4 research outputs found
Reactivation of Fault Systems by Compartmentalized Hydrothermal Fluids in the Southern Andes Revealed by Magnetotelluric and Seismic Data
In active volcanic arcs such as the Andean volcanic mountain belt, magmaticallyâsourced fluids are channelled 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 NNEâtrending, marginâparallel faults and marginâoblique, NWâtrending Andean Transverse Faults (ATF). The Tinguiririca and PlanchĂłnâPeteroa volcanoes in the Andean Southern Volcanic Zone (SVZ) demonstrate this relationship, as their spatially associated thermal springs show strike alignment to the NNEâoriented 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 WNWâtrending 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 brittleâductile transition. As seismicity is not seen west of the El Fierro fault, we hypothesize that this structure plays a key role in compartmentalizing magmaticallyâderived hydrothermal fluids to the east, where the fault zone acts as a barrier to crossâfault fluid migration and channels faultâparallel fluid flow to the surface from depth. Increases in fluid pressure above hydrostatic may facilitate reactivation. This siteâspecific case study provides the first threeâdimensional seismic and magnetotelluric observations of the mechanics behind the reactivation of an ATF
Reactivation of fault systems by compartmentalized hydrothermal fluids in the Southern Andes revealed by magnetotelluric and seismic data
In active volcanic arcs such as the Andean volcanic mountain belt, magmaticallyâsourced fluids are channelled 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 NNEâtrending, marginâparallel faults and marginâoblique, NWâtrending Andean Transverse Faults (ATF). The Tinguiririca and PlanchĂłnâPeteroa volcanoes in the Andean Southern Volcanic Zone (SVZ) demonstrate this relationship, as their spatially associated thermal springs show strike alignment to the NNEâoriented 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 WNWâtrending 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 brittleâductile transition. As seismicity is not seen west of the El Fierro fault, we hypothesize that this structure plays a key role in compartmentalizing magmaticallyâderived hydrothermal fluids to the east, where the fault zone acts as a barrier to crossâfault fluid migration and channels faultâparallel fluid flow to the surface from depth. Increases in fluid pressure above hydrostatic may facilitate reactivation. This siteâspecific case study provides the first threeâdimensional seismic and magnetotelluric observations of the mechanics behind the reactivation of an ATF