Volcano geochemistry in Antarctica

Volcano geochemistry in Antarctica

The distance from anthropized regions and extreme weather conditions have meant that the Antarctic continent has been explored and studied in limited areas only. Active volcanism at Mt. Erebus, Mt. Melbourne and Mt. Rittman is already known from the early explorations of the Antarctic region but studies are still restricted to specific areas and disciplines.  Moreover, the main geological features of these volcanoes have been partially explored while fluid geochemical studies have lagged behind. The available literature is, therefore, scarce and mainly focused on the Mt. Erebus volcano. The ICE-VOLC project aims to address the gap in existing knowledge with a research task focused on fluid geochemistry at Mt. Melbourne and Mt. Rittmann volcanoes (northern Victoria Land).

The geochemical approach to volcanism consists in the definition and characterization of “volcanic fluids” (hereafter inclusive of all liquid and gas phases originally released by a magmatic batch) in order to gain an understanding of their origin and circulation within the volcanic system. Volcanic fluids may be released in several ways: by fumaroles or mofettes; dissolved in aquifers; emitted diffusively from the soil or from open vent as volcanic plume.

Simplified description of a volcanic system showing the main geochemical characteristics. Modified from Fisher & Chiodini 2015 - The Encyclopedia of Volcanoes.

In the case of volcanic and/or geothermal systems, these manifestations are fed by fluids released by the magma during the transfer process to the surface or during the storage/crystallization process and their interaction with the surrounding environment. The change in compositional, mass flux, energy, etc. that can occur are, therefore, strictly dependent on the magmatic dynamic and on the interaction processes involving the natural fluids, wall rocks and the eventual crustal fluids.

View of one of the laboratories (Noble gases) of INGV of Palermo (http://www.pa.ingv.it/index.php/laboratori/) where are been analysed the samples collected during the ICE-VOLCproject Antarctic expedition.

The theoretical toolkit  for geochemical investigations of volcanism is based on the laws of thermodynamics and on the knowledge of chemical and isotopic equilibriums, which in our study are specifically focused on the chemical-physical processes related to the ascent of the magma to the surface. Within this framework, volcanic fluids perform the role of a deep information vehicle, through which it is possible to infer potential emplacement and/or  input of magma into the plumbing system of a volcano. In addition, knowledge on gas chemical compositions also provides a means to better understand magma transfer processes within the crust, verify phenomena of gas accumulation and hypothesise in the short and medium-term on potential evolution of a volcanic system.

Mt. Melbourne and Mt. Rittmann volcanoes are located along the Transantarctic Mountain range in the Northern Victoria Land region and are both characterised by persistent fumarolic activity. This feature gives a particular significance to these two volcanic areas, as the stable fumarole activity gives both the Melbourne and the Rittmann the status of “active” volcanoes.

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The fumarolized areas are characterized by the presence of peculiar shapes known as ice towers or ice pinnacles (chimney-like). These shapes have diameters and heights up to several metres and are caused by the condensation and freezing of water vapour emitted to the surface. 

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The geochemical unit RU4 operated on fumaroles located on the volcanoes flanks and below the snow surface (ice caves and ice tower).

The remote location and the difficulty in access to Mt. Melbourne and Mt. Rittmann, have prevented a proper geochemical study of these volcanoes in the past. The RU4 research line of the ICE-VOLC project proposed to explore the fumarolized areas of the two volcanoes using both direct and remote sampling of the geochemical survey methods.

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