The Solid Earth dynamics, hazards and resources group focuses on solid Earth geodynamics, with emphasis on ocean islands, continents and continental margin processes. The group investigates mantle, crustal and surface processes, with the goal of tackling critical challenges: 1) Earthquake and volcanism, from the fundamental investigation of seismogenesis and volcanogenesis to the development of innovative monitoring techniques; 2) Mineral and hydrocarbon resources, from understanding their genesis to their exploration and exploitation; 3) Understanding past environments, climates, and their evolution based on the geological record. In order to build a solid knowledge foundation that allows us to better tackle these challenges, we undertake research on the composition, structure and dynamics of the crust and mantle in different tectonic settings. Particular attention is given to the privileged natural laboratory of the Atlantic basin, with its volcanic islands, margins, and continental surroundings.
Group Leaders: Graça Silveira and Ícaro F. Dias da Silva.
Scientific Highlights 2020
In 2020 RG3 published more than 60 papers in peer review journals, including some high impact factor journals such as Nature, Nature Communications, Nature Geosciences. We secured several projects, including 2 FCT standard grants, 1 individual Marie Skłodowska-Curie Action, 1 ERA-MIN (EU network) and 1 Portugal2020. We integrated 3 new members and 2 PhDs were successfully concluded.
Solid Earth Dynamics, Tectonics and magmatism
In 2020, we provided new insights into several key geodynamic problems. For example, we helped unravel the origins of carbonatites, showing that these exotic rocks likely result from the deep recycling of ancient marine carbonates in the mantle, also exposing implications to the minimum age for the onset of plate tectonics. More regionally, we unravelled a lateral extrusion thin-skinned structure in NW Iberia, thus providing fresh insights into the collapse of the Variscan Belt. We also deciphered the role of fluid-absent reactions without isotopic-disequilibrium in the generation of migmatites and their associated S-Type granites, as well as their exhumation processes during the final stages of the Variscan orogeny in Iberia. We observed that the subduction below the Gibraltar Arc is currently in the middle of a disruption process, and the interplay between slab dynamics, mantle flow, and plate convergence explains much of the observed residual topography, surface motion, seismicity, and mantle structure. A study in the Lesser Antilles revealed that a variable water input controls the evolution of its volcanic arc. Using high-resolution marine geophysics, we also provided evidence that volcanism at Santa Maria Island may have extended well into the late Pleistocene, with critical hazard implications. We also analyzed the crustal stress state in several Azores Islands using seismic anisotropy. At a broader scale, we confirm the effects of the asthenospheric anelasticity on ocean tide loading around the East China Sea observed with GPS. We made high-precision age determinations with implications for the evolution of Pan-African and Cadomian orogenies in Morocco and the Yanshanian orogeny (SW China).
Using ambient noise and teleseismic events, J. Carvalho PhD thesis provided a new image of the Cape Verde Lithospheric structure. The PhD work of J. Ferreira allowed us to answer some key questions regarding the formation and evolution of shear zones and their role in the exhumation of anatectic complexes.
We started the project RESTLESS (PTDC/CTA-GEF/6674/2020), where we propose to integrate cross-disciplinary high-resolution observations of the spatio-temporal evolution of seismic activity, Earth structure at depth, crustal fluids, and sensitivity to external forcings, to quantify the state of geologically active systems.
Geohazards
In terms of geohazards, in 2020, RG3 provided key insights to themes as diverse as eruption behaviour, the hazard potential of volcanic flank collapses, and tsunami genesis, frequency and impacts. First, using eruptions from Iceland and Fogo, we showed how tidal forces might influence volcanic activity, a cause-effect relationship that remained elusive partly on account of the difficulty of isolating its effects. We also contributed to a new modelling framework for large volume effusive eruptions with relatively minor observed precursory signals, whose behaviour is very challenging to forecast. We also undertook critical fieldwork to reconstruct the latest eruptions and reassess volcanic hazards at Flores Island. Using marine geophysics, we helped unravel the geometry and mode of emplacement of Fogo’s tsunamigenic flank collapse. Critically, we showed that Maio Island in Cape Verde was impacted by at least 3 mega-tsunamis in the last 400 ka, contributing to our knowledge of the frequency of such events. In collaboration with colleagues from RG2, we also provided a comprehensive appraisal of tsunami deposits in the Atlantic basin. We also probed seismic microzonation in Lisbon using geotechnical data and geophysical and borehole data to characterize an intraplate seismogenic zone. We also assessed coastal erosion rates at lava deltas worldwide, with implications to ongoing research in the Azores. We inferred vertical land motion in the Iberian Atlantic coast and unravelled implications for sea-level change evaluation using precise GPS measurements. We contributed to the study of climate-induced warming of permafrost soils by providing accurate detection of active layer freeze-thaw dynamics using quasi-continuous electrical resistivity tomography (Deception Island, Antarctica).
