One of the leading hydrothermal alteration processes in volcanic environments is when rock‐forming minerals with high concentrations of iron, magnesium, and calcium react with CO2 and water to form carbonate minerals. This is used to the advantage of geologic sequestration of anthropogenic CO2. Here we experimentally investigate how mineral carbonation processes alter the rock microstructure due to CO2‐water‐rock interactions. In order to characterize these changes, CO2‐water‐rock alteration in Auckland Volcanic Field young basalts (less than 0.3 Ma) is studied before and after a 140 day reaction period. We investigate how whole core basalts with similar geochemistry but different porosity, permeability, pore geometry, and volcanic glass content alter due to CO2‐water‐rock reactions. Ankerite and aluminosilicate minerals precipitate as secondary phases in the pore space. However, rock dissolution mechanisms are found to dominate this secondary mineral precipitation resulting in an increase in porosity and decrease in rigidity of all samples. The basalt with the highest initial porosity and volcanic glass volume shows the most secondary mineral precipitation. At the same time, this sample exhibits the greatest increase in porosity and permeability, and a decrease in rock rigidity post reaction. For the measured samples, we observe a correlation between volcanic glass volume and rock porosity increase due to rock‐fluid reactions. We believe this study can help understand the dynamic rock‐fluid interactions when monitoring field scale CO2 sequestration projects in basalts.

Hydrothermal alteration by2 SO E -rich fluids governs the physicochemical properties of stratovolcanoes worldwide (Mayer et al., 2016;Zimbelman et al., 2005). As these fluids alter the conduit rocks, inevitable changes in rock porosity and permeability can limit outgassing and promote explosive volcanic behavior. This was observed at Poás volcano (Costa Rica), where the formation of a pressurized hydrothermal seal by secondary mineral precipitation and volatile accumulation limited 2 SO E -emissions for two years and triggered the 2017 phreatomagmatic eruption (de Moor et al., 2019). Similar hydrothermal sealing driven by acid-sulphate alteration also played a role in triggering phreatic and phreatomagmatic eruptions at Soufrière Hills (Montserrat) (Edmonds et al., 2003), and Ontake (Japan) (Stix & de Moor, 2018). At Whakaari-White Island volcano (New Zealand), a partially sealed hydrothermal system is implied to have played a role in the recent 2019, and past eruptions (Burton et al., 2021;Christenson et al., 2017). However, mineralogical and microimaging evidence of such sealing and its evolution for different lithologies within the conduit is lacking. Moreover, the effect of such hydrothermal processes on the fluid flow and elastic properties of conduit-filling rocks remains unconstrained, despite being of paramount importance for accurately inverting geophysical data to understand volcano pressurization.The development of an effective seal requires conduit rocks with low porosity and low permeability that limit outgassing and favor fluid accumulation and pressure build-up (Stix & de Moor, 2018). So far, experimental studies on the effects of alteration on porosity and permeability of volcanic rocks have been mainly based on surface-collected rocks and show conflicting observations. For example, pore and fracture filling secondary minerals in lavas (

Magnetic surveys are used to identify and monitor hydrothermally altered regions on volcanoes. Commonly such magnetic data are interpreted on the premise that hydrothermal alteration consumes Fe‐Ti oxides in the host rocks, reducing their total magnetization. Here, we report a contrasting observation from Whakaari (White Island) volcano in New Zealand. We study the magnetic properties of 42 conduit‐filling and surficial lithologies that have undergone varying degrees of acid‐sulfate alteration. We find that while the induced magnetization of lavas decreases with hydrothermal alteration, some altered lavas have an order of magnitude higher remanent magnetization than fresh lavas. We discuss plausible mechanisms by which altered lavas can retain high remanent magnetization including the importance of magnetic mineralogy and grain size. Our results urge caution in correlating reduced magnetization with hydrothermally altered regions. Furthermore, they highlight the importance of measuring both the induced and remanent magnetization of samples used to interpret field‐scale data.

Over the past decade, computing power has increased, new sensing technologies have been developed, and our understanding of how we interact with the earth has evolved, leading to new opportunities and priorities in geophysical research. These changes have been more rapid in some areas than others, and new topics have emerged as well. It is challenging for geophysicists, including junior staff and undergraduates starting their geophysics journeys, to stay abreast of scientific and industrial trends. Thus, the Early Career Subcommittee of the SEG Research Committee (RC) thought it imperative to survey members of the RC in 2022. To that end, a survey was conducted, and responses were collected from 43 RC members.

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