Goldschmidt 2015: Talks and Sessions of Interest

Talks and sessions of interest to the deep carbon community at the 2015 Goldschmidt conference.

Please contact the DCO Engagement Team to add additional talks or sessions to this list. 
Full program available here.


Plenary Talks of Interest:

Wednesday 19th August 11:30-12:30 in Congress Hall
Barbara Sherwood Lollar
Dark Energy from the Deep Hydrosphere: Water-Rock Reactions Sustaining Deep Subsurface Microbiology

Barbara Sherwood Lollar (F.R.S.C.) obtained her Bachelor's at Harvard University (1985) and PhD at the University of Waterloo (1990). After completing a Postdoctoral Fellowship at University of Cambridge, United Kingdom she joined the University of Toronto in 1992. She is a University Professor in Geology, Director of the Stable Isotope Laboratory and Canada Research Chair in Isotopes of the Earth and Environment. Her specialty is stable isotope geochemistry - integrating carbon, hydrogen and noble gases to investigate microbial cycling of hydrocarbon contaminants in near surface aquifer; to delineate the sources and sinks of carbon dioxide, methane and hydrogen in the crust; and to investigate the role of subsurface microbiology in carbon cycling in the deep Earth with implications for astrobiology.

Thursday 20th August 11:30-12:30 in Congress Hall
Andrew Revkin
Can Science Help Shape a “Good” Anthropocene?

Andrew Revkin, the Senior Fellow for Environmental Understanding at Pace University, has been writing about environmental and social sustainability for more than three decades, from the Amazon to the White House, the Hudson Valley to the North Pole, mainly for The New York Times. He has won the top awards in science journalism multiple times, along with a Guggenheim Fellowship. He has written on global warming science and solutions, biodiversity conservation and energy issues since the 1980s. At Pace, he teaches courses in blogging, environmental communication and documentary film. He has written acclaimed books on global warming, the changing Arctic and the violent assault on the Amazon rain forest, as well as three book chapters on science communication. Drawing on his experience with his Times blog, Dot Earth, which Time Magazine named one of the top 25 blogs in 2013, Revkin speaks to audiences around the world about paths to progress on a turbulent planet. In spare moments, Revkin is a performing songwriter. He was a longtime accompanist for Pete Seeger and recently released his first album of original songs, which was hailed as a “tasty mix of roots goulash” on Jambands, an influential music website. Two films have been based on his work: “Rock Star” (Warner Brothers, 2001) and “The Burning Season” (HBO, 1994), which starred Raul Julia and won two Emmy Awards and three Golden Globes. Click here for more information on Andrew Revkin.

Sessions of Interest

04cSpatio-Temporal Trends of Contaminants and Tracers: Processes and Impacts on the Environment
Convenors: Francois De Vleeschouwer, Sebastien Bertrand, Saugata Datta, Rudolph Hon, Karen Johannesson
Keynote: Vojtech Ettler (Charles University Prague) 

Understanding the trends in contaminants and geochemical tracers in environmental archives is crucial to better tackle changes induced either by natural or anthropogenic forcing. Environmental archives as well as soils and aquifers have proven to be not only valuable recorders of variations in the fluxes of inorganic and organic species (REE, Ti, halogens, Pb, As, Sb, Hg, carbon, POPs, radionuclides and others) on timescales from multiyear to millennia, but also sources and sinks of contaminants, which are of major concern due to elevated risks of exposure to the environment and humans. These archives are increasingly used to reconstruct ancient and recent fluxes of natural and anthropogenic compounds that effectively track past environmental changes on local to global scales. Moreover, as dynamic geochemical systems, some of these archives (e.g. peatlands, overburden sediments, lake or coastal sediments) may store or release toxic elements (e.g. Pb, Hg, As, U) as a result of climate change and human disturbances. 

This session aims at contributions that deal with unraveling natural and anthropogenic environmental changes as well as providing an unconstrained platform for near surface aquatic, biogenic, and solid earth material interactions exploring sources, sinks, and mobilization processes on different spatial and temporal scales. In addition, we welcome papers focusing on the application of new analytical techniques, novel geochemical proxies (e.g. non traditional stable isotopes) or instrumental and statistical/modeling techniques approaches to link terrestrial environments to processes that can affect human health and the environment. Young researchers are warmly welcome to present their work. This session aims at gathering contributions that deal with reconstructions of natural and anthropogenic environmental changes from geochemical proxy archives. In addition, we welcome papers focusing on the application of new analytical techniques, novel geochemical proxies (e.g. non traditional stable isotopes) and statistical techniques to link terrestrial (lake, peat, loess, speleothems), marine and ice core records. Young researchers are warmly welcomed to present their work.

