Reactivation of Fault Systems by Compartmentalized Hydrothermal Fluids in the Southern Andes Revealed by Magnetotelluric and Seismic Data
Reactivation of Fault Systems by Compartmentalized Hydrothermal Fluids in the Southern Andes Revealed by Magnetotelluric and Seismic Data
复制标题
大地电磁和地震数据揭示了安第斯山脉南部分区热液流体对断层系统的重新激活
作者：
R. Pearce;A. S. D. L. Muela;M. Moorkamp;James O.S. Hammond;Thomas M. Mitchell;J. Cembrano;J. A. Vargas;Philip G. Meredith;Pablo Iturrieta;N. Pérez;N. Marshall;J. Smith;Gonzalo Yáñez;W. A. Griffith;C. Marquardt;A. Stanton‐Yonge;R. C. Nuñez
在活跃的火山弧，如安第斯火山带，岩浆来源的流体通过断层和裂缝网络引导通过脆性地壳。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的NW向安第斯横向断层（ATF）具有空间和成因关系。安第斯南部火山带（SVZ）的Tinguiririca和Planchón-Peteroa火山证明了这种关系，因为它们在空间上相关的温泉显示出与NNE方向的El Fierro逆冲断层系统的走向对齐。我们约束断层系统的架构和它的相互作用与火山源热液流体使用相结合的大地电磁（MT）和地震调查，部署了20个月。高传导率区域位于活动火山链的轴向沿着，描绘出流体和/或熔体。一个明显的WNW向地震活动集群与电阻率对比相关，被认为是一个重新激活的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局部的脆韧性转变。由于El Fierro断层以西没有地震活动，我们假设该结构在将岩浆热液流体划分到东部方面发挥了关键作用，其中断层带作为跨断层流体迁移的屏障，并将平行于断层的流体流从深处引导到地表。流体压力增加到流体静力学以上可能有助于重新激活。这个特定场地的案例研究提供了ATF重新激活背后的力学的第一个三维地震和MT观测。
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 Planchón‐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.
DOI：
10.1029/2009jb006369
发表时间：
2010-04
期刊：
Journal of Geophysical Research: Solid Earth
影响因子：
--
作者：
M. Moorkamp;Alan G. Jones;S. Fishwick
通讯作者：
M. Moorkamp;Alan G. Jones;S. Fishwick
影响因子：
2.8
作者：
Drew, Julian;White, Robert S.;Tarasewicz, Jon
通讯作者：
Tarasewicz, Jon