Volatile metal emissions from volcanic degassing and lava–seawater interactions at Kīlauea Volcano, Hawai’i

Volcanoes represent one of the largest natural sources of metals to the Earth’s surface. Emissions of these metals can have important impacts on the biosphere as pollutants or nutrients. Here we use ground- and drone-based direct measurements to compare the gas and particulate chemistry of the magmatic and lava–seawater interaction (laze) plumes from the 2018 eruption of Kīlauea, Hawai’i. We find that the magmatic plume contains abundant volatile metals and metalloids whereas the laze plume is further enriched in copper and seawater components, like chlorine, with volatile metals also elevated above seawater concentrations. Speciation modelling of magmatic gas mixtures highlights the importance of the S2− ligand in highly volatile metal/metalloid degassing at the magmatic vent. In contrast, volatile metal enrichments in the laze plume can be explained by affinity for chloride complexation during late-stage degassing of distal lavas, which is potentially facilitated by the HCl gas formed as seawater boils.

Trends in volcanic degassing through eruption cycles: insights from satellite measurements

<p>Effective use of volcanic gas measurements for eruption forecasting and hazard mitigation at active volcanoes requires an understanding of long-term degassing behavior as context. Much recent progress has been made in quantifying global volcanic emissions of sulfur dioxide (SO<sub>2</sub>) and other gas species by expanding the coverage of ground-based sensor networks and through analysis of decadal-scale satellite datasets. Combined, these advances have provided valuable constraints on the magnitude and variability of SO<sub>2</sub> emissions at over 120 actively degassing volcanoes worldwide. Being less constrained by the style or location of volcanic activity, satellite measurements can provide greater insight into trends in volcanic degassing during eruption cycles. Here, we present an analysis of ~15 years of volcanic SO<sub>2</sub> measurements by the ultraviolet (UV) Ozone Monitoring Instrument (OMI) aboard NASA’s Aura satellite, focused on observed trends in SO<sub>2</sub> emissions spanning eruptions of varying magnitude. The Aura/OMI measurements have been used to estimate annual mean SO<sub>2</sub> emissions at ~100 volcanoes active between 2005 and 2020, around 80 of which erupted during the 15-year period. Superposed epoch analysis (SEA) of SO<sub>2</sub> emission trends for the erupting volcanoes (with eruption magnitudes ranging from Volcanic Explosivity Index [VEI] 2 to 4) provides evidence that volcanoes exhibiting higher levels of SO<sub>2</sub> emission in the years prior to eruption typically produce eruptions of lower magnitude, and vice versa. Post-eruptive SO<sub>2</sub> degassing exceeds pre-eruptive emissions for several years after eruptions with VEI 3-4 and may scale with eruption size; perhaps consistent with larger eruptions being supplied by larger magma intrusions which continue to degas in subsequent years. The SEA is most robust for eruptions of intermediate magnitude (VEI 3) which are the most common events in the recent global eruption record covered by the OMI measurements. Limited observations of larger eruptions (VEI 5+) suggest significant differences in degassing trends during these larger events. Future work will extend the satellite-based estimates of volcanic SO<sub>2</sub> emissions both forward and backward in time using other UV satellite instruments, generating longer records of SO<sub>2</sub> degassing (extending back to 1978 for the strongest volcanic sources of SO<sub>2</sub>) that will be used to further explore and constrain these relationships.  </p>

An over-used ocean island coastal aquifer, Tenerife (Spain) – tracing inputs for improved resource management