06d: Geo-Genomics
Convenors: Victoria Orphan, Gregory Dick
Keynote: Jill Banfield (University of California, Berkeley)

The evolution of microbial life and the evolution of Earth have occurred in lock step over the course of billions of years. Held within the genomes of microbial life today is a rich record of this history, harboring clues to unique adaptations, metabolic innovation, interactions, and the chemical, isotopic and physical biosignatures recorded over time. Recent technological advancements in next generation sequencing and mass spectrometry have provided access to this valuable molecular data, stimulating a new age of discovery-driven science and hypothesis testing in a range of environmental systems using DNA, RNA, protein, and lipid-based analyses. In this session we will cover some of these new methodological developments, and studies which integrate ‘omics with geobiological research to explore topics such as the evolution of key metabolisms and biosignatures, diversity of organisms, interactions and metabolic pathways linked to geochemical or mineralogical transformations, and mechanisms of adaptation in diverse ecosystems.

06f: Marine and Terrestrial Subsurface Microbiology
Convenors: Kirsten Kuesel, Matthew Fields, Anna Neubeck, Magnus Ivarsson
Keynote: Denise Akob (US Geological Survey)

Subsurface microbiology is the gateway to the deep hidden biosphere, which is assumed to contain as much as 40% of the Earth´s microbial species that remain largely uncharacterized. Geological properties shape the transfer and diffusion of water and nutrients between surface and subsurface environments and most likely contribute significantly to the ratio between lithoautotrophic and heterotrophic microbial reactions in the subsurface. The conditions are likely harsh and characterized by slow rates of energy and trace element circulation. This emerging field covers a wide range of scales: from novel isolates, complex consortia, fossilized structures/biomarkers to the fascinating research of subseafloor sediment microbiology, subseafloor crust, caves, fractured rock, and shallow to deep aquifers. We invite contributions dealing with the biogeochemical prerequisites of life in the subsurface both from pristine and contaminated deep sites, but also studies addressing the transport and fate of microorganisms under feast and famine conditions.

06i: Modern and Past Microbialites: How do They Form? What Have We Learnt?
Convenors: Karim Benzerara, Pieter T Visscher, Martin Van Kranendonk
Keynote: Christophe Dupraz (Stockholm University)

Microbialites are organosedimentary formations resulting from the microbially mediated precipitation of carbonates and other mineral phases. They have been emblematic to the field of Geobiology as targets for the search of the most ancient traces of life or complex model ecosystems where interactions between microbes and minerals are very strong. A very broad interdisciplinary community including isotope geochemists, mineralogists, organic geochemists, sedimentologists, microbiologists and molecular biologists have worked on these ecosystems over the last years and we aim at gathering them at Goldschmidt 2015 in Prague. Here we invite any contribution aiming at e.g., better understanding the formation of modern and past microbialites, investigating associated microbial communities by modern molecular tools, assessing potential biogenicity traces left within microbialites or dealing with organic matter within past microbialites, ultimately with the goal to link the present to the past.

09d: Origin and Fate of Organic Compounds in Hydrothermal Systems
Convenors: Qi Fu, William E. Seyfried, Jr.
Keynote: Barbara Sherwood Lollar (University of Toronto)

Organic compounds have been observed in a variety of hydrothermal environments, and may play a fundamental role in chemical evolution and biogeochemical cycles on Earth. They may represent the products of complex fluid-rock interaction in the depth of terrestrial and extraterrestrial systems, and/or an integral part of deep subsurface biosphere. The formation processes of organic compounds (biotic vs abiotic) and subsequent interaction with inorganic minerals have been one of the research focal points in the field of geochemistry. This session will bring together recent studies on organic synthesis and reaction processes in hydrothermal systems under a wide range of physical and chemical conditions. Contributions from field observation, theoretical modeling, laboratory experiments, and analytical characterization approaches (stable isotopes, advanced mass spectrometry, etc.) are welcome. The goal is to advance our knowledge of deep-seated organic formation and interaction processes under hydrothermal conditions, and to facilitate understanding of similar processes on other planetary bodies.

