Jacqueline Vander Auwera Earth & Environment ︱ The types of boundaries between tectonic plates help to describe how the different types of crust move in relation to each other across Earth’s surface. At convergent boundaries, two tectonic plates push against each other. The denser plate will Magma differentiation begin to subduct or sink into the mantle below. Where an oceanic plate meets The complex processes behind active volcanism a continental plate, the denser oceanic plate will sink below the continental plate, creating a subduction zone. Active volcanism is prevalent olcanoes and earthquakes are the of igneous rock samples from volcanic across much of the Earth’s most obvious sign that the Earth eruptions in order to understand the VOLCANOES AND is a dynamic, geologically active geochemical processes within the surface, yet the deep mantle V PLATE TECTONICS Cerro La Picada, Chile. and crustal processes planet. They are a visible representation magma prior to its eruption. Professor Vander Auwera is particularly Left: as seen from Putrehue river. that drive it are still being of plate tectonics: the slow movement interested in volcanoes that form above understood by geologists. of the Earth’s outermost, brittle layer. WHAT ARE PLATE TECTONICS? subduction zones, such as the Andean Untangling the complex The exact mechanism for how and why The Earth is divided into layers, which Arc in South America. This volcanic belt chemical relationships these plates move is still hotly debated differ in both physical and chemical runs down the western edge of the South Geochemists untangle complex chemical that arise from magma by geologists. There are around 1,500 properties. The outermost layer of Earth American continent from Columbia down differentiation offer some active volcanoes on Earth. Many of these is wrapped in tectonic plates. These to Chile, part of the long Andes mountain relationships between minerals, parent clues as to the relationships are situated along plate boundaries make up the brittle ground surface range. Along its length, denser oceanic between melting of mantle amongst large populations of people. above the ocean (continental crust) and plates are subducting below the South magmas and original mantle rock to rock and crystallisation of Understanding the hazards that surround the thinner ocean floor (oceanic crust), American continental plate, and this has determine how igneous rocks crystallise. molten magma to igneous volcanoes is important for communities and both rest on the uppermost section created many active volcanoes. rocks. Professor Vander who live under their shadow, highlighting of the Earth’s mantle. Geologists refer to overriding South American continental crystallisation of magmas, which are often Auwera at the University of the importance of volcano research by the brittle crust and mantle layer beneath The Andean Arc is so long that geologists plate, there is a ‘mantle wedge’, and very chemically complex. They are made Liège uses geochemistry geologists and volcanologists. as a single unit called the lithosphere. split it into four key areas, and Professor these fluids allow the mantle wedge rock of a variety of major elements, which form to study these complex Beneath the lithosphere lies the Vander Auwera’s work is focused on the to melt at a slightly lower temperature. particular mineral structures, such as the processes at the subduction To understand what types of eruption to asthenosphere, where the mantle rock Southern Volcanic Zone in Chile. Here It generates molten magma through a magnesium and iron-rich magmas that zone that forms the long Andean Arc in South America. expect and the risks that volcanism poses, is almost at melting point. This layer is the Nazca oceanic plate is subducting process known as partial melting, and as form basalt rock. geologists research must answer many weak and can deform over long periods beneath the South American continent, the molten magma is less dense than the questions. What type of plate boundary of time. The lithosphere moves slowly and stratovolcanoes such as La Picada surrounding mantle, it rises through the The partial melting process that is the volcano formed on? What kind over the top of the thin asthenosphere are located along the continent’s western continental crust. The magma will start generates molten magma and the of magma chemistry fuels the volcano? layer, moving the tectonic plates across margin. Stratovolcanoes are steep, to solidify the higher it rises through the crystallisation process during cooling What are the subsurface structures Earth’s surface. But what might be conical-shaped volcanoes built up from cooler continental crust, but can form cause further complexities in igneous around the volcano? Geologists like driving this movement and how does this many layers of repeated eruptions. chambers of molten magma which are rock chemistry. Deep mantle rock is only Professor Jacqueline Vander Auwera generate volcanoes? the source of erupted lavas. melted in small amounts, with some rock study previous eruptions and magmatic The magmas that are generated from remaining solid (partial melting). The melt material to discover answers to some Whilst the Earth can be split into layers melting of the mantle will rise up THE COMPLEXITIES can be quite different in composition to of these questions. She is a geochemist based on its physical properties, such through the continental crust above. As OF IGNEOUS PETROLOGY its parent rock type because the elements at the University of Liège, Belgium, and as brittle or soft plastic layers, it can pressure and temperature increase for Professor Vander Auwera and her are variably split between the solid and

stihii/Shutterstock.com completes in-depth chemical analyses also be divided based on its chemistry. the subducting crust, the minerals that colleagues study the formation and liquid. When this melt rises into the And differences in chemistry are contain water (hydrous minerals) are crystallisation of these magmas, a branch cooler crust, it will progressively solidify dependent on what type of rock is destabilised, and release fluids. Between of geology known as igneous petrology. by crystallising a series of minerals. present. Geologists categorise igneous the subducting Nazca plate and the Igneous rocks are formed from the Sometimes, a mineral that crystallised rocks by the minerals they can identify within them. The minerals that form depend on the chemistry of the magma (molten mantle rock) that igneous rocks form from. Oceanic crust is thin, only about 7km thick, and is made of a dark, dense igneous rock called basalt. The continental crust has a significantly different chemistry to oceanic crust. It is much thicker, reaching up to around 70km depth, and has a more complex chemistry with an overall granitic Professor Vander Auwera’s work is focused on the Southern Volcanic Zone in Chile. Here, the Nazca oceanic plate is composition in its uppermost layer that subducting beneath the South American continent. has a lower density than basalt.

