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Theme 2: Magmatic and metamorphic systems

(Wolfgang Bach, Francois Holtz, Gerhard Wörner)

Session 2.1: Mass transfers in oceanic spreading centers

Christoph Beier (University of Erlangen), Jürgen Koepke (University of Hannover), Colin Devey (GEOMAR, Kiel), Wolfgang Bach (MARUM, Bremen)

Along 55,000 km of mid-ocean ridges and 11,000 km backarc spreading centers 20 cubic kilometers of new crust are formed annually, making oceanic spreading centers the geotectonic setting with the highest magma flux on Earth. Over 1000 hydrothermal vent fields are predicted to occur in this setting, which hosts several hundred million tons of polymetallic sulfide. In this session, we invite contributions concerning mechanisms of mantle melting and lithospheric accretion in oceanic spreading centers – from volcanically starved segments with oceanic core complexes to systems with excessive magma flux. We also welcome presentations of research addressing element transport in marine hydrothermal systems. Papers discussing magmatic-tectonic-hydrothermal linkages are particularly invited. Submissions can include work in modern ocean crust as well as in ophiolites.


Session 2.2: Intraplate volcanoes: evolution, processes and hazards

Christoph Breitkreuz (TU Freiberg), Andreas Klügel (University of Bremen), Thomas Walter (GFZ Potsdam)

Intraplate volcanism occurs over hot spots, rifts and strikeslip systems, and is widespread in both oceanic and continental settings. The surface expression ranges from small volcanic fields dominated by maars and scoria cones, to stratovolcanoes, calderas, seamounts, oceanic plateaus, and ocean islands, which form the largest volcanic edifices of our planet. Processes at intraplate volcanoes include eruptive and intrusive magmatism, interrupted by episodic and continuous erosion and landslides, all of which are complexly interacting with the environment; the details of these processes are hardly understood. Intraplate volcanoes also comprise almost the entire compositional spectrum known for volcanic rocks. The aim of this session is to bring together scientists working on the evolution of continental or oceanic intraplate volcanoes, their growth and decline, and interactions with the environment. The session seeks contributions from a wide field of geosciences, including but not limited to studies of the geological evolution, structural and tectonic analysis, chemical and petrological investigations, geophysical and remote sensing applications, and process modelling. Moreover, analysis of constructive and destructive processes at oceanic island volcanoes associated with sea level changes, and the related hazards, are welcome in this interdisciplinary session.


Session 2.3: Processes in layered mafic magma chambers and formation of associated ore deposits

Olivier Namur (University of Hannover), Kathrin Faak (Ruhr University Bochum), Robert Trumbull (GFZ Potsdam), Ilya Veksler (GFZ Potsdam)

Layered mafic intrusions such as Skaergaard, Stillwater and Bushveld have inspired the development of classic petrologic concepts of fractional crystallization and crystal sorting, but other processes including magma mixing, silicate liquid immiscibility and interaction with hydrous fluids clearly also play a role in their evolution. Among the most important features of layered mafic intrusions are the rich ore deposits of chromium, nickel and and platinum group elements (PGE) hosted within them. What combination of processes is needed to produce these world-class ore deposits?
This session welcomes contributions from studies of natural rocks and ores, experiments and numerical modelling that address these issues.


Session 2.4: Compositional evolution, dynamics and physical properties of Earth's mantle

Sergio Speziale (GFZ Potsdam), Andreas Stracke (University of Münster), Hauke Marquardt, Dan Frost (University of Bayreuth)

Our knowledge of the structure and composition of Earth’s mantle has evolved considerably in the last decades. However, many questions are still open such as those regarding the global geochemical cycles that determine its compositional evolution, including the volatile elements, which also have a profound influence on its fluid dynamics, the origin of seismic patterns, especially those in the lowermost mantle, and how mineral physics affects the large scale properties of Earth's mantle. This session will explore the global geochemical cycles, the properties and behavior of geomaterials, and the global dynamics of Earth's interior. Contributions based on geochemical, isotopic, experimental, or computational data and geodynamic modeling are encouraged.


Session 2.5: Subduction zone magmatism and crustal evolution

Gerhard Wörner (University of Göttingen), Karsten Haase (University of Erlangen)

Subduction zone magmatism is a major player in the transfer and fractionation of elements between the mantle and the Earth’s crust. New crust is formed from mantle melting and delamination processes and elements from the Earth’s surface are recycled back into the mantle. Intra-crustal differentiation takes place in thickened crust regimes at active continental margins.
Several crucial questions should be addressed in our session: When did the „modern“ plate tectonic subduction regime initiate? What controls differences in subduction and crust-formation processes at the Archean-Proterozoic transition? What are the processes, components and fluxes of fluid-mediated elemental transfer in modern subduction zones? What are the respective contributions of different geochemical components in arc magmas and how may these change in space and time. We invite contributions from all fields of geochemistry and geodynamics that will address these questions.


Session 2.6: High-resolution geochronology and isotope tracing of high-temperature geological processes

Winfried Schwarz (University of Heidelberg), Jörn-Frederik Wotzlaw (ETH Zürich, CH), Stefan Weyer (University of Hannover)

Unraveling the timescales of magmatic and metamorphic processes along with a thorough characterisation of geo-reservoirs is essential for a quantitative understanding of geodynamics. This session aims at bringing together scientists from all fields of geo- and thermochronology as well as high-temperature isotope geochemistry. We invite contributions addressing a wide range of questions employing state-of-the-art analytical techniques. These may include studies quantifying the timescales of magmatic processes, tracking the pace of metamorphic events and constraining the rates of crustal deformation and exhumation using radiometric geo- and thermochronological methods (e.g., U-Pb, U-Th, Ar-Ar, Lu-Hf, Sm-Nd) or isotopic zoning of magmatic and metamorphic minerals. We also invite contributions using radiogenic and stable isotopes as tracers of high-temperature processes, such as mixing of mantle reservoirs and mantle-crust interaction.


Session 2.7: Rates and timescales of magmatic and metamorphic processes

Sumit Chakraborty (University of Bochum), Horst Marschall (University of Frankfurt), Andreas Stracke (University of Münster)

Igneous and metamorphic processes in different tectonic settings, from the deep mantle to shallow volcanic reservoirs, are often linked, but operate on a range of timescales. For example, geochemical reservoirs in the mantle exist for billions of years, roots of mountains at subduction and collision zones evolve on timescales of several millions of years, associated volcanic and plutonic systems over several hundred thousand years, and processes within crustal magma reservoirs that ultimately lead to triggering of eruptions operate over decades, years, or even weeks. Processes such as fluid / melt flux in metamorphic - hydrothermal systems may span a range of these timescales, depending on the tectonic setting and the mode of fluid flow. A challenge for modern geochemistry and petrology is to determine these diverse rates and durations, to associate them with the correct physicochemical or mechanical processes, and to reveal how they are linked. We invite contributions that use the full spectrum of tools from isotope geochemistry, to crystal growth kinetics (CSD studies, tomography) and diffusion chronometry, to address these questions. Contributions dealing with development of relevant analytical (e.g. spatially resolved measurements of novel isotope fractionations) or modelling tools (e.g. multistage processes in diffusion chronometry), applications to specific settings, and discussion of specific aspects of debates (e.g. is UHT metamorphism a long- or a short-lived process?) are invited for this broad interdisciplinary session.