10aTransient Trace Gases in Aquatic Systems: From Noble Gases to Reactive Species
Convenors: Florent Barbecot , Matthias Brennwald , Rolf Kipfer , Roland Purtschert 
Keynote: Ilka Wallis (LBEG (Survey for Mining, Energy & Geology), BRD) 

Stable and radioactive noble gases, and other transient tracers (e.g., SF6, CFCs, 3H) are traditionally applied to date water masses and to quantify rates of water renewal and air/water partitioning. New experimental techniques and novel conceptual approaches broadened the field considerably. On the one hand, noble gases are not only used in classical aquatic systems to reconstruct past environment conditions on various timescales, but also in the pore waters of sediments and fluid inclusions. On the other hand, portable mass-spectrometers allow dissolved gas concentrations to be determined in-situ in the field, for instance to quantify O2 consumption in real time. This session aims to point out the present state of the art of the application of transient trace gases in conventional and unconventional aquatic systems and is thought to stimulate a broader discussion within the field.

13fFrom Source to Seep: Geochemical Applications in Hydrocarbon Systems
Convenors: Michael Lawson, Michael Formolo, John Eiler, Alan Brandon
Keynote: Lori Summa (ExxonMobil Upstream Research Company) 

Hydrocarbon systems, by nature, are a complex interplay of elements that must be spatially and temporally aligned to result in the generation and preservation of subsurface hydrocarbon accumulations. To meet the increasing challenges of discovering hydrocarbon resources, it is essential we advance our understanding of these systems through new geochemical approaches and analytical developments. Such development requires that academic and industry led research efforts converge in ways that are unique to the geosciences. This session invites contributions that incorporate geochemical and isotopic techniques (e.g. clumped isotopes, noble gases, Re-Os, geochemical modelling, stable and molecular geochemistry) aimed at developing an improved understanding of any of the play elements in a hydrocarbon system. In particular, new techniques focused on understanding the temperatures and timing of source rock deposition and maturation, and the mechanisms and timescales associated with hydrocarbon migration, trapping, storage and alteration in the subsurface would contribute significantly to the current state-of-the-art. The aim of this session is to bring together a multidisciplinary geochemical community from industry and academia working in hydrocarbons systems to stimulate discussion on recent advances and to encourage future collaborative efforts to resolve the many remaining questions in hydrocarbon systems analysis.

14d: Reaction Mechanisms, Rates and Transport Processes in Minerals, Glasses and Melts
Convenors: Dave Cole, Nancy Ross

Geochemical processes at mineral-water, mineral-gas and mineral-melt interfaces directly affect a number of key geochemical processes such as contaminant fate, nutrient availability, aerosol formation and growth, photochemical reactions, nanoparticle aggregation and dispersion, chemical weathering, the composition of natural waters, hydrothermal alteration, and element and isotopic redistribution among melts, minerals and fluids. Indeed, energy and mass transport observed in nature are controlled by processes occurring at interfaces – grain boundaries, within pores or along dislocations or fractures. In this session we seek contributions that provide new molecular- to microscopic insight into the properties and dynamics of interfacial reactions relevant to geochemical conditions ranging from surficial to the deep earth. Of particular interest is the behavior of water, dissolved ions, molecules, or gases at mineral surfaces, the structure and properties of the interfacial region, surface charging phenomena, interparticle interactions, nanoscale confinement effects on fluids and mineral reactions, nucleation from gas and aqueous phases, heterogeneous catalysis and transport within minerals and/or melts. Beside spectroscopic and theoretical studies we also welcome novel thermodynamic and kinetic approaches to describe and predict interfacial processes.

16h: Probing the Record of Mantle Processes and Crust-Mantle Interactions in Minerals, Rocks and their Geochemical Properties
Convenors: Yildirim Dilek, Jana Kotkova, David van Acken
Keynote: Graham Pearson (University of Alberta)

Mantle processes have a profound impact on global element cycles. In order to obtain a more comprehensive understanding of element fluxes and material recycling between and within the mantle and crust, geochemical, structural and geodynamic data need to be considered in parallel with mineralogical, experimental and petrological constraints obtained from deeply subducted and exhumed continental crust and mantle units. Major minerals and trace phases, such as diamonds, oxides and sulfides, along with fluid inclusions, can be used to constrain the geochemical compositions of mantle reservoirs and crust-mantle fluxes. In this session, we will examine and discuss new observations and data based on solid and fluid inclusions, microstructures of major and accessory minerals, ultra-high pressure experiments on phase transformations, trace elements and isotopes, as well as advanced analytical and experimental techniques at all scales, aimed at improved understanding of a wide range of processes, including partial melting and basalt generation during lithosphere formation, and recycling of crustal materials in mantle domains. We invite contributions linking mineralogical, structural and geochemical properties of earth materials from ultrahigh-pressure metamorphic rocks and upper mantle peridotites-chromitites.

