GD2 – Crust, Lithosphere, and Asthenosphere: Observations and models
Crust-Lithosphere-Asthenosphere Interplay, Deformation and Dynamics
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.
Greg Houseman (Institute of Geophysics and Tectonics, University of Leeds)
Agnes Kiraly (Department of Geosciences, University of Oslo)
Geodynamics of continental crust and upper mantle, and the nature of mantle discontinuities
We invite, in particular multidisciplinary, contributions which focus on the structure and evolution of the continental crust and upper mantle and on the nature of mantle discontinuities. The latter include, but are not limited to, the mid-lithosphere discontinuity (MLD), the lithosphere-asthenosphere boundary (LAB), and the mantle transition zone, as imaged by various seismological techniques and interpreted within interdisciplinary approaches. Papers with focus on the structure of the crust and the nature of the Moho are also welcome. Methodologically, the contributions will include studies based on seismic, thermal, gravity, petrological, and/or electro-magnetic data interpretations.
Confirmed invited speaker: Arwen Deuss on Upper Mantle Doscontinuities
Geochemical and geodynamic perspectives on the origin and evolution of deep-seated mantle melts and their interaction with the lithosphere
The origin and evolution of the continental lithosphere is closely linked to changes in mantle dynamics through time, from its formation through melt depletion to multistage reworking and reorganisation related to interaction with melts formed both beneath and within it. Understanding this history is critical to constraining terrestrial dynamics, element cycles and metallogeny. We welcome contributions dealing with: (1) Reconstructions of the structure and composition of the lithospheric mantle, and the influence of plumes and subduction zones on root construction; (2) Interactions of plume- and subduction-derived melts and fluids with continental lithosphere, and the nature and development of metasomatic agents; (3) Source rocks, formation conditions (P-T-fO2) and evolution of mantle melts originating below or in the mantle lithosphere; (4) Deep source regions, melting processes and phase transformation in mantle plumes and their fluids; (5) Modes of melt migration and ascent, as constrained from numerical modelling and microstructures of natural mantle samples; (6) Role of mantle melts and fluids in the generation of hybrid and acid magmas.These topics can be illuminated using the geochemistry and fabric of mantle xenoliths and orogenic peridotites, mantle-derived melts and experimental simulations.
Imaging, modelling and inversion to explore the Earth’s crust and upper mantle
This session will cover applied and theoretical aspects of geophysical imaging, modelling and inversion using both active- and passive-source seismic measurements as well as other geophysical techniques (e.g., gravimetry, magnetic and electromagnetic) to investigate the Earth’s crust and uppermost mantle. We invite contributions focused on methodological developments, theoretical aspects, and applications. Studies across the scales and disciplines are particularly welcome.
Among others, the session may cover the following topics:
- Active- and passive-source imaging using body- and surface-waves;
- Full waveform inversion developments and applications;
- Advancements and case studies in 2D and 3D active-source imaging;
- Interferometry and Marchenko imaging;
- Seismic attenuation and anisotropy;
- Developments and applications of multi-scale and multi-parameter inversion;
- Joint inversion of seismic and complementary geophysical data;
- Applications of new acquisition systems.
Monitoring and modelling of geodynamics and crustal deformation: progress during 38 years of the WEGENER initiative
The processes of the Earth deformation can be revealed by means of diverse methods of investigations. The seasonal distribution of surface loading, the earthquake cycle, volcanic processes (eruptions, dike intrusions, induced seismic activity), near surface motions (landslides, induced and natural superficial subsidence/collapse).
Recently, major earthquakes in Sumatra (2004, Mw 9.2), Maule (2010, Mw 8.8), Haiti (2010, Mw 7.1) and Tohoku (2011, Mw 9.0) have exposed the impact of such events and the need for better understanding of Earth deformation processes. These events illustrate the geodynamic complexities that include subduction zones and giant earthquakes, continental faults and depth versus surface deformation, the seismic cycle and seismotectonics of active zones, magmatism processes and crustal deformation. The observation techniques, methods and data analysis need the Earth observation systems and reference frames that include remote sensing and surface and satellite gravity observations
This session is conducted in the frame of the WEGENER consortium*) and we seek submissions that emphasize multidisciplinary studies of Earth deformation using geodetic techniques (GPS, InSAR, LiDAR, space/air/terrestrial gravity, ground-based geodetic observations), complementary tectonic and geophysical observations, and modeling approaches focusing on the European-Mediterranean and Northern African regions. We also welcome contributions discussing the realization and outcomes of Supersites in the frame of the GEO initiative, as well as fundamental studies of natural and induced physical phenomena, strategies to develop early warning and rapid response systems.
