Deep magma storage during the 2021 La Palma eruption

Abstract

The 2021 La Palma eruption provided an unpreceded opportunity to test the relationship between earthquake hypocenters and the location of magma reservoirs. We performed density measurements on CO 2 -rich fluid inclusions (FIs) hosted in olivine crystals that are highly sensitive to pressure via calibrated Raman spectroscopy. This technique can revolutionize our knowledge of magma storage and transport during an ongoing eruption, given that it can produce precise magma storage depth constraints in near real time with minimal sample preparation. Our FIs have CO 2 recorded densities from 0.73 to 0.98 g/cm 3 , translating into depths of 15 to 27 km, which falls within the reported deep seismic zone recording the main melt storage reservoir.

Discrete magma injections drive the 2021 La Palma eruption

“…3). Our results agree with high-precision barometry in olivine-hosted fluid inclusions across the eruption, which suggest a final, main level of magma stagnation between 420 and 780 MPa (28). Thermobarometry on clinopyroxene-melt equilibrium pairs from previous Cumbre Vieja eruptions suggests that magma fractionation focuses mostly between 430 to 780 MPa and 1100°to 1160°C (29), also in agreement with our data.…”

“…Our final clinopyroxene crystallization depths also agree with high-precision olivine-hosted fluid inclusion barometry recording the main melt storage reservoir [420 to 780 MPa, (28); 16 to 29 km using our density model as shown in Fig. 3, similar to 15 to 27 km calculated assuming densities of 2.8 kg/m 3 for 14 km of crust and 3.1 kg/m 3 for the upper mantle with presence of melt; (28)]. We propose clinopyroxene rims and microcrysts crystallized upon mafic recharge, mush remobilization, and ascent, imposing conditions of undercooling and dynamic crystallization conducive to the development of sector zoning (30).…”

A lesson from a magnificent eruption: year 2021, La Palma, Canary Islands

“…Given that FIs can react to pressure conditions rapidly (hours to days), the uid inclusion barometer has the potential to identify ephemeral magma stagnation levels during multistage ascent (Longpré et al, 2014). Knowing that magma is fed from deep levels, CO 2 uid inclusions should record pressures spanning all levels, from deep to close to the surface, at least − 6 km (D'Auria et al, 2022), which is much shallower than the minimum − 15 km estimated by Dayton et al (2023). An alternative, physically more robust, explanation is that FIs have indeed recorded much shallower levels, which means that overpressure was high, in the order of P D /P L = 2.5 (15/6 = 2.5), i.e.…”

DiadFit: An Open-Source Python3 Tool for Peak fitting of Raman Data from silicate melts and CO2 fluids

“…Since 2014, there has been a growing amount of interest in using Raman Spectroscopy to measure the density of CO 2 -rich fluids in melt inclusion vapour bubbles, to obtain accurate estimates of magma storage depths (Hartley et al [2014], Moore et al [2015], Wieser et al [2021] Lamadrid et al [2017], Allison et al [2021]). Raman spectroscopy also shows enormous potential to quantify the densities of CO 2 -rich fluid inclusions (Wang et al [2011]), allowing rapid and precise estimates of magma storage depths (Dayton et al [2023]).…”

“…For example, fitting the Neon and diad data collected over a 24 hour period during instrument calibration by DeVitre et al [2021] took at least a day to process using Fityk, but can be processed in ∼15 minutes using DiadFit on a typical laptop with 16 GB of RAM. Given the potential for Raman spectroscopy to provide rapid estimates of magma storage depths from fluid inclusions during volcanic crises (Dayton et al [2023]), it is vital to speed up data processing as much as possible to reap the full benefits of this technique. We anticipate that users who are not familiar with Python will simply use the provided Jupyter Notebooks and narrated YouTube videos, changing simple parameters like the path to their files.…”