Project PTDC/GEO-FIQ/1088/2014

As summarized below, our proposed investigation of the aforementioned volcanoes aims to:

Locate your magma storage areas and relate them to the local geodynamic framework. Physical discontinuities, such as the Moho Transition Zone (MTZ), can act as a density barrier for rising basalts, promoting their accumulation, fractionation and degassing;

Moderate geochemical processes in reservoirs. Polybaric fractional crystallization is a fundamental process in the evolution of magma, responsible for the enrichment of volatile elements (eg water) in the evolved liquids. However, large explosive events can also be triggered by the influx of new, more primitive, volatile-rich magma that mixes with evolved magma stored in shallow reservoirs. Fundamental information about these processes can be obtained by measuring and correlating the geochemistry of fluids and fluid inclusions trapped in the mineral phases of solid products of explosive eruptions and the geochemistry of fluids emitted to the surface;

Defining the time scale of processes. During mixing of magmas, chemical exchanges occur at a rate characteristic for each element, depending on its relative diffusivity and chemical and thermal gradients. The distribution of elements, “frozen” in the rock, can be used to infer the time elapsed between the start of mixing and the eruption. It thus serves as a timescale geospeedometer of the mixture. The different diffusion rates of chemical elements through crystals can also provide similar information.

Quantify the depth and size of magma sources that sustain permanent gas emissions, and which are essentially made up of CO2-rich fluids that escape through fractures and tectonic discontinuities, possibly rising from Moho and/or surface magmatic reservoirs.

Predicting the occurrence of volcanic eruptions represents a major challenge for researchers in Geosciences. Every year, several eruptions cause significant losses in inhabited areas around active volcanoes at a global level. The environmental, social and economic impact depends on the type, magnitude and duration of the events, but also on the level of preparedness of the scientific community and the Authorities. Currently, the ability of scientists to understand and interpret the warning signals of a future eruption depends heavily on their knowledge of the behavior of volcanic systems and the magmatic processes that occur deep in the feed system.

Normally, a volcano's power system can be investigated using geophysical methods, which allow the detection of anomalies caused by magmatic intrusions. However, the interpretation of geophysical signals is rarely straightforward, and entails limitations of spatial resolution and knowledge of geological structures in depth. An alternative and complementary approach to overcome these limitations and better characterize the magmatic feed system can be achieved through the development of geochemical studies of the eruptive products. It is important to note that this approach does not have time limitations as ongoing, recent or old eruptions can also be investigated.

This project aims to study the volcanic products of some of the volcanic systems historically active on the islands of Macaronesia: Pico, Água de Pau and Furnas in the Azores; La Palma, Tenerife and Lanzarote , in the Canaries and Fogo, in Cape Verde.

The available data on the magmas emitted by these systems show a progressive change from basalts to more evolved magmas (trachytes and phonolites) responsible for explosive eruptions. Such events, particularly an explosive eruption of great magnitude, can thus cause serious economic and environmental consequences on these islands.

This study presents a multidisciplinary research approach that will make use of the most advanced analytical technologies and will be conducted by an international team of researchers with high quality scientific activity, certified by the high number of publications and citations.

This proposal arises from discussions and exchange of ideas between the P.I. and the members of this team, during previous and ongoing research activities funded by regional, national and international projects (i.e. TERCO2 DCODECADE, PLUSYS FCT, MEMOVOLC and MEDSUV ERC projects), which also included the islands of the Azores and the Canaries.

The knowledge acquired within the scope of this project will be published in high-impact international magazines and newspapers and disseminated at international meetings.