Active, large volume, silicic magma systems are potentially the most hazardous form of volcanism on Earth. Knowledge of the location, size, and physical properties of silicic magma reservoirs, is therefore important for providing context in which to accurately interpret monitoring data and make informed hazard assessments. Accordingly, we present the first geophysical image of the Laguna del Maule volcanic field magmatic system, using a novel 3D inversion of gravity data constrained by thermodynamic modelling. The joint analysis of gravity and thermodynamic data allows for a rich interpretation of the magma system, and highlights the importance of considering the full thermodynamic effects on melt density, when interpreting gravity models of active magmatic systems. We image a 30 km 3 , low density, volatile rich magma reservoir, at around 2 km depth, containing at least 85 % melt, hosted within a broader 115 km 3 body interpreted as wholly or partially crystallised (>70 % crystal) cumulate mush.Our model suggests a magmatic system with shallow, crystal poor magma, overlying deeper, crystal rich magma. Even though a large density contrast (-600 kg/m 3 ) with the surrounding crust exists, the lithostatic load is 50 % greater

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Combining 3‐D inversion of high‐resolution aeromagnetic data with airborne hyperspectral imaging creates a new method to map buried structure and hydrothermal alteration, applied to Mt. Ruapehu volcano, New Zealand. Hyperspectral imaging is sensitive to surface mineralogy including alteration minerals, while magnetic vector inversion reveals the volumetric distribution of magnetic susceptibility from which we interpret buried geology. Probability assessment from multiple model regularizations provides an important model uncertainty estimate. At Ruapehu, hyperspectral imaging highlights two main regions of surface alteration: the Pinnacle Ridge and the southeast flanks. The magnetic model of Pinnacle Ridge shows that alteration seen at surface continues to depth, but strongly magnetic, unaltered dikes form the core of the ridge. On the southeast flanks, the magnetic model also shows alteration imaged on the surface continues to depth; however, a previously unknown, magnetized sill intrudes part of the flank. Several smaller demagnetized regions are modeled, unlike at neighboring Mt. Tongariro where the hydrothermal system created a large demagnetized core. We propose that these differences relate to spatially focused (Ruapehu) vs distributed (Tongariro) eruption vents, the degree of faulting of the edifice and its glaciation history. Lava‐ice interaction produces fine‐grained lavas with measured magnetic susceptibilities similar to some moderately altered lavas, illustrating that care must be taken in the interpretation of magnetic data in the absence of geological information. The combination of hyperspectral imaging and aeromagnetic data inversion distinguishes shallow surface weathering from deeper‐seated hydrothermally altered rock masses, with implications for the magnitude and probability of collapse events.

The geologically distinct DO-27 and DO-18 kimberlites, often called the Tli Kwi Cho (TKC) kimberlites, have been used as a testbed for airborne geophysical methods applied to kimberlite exploration. This paper focuses on extracting chargeability information from time-domain electromagnetic (TEM) data. Three different TEM surveys, having similar coincident-loop geometry, have been carried out over TKC. Each records negative transients over the main kimberlite units and this is a signature of induced polarization (IP) effects. By applying a TEM-IP inversion workflow to a versatile time domain EM (VTEM) data set we decouple the EM and IP responses in the observations and then recover 3D pseudo-chargeability models at multiple times. A subsequent analysis is used to recover Cole-Cole parameters. Our models demonstrate that both DO-18 and DO-27 pipes are chargeable, but they have different Cole-Cole time constants: 110 and 1160 μs, respectively. At DO-27, we also distinguish between two adjacent kimberlite units based on their respective Cole-Cole time constants. Our chargeability models are combined with the density, magnetic susceptibility and conductivity models to build a 3D petrophysical model of TKC using only information obtained from airborne geophysics. Comparison of this final petrophysical model to a 3D geological model derived from the extensive drilling program demonstrates that we can characterize the three main kimberlite units at TKC: HK, VK, and PK in three dimensions by using airborne geophysics.

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