Browsing by Autor "Ruben Tintaya"

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Dissecting a Zombie: Joint Analysis of Density and Resistivity Models Reveals Shallow Structure and Possible Sulfide Deposition at Uturuncu Volcano, Bolivia
(Frontiers Media, 2021) Patricia MacQueen; Joachim Gottsmann; M. E. Pritchard; Nicola Young; Faustino Ticona J.; Eusebio Ticona; Ruben Tintaya
The recent identification of unrest at multiple volcanoes that have not erupted in over 10 kyr presents an intriguing scientific problem. How can we distinguish between unrest signaling impending eruption after kyr of repose and non-magmatic unrest at a waning volcanic system? After ca. 250 kyr without a known eruption, in recent decades Uturuncu volcano in Bolivia has exhibited multiple signs of unrest, making the classification of this system as “active”, “dormant”, or “extinct” a complex question. Previous work identified anomalous low resistivity zones at &lt;10 km depth with ambiguous interpretations. We investigate subsurface structure at Uturuncu with new gravity data and analysis, and compare these data with existing geophysical data sets. We collected new gravity data on the edifice in November 2018 with 1.5 km spacing, ±15 μ Gal precision, and ±5 cm positioning precision, improving the resolution of existing gravity data at Uturuncu. This high quality data set permitted both gradient analysis and full 3-D geophysical inversion, revealing a 5 km diameter, positive density anomaly beneath the summit of Uturuncu (1.5–3.5 km depth) and a 20 km diameter arc-shaped negative density anomaly around the volcano (0.5–7.5 depth). These structures often align with resistivity anomalies previously detected beneath Uturuncu, although the relationship is complex, with the two models highlighting different components of a common structure. Based on a joint analysis of the density and resistivity models, we interpret the positive density anomaly as a zone of sulfide deposition with connected brines, and the negative density arc as a surrounding zone of hydrothermal alteration. Based on this analysis we suggest that the unrest at Uturuncu is unlikely to be pre-eruptive. This study shows the value of joint analysis of multiple types of geophysical data in evaluating volcanic subsurface structure at a waning volcanic center.
Dissecting a Zombie: Joint analysis of density and resistivity models reveals shallow structure and possible sulfide deposition at Uturuncu Volcano, Bolivia
(2021) Patricia MacQueen; Joachim Gottsmann; M. E. Pritchard; Nicola Young; Faustino Ticona; Eusebio Ticona; Ruben Tintaya
Earth and Space Science Open Archive This preprint has been submitted to and is under consideration at Other. ESSOAr is a venue for early communication or feedback before peer review. Data may be preliminary.Learn more about preprints preprintOpen AccessYou are viewing the latest version by default [v1]Dissecting a Zombie: Joint analysis of density and resistivity models reveals shallow structure and possible sulfide deposition at Uturuncu Volcano, BoliviaAuthorsPatriciaMacQueeniDJoachimGottsmanniDMatthew EPritchardiDNicolaYoungFaustinoTiconaEusebioTiconaRubenTintayaSee all authors Patricia MacQueeniDCorresponding Author• Submitting AuthorCornell UniversityiDhttps://orcid.org/0000-0001-7692-3416view email addressThe email was not providedcopy email addressJoachim GottsmanniDUniversity of BristoliDhttps://orcid.org/0000-0001-9280-4011view email addressThe email was not providedcopy email addressMatthew E PritchardiDCornell UniversityiDhttps://orcid.org/0000-0003-3616-3373view email addressThe email was not providedcopy email addressNicola YoungUniversity of Bristolview email addressThe email was not providedcopy email addressFaustino TiconaEscuela Militar de Ingenieríaview email addressThe email was not providedcopy email addressEusebio TiconaUniversidad Mayor de San Andrésview email addressThe email was not providedcopy email addressRuben TintayaObservatorio San Calixtoview email addressThe email was not providedcopy email address
Dissecting a Zombie: Shallow Volcanic Structure Revealed by Multiple Geophysical Data Sets at Uturuncu Volcano, Bolivia
(2021) Patricia MacQueen; Joachim Gottsmann; M. E. Pritchard; Nicola Young; Faustino Ticona J.; Ruben Tintaya; Thomas Hudson; Ying Liu; J. M. Kendall; Matthew J. Comeau
Uturuncu volcano in southern Bolivia is something of a “zombie” volcano – presumed dead, but showing signs of life. The volcano has not erupted in 250 kyr, but is exhibiting unrest in the form of ground deformation, seismicity, and active fumaroles. Elucidating the subsurface structure of the volcano is key for interpreting this recent unrest. Magnetotelluric measurements revealed alternating high and low resistivity anomalies at depths <10 km beneath the volcano, with a low-resistivity anomaly directly beneath Uturuncu. A key question is, what is the nature of this anomaly? To what extent is it partial melt, a hydrothermal brine reservoir, or a mature ore body? Knowing the density of this anomaly could distinguish between these scenarios, but existing density models of the area lack sufficient resolution. To address this issue, we collected additional gravity measurements on the Uturuncu edifice with 1.5 km spacing in November 2018. Gradient analysis and geophysical inversion of these data revealed several features: a 5 km diameter, high density anomaly beneath the summit of Uturuncu (1 – 3 km elev.), a 20 km diameter ring-shaped negative density anomaly around the volcano (-3 – 4 km elev.), a NNE trending, positive density anomaly northwest of the volcano (0 – 4 km elev.), and a NW trending, negative density anomaly to the southeast. These structures often (but not always) align with resistivity anomalies, features in new seismic tomography models, and relocated earthquake hypocenters. Based on a joint analysis of these data, we interpret the positive density anomaly as a crystallizing dacite pluton, and the negative density ring anomaly as a zone of hydrothermal alteration. Earthquakes around the edges of the crystallizing pluton may represent escaping fluids as the magma cools. The high density anomaly to the northwest likely represents a solidified pluton, and the low density anomaly to the southeast may represent a fractured fault zone. We posit that the alternating zones of high and low resistivity anomalies represent zones of low and high fluid/brine content, respectively. Based on this analysis we suggest that the unrest at Uturuncu is unlikely to be pre-eruptive. This study shows the value of joint analysis of multiple types of geophysical data in evaluating volcanic subsurface structure.