We also started the project HAZARDOUS (PTDC/CTA-GEO/0798/2020), which aims to explore the hazards associated with the formation and development of detrital and lavic “fajãs” in the Portuguese volcanic archipelagos, using an integrative onshore/offshore approach.
Mineral and Energy Resources and Basin Analysis
In 2020, we secured and started critical projects, MOSTMEG and INOVMINERAL4.0, aimed at refining connections between the Mining Life Cycle and Product Life Cycle, which will impact the building of modern mineral-based value chains, aiming at the secure supply of raw materials from primary and secondary sources.
An RG3 member received an individual EU-funded project to unravel how sulfur and metals are mobilised during hydrothermal circulation and transported to form VMS deposits close to the seafloor.
We investigated the basement and margin structure off Natal Valley, offshore Mozambique, with wide-angle seismic data, revealing a 30 km‐thick continental crust 1 km below sea level, thus implying a complex history with potential mantle‐derived intrusions.
We combined multi-scale and new approaches to investigate depositional conditions towards a better understanding of various processes leading to massive mineral deposits to reservoir formation whose scientific and societal impacts are crucial in modern society. Regarding basin and environmental analysis, we proposed new approaches and tools based on original combinations of geochemical analysis but also multi-disciplinary datasets and mineral properties to provide new constraints on paleo-reconstructions, basin formation as well as the recognition of dominant reservoir-type facies which is particularly important for mineral exploration. These approaches revealed a rapid post-accretion and collision uplift of the Variscan orogenic belt in SW Iberia, the contribution of West African cratons in the material deposited in the Central Iberian Zone and the Iberian Allochthonous Domains and a new stratigraphic evolution of the Potiguar Basin (NE Brazil).
Our research tackles depositional processes at a more local scale with important contributions for mineral and hydrocarbon exploration as illustrated by the special issue co-edited in Ore Geological Review and the chapter in the Encyclopedia of the UN Sustainable Development Goals. The review of high-resolution sequence stratigraphy shows how such an approach is relevant to characterize reservoir zonation at a finer scale, becoming an indispensable methodology for optimizing hydrocarbon production. Redox conditions in anoxic/oxic environments play a key role in the formation of hydrocarbon reservoirs and massive sulfide deposits. They were characterized at the scale of the Lusitanian Basin allowing to estimate sectors where organic matter should be better preserved. In the Iberian Pyrite Belt and the Beja Layered Gabbroic Sequence, these conditions also exposed the role of interaction with hydrothermal fluids and the presence of faults in the massive deposition of sulfides.
By surveying waters, soils and plants across northern Portugal, we provided more insights into the highly complex Bromine cycling. We also provided a new way to predict soil salinity and sodicity in soils using electromagnetic conductivity imaging.
Collaborations
Charles University, Prague, Czech Republic
Dublin Institute of Advanced Studies, Ireland
GFZ, Potsdam, Germany
IFREMER, France
Institute for Geophysics, University of Münster, Germany
Instituto de Geociências, Universidade de São Paulo, Brazil
Instituto Jaume Almera, Barcelona, Spain
Lamont-Doherty Earth Observatory of Columbia University, New York, USA
School of Earth Sciences, University of Bristol, UK
S. Diego State University, California, USA
Universidad Complutense de Madrid, Spain
Universidad de La Laguna, Tenerife, Spain
Universidad de Salamanca, Spain
Universidade da Madeira, Portugal
Universidade de Évora, Portugal
Universidade dos Açores, Portugal
Universidade Nova de Lisboa, Portugal
University of Kiel, Germany
GEOMAR Helmholtz Centre for Ocean Research, Kiel, Germany
MARUM, University of Bremen, Germany
University of Münster, Germany
Instituto de Investigação em Vulcanologia e Avaliação de Riscos, Portugal
Institut de Physique du Globe de Paris, France