Hydrothermal and magmatic reservoirs at Lazufre volcanic area, revealed by a high-resolution seismic noise tomography

Abstract

Artículo de publicación ISIWe determine here for the first time the geometry and location of the hydrothermal and magmatic reservoirs in the Lazufre volcanic area. This furthers the understanding of the origin of one of the largest worldwide volcanic uplift regions, both in space and amplitude. The exact locations and shapes of the sources generating a double-wide uplift region in the Lazufre found by past deformation data (InSAR and GPS) and generating hydrothermal and magmatic fluids found by geochemical gas analysis have not been well-delimited. In this study, we use seismological data to perform a 3-D high-resolution S-wave velocity model, which allows defining better the locations and shapes of the sources of the deformations and the hydrothermal and magmatic reservoirs. We find three anomalies. Two of them (with S-wave velocity of about 1.2–1.8km/s) are located below the Lastarria volcano. The shallow one (<1km below the volcano base) has a funnel-like shape. The deeper one is located between a depth of 3 and 6km below the volcano base. Both are strongly elliptical in an EW direction and separated by a 2–3km thick zone with Vs of ∼1.5–2km/s. As far as these anomalies are located under the hydrothermal activity of Lastarria volcano, they are interpreted as a double hydrothermal (the shallow part) and magmatic source (the deeper part). The lattercan feed the former. This double hydrothermal and magmatic source is in agreement with previous geochemical, deformation (GPS and InSAR) and magneto-telluric studies. In particular, it explains the double origin of the gases (hydrothermal and magmatic). The third low-velocity zone (with S-wave velocity of about 2.3km/s) located at 5km depth and deeper is centered beneath an area of surface uplift as determined by InSAR data. We compare the seismic tomography and InSAR results to propose that this low-velocity zone is at the top of a large reservoir, hosting hydrothermal fluids and possibly also magma.PLUTONS project funded by the National Science Foundation (grant #EAR-0909254). The research was supported by the Chilean CONICyT-Fondecyt project #1061253, and the Mexican CONACyT projects #129820 and #221165

Three‐dimensional resistivity image of the magmatic system beneath Lastarria volcano and evidence for magmatic intrusion in the back arc (northern Chile)

“…A small‐scale magma chamber or magmatic conduit directly below the Lastarria edifice would be difficult to resolve; therefore, the presence of this kind of structures cannot be discarded. The interpretation of C1 and C2 anomalies as hydrothermal and magmatic reservoirs shows a remarkable agreement with results of a seismic noise tomography in the Lazufre area, recently published by Spica et al [], considering both location and extension of these features.…”

Persistent uplift of the Lazufre volcanic complex (Central Andes): New insights from PCAIM inversion of InSAR time series and GPS data

“…Thus, even if the inversions do not provide very good constraints on the model depth, the range of acceptable values (2000–14,000 m) clearly suggests a source within the upper crust. In addition, preliminary results of a study based on seismic noise correlation [ Spica et al ., ] suggest that the source may be deeper than 7 km. The volume estimate for the truncated elliptical cone model lying at shallow depth (<8000 m) might seem large (greater than 400 km 3 , Figure c) but it is plausible in view of the volume of some ignimbrites emitted in the vicinity of Lazufre. The Cerro Galan caldera, for instance, is the source of a ∼1000 km 3 ignimbrite [ Francis et al ., ] and La Pacana caldera is the source of at least two major ignimbrite eruptions with a combined estimated volume of some 2700 km 3 [ Lindsay et al ., ]. The estimated rate of volume change, whatever the source type, is about 12.5 × 10 6 −14.8 × 10 6 m 3 yr −1 .…”

Response of hydrothermal system to stress transients at Lassen Volcanic Center, California, inferred from seismic interferometry with ambient noise

“…In the last several years, seismic interferometry has become one of the most effective seismological tools for time-lapse monitoring of hydrothermal and magmatic reservoirs (e.g., Brenguier et al 2008bBrenguier et al , 2011Brenguier et al , 2016Haney et al 2009;Nagaoka et al 2010;Jaxybulatov et al 2014;Caudron et al 2015;Spica et al 2015). Here, we apply seismic interferometry to continuous seismic recordings for investigating the temporal seismic behavior of the Lassen hydrothermal system.…”