Emisión difusa de dióxido de carbono en el Volcán Irazú, Costa Rica

Abstract

The first study of diffuse CO 2 degassing was performed at Irazú volcano in 2001, with the goal to evaluate the origin and spatial distribution of CO 2 efflux as well as the total output of CO 2 to the atmosphere. Most of the study area showed background values of CO 2 efflux, < 20 g m -2 d -1 . The highest value was 316 g m -2 d -1 , which is relatively lower than the observed highest values for other volcanic systems within the same volcano-tectonic framework. The relatively high CO 2 efflux values were located in the NE sector of the main crater and in the northern side of Diego de la Haya crater. Carbon isotopic signatures showed a wide range of δ 13 C-CO 2 values from -65.3 to -19.8 ‰ suggesting a strong biogenic component. The estimated total output of diffuse CO 2 degassing to the atmosphere from the study area was 44 t d -1 . The studied fumarolic gases showed that the 3 He/ 4 He ratio had a characteristic value for volcanoes related with subduction areas (6.6 R A ), and that 90% of the CO 2 emitted comes from calcareous sediments incorporated during the subduction process.Keywords: Irazú volcano, CO 2 , diffuse degassing, calcareous sediments, subduction, isotopes, fumaroles. RESUMEN:El primer estudio sobre desgasificación difusa de CO 2 en el volcán Irazú se realizó en el 2001, con el objetivo de evaluar el origen y la distribución espacial del flujo difuso de CO 2 así como la tasa de emisión de CO 2 a la atmósfera. La mayor parte del área de estudio presentó valores de fondo para el flujo difuso de CO 2 < 20 g m -2 d -1 . El mayor valor medido fue de 316 g m -2 d -1 , que es relativamente inferior a los mayores valores medidos en otros sistemas volcánicos asentados en el mismo ambiente volcano-tectónico. Los mayores valores de flujo difuso de CO 2 se detectaron en el borde NE del cráter Principal y al N del cráter Diego de La Haya. La firma isotópica del carbono en el CO 2 de la atmósfera del suelo presentó un amplio rango de valores δ 13 C-CO 2 , entre -65,3 y -19,8 ‰, que sugiere una importante contribución biogénica. La tasa de emisión difusa de CO 2 para el área de estudio en el Irazú se estimó en 44 t d -1 . El estudio de los gases fumarólicos mostró una relación 3 He/ 4 He característica de volcanes relacionados con zonas de subducción (6,6 R A ), y que el 90% del CO 2 emitido procede de la incorporación de sedimentos calcáreos en el proceso de subducción.Palabras clave: Volcán Irazú, CO 2 , emisión difusa, sedimentos calcáreos, subducción, isótopos, fumarolas.

Relationship between Diffuse CO2 Degassing and Volcanic Activity. Case Study of the Poás, Irazú, and Turrialba Volcanoes, Costa Rica

“…In our case, Turrialba volcano has experienced a reawakening process which has lasted ∼20 years (Martini et al, 2010;de Moor et al, 2016a) and Poás' activity is particularly variable (Fischer et al, 2015;de Moor et al, 2016b) and seems to have stages of enhanced volcanic activity and stages of quiescence that alternate every 6-12 years (Rymer et al, 2000(Rymer et al, , 2005(Rymer et al, , 2009. Diffuse degassing monitoring could thus be an interesting tool for long term monitoring (Allard et al, 1991;Chiodini et al, 1996Chiodini et al, , 1998Chiodini et al, , 2001Giammanco et al, 1998;Hernández et al, 1998Hernández et al, , 2001Melián et al, 2001Melián et al, , 2010Salazar et al, 2001;Shimoike et al, 2002;Hernández Perez et al, 2003;Carapezza and Granieri, 2004;Galindo et al, 2004;Lewicki et al, 2005;Notsu et al, 2006;Werner and Cardellini, 2006;Carapezza et al, 2009;Viveiros et al, 2010;Peltier et al, 2012;Werner et al, 2014).…”

“…The same procedure was applied to Galindo et al (2004) work for Irazú volcano, who investigated in fact over an area of 3,500,000 m 2 . " * " Means that results were normalized regarding the 2015 investigated area.…”

“…The main aim of this study is thus to quantify total CO 2 flux emissions for Turrialba (10. (Melián et al, , 2010Galindo et al, 2004;Aiuppa et al, 2014) in order to highlight the evolution of volcanic activity over time. Turrialba, Poás, and Irazú volcanoes are three active Costa Rican volcanoes near the capital city of San José.…”

Extremely high diversity of sulfate minerals in caves of the Irazú Volcano (Costa Rica) related to crater lake and fumarolic activity

“…Irazú Volcano also presents an important diffuse CO 2 flux: Galindo et al (2004) established a CO 2 base flux at ~20 gm -2 d -1 and maximum values of 316 g m -2 d -1 for sites studied in 2001, while Epiard et al (2017) reported maximum values of 2.71 x 10 4 gm -2 d -1 for the northern flank and 2.17 x 10 3 gm -2 d -1 north of the main crater in 2015. Those diffuse CO 2 flux anomalies are located in areas close to active fault traces, being the structural control very important for the escape of gases and associated rock alteration, but probably with less relevance for the formation of speleothems in the caves of the Irazú Volcano.…”

“…1A). This area is characterized by its intense volcanic influence, with relevant CO 2 emissions (Galindo et al, 2004;Epiard et al, 2017) and evidence of passive fumarole activity and hydrothermalism (Alvarado et al, 2006). Here, we discuss factors related to minerogenesis, the formation of the caves themselves and their linkage with the hydrothermal system.…”