17d: Volatiles, Redox State, and Partial Melts in the Asthenosphere Down to the Transition Zone
Convenors: Fabrice Gaillard, Arno Rohrbach, Sebastian Tappe
Keynote: Dan Frost (Bayerisches GeoInstitut)

Hardly any direct samples derived from the asthenosphere and below are available for study. Our knowledge about the Earth’s deep upper mantle is therefore inferred from geophysical surveys, from experimental and numerical simulations of high-P-T mineral assemblages, from rare sublithospheric diamonds and their inclusions, and from studying high-pressure incipient melting products of mantle materials (e.g., kimberlites, carbonatites, melilitites, alkaline basalts). These exotic low-degree melts are a distinct feature of the asthenosphere possibly affecting large-scale properties and, importantly, concentrating incompatible elements. As suggested by phase equilibria constraints, the thermodynamic stability of partial melts in the deep upper mantle critically depends on the presence and speciation of C-O-H-S-Cl-F volatiles. Volatile speciation is closely related to the redox state of the surrounding mantle rocks. It, however, remains unclear whether melt – rock exchanges or solid state mineral reactions can buffer the redox state at depth. The prevailing process may depend on the geodynamic setting since the latter can, for example, trigger fluxing in an open system or impose decompression-induced reactions in a closed system. In this session, we will discuss the complex interplays between redox state, volatiles (contents, compositions, speciations) and the P-T conditions of melting in the deep upper mantle. Whether melting is locally restricted or rather widespread in the convecting upper mantle has profound geodynamic implications. We invite petrological and geochemical studies on deep-seated magmatic rocks (continental and oceanic), as well as experimental and numerical simulations of melting processes generating these magmas. Integrations with geophysical datasets and discussions on the secular evolution of the volatile cycling and redox state of the Earth’s mantle are also welcome.

17e: Sulfur: Trace but Mighty in Redox, Degassing, Magmatic Processes, and Mineralization
Convenors: Rita Economos, Marc-Antoine Longpré, Marie Edmonds, Roberto Moretti
Keynote: Jim Mungall (University of Toronto)

The last 5 years have seen significant advances in understanding of the behavior of sulfur as a trace element in magmatic systems at the macro- and micro-scales. First-order models and thought-provoking results inform sulfur cycling in systems as large as magmatic arcs and on timescales of mantle recycling. These systems are being approached from mass-balance and novel isotopic perspectives. The complex relationship between sulfur and redox is being explored empirically at the global level and in experimental and equilibrium modeling environments. In addition, sulfur solubility in silicate melts and the saturation behavior of sulfur-bearing phases are enlightened by the application of micro-XANES analyses to experimental and natural samples. This session will bring together researchers working on sulfur and its role in global and local redox, degassing, magmatic processes, and mineralization.

18a: The Mineral Record of Crustal Evolution
Convenors: Craig Storey, Gerdes Axel
Keynote: Bob Hazen (Deep Carbon Observatory)

Earth’s continental crust is long-lived, with the precise details of the very earliest crust, in terms of timing and composition, still under debate. Its longevity means that we can potentially sample in tact records of Earth’s evolution throughout nearly all of its history. However, the whole rock record is incomplete and, particularly in ancient samples, prone to overprinting by metamorphism and alteration. A way to circumvent this problem is by the use of robust minerals that can withstand some of these processes and can also be preserved as detritus in younger sedimentary belts. This offers a potential way of avoiding the bias of the exposed rock record. However, we need to be able to use geochemical and isotopic tools in order to unlock the potential of such minerals. Zircon is the most common mineral used in such studies and it can be dated by U-Pb and souced by Hf and O isotopes. However, recent work has demonstrated the promise of rutile, apatite and also titanite. Minerals such as monazite, xenotime, allanite and baddeleyite may also be of great utility and here we invite contributions on the use of such accessory minerals in the understanding of the evolution of Earth’s continental crust.

