Bromine and chlorine emissions from Plinian eruptions along the Central American Volcanic Arc: From source to atmosphere

摘要: Highlights • Data set of Br and Cl emissions from 29 large CAVA eruptions (VEI > 5). • Melt inclusions are strongly enriched in chlorine bromine compared to their respective matrix glasses. • Fluid partitioning is 4 68 times more efficient for than Cl. • Subducted calcareous sediments the major control on arc-magmatic contents. • Average eruption would add 368% EESC recent annual loading stratosphere. Abstract Large explosive volcanic inject gases, aerosols, fine ashes into stratosphere, potentially influencing climate atmosphere composition a global scale. Although potential effect (Cl) (Br) injections stratosphere known, mass fluxes poorly constrained. In this study we focus magmatic degassing systematics budgets Cl, constraining sources subduction setting. We therefore present regional time series highly throughout Central American Volcanic Arc (CAVA), covering last 200 ka, range compositions magnitudes. have measured glasses melt using synchrotron radiation micro X-ray fluorescence spectrometry (SR micro-XRF) electron microprobe, respectively. tephras generally higher (0.9 17.9 ppm) (770 3800 contents (0.39 1.5 ppm Br, 600 2800 ppm Cl). Moreover, difference between maximum minimum concentrations observed given sample ranges 9 90% concentration Br, 2 40% Cl. Such intra-sample variations arise variable pre-eruptive these halogens fluid phase. The relative loss that Cl. The masses (2–1100 kt) (0.1 800 Mt) emitted by generate instantaneous additions amounting ∼6–5600% present-day stratospheric Equivalent Effective Stratospheric Chlorine. As size impact primarily function magnitude, use magnitude-frequency relationships estimate adding ∼10% resident occur every <40 years while ∼200 an double loading. Comparing particularly Cl/Br ratios with geochemical trace-element proxies (e.g. U/La, Ba/Th) lead-isotope compositions, which change along arc response changing conditions, suggest subducted sediment source but also infer important role fluids expelled serpentinized mantle. Extrapolation system thus needs consider nature lithologies.