A Wilson cycle (first coined by Dewey and Burke in 1977) describes the sequence of continental rifting, the opening of an ocean basin, the subsequent destruction of an oceanic basin by subduction, and finally ocean closure and continent-continent collision. The Caledonian orogenic cycle is the “original” Wilson cycle as described by J. Tuzo Wilson in 1966. It commenced in the late Proterozoic with the protracted disassembly of the Rodinia supercontinent and the formation of the Iapetus ocean. The closure of the Iapetus began in the early Palaeozoic and the final continent-continent collision between Laurentia and Baltica took place in the Silurian-Devonian, shortly followed by orogenic extension in the Devonian-Carboniferous.

The Caledonian mountain belt represents a world-class example of a deeply denudated Himalayan-style orogen. The exposed crustal sections allow the study of all stages of the Wilson cycle and may contribute to our understanding of many of the fundamental questions in plate tectonics, including (1) the role of inheritances during rifting and collision, (2) continental-rifting, break-up and ocean formation, (3) subduction, (4) marginal basin formation, (5) arc-continent and continental collisions, (6) (U)HP metamorphism, (7) orogenic wedge formation and dynamics, (8) the formation of crustal-scale shear zones, (9) ductile and brittle deformation mechanisms, and (10) the dynamics of late- to post-orogenic extension and deep crustal exhumation.

This session aims to bring together scientists studying rocks and geological processes from all stages of the Caledonian Wilson cycle, i.e. from rifting to collision and post-orogenic extension, and welcomes sedimentological, petrological, geochemical, geochronological, geophysical, structural, and modelling contributions that help to improve our understanding of the Caledonides and mountain belts in general.

Serpentinization is a mantle hydration reaction of major interest because of its implication in the evolution of rifted margins, mid-ocean ridges, and subduction zones. Serpentinization leads to weak hydrous minerals crystallization that yields to a reduction in the friction coefficient and an increase in the volume of mantle rock.

In rifted margins and mid-ocean ridges, weak serpentinized peridotite and serpentinization-driven fluid overpressure are known to have a critical role in the kinematics of low-angle detachment faulting that exposes mantle lithology to the seafloor. At mid-ocean ridges, these low-angle structures control the formation of oceanic core complexes, while at rifted margins control the exhumation of large portions of sub-continental mantle. Serpentinization is also an exothermic reaction that can produce significant heat and derive serpentinite hosted hydrothermal systems, and thus impact the submarine ecosystems.
In subduction zones, crustal-scale normal faulting associated with the bending of the incoming oceanic plate at the outer rise enables water percolation to the oceanic mantle, triggering serpentinization. Multi-stage fluid release from the subducting slab caused by the breakdown of hydrated mantle minerals triggers the production of flush melting and consequently the arc volcanism. The heterogeneous water release controls also the depth of earthquake generation and therefore the size of the seismogenic zone.
Overall, understanding mantle serpentinization is critical to understand the dynamics of plate tectonics. To this end, this session aims at bringing together researchers of divergent and convergent settings to enhance our understanding of the kinematics of mantle serpentinization and its geodynamic implications. We encourage all related contributions, from geophysical and/or petrological studies to numerical/analogue modelling that provide temporal and spatial constraints of the process of serpentinization, as well as insights into its role during the evolution of rifted margins, oceanic ridges, and subduction zones. We strongly encourage the contribution of young researchers.

Mantle upwellings are an important component of the Earth’s convective system that can cause volcanism and anomalies in surface topography. Upwellings can rise from thermal boundary layers as hot “mantle plumes”. Alternatively, they can be the response to upper-mantle convective flow, subduction, or rifting. Clearly, different mechanisms sustain mantle upwellings of various temperature, vigour and composition, causing characteristic signals that can potentially be imaged using geophysical data, as well as expressed in the geochemistry and petrology of related magmatism.

This session invites contributions that focus on mantle upwellings from geophysics, geochemistry, and modelling perspectives. Our aim is to bring together constraints from multiple disciplines to understand the origin and dynamics of mantle upwellings, as well as their potential to trigger mantle melting, create volcanism, generate ore deposits, and build dynamic topography.