<p>The island of Tenerife (Canary Islands, Spain) relies on basalt-hosted aquifers to provide 90% of water for agriculture and human consumption. The island is characterised by a low-permeability core, overlain by permeable materials which are cut by impermeable dykes. The effect is a compartmentalised aquifer, which is exploited sequentially as each “pocket” of water is exhausted. The island is home to ~1 million people (with an additional 5 million visiting tourists per year), and although rain/snowfall can be heavy in winter storms, it is unpredictable from year to year, and rapid surface water run off occurs due to the steep geography. While net recharge into the upper zones of the Tenerife aquifer have been quantified (around 2 months between intense rainfall and water table fluctuations), water must then follow a tortuous path to recharge lower zones and aquifer “pockets”. Water recharge to the coastal aquifers is also interrupted and extracted during its journey. Human and agricultural pressure is highest near the coast, and has led to intensive exploitation of existing wells and horizontal galleries. In response to the intensification of water extraction and slow recharge rates, marine intrusions into the coastal aquifers of Tenerife have occurred, traditionally recorded by rising chloride levels and resulting in well/gallery closures as well as increased pressure on other extraction sites. However, in a volcanic ocean island setting, natural processes can mimic the appearance of salinisation in a coastal aquifer. Management of aquifer resources require careful consideration of seawater incursions vs. volcanic degassing contributions vs. ocean island rainfall. Full hydrochemical breakdown of 43 coastal aquifer extraction sites reveal seawater intrusion is affecting the western coastal aquifer, with the agreement of multiple parameters. The strontium isotopic signature of well samples was also measured, because it is not subject to the biological or physical fractionation processes of other isotopic systems, thereby forming distinct reservoirs for groundwater (<sup>87</sup>Sr/<sup>86</sup>Sr of host rock), and seawater. <sup>87</sup>Sr/<sup>86</sup>Sr signatures suggest the northern coastal aquifers are also subject to seawater incursions. This parameter may be a more sensitive indicator than chlorides and conductivity markers for salinisation, especially in an ocean island environment where coastal aquifers are subject to intensive land use practices, seawater spray, and affected by diffuse volcanic degassing.</p>

Transient HCl in the atmosphere of Mars

A major quest in Mars’ exploration has been the hunt for atmospheric gases, potentially unveiling ongoing activity of geophysical or biological origin. Here, we report the first detection of a halogen gas, HCl, which could, in theory, originate from contemporary volcanic degassing or chlorine released from gas-solid reactions. Our detections made at ~3.2 to 3.8 μm with the Atmospheric Chemistry Suite and confirmed with Nadir and Occultation for Mars Discovery instruments onboard the ExoMars Trace Gas Orbiter, reveal widely distributed HCl in the 1- to 4-ppbv range, 20 times greater than previously reported upper limits. HCl increased during the 2018 global dust storm and declined soon after its end, pointing to the exchange between the dust and the atmosphere. Understanding the origin and variability of HCl shall constitute a major advance in our appraisal of martian geo- and photochemistry.

Volatile metal emissions from volcanic degassing and lava-seawater interactions at Kīlauea Volcano, Hawai’i

The authors have withdrawn this preprint due to author disagreement.

Carbonate platform production during the Cretaceous

Platform carbonates are among the most voluminous of Cretaceous deposits. The production of carbonate platforms fluctuated through time. Yet, the reasons for these fluctuations are not well understood, and the underlying mechanisms remain largely unconstrained. Here we document the long-term trend in Cretaceous carbonate platform preservation based on a new data compilation and use a climate-carbon cycle model to explore the drivers of carbonate platform production during the Cretaceous. We show that neritic carbonate preservation rates followed a unimodal pattern during the Cretaceous and reached maximum values during the mid-Cretaceous (Albian, 110 Ma). Coupled climate-carbon cycle modeling reveals that this maximum in carbonate deposition results from a unique combination of high volcanic degassing rates and widespread shallow-marine environments that served as a substrate for neritic carbonate deposition. Our experiments demonstrate that the unimodal pattern in neritic carbonate accumulation agrees well with most of the volcanic degassing scenarios for the Cretaceous. Our results suggest that the first-order temporal evolution of neritic carbonate production during the Cretaceous reflects changes in continental configuration and volcanic degassing. Geodynamics, by modulating accommodation space, and turnovers in the dominant biota probably played a role as well, but it is not necessary to account for the latter processes to explain the first-order trend in Cretaceous neritic carbonate accumulation in our simulations.

Real time and in-situ analysis of the gas-emissions of the Eastern Carpathians: results and perspectives

