地电磁和地震数据揭示的南安第斯山脉分隔热液对断层系统的再激活

在安第斯火山带等活动火山弧中，岩浆来源的流体通过断层和裂缝网络穿过脆性地壳。在安第斯山脉，火山、地热泉和主要矿床与 NNE 向、边缘平行断层和边缘倾斜、NW 向的安第斯横向断层 (ATF) 具有空间和成因关系。安第斯南部火山带 (SVZ) 的 Tinguirrica 和 Planchon-Peteroa 火山证明了这种关系，因为它们的空间相关温泉显示出与 NNE 导向的 El Fierro 逆冲断层系统的走向对齐。我们使用部署了 20 个月的大地电磁 (MT) 和地震调查相结合的方法来限制断层系统结构及其与火山源热液的相互作用。高导区位于活火山链的轴线上，描绘了流体和/或熔体。一个独特的 WNW 趋势地震活动集群与电阻率对比相关，被认为是重新激活的 ATF。地震活动发生在 4 公里以下，表明活动仅限于基底岩石，而 9 公里处地震活动的停止描绘了当地的脆性-韧性转变。由于在 El Fierro 断层以西看不到地震活动，我们假设该结构在将岩浆衍生的热液流体划分到东部方面起着关键作用，其中断层带作为跨断层流体运移的屏障并与断层平行流体从深处流向地表。流体压力的增加高于静水压力可能有助于重新激活。