Decelerating Uplift at Lazufre Volcanic Center, Central Andes, from A.D. 2010 to 2016, and Implications for Geodetic Models GEOSPHERE; V
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Research Paper THEMED ISSUE: PLUTONS: Investigating the Relationship between Pluton Growth and Volcanism in the Central Andes GEOSPHERE Decelerating uplift at Lazufre volcanic center, Central Andes, from A.D. 2010 to 2016, and implications for geodetic models GEOSPHERE; v. 13, no. 5 Scott T. Henderson1,2, Francisco Delgado2, Julie Elliott3, Matthew E. Pritchard2, and Paul R. Lundgren4 1Departamento de Geociencias, Universidad de los Andes, Cr 1 #18A-12, Bogotá, Colombia doi:10.1130/GES01441.1 2Department of Earth and Atmospheric Sciences, Cornell University, Ithaca, New York 14853, USA 3Department of Earth, Atmospheric, and Planetary Sciences, Purdue University, West Lafayette, Indiana 47907, USA 12 figures; 5 tables; 1 supplemental file 4Jet Propulsion Laboratory, California Institute of Technology, Pasadena, California 91109, USA CORRESPONDENCE: sth54@cornell .edu ABSTRACT vicinity of uplift since the late Pliocene (Naranjo, 2010). Although the majority CITATION: Henderson, S.T., Delgado, F., Elliott, J., of dated eruptive products have Pleistocene ages, the most recent lava flow Pritchard, M.E., and Lundgren, P.R., 2017, Deceler ating uplift at Lazufre volcanic center, Central Andes, Interferometric synthetic aperture radar (InSAR) and GPS measurements at Lastarria has been dated at ~2500 yr old (Naranjo, 2010), and at Cordon from A.D. 2010 to 2016, and implications for geo beyond 2010 are presented for the first time for the Lazufre volcanic center del Azufre flows have been dated to 0.3 ± 0.3 Ma (Wilder, 2015). The strike detic models: Geosphere, v. 13, no. 5, p. 1489–1505, in the Central Andes. Vertical uplift at Lazufre was known to affect an area axis of current uplift is NNE-SSW and aligned with structural lineaments, and doi:10.1130/GES01441.1. >50 km in diameter at rates exceeding 3 cm/yr between 1997 and 2010. Analy the spatial footprint contains a high concentration of volcanic vents (Ruch and sis of new InSAR data through August 2016 indicates that the spatial pattern Walter, 2010). Furthermore, topographical analysis combined with dated flows Received 7 October 2016 Revision received 16 May 2017 of uplift is relatively unchanged but the amplitude of uplift has significantly de suggests persistent tumescence at the location of uplift since at least 400 ka Accepted 5 July 2017 creased to <1.5 cm/yr since at least December 2011. We present a time series (Perkins et al., 2016). Published online 9 August 2017 inversion for InSAR data between 1996 and 2016 that is well fit by a double A striking characteristic of the Lazufre system is extremely vigorous degas- exponential model, with an inflection point occurring in 2006. For two con sing from the Lastarria edifice. In fact, localized uplift of the edifice of Lastarria tinuous GPS stations installed within the deformation footprint in November volcano has prompted the hypothesis that Lastarria may act as a “pressure 2010, we have determined vertical velocities through 2014 or 2015 (depending valve” for a deeper magmatic plumbing system (Froger et al., 2007; Ruch on the station) that agree with contemporaneous InSARderived velocities. et al., 2009). Furthermore, recent in situ studies of gas composition at Lastarria Velocities from campaign GPS benchmarks established in November 2011 and have suggested a possible transition from a hydrothermal character between reoccupied in March 2014 are also presented. We use a previously proposed A.D. 2006 and 2009 (Aguilera et al., 2012) to a shallow magmatic source in 2012 model of an inflating sill at 10 km depth to explain geodetically observed dis (Tamburello et al., 2014). Remote sensing measurements of SO2 emissions at placements. Opening rates are halved (6.8 ± 1.25 × 106 m3/yr) compared to in Lastarria from 2004 onwards also suggest a possible time dependence with ferred values using data prior to 2010. Subsurface heterogeneity is accounted a peak in 2006 (Carn et al., 2013). The recent temporal changes in gas emis- for by assigning elastic parameters based on local seismic tomography in a sions at Lastarria provide evidence for changes to the subsurface magmatic finiteelement model. Surface displacements (or inferred volume change esti system, which motivates examining recent geodetic measurements for tran- mates) for heterogeneous models compared to homogeneous models are sient signals. ampli fied by up to 7% within a 10 km radius of the center of uplift. Uplift began at Lazufre between late 1997 and 2000, accelerating to a maxi- mum line-of-sight (LOS) velocity of 3.5 cm/yr and affecting a broad region >50 km in diameter (e.g., Henderson and Pritchard, 2013). A second, smaller INTRODUCTION region (~2 km across) of uplift of about ~0.5 cm/yr starting in 2002 has been observed on top of Lastarria volcano (e.g., Froger et