Since the 1960’s plate tectonics has been accepted as a surface expression of the earth's convecting mantle, and yet numerous geological features of plate interiors remain unexplained within the plate tectonic paradigm, including intraplate earthquakes and large-scale vertical motions of continents as epitomized by the uplift history of Africa. Kevin Burke (1929-2018), one of the greatest geologists of our time who published original and thought-provoking contributions for six decades, was one of the most vocal scientists to assert that plate tectonics is an incomplete theory without a clear understanding of its links with deep Earth processes, including the role of mantle plumes. In this session we commemorate the pioneering work of Kevin and explore contributions from across the diverse fields that interested him, including global tectonics, the Wilson Cycle, the origin of Precambrian greenstone belts, the evolution of the Caribbean, and the uplift history of Africa and other continents. We discuss the state-of-the art of the plume mode of mantle convection, its influence on the dynamics of the asthenosphere and the lithosphere, and its expression at the earth’s surface. We seek contributions from natural case studies (tectonic evolution, sedimentology, thermochronology, geophysics, palaeoclimate) and from geodynamics or geomaterials oriented (analog and numerical) modeling, which address the interplay of deep mantle – asthenosphere – lithosphere – basin – surface processes in all plate environments. In particular, we appreciate studies that contribute to the understanding of feedback processes causing the evolution of dynamic topography and welcome contributions that examine surface and deep Earth links based on observations and numerical models (although notably the latter never seduced Kevin).

Knowledge of the lithosphere-asthenosphere system and its dynamics is one of the key questions for understanding geological processes. Constraints on the style, mechanism, and pattern of deformation in the crust and upper mantle come from direct and indirect observations using a variety of methods. Seismological studies focusing on anisotropy have successfully improved our knowledge of deformation patterns, and when combined with tomographic models, anisotropy can shed light on the geometry of deformation in the lithosphere and asthenosphere. Sophisticated geodynamic modeling (numerical and physical analogue) and laboratory (rock physics) experiments enhance our understanding of flow patterns in the Earth’s upper mantle and their bearing on vertical motions of crust and lithosphere. Combined with seismic anisotropy data these methods have the potential to reveal the mechanisms that create deformation-induced features such as shape preferred orientation (SPO) and lattice-preferred orientation (LPO). Structural and kinematic characterization of deformation events by geometric and kinematic analyses infer the direction and magnitude of the tectonic forces involved in driving deformation within crust and upper mantle. Additionally, physical analogue and numerical modeling studies have fostered our understanding of complex 3D-plate interaction on various time-scales, regulated through the degree of plate coupling and the rheology of the lithosphere.

However, more work is required to better integrate the various experimental and modelling techniques and to link them to multi-scale observations. This session will bring together different disciplines that focus on the deformation of the lithosphere and upper mantle as well as on the dynamics and nature of the lithosphere-asthenosphere system. The main goal is to demonstrate the potential of different methods, and to share ideas of how we can collaboratively study lithospheric deformation, and how it relates to the ongoing dynamics within the asthenospheric mantle. Contributions are sought from studies employing seismic observation, geodynamical modeling (analogue and numerical), structural geology, and mineral and rock physics.

Invited Speakers:
Greg Houseman (Institute of Geophysics and Tectonics, University of Leeds)
Agnes Kiraly (Department of Geosciences, University of Oslo)

The lithosphere, the outermost shell of the Earth, constitutes the upper thermal boundary layer of mantle convection. It is well established that its properties play a central role in the development of solid Earth dynamics. Through its properties the lithosphere also provides a primary source of thermal and chemical anomalies for mantle convection when it is injected in the mantle as subducting slabs. Here, the subduction of cold and dense oceanic lithosphere into the underlying mantle acts as the major driving force of plate motion, and as a key component of the water and carbon cycles throughout the Earth. At the global scale, some of these lithosphere heterogeneities include rheological stratifications, sutures, fracture zones, and lateral and vertical variations in temperature and composition. These exist at various scales and play a major role in determining subduction dynamics and the degree of lithosphere-mantle decoupling. Deciphering the interaction of the lithosphere with the underlying asthenosphere and deeper mantle is critical to understanding the secular evolution of the Earth system and to reconcile models with natural observations. This session aims to highlight recent advances in constraining the scales and amplitudes of heterogeneities in the lithosphere as well as their dynamic role. We welcome multidisciplinary contributions. Some key areas of interest are lithospheric structure and morphology, subduction kinematics and dynamics, slab-mantle interaction and slab deformation, active margin tectonics and subduction-induced seismicity.