18b: Earth's Early Crust and the Evolution of Plate Tectonic Processes
Convenors: Bennett Vickie, Hoffmann Elis, Martin van Kranendonk
Keynote: Blair Schoene (Princeton)

The timing and the processes behind the formation of Earth’s stable continental crust from the Hadean through the Archean remain enigmatic. To what degree did mantle melting and/or plate tectonic processes contribute to early crust formation? Changing tectonic styles throughout the first two billion years of Earth history resulted in different types of crust, and in mantle and crustal differentiation, culminating in a modern style plate tectonic regime by at least the end of the Archean. However, questions of when and how plate tectonics started, how convergent margin processes have evolved and how interactions among Earth’s major chemical reservoirs responded to these changes are currently hotly debated. For this session we invite contributions from a broad range of disciplines including geochemistry, geochronology, geodynamic modeling, metamorphic petrology, field geology and studies that use modern analogues to address these topics.

18c: Making Intermediate Magmas: From the Archean to the Present
Convenors: Kristoffer Szilas, Peter Kelemen
Keynote: Oliver Jagoutz (MIT)

Intermediate magmatic rocks, particularly “calc-alkaline” andesites, dacites and plutonic rocks, closely resemble the composition of continental crust. They are complex and can form by many different processes including: fractional crystallization, magma mixing, mantle assimilation, crustal assimilation, and – for the crust - mechanical juxtaposition of mafic and felsic rocks. Although intermediate magmas can potentially form in any tectonic setting, they are usually found in subduction-related volcanic arcs. Indeed, calc-alkaline andesites and dacites are found almost exclusively in arcs, leading to the hypothesis that the formation of continental crust occurs in the subduction zone environment. In any case, the petrogenesis of intermediate magmatic rocks may help shed light on the details of the processes that led to the formation of the continents. We invite contributions to this session that concern intermediate magmas in the broadest sense, including presentation of field-based studies, geochemical analyses, thermodynamic modeling, or experimental work, that can lead to new insights on formation of intermediate magmas throughout Earth history.

18dCrustal Recycling: Subduction, Delamination and Other Processes
Convenors: Catherine Chauvel, Mihai Ducea, Kaj Hoernle
Keynote: Julie Prytulak (Imperial College) 

We have known for decades that continental material is recycled through subduction zones and in the past have primarily focused on recycling of subducted sediments. Increasingly the importance of continental crustal recycling through delamination/detachment and subduction erosion are being recognized as important processes affecting both the long-term evolution of continental crust and the mantle. The relative importance of these processes remains poorly constrained and the object of major debate in the scientific community. This session welcomes contributions that use petrological, geochemical and/or geophysical data to address fundamental questions concerning these processes, including large-scale questions such as: How important are these processes in creating and recycling continental crust? How much crustal material has been and is presently being recycled? Where are the key locations and what are the fundamental processes involved? How different is the composition of the recycled material from that of the average crust? Have the processes and scale of recycling changed through Earth history? How can we better constrain these recycling processes and the amounts of recycled material?

19b: From the Slab, Through the Mantle Wedge: Processes and Transformations at the Sub-Arc and Beyond
Convenors: Craig Manning, Tatsuhiko Kawamoto
Keynote: Dimitri Sverjensky (Johns Hopkins University)

The subducting slab-mantle wedge system is one of Earth's most important regions of chemical reaction and change. Fluids, melts, and rocks derived from subducting lithosphere interact with depleted mantle in a region of profound chemical and physical gradients. These interactions produce arc magmas and continental crust, mediate planetary-scale volatile cycling, and yield modified subducted lithosphere and mantle-wedge which possess chemical signals that may persist in the deep Earth for billions of years. We welcome all contributions on the processes and transformations from the sub-arc slab-mantle wedge region and beyond, through geologic time.

19d: Arc Volcanism: Petrogenesis, Ascent Dynamics, and Eruption Style Controls
Convenors: Georg Zellmer, Victoria Smith
Keynote: Marie Edmonds (University of Cambridge)

Arc volcanism is characterized by an extreme range of eruption products, from small mafic lava flows to widespread felsic tephra deposits. What are the parameters that control this variety in magma composition, eruption style, and scale? We invite contributions that address any or all of these topics, using analytical, experimental, and/or computational approaches. We particularly welcome studies that put constraints on the role of volatiles; the timescales of magma evolution, ascent, and potential storage; and how subvolcanic processes lead up to volcanic eruption.