al., 2007; Ruch et al., 2009) The Lazufre volcanic uplift signal is centered between the summits of but is not discussed in this paper because it is not well resolved by the data Lastarria volcano (25.168°S, 68.507°W, 5706 m elevation) and Cordon del sets used in this study. Owing to the remote location of Lazufre, deformation Azufre volcano (25.336°S, 68.521°W, 5481 m elevation) in the Central Andes measurements have mostly been made with interferometric synthetic aperture Volcanic Zone (CVZ) of northern Chile and Argentina (Fig. 1). These volcanoes radar (InSAR); however, due to the end of Envisat (European Space Agency were identified as having had Holocene activity based on remotely sensed [ESA]) satellite observations in 2010, there was a gap in observations. For morphological indicators such as post-glacial eruptive features (Francis and de the first time, we present post-2010 InSAR observations along with continu- For permission to copy, contact Copyright Silva, 1989). Subsequently, extensive regional geological mapping has been ous GPS observations at Lazufre to address the question of whether previous Permissions, GSA, or [email protected]. conducted, which indicated ~120 km3 of erupted material from vents in the spatio temporal surface uplift trends have continued in the past 6 yr. © 2017 Geological Society of America GEOSPHERE | Volume 13 | Number 5 Henderson et al. | Decelerating uplift at Lazufre volcanic center and implications for geodetic models Downloaded from http://pubs.geoscienceworld.org/gsa/geosphere/article-pdf/13/5/1489/3995723/1489.pdf 1489 by guest on 28 September 2021 Research Paper N Figure 1. Overview map of Lazufre defor mation and GPS network, Central Andes. Circles are continuous GPS sites installed in November 2010; squares are campaign GPS benchmarks installed and surveyed in November 2011. Eastwest (Ux) and vertical (Uz) components of displacement (in cm/yr) are derived from InSAR data from between May 2006 and November 2008 (Remy et al., 2014). Black star marks the center of vertical uplift (25.259°S, 68.483°W). Black triangles are active vol canoes from the Smithsonian Global Vol canism Catalog. Curving black line is the international border between Chile and Argentina. Black triangles are active vol canoes from the Smithsonian Global Vol canism (http:// volcano .si .edu). To date, many source models of deformation at Lazufre have been con- All geodetic models to date for Lazufre have assumed that the crustal struc- strained by a single LOS viewing geometry, utilizing data from European ture is homogeneous and elastic. In recent years however, seismic tomog- Remote Sensing [ERS] Satellites 1 and 2 from ESA and Envisat tracks 282 raphy and conductivity models have been published, which help constrain spanning July 1995 to May 2010 (Pritchard and Simons, 2002, 2004; Froger subsurface heterogeneity under the Lazufre region. In particular, magneto- et al., 2007; Ruch et al., 2008). Owing to the nonunique nature of geodetic telluric data revealed a strong conductor under the deformation anomaly dip- models, there has been some disagreement as to whether the source was a ping eastward to the base of the crust. Modeling suggests that the feature laterally propagating sill (e.g., Ruch et al., 2008; Anderssohn et al., 2009) or could be due to 5–8 vol% partial melt which is feeding current sill inflation had a fixed geometry with variable opening rate. These models were based in the upper crust (Budach et al., 2013). A follow-up study with additional lo- on a rectangular elastic dislocation model (Okada, 1985). All available as- cal instrumentation defined several distinct low-conductivity anomalies—one cending and descending data through 2010 were used recently by Pearse and directly under Lastarria volcano (1–10 W·m) to 1 km depth, another south of Lundgren (2013) to address the question of lateral growth of the sill, and the the edifice (5–10 W·m) at 7–8 km depth, and finally an anomaly (0.1–1 W·m) best-fitting source was concluded to have a fixed geometry with a depth of at 5–15 km depth under the deformation centroid (Diaz et al., 2015). These 8 km, strike of 10° east of north, dip of 10°, length of 30 km, width of 20 km, results match quite well with local seismic tomography in which roughly co- and maximum opening rate of 5 cm/yr (implying volume change on the order incident low S-wave velocities were observed: 1.2–1.8 km/s, 1.5–2 km/s, and of 0.01 km3/yr). Note that the depth in this case describes the middle of the 2.3 km/s, respectively (Spica et al., 2015). The prevailing interpretation is that sill below the local average elevation of 4.8 km. Remy et al. (2014) modeled, magmatic fluids migrate upward to ~6 km from a reservoir at 10 km depth, with different methodologies, the same InSAR data set, adding campaign thereby providing heat to the extensive and shallow hydrothermal system GPS observations spanning 2006–2008, and pointed out that either a trun- (Spica et al., 2015).