The Oman Drilling Project (OmanDP; 2016-2018) has recovered 3200 m of diamond drillcore that sample three intervals within the gabbroic lower crust, the crust-mantle transition, partially serpentinised peridotite undergoing active alteration, and the transition from the mantle into the underlying metamorphic sole of the Samail ophiolite in Oman, arguably the best-preserved ophiolite. Most of the boreholes have been geophysically logged and the cores have undergone extensive IODP standard core description onboard the DV Chikyu, supplemented with X-ray CT and high resolution infrared scanning of the entire core. These cores and boreholes can be used to investigate the full spectrum of processes operating during the formation and modification of oceanic crust and shallow mantle. These processes involve mass and energy transfer between all the major components of the Earth system (the mantle, the crust, the hydrosphere, the atmosphere and the biosphere) and occur over a broad range of temperatures, depths and tectonic settings. In this session, we invite abstracts relating to the Oman Drilling Project including core analysis, geophysical logging and microbial studies as well as studies related to the Samail ophiolite and the oceanic lithosphere in general.

Subduction zones are arguably the most important geological features of our planet, where plates plunge into the deep, metamorphic reactions take place, large earthquakes happen and melting induces volcanism and creation of continental crust. None of these processes would be possible without the cycling of volatiles, and this session aims to explore their role in convergent margins. Questions to address include the following. Do Atlantic and Pacific subduction zones cycle volatiles in different ways? What dynamic or chemical roles are played by subducted fracture zones and plate bending faults? How do fluids and melts interact with the mantle wedge and overlying lithosphere? Why do some of the Earth’s largest mineral resources form in subduction settings? We aim to bring together geodynamicists, geochemists, petrologists, seismologists, mineral and rock physicists, and structural geologists to understand how plate hydration/slab dynamics/dehydration, and subsequent mantle wedge melting/fluid percolation, and ultimately melt segregation/accumulation lead to the diverse range of phenomena observed at convergence zones around the globe.

Invited speakers:
Lena Melekhova (Bristol University)
Ingo Grevemeyer (GEOMAR)

Subduction drives plate tectonics, generates the major proportion of subaerial volcanism, forms continents, and entrains surface material back to the deep Earth. Therefore, it is arguably the most important geodynamical phenomenon on Earth and the major driver of global geochemical cycles. Seismological data show a fascinating range in shapes of subducting slabs. Arc volcanism illustrates the complexity of geochemical and petrological phenomena associated with subduction. Surface topography provides insight in the orogenic processes related to subduction and continental collision.

Numerical and laboratory modelling studies have successfully built our understanding of many aspects of the geodynamics of subduction zones. Detailed geochemical studies, investigating compositional variation within and between volcanic arcs, provide further insights into systematic chemical processes at the slab surface and within the mantle wedge, providing constraints on thermal structures and material transport within subduction zones. However, with different technical and methodological approaches, model set-ups, inputs and material properties, and in some cases conflicting conclusions between chemical and physical models, a consistent picture of the controlling parameters of subduction-zone processes has so far not emerged.

This session aims to follow subducting lithosphere on its journey from the surface down into the Earth's mantle, and to understand the driving processes for deformation and magmatism in the over-riding plate. We aim to address topics such as: subduction initiation and dynamics; changes in mineral breakdown processes at the slab surface; the formation and migration of fluids and melts at the slab surface; primary melt generation in the wedge; subduction-related magmatism; controls on the position and width of the volcanic arc; subduction-induced seismicity; mantle wedge processes; the fate of subducted crust, sediments and volatiles; the importance of subducting seamounts, LIPs, and ridges; links between near-surface processes and slab dynamics and with regional tectonic evolution; slab delamination and break-off; the effect of subduction on mantle flow; and imaging subduction zone processes.

With this session, we aim to form an integrated picture of the subduction process, and invite contributions from a wide range of disciplines, such as geodynamics, modelling, geochemistry, petrology, volcanology and seismology, to discuss subduction zone dynamics at all scales from the surface to the lower mantle, or in applications to natural laboratories.

The Azores archipelago is located in the triple junction of the North American, Eurasian and Nubian tectonic plates. The origin of the magmatism in the archipelago remains controversial even though it has generally been associated with a mantle plume interacting with the local structural regime. Due to this peculiar geodynamic setting, earthquakes, subaerial and submarine volcanic eruptions may occur in the archipelago. The identification of possible signs of unrest of the volcanoes is challenging and much of the recent volcanic activity is characterized by the occurrence of seismic swarms, ground deformation episodes and the presence of secondary manifestations of volcanism. The archipelago is located in the vicinity of the central Northern Atlantic Ocean, what makes the islands vulnerable to storms, floods and landslides. The islands are thus ideally suited to apply different multidisciplinary methodologies for the study of geological hazards.
This session aims to focus on the Azores submarine plateau and islands as a natural laboratory for the study of different geological processes. Here, we aim at contributions from the different fields of Geology, Geophysics and Geochemistry dealing with the geodynamic context of the Azores, studying the evolution and geological diversity of the Azores and evaluate hazards that can affect the islands.