EGU2020-2028
https://doi.org/10.5194/egusphere-egu2020-2028
EGU General Assembly 2020
© Author(s) 2020. This work is distributed under
the Creative Commons Attribution 4.0 License.

Analysis of the Magmatic – Hydrothermal Volcanic Field of Tacora Volcano, Northern Chile, using Travel Time Tomography

Diana Comte1, Claudia Pavez2, Francisco Gutierrez3, and Diego Gaytan4
Diana Comte et al.
  • 1Universidad de Chile, Advanced Mining Technology Center, Department of Geophysics, Santiago, Chile (dcomte@dgf.uchile.cl)
  • 2Geological Survey of Norway, Trondheim, Norway (claudia.pavez@ngu.no)
  • 3GeoExpedition, Santiago, Chile (francisco@geoexpedition.cl )
  • 4INFINERGEO SpA, Santiago, Chile

Tacora Volcano (17º43’S – 69º46’W) is a composite stratovolcano that lies at the southernmost end of a 10 km-long volcanic lineament that extends between Chile and Perú. Around Tacora volcano, current thermal manifestations are two active fumarolic fields located at the western flank of the stratovolcano and at the volcano summit, indicating active magma degassing in a shallow hydrothermal system. Beneath Tacora volcano is located the NW Challaviento reverse fault that belongs to the Incapuquio - Challaviento fault system of Middle Eocene age. To complement previous exploration results and conceptual modeling developed by INFINERGEO SPA, seventeen short period seismic stations were installed around Tacora volcano, between August and December 2014. Using the P and S wave arrival times of locally recorded seismicity, a 3D velocity model was determined through a travel time tomography. According with the results, we interpreted high Vp /Vs values as water-saturated areas, corresponding to the recharge zone of Tacora hydrothermal system. In addition, low values of ΔVp/Vp (%) and Vp/Vs ratio represent the location of a gas-saturated magmatic reservoir between sea level and 2 km depth and circulation networks of magmatic-hydrothermal fluids. Low Vp/Vs volumes (magma reservoir / high temperature hydrothermal fluids), the presence of fumarolic fields and surface hydrothermal alteration have a spatial correlation. The above suggests a structural control of the Challaviento fault in the hydrothermal flow as well as a primary influence in the emplacement and location of the magmatic-hydrothermal reservoir. Finally, we present a cluster analysis using the ΔVp/Vp (%) parameter. Through this analysis, we found a method for the identification of a key structure in depth composed by the magma reservoir (low Vp/Vs ratios, low ΔVp/Vp (%)), clay level areas (intermediate values of ΔVp/Vp (%)), and degasification zones (low values of ΔVp/Vp (%)) directly related with the surface thermal manifestations.

How to cite: Comte, D., Pavez, C., Gutierrez, F., and Gaytan, D.: Analysis of the Magmatic – Hydrothermal Volcanic Field of Tacora Volcano, Northern Chile, using Travel Time Tomography, EGU General Assembly 2020, Online, 4–8 May 2020, EGU2020-2028, https://doi.org/10.5194/egusphere-egu2020-2028, 2020

Comments on the presentation

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Presentation version 1 – uploaded on 14 Apr 2020
  • CC1: deltaVp/Vp (%), Vincenzo Serlenga, 05 May 2020

    Hi Claudia,

    what would you like to image with deltaVp/Vp (%) representation? The "DeltaVp" with respect to what has been computed?

    Regards,

    Vincenzo 

    • AC2: Reply to CC1, Claudia Pavez, 05 May 2020

      As an extra comment, if you are interested you can find more info in the published article. 

      regards, 

      Claudia

  • AC1: Comment on EGU2020-2028, Claudia Pavez, 05 May 2020

    Hi Vincenzo, 

    Thanks for your question. The %dVp is calculated in base of the variation with respect to the initial velocity models. As the shear modulus in the Vs tomography was not really clear to interpret our results, which consider several phases and temperatures, we decided to describe what we were seeing using the bulk modulus as well. According to this, we could corroborate the location of the magma reservoir. 

    Please feel free to contact me if you want to discuss more, 

    Claudia 

    • CC2: Reply to AC1, Vincenzo Serlenga, 05 May 2020

      Ok, thank you very much. Very clear.

      Best wishes,

      Vincenzo