Partitioning of elements between high-temperature, low-density aqueous fluid and silicate melt as derived from volcanic gas geochemistry

Probing the hidden magmatic evolution of El Misti volcano (Peru) with the Pb isotope composition of fumaroles

“…3. The 260°C gas condensate contains 177 ppb Pb, 37-38 ppb of Tl and Zn, and 9-12 ppb of Bi, Cu, and Sb, with the latter concentrations being at the low range of volcanic gases (Zelenski et al, 2021). The condensate also contains significant amounts of refractory elements (244 ppb Ba, 45-46 ppb of Sr and Ti).…”

Volatile trace metals deposited in ice as soluble volcanic aerosols during the 17.7.ka eruptions of Mt Takahe, West Antarctic Rift

“…To aid interpretation, the eruption sequence, which spans 192 years, has been divided into three stages (A-C; Figure 1). Stage A contains high concentrations of Cl, refractory (non-volatile) elements (Mn, La, and Ce) and volatile metals (McConnell et al, 2017;Zelenski et al, 2021), which we interpret to reflect that this stage of the eruption was characterised by plumes rich in both silicate material (ash), which hosted the refractory elements, as well as soluble aerosol (which hosted the Cl and S and a fraction of the volatile metals). In stage B, Cl and volatile metal concentrations remain high, but concentrations of refractory elements decrease, consistent with ash being less abundant but plumes remaining rich in aerosol.…”

“…The speciation of volatile trace elements during degassing provides key initial conditions for the subsequent atmospheric transport, solubility, deposition and resulting hazard from these elements (Ilyinskaya et al, 2021). Major elements-such as S, oxygen (O), hydrogen (H) and Cl (and other halogens)-are the main ligand-forming elements for volatile trace metals and metalloids in volcanic gas emissions, e.g., as sulfates (SO 2− 4 ), sulfides (S 2− ), chlorides (Cl − ), bromides (Br − ), fluorides (F − ), oxides (O 2− ) and hydroxides (OH − ) (Zelenski et al, 2021). Factors that control the speciation of elements in volcanic gas emissions at the point of degassing include the composition of the volatiles released from the melt, as well as temperature, pressure, and the composition of the magma from which degassing occurs (i.e., its oxidation state).…”

“…Emanation coefficients (Lambert et al, 1985;Pennisi et al, 1988) (the proportion of the metal in the volcanic gas phase over the silicate melt or magma) may be ~70%-90% for Tl and Cd and ~1% for Pb (Rubin, 1997;Gauthier and Le Cloarec, 1998;Aiuppa et al, 2000). Volcanoes in subduction zones, which tend to produce large explosive eruptions with the potential to impact global climate, produce gases and aerosols rich in elements carried by fluids devolatilized from subducting slabs (e.g., Tl, Bi, Pb, and As) (Cox et al, 2019), as well as metals whose solubility in silicate melts is optimised under oxidising conditions, e.g., Au (Botcharnikov et al, 2011), and those that tend to speciate with chlorine, a ligand inherently rich in "arc" melts and exsolved fluids (e.g., Pb, Bi, and Cd) (Edmonds et al, 2018;Zelenski et al, 2021).…”

Spatial Variations in Magmatic Volatile Influx and Fluid Boiling in the Submarine Hydrothermal Systems of Niuatahi Caldera, Tonga Rear‐Arc

“…This is recorded by high Te/Au values in pyrite (>10, Figure 7e), sphalerite (>1, Figure 8d), and chalcopyrite (>1, Figure 9d) at Niuatahi South‐Central compared to Niuatahi Southwest and North, which is caused by their precipitation from the low Cl vapor‐rich fluids which are actively discharged at this vent site. Importantly, the high Te/As and Te/Au ratios in the hydrothermal sulfides (Figures 7a, 7b, 8c, 8d,9c and 9d) cannot be explained by fluid‐melt trace element fractionation during magma degassing, because the comparable partition coefficient of Te (Kd fluid‐melt = 2.9), Au (Kd fluid‐melt = 3.1), and As (Kd fluid‐melt = 3.7) indicate that ratios of these elements do not vary significantly as a result of magma degassing (Guo & Audétat, 2017; Zelenski et al., 2021), as also expressed by similar ratios in the host rocks and in native S (e.g., Figures 7a and 7b). The fact that we find similar Te/As and Te/Au signatures in pyrite, sphalerite and chalcopyrite relative to the different vent sites also suggest that the observed variations reflect a hydrothermal process rather than a competitive incorporation of trace elements between different sulfides with respect to their paragenetic relations (Table 5).…”