www.researchoutreach.org www.researchoutreach.org Behind the Research Dr Jacqueline Vander Auwera

E: [email protected] T: +32 4 3662253 W: http://labos.ulg.ac.be/geopetro/

Research Objectives References

Jacqueline Vander Auwera’s research is focused on Vander Auwera, J., Namur, O., Dutrieux, A., Wilkinson, magmatic rocks, from the production of the magmas CM., Ganerød, M., Coumont, V., Bolle, O. (2019). Mantle at their source region to their crystallisation and Composition of La Picada lavas in the TAS Composition of La Picada lavas in CaO and SiO (wt.%) showing Melting and Magmatic Processes Under La Picada 2 final emplacement. (Total alkali (Na2O+K2O) - SiO2: wt.%) diagram. the compositional gap. Stratovolcano (CSVZ, Chile). Journal or Petrology 60(5), 907-944. doi:10.1093/petrology/egz020 formed, which represents the depth of The team calculated that the majority of formation in the crust. Detail Higgins, M.D., Voos, S., Vander Auwera, J. (2015). Magmatic processes under Quizapu volcano, Chile, mineral crystallisation occurred at about The lava samples ranged from basaltic Jacqueline Vander Auwera identified from geochemical and textural studies.Contrib 7-11 kilometres depth in the crust. samples through to dacites, which Petrology, Université de Liège, Quartier Agora (B20) Mineral Petrol 170:51. doi:10.1007/s00410-015-1209-5 are more like a granite in mineral Allée du Six Août 12, B-4000 Liège, Belgium (becomes solid) at higher temperature samples from the different volcanic units composition. The team calculated that Higgins, M.D., Debecq, A., Vander Auwera, J., Nomikou, can later react with the leftover melt and that formed La Picada during its active the majority of mineral crystallisation Bio P. (2018). Evolution of the Kameni Islands volcanic centre form a completely new mineral. The period. To analyse the igneous petrology occurred at about 7-11 kilometres depth Jacqueline Vander Auwera is Professor at the University (Greece) from chemical and textural studies. Abstract: challenge for geochemists is to untangle of these samples, Professor Vander in the crust, the main magma storage of Liège. She completed her Masters Science in 1984 at Volcanic and Magmatic Studies Group Meeting. Available these complex chemical relationships Auwera and her colleagues completed region. Interestingly, when the magmas the University of Brussels and her PhD at the University at: https://vmsg2018.leeds.ac.uk/wp-content/uploads/ between the minerals, their parent a suite of tests. They made thin slices crystallised here, they hardened so of Louvain in 1988. She was a Fulbright exchange sites/18/2017/12/VMSG2018-Scientific-Programme.pdf magmas and the original mantle rock to of the rocks and studied these under a much that much of the magma began researcher at Lamont-Doherty Earth Observatory (accessed 19/6/2020) determine how igneous rocks crystallise. microscope to identify all the minerals behaving as a solid and could no longer (Columbia University) in 1991. present and the texture of the rock (how be erupted. However, the remaining melt Personal Response LA PICADA MAGMA CHEMISTRY much is formed of larger, well-developed liquid could escape from this crystalline Funding The team collected samples from La crystals compared to the microcrystalline mush to produce even more evolved Fonds National de la Recherche Scientifique (FNRS) Picada, which is an extinct stratovolcano groundmass). They also ground up the lavas. The basalts that were collected University of Liège What first sparked your interest in igneous petrology and the complex geochemistry of magmas? with a similar geochemistry to the active rock samples and identified how old they were enriched in mineral components volcano Osorno that sits partly above were (when the eruption occurred) and that were drawn down with the Collaborators I was curious to understand how the magmas are it. The two volcanoes are likely to share measured their composition of major subducting slab, and were also enriched • Prof Olivier Namur, Katholieke Universiteit initially formed and how the process of solidification can produce the large variety of igneous rocks we can ‘plumbing systems’, the interconnected and trace elements. They studied the in water molecules, suggesting the initial Leuven (KUL) observe at the Earth’s surface. Also, the theory of plate chambers and channels along which element compositions of the crystals mantle was melted in relatively wet • Dr Olivier Bolle, Université de Liège tectonics, that was accepted in the seventies by most magma moves. They collected 47 to calculate the pressure at which they conditions. The team also confirmed that • Prof Michael Higgins, Université du Québec à Chicoutimi geologists as the new paradigm of the Earth Sciences, the magma ascended rapidly, aided by provides an exciting unifying model for explaining the the presence of large fault systems within origin of igneous rocks. Volcanism is an active process the continental crust. that we can observe happening today, something rare for geologists who usually analyse the remnants of past Magma differentiation is incredibly processes to decipher their origin. complex, and no single volcanic system is completely identical to another. The underground ‘plumbing’, the melting processes within the mantle and the type of plate boundary that forms the volcano all have complex controls on its development as well as the frequency and type of eruption. By studying these past volcanic events and the igneous petrology of magmatic materials, geologists can begin to understand the processes that are currently ongoing deep in the crust Samples from extinct stratovolcano La Picada: basalt with olivine crystals. and aid predictions about how volcanoes

may behave in the future. Pascual Bernad/Shutterstock.com

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