20f: Mantle-Derived Intraplate Magmas, their Xenolith and Diamond Cargo: Processes, Timescales, and Geodynamic Implications
Convenors: Sebastian Tappe, Brendan Hanger, Tyrone Rooney, Andrea Giuliani, Alex McCoy-West, Greg Yaxley
Keynote: Matthew Jackson (University of California, Santa Barbara)

Mantle melting that occurs away from subduction zones and mid-oceanic ridges are important though often overlooked processes by which both oceanic and continental lithosphere can grow and stabilize, or even weaken. In contrast to other tectonic settings, the intraplate environment produces an enormous range of primitive magma types (e.g., alkaline basalts, ferropicrites, kimberlites, carbonatites) with diverse isotopic compositions. The compositional diversity is commonly explained by variable thickness and enrichment style/history of the affected lithospheric plates. However, whether the lithospheric mantle is actively involved in melt generation and to what extent, remains a controversial subject. It also remains poorly understood whether some intraplate magmatic provinces are sourced from deep-rooted thermochemical plumes or simply derived from convecting upper mantle materials by decompression melting. Equally, differences in COH-volatile speciation, as a function of mantle oxidation state, may have profound effects on melting and phase relations in both peridotitic and eclogitic sources.

We welcome contributions based on observation, experimentation, and modeling that: (1) investigate the generation and evolution of primitive magmas in intraplate settings, (2) study the processes and products associated with melt/fluid-facilitated overprinting of mantle lithosphere, such as cryptic and modal metasomatism, including megacryst and diamond formation, (3) examine plume-lithosphere interactions, and (4) study the potential links between volatile mobility and fluid speciation in Earth’s mantle and processes that lead to lithosphere destruction and continental break-up. We particularly invite research that exploits modern analytical tools at the micro-scale or smaller to address large-scale phenomena observed within intraplate magmatic provinces, their plumbing systems, and xenolith/diamond cargo.

21c: Geochemistry of Earth's Core
Convenors: Yingwei Fei, Kenji Ohta
Keynote: Jackie Li (University of Michigan)

The chemistry of Earth’s predominantly iron core determines the deviations for the melting temperature and other physical properties from those of pure iron. The light element partitioning between the liquid outer core and solid inner core drives the core convection. Recent advances in high-pressure techniques and analytical tools have provided new capabilities of determining the effect of chemical composition on physical properties of core materials, element partitioning under extreme conditions, and isotope fractionation during core formation, leading to a better understanding of the composition of the Earth’s core. This session invites contributions from experimental and theoretical studies that may provide constraints on the composition of the core.

21d: Volatile Cycles and Volatile-Rich Magmas in the Deep Earth
Convenors: Jaime Barnes, Adrian Jones, Sujoy Mukhopadhyay, Mark Kendrick, Andrei Shiryaev, Max Wilke
Keynote: Bernard Marty (CNRS Nancy)

Earth´s atmosphere and oceans likely formed by impact degassing during accretion followed by degassing of the mantle. In recent years, it has been increasingly recognized that extensive recycling of volatiles into the mantle also occurs, and that the mantle is still an important reservoir of volatiles today. However, the efficiency of recycling and degassing is poorly constrained; estimates of the present deep Earth volatile budget vary widely and the evolution of global volatile cycles with geologic time is poorly understood. The significance of various types of magmatism — silicate vs. carbonatite, plate boundary vs. intraplate, etc. — is debated. The possible role of the core in storing volatiles is hardly constrained. This session therefore invites contributions from experimental, observational, and modeling studies that may shed light on the deep cycles of hydrogen, carbon, nitrogen, noble gases, halogens and sulfur. We particularly encourage studies linking the behaviour of multiple volatile elements or their isotopes. Studies investigating the phase equilibria of volatile-bearing mantle assemblages and mantle-derived magmas and the effect of volatiles on the physical properties — viscosity, density, seismic velocity, conductivity, permeability, etc. — of the mantle and of melts are also welcome.

