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Basaltic fissure eruptions emit volatile and environmentally reactive gases and particulate matter (PM) into the lower troposphere (e.g., SO2, HCl, and HF in the gas phase; Se, As, Pb as complexes in the PM phase). Lava flows from fissure eruptions can be spatially extensive, but the composition and fluxes of their emissions are poorly characterized compared to those from main vent(s). Using uncrewed aircraft systems‐mounted (drone) samplers and ground‐based remote Fourier Transform Infrared Spectroscopy, we investigated the down‐flow compositional evolution of emissions from active lava flows during the Fagradalsfjall 2021–2023 eruptions. The calculated fluxes of volatile trace metals from lava flows are considerable relative to both main vent degassing and anthropogenic fluxes in Iceland. We demonstrate a fractionation in major gas emissions with decreasing S/halogen ratio down‐flow. This S‐Cl fractionation is reflected in the trace element degassing profile, where the abundance of predominantly sulfur‐complexing elements (e.g., Se, Te, As, Pb) decreases more rapidly in down‐flow emissions relative to elements complexing as chlorides (e.g., Cu, Rb, Cs), oxides (e.g., La, Ce) and hydroxides (e.g., Fe, Mg, Al, Ti). Using thermochemical modeling, we explain this relationship through temperature and composition dependent element speciation as the lava flow ages and cools. As a result, some chloride‐complexing elements (such as Cu) become relatively more abundant in emissions further down‐flow, compared to emissions from the main vent or more proximal lava flows. This variability in down‐flow element fluxes suggests that the output of metals to the environment may change depending on lava flow age and thermal evolution. Plain Language Summary: Lava flows, such as those formed during the recent eruptions in Iceland (2021–2023), emit gases, particles and droplets to the atmosphere. These include an array of different metals, some of which may be harmful to the environment and human health. In this study, we use drone‐mounted equipment and a remote‐sensing spectrometer to collect samples and the measure gases and particles above lava flows at increasing distances from the vent. Some elements that predominantly bond with sulfur tend to diminish in abundance as the lava flow ages, while those elements that predominantly bond with chloride increase in abundance with increasing distance from the vent. By modeling how elements preferentially bond together at different temperatures, we can explain how different elements behave when emitted from increasingly colder lava flows. Overall, the quantity of metals emitted from lava flows during the Fagradalsfjall eruption is equal to or greater than emissions from human‐related activity in Iceland during 2021. Key Points: Particulate matter and gases were measured in lava flow emissions at increasing distances from the crater (increasing lava ages) as well as above a stagnant lava pond at the Fagradalsfjall 2021–2023 eruptionsThermochemical modeling suggests that speciation is a key control on the down‐flow fractionation in trace element outgassing from cooling lavasSulfur‐complexing element (Se, Te, As) emissions decreased most rapidly down‐flow whilst some chloride‐complexed (Cu, Rb, Cs) elements became more abundant relative to at‐crater emissions [ABSTRACT FROM AUTHOR]

The metamorphic rocks of the Ivrea Zone in NW Italy preserve a deep crustal metamorphic field gradient. Application of quantitative phase equilibria methods to metapelitic rocks provides new constraints on the P-T conditions recorded in Val Strona di Omegna, Val Sesia and Val Strona di Postua. In Val Strona di Omegna, the metapelitic rocks show a structural and mineralogical change from mica-schists with the common assemblage bi-mu-sill-pl-q-ilm ± liq at the lowest grades, through metatexitic migmatites (g-sill-bi-ksp-pl-q-ilm- liq) at intermediate grades, to complex diatexitic migmatites (g-sill-ru-bi-ksp-pl-q-ilm- liq) at the highest grades. Partial melting in the metapelitic rocks is consistent with melting via the breakdown of first muscovite then biotite. The metamorphic field gradient in Val Strona di Omegna is constrained to range from conditions of ∼3.5-6.5 kbar at ≈650 °C to ∼10-12 kbar at >900 °C. The peak P-T estimates, particularly for granulite facies conditions, are significantly higher than those of most earlier studies. In Val Sesia and Val Strona di Postua, cordierite-bearing rocks record the effects of contact metamorphism associated with the intrusion of a large mafic body (the Mafic Complex). The contact metamorphism occurred at lower pressures than the regional metamorphic peak and overprints the regional metamorphic assemblages. These relationships are consistent with the intrusion of the Mafic Complex having post dated the regional metamorphism and are inconsistent with a model of magmatic underplating as the cause of granulite facies metamorphism in the region. [ABSTRACT FROM AUTHOR]