<p>The Carpathian-Pannonian region was dominated by diverse volcanic activity for the last 20 million years, and even 1 million years ago there was precedent for active zones.  Although volcanic eruptions are very uncommon in the region today, however the frequent earthquakes in the Carpathian-bend, the numerous appearance and intense manifestation of gas-emissions in the southeastern areas of the region and many petrochemical and geochemical volcanologic studies as well, indicate that the area is likely not completely inactive. The gas emissions investigated by us may be directly related to these geodynamic processes [1].</p><p>In Romania, the Eastern Carpathian Neogene-Quaternary volcanic chain and it’s neighbouring zones contain most of the carbon dioxide rich gas emissions, which also occur in the form of natural mofettes, bubbling pools and springs. They can appear in frequently populated settlements more often in cellars, which puts the inhabitants in direct danger due the lack of information in the public knowledge.</p><p>The motivation of our work is to gather real time and in-situ information with the help of Multi-Gas instrument about the composition of the gas-emissions across the Eastern Carpathians and to create a high resolution geological map from the measured sites in the mentioned area above. Furthermore, we would like to clarify if there is any relation between the tectonic characteristics of the study area and the manifestation, concentration of gas-emissions.</p><p>In total, 205 gas emissions were investigated for their CO<sub>2 </sub>(0-100%), CH<sub>4 </sub>(0-7%) and H<sub>2</sub>S (0-200 ppm) concentrations. The composition of the different gas-species varied according to the geological context. The <strong>CO<sub>2</sub></strong> concentrations varied between 0.96 and 98.08 %. The highest values were measured in the the Quaternary volcanic area of Ciomad, and also in the neighbouring thrusted and folded area of the Carpathian Flysch which suggests a tectonic control over the appearance of the gas emissions.</p><p>The <strong>CH<sub>4</sub></strong> concentrations ranged between 0.21 and 6.76% and were higher at hydrocarbon-prone areas, such as the sedimentary deposits of the Transylvanian Basin and Carpathian Flysch. In these cases the CO<sub>2</sub> concentrations were low (up to 4.6%).</p><p>The <strong>H<sub>2</sub>S</strong> concentrations varied between 0.21 and 200 ppm, according to our knowledge, these are the first H<sub>2</sub>S in-situ measurements in the gas emissions of the study area. The concentrations of H<sub>2</sub>S were higher at the volcanic area of Ciomad, reaching values above the detection limit (~200 ppm) which are related to volcanic degassing.</p><p>In conclusion, based on the investigated sites, there is a spatial correlation between the appearance of mineral water springs, gas emissions on surface and the neighbouring tectonic structures. The Multi-Gas proved to be a useful tool in the in-situ investigation of gas emissions of the Eastern Carpathians, being efficient especially for the measurement of the H<sub>2</sub>S concentrations that are very sensitive for oxidation processes.</p><p><strong>Bibliography:</strong></p><p>1.Kis B.M., Caracusi, A., Palcsu, L., Baciu, C., Ionescu, A., Futó, I., Sciarra, A., Harangi, Sz., Noble Gas and Carbon Isotope Systematics at the Seemingly Inactive Ciomadul Volcano (Eastern‐Central Europe, Romania): Evidence for Volcanic Degassing, Geochemistry, Geophysics, Geosystems, vol.20, issue 6, 2019, 3019-3043.</p>

Volcanic degassing along the enigmatic South Sandwich volcanic arc

<p>The South Sandwich Islands (SSI) are a chain of active volcanoes in the Southern Ocean and remain one of the most remote and enigmatic island arcs on Earth. The relatively recent development of the SSI over the past 20 million years has been closely linked with the formation of the Drake Passage, making this one of the youngest known volcanic arcs and therefore one of the most critical for understanding the early stages of arc geochemical evolution. Recent volcanic eruptions in the SSI have had significant impacts on local terrestrial and marine ecosystems, including some of the largest penguin colonies ever observed, through tephra deposition and from sustained volcanic degassing. Rare cloud-free satellite images over the last two decades have indicated that the summit of Mt Michael (Saunders) hosts a sustained lava lake, but until now these observations have not been ground-truthed by in-situ measurements. Long-term persistent passive outgassing at many of these volcanoes, even between eruptive phases, suggests that the SSI volcanic arc could be a significant source of volatiles to our atmosphere, and yet we lack any constraints on the degassing budgets of this volcanic arc. Here, we present novel measurements of gas chemistry, aerosol composition, and carbon isotope signature from along the South Sandwich Island arc. By combining ground-based measurements of SO<sub>2</sub> flux with in-situ samples of plume composition using Unoccupied Aerial Systems (UAS), we present multi-species volatile fluxes for the major along-arc degassing sources. Further, by evaluating the carbon to sulfur ratio (C/S<sub>T</sub>) and carbon isotope composition in emitted gases together with petrological constraints from erupted tephra, we aim to test the hypothesis that carbon is supplied to the SSI by subduction of oceanic carbonated serpentinite, and thus contribute to our understanding of carbon recycling at subduction zones.</p>