21f: Chemical Geodynamics Through Time
Convenors: Matthew Jackson, Peter van Keken
Keynote: Janne Blichert-Toft (ENS Lyon, France)

The Earth’s mantle is the largest reservoir in the Earth and it preserves an integrated record of the long-term geochemical and geodynamic evolution of the planet. Geochemical differentiation of the planet, from accretion to the present day, has modified the chemical composition of the Earth’s interior: subduction zone processes, continental crust extraction and injection of oceanic plates and sediments continuously change the mantle’s make-up. Mixing of chemical heterogeneity and the apparent long-term preservation of early Earth events require a fundamental understanding of the dynamic properties of the Earth and how these have changed over time. Geochemists are gaining new and more detailed insights into the geochemical make-up of the mantle and the early-Earth events, and subsequent geochemical processes that helped shape the current composition of the Earth, but geodynamics places fundamental constraints on possible models for the evolutionary path of the mantle. We encourage both geophysicists and geochemists to contribute to this session to build a dynamical understanding of the geochemistry of the mantle.

22a: The Record and Influence of Impacts and Volcanism on the Early Earth
Convenors: Alexandra Krull Davatzes, Fabrice Gaillard, Steven Goderis
Keynote: Kevin Zahnle (NASA Ames Research Center)

Surface conditions on the early Earth were influenced by external delivery of material through meteor impacts as well as emissions from the interior via volcanic activity. Both of these processes cause significant and sudden environmental disturbances to the atmosphere, hydrosphere, and to life. Recent work has begun to re-evaluate the impact flux to the early Earth: was there a Late Heavy Bombardment, a continual and rapid decline of impact rate in the Hadean, or a continual delivery of large bolides to the surface throughout the Precambrian? How have impacts throughout the Archean and Proterozoic created transient or permanent shifts in climate or biology? Was the Archean Earth continuously producing large igneous provinces or was subduction and the associated volcanic activities already operating? What is seen in the geological record that would allow us to better understand the evolution of the nature, style and impact of volcanism on early Earth? And finally how does the hydrothermal or surficial alteration of volcanic rocks produce biologically favorable or adverse conditions? We invite contributions using observations from the geological record, experimental data, and models that explore the rate(s) and effects of these events to the earliest history of our planet. This session also includes observations and models from the Moon, Mars, and asteroids/meteorites that inform our models for early Earth’s evolution.

22b: The Co-evolution of Microbial Life and Environments in the Precambrian
Convenor: Jochen Brocks
Keynote: Shuhei Ono (MIT)

Geological processes have driven the evolution and expansion of new metabolic processes throughout the Precambrian, and microorganisms in turn have helped shaping Earth’s surface environments. This session invites contributions that investigate the co-evolution of environments and microbial life in the Precambrian, from the mid-Archean to the Neoproterozoic-Cambrian boundary. In particular, we invite contributions that investigate (a) the interplay between redox conditions, nutrient levels and biology, (b) causes and consequences of major glaciations, disturbances of the carbon cycle and evolutionary innovations, and (c) connections between the emergence of complex cells and multicellularity and changing modes of carbon burial and preservation.

22d: Mantle Thermal Peaks, Crustal Growth and the Inception of Plate Tectonics
Convenors: Tracy Rushmer, Nicolas Coltice, van Kranendonk Martin, Johnson Tim
Keynote: Nick Arndt (University Joseph Fourier - Grenoble 1)

This session addresses the interplay between mantle thermal peaks, early crustal growth and the beginning of plate tectonics. The early Earth is an active area of debate and research as we have little direct information and many fundamental problems remain. Questions to be addressed in this session include: What is the nature of mantle partial melting early in Earth’s history? What is the rate(s) at which the crust grew? What are the volumes of crust present during Hadean and Archean? What is the role of plate tectonics in generating Earth’s earliest crust? What are the links between thermal peaks and crustal growth and plate tectonics? This session invites contributions that address these major processes and events through new field observations, isotopic geochemistry, geodynamic modeling, computational and experimental approaches

25b: Element Speciation and Thermodynamic Properties of Aqueous Fluids and Melts
Convenors: Sandro Jahn, Terry Seward
Keynote: Carmen Sanchez-Valle (University of Münster)

Aqueous fluids and melts play an important role in many geological processes of the Earth’s crust and mantle. Fluid-rock interactions are driven by thermodynamics, which in turn is determined by the molecular structure and chemical bonds. Recent developments in analytical and computational methods have allowed in situ investigations of the structure, electronic and vibrational properties of fluids and melts in a wide range of temperatures, pressures and compositions. For this session, we invite contributions from experimental and computational studies of the molecular structure of aqueous fluids and melts, from species-related thermodynamic modeling and their application to natural systems.

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