*) The World Earthquake GEodesy Network for Environmental Hazard Research (Sub-commission 3.5 of IAG commission 3, namely Tectonics and Earthquake Geodesy)
Achievements and perspectives in scientific ocean and continental drilling
Scientific drilling through the International Ocean Discovery Program (IODP) and the International Continental Scientific Drilling Program (ICDP) continues to provide unique opportunities to investigate the workings of the interior of our planet, Earth’s cycles, natural hazards and the distribution of subsurface microbial life. The past and current scientific drilling programs have brought major advances in many multidisciplinary fields of socio-economic relevance, such as climate and ecosystem evolution, palaeoceanography, the deep biosphere, deep crustal and tectonic processes, geodynamics and geohazards. This session invites contributions that present and/or review recent scientific results from deep Earth sampling and monitoring through ocean and continental drilling projects. Furthermore, we encourage contributions that outline perspectives and visions for future drilling projects, in particular projects using a multi-platform approach.
Metamorphic minerals: time capsules from a dynamic lithosphere
Metamorphic minerals document the dynamic evolution of our planet, from the Archean to Present and from the grain- to plate-scale. Deciphering these records requires an approach that integrates petrology, geochemistry, chronology, structural analysis and modelling. Our ability to study our dynamic lithosphere through metamorphic geology continues to improve. At the same time, new analyses and approaches reveal issues and pitfalls that inspire future development.
This session aims to highlight integrated metamorphic geology and its use in elucidating the processes that shaped cratons and mountain belts through time. We welcome contributions in petrology, geo- and thermo-chronology, trace-element and isotope geochemistry, thermodynamic modelling, and structural geology—all with a specific focus on studying metamorphosed-metasomatised rocks. Part of the session will be devoted to novel developments and applications in geochronology and micro- to nano-analytical methods.
Robert Holder (Johns Hopkins University): "Monazite Eu anomalies revisited: beyond feldspar"
Pierre Lanari (Universität Bern): "An integrated modelling framework for tracing equilibrium relationships in metamorphic rocks"
Integrated approaches to bridge Long-term Tectonics and Earthquake cycles: Observations, Experiments, and Models
Our first-order understanding of earthquake cycles is limited by our ability to detect and interpret natural phenomena or their relict signatures on faults. However, such observations allow us to define fundamental hypotheses that can be tested by way of experiments and models, ultimately yielding deeper insights into mechanics of faulting in nature. Inter-, co-, and post-seismic deformation can be documented geodetically, but the sparseness of the data and its large spatial and temporal variability do not sufficiently resolve their driving mechanisms. Laboratory experiments under controlled conditions can narrow down the possibilities, while numerical modelling helps extrapolating these results back to natural conditions. Thus, integrated approaches to bridge long-term tectonics and the earthquake cycle that combine observation, interpretation, experimentation, and finally, physical or numerical modelling, are key for our understanding of the deformation behaviour of complex fault systems.
This session seeks contributions toward an integrated perspective on the earthquake cycle that span a wide range of observations, methodologies, and modelling over a variety of spatial and temporal scales. Presentations can cover brittle and ductile deformation, from microstructures to mantle rheology and with applications to earthquake mechanics, geodynamics, geodesy, geohazards, and more. Specific questions include: How do long-term crustal and lithospheric deformation affect short-term seismicity and earthquake cycle behaviour? What is the long-term topographic signature of the earthquake? What are the relative contributions of rheology and geometry for seismic and aseismic slip? What are the roles of on- and off-fault deformation in shaping the landscape and partitioning seismic and aseismic energy dissipation? We welcome submissions by early-career scientists in particular.
— Invited speaker: Luc L Lavier, Jackson School of Geosciences | The University of Texas at Austin