Goldschmidt 2017: Sessions of Special Interest to DCO

The 27th Goldschmidt Conference will take place at Le Palais des Congrès de Paris, Paris, France, from 13-18 August 2017. 

The 27th Goldschmidt Conference will take place at Le Palais des Congrès de Paris, Paris, France, from 13-18 August 2017. The full program of the meeting is available here.

Please contact the DCO Engagement Team to add additional talks or sessions to this page. 

 

ABSTRACT SUBMISSION DEADLINE: 1 APRIL 2017 (WEBSITE)

 

Workshops

6th International Clumped Isotope Workshop 2017

The 6th International Clumped Isotopes Workshop will be held in the Institut de Physique du Globe de Paris (IPGP) right before the 2017 Goldschmidt conference, from Thursday, 10 August to Saturday, 12 August 2017.

Registration deadline: 15 April 2017

 

Sessions

Theme 01: Early Solar System

01c: The Origin and Early Evolution of Volatile Elements in Planets and Meteorites

Convenors: Guillaume Avice, Ko Hashizume

Keynote: Bernard Marty (CRPG - Universite de Lorraine)

For decades, geochemists have tempted to establish the genetic link between volatile elements in terrestrial planets and satellites and those contained in meteorites, the remnant of the time of solar system formation. Here we consider volatile elements in a large sense. It includes H, C, N, halogens noble gases but also moderately volatile elements such as K, Cu, Zn, S etc... Even if a broad picture is emerging major key points need clarification, for example: How did some volatile-rich extraterrestrial bodies acquire their volatile elements? What was the exact delivery mix of these elements to terrestrial planets? Why are the elemental budget and isotopic compositions of volatile elements so different from one terrestrial planet to another? How do these elements play a role in the distribution of other chemical elements in the Earth's system? What was the early evolution of volatile elements on Earth and its consequences for the development of life? The development of new analytical techniques and models, the discovery of unique and pristine terrestrial and extraterrestrial samples as well as successful international space programs are now bringing us data, interpretation and ideas that permit us to keep answering these essential questions. The aim of this session is to present recent advances covering these topics.

Theme 02: Making of Planets

02d: Origin, Evolution and Budget of Volatiles in the Terrestrial Planets

Convenors: Evelyn Füri, Alberto Saal

Keynote: Alex Halliday (University of Oxford)

Volatile elements have a key influence on the evolution of planetary bodies as they control mantle dynamics and large-scale geochemical differentiation, magma evolution and eruptive dynamics, the development of planetary atmospheres, and the maintenance of equable climates and planetary habitability. However, the abundance and origin of volatile elements in the inner Solar System remains a subject of debate and controversy. Did the growing planets trap nebular gas during the earliest stages of accretion? To what extent did 'wet' bodies from increasing heliocentric distances contribute to the volatile budget of the terrestrial planets? What was the role of the 'late veneer', 'late accretion', or 'late heavy bombardment'? What was the nature (meteoritic vs. cometary) of the accreted volatile-rich impactors? How did magmatic degassing affect the volatile contents of erupted magmas, and, therefore, the estimated volatiles budget in the interior of the terrestrial planets? The purpose of this session is to bring together scientists from different fields to present new data and models that will improve our understanding of the origin, evolution and budget of highly and moderately volatile elements in the interior, as well as at the surfaces (regolith, cold traps, atmosphere), of the terrestrial planets. We welcome contributions from all areas of planetary sciences, including, but not limited to, analytical geochemistry, experimental petrology, numerical modeling, and remote observations. Submissions from early career scientists and underrepresented groups are strongly encouraged.

Theme 03: Early Earth

03c: Hadean Astrobiology: Early Habitability and Relationships to the Oceans, Atmospheres, and Life that Followed

Convenors: Timothy Lyons, Edward Young

The past two decades have witnessed remarkable advances in our understanding of Earth’s first ca. 500 million years, including claims of liquid oceans; the emergence of crust, continents, and incipient plate tectonics; a possible magnetic field; and even life. These pictures of very early habitability on Earth are coloring our views of the earliest evolution of life. Of equal excitement are recent challenges to traditional views on the magnitude and temporal patterns of the late heavy bombardment. Even the existence of the lunar cataclysm has been called into question. The likelihood of life-sterilizing impacts are being reevaluated, leaving open the possibly that early life and the conditions that favored it may have persisted across the Hadean/Archean transition. If true, this continuity may have set the stage for the oceans, atmosphere, and life of the Archean—thus helping to explain suggestions of advanced metabolisms as early as 3.7 to 3.8 billion years ago. The focus of this session is Hadean and earliest Archean habitability as a cradle to the earliest life and as a prelude to the biosphere that followed. Topics of interest include earliest crustal evolution, continents, and tectonics; the latest on the LHB; updated hydrosphere arguments; models for the earliest oceans and atmosphere; greenhouse gas scenarios; the earliest signs of life; and the early magnetic field. The overarching goal is to bring together a rigorous set of presentations pitched around evidence for—and controls on—our earliest biosphere and possible utility for life exploration beyond Earth and our solar system.

03d: The Archean Volatile Cycle: Constructing a Modern Earth

Convenors: Oliver Warr, Michael Broadley

The Archean Eon represents a great transitionary period in the Earth’s history during which key processes such as mantle differentiation, subduction and crustal formation all shaped the modern Earth. These processes set in motion the Earth’s volatile cycle, partitioning volatile species such as the noble gases, halogens, carbon, water and nitrogen between major geochemical reservoirs throughout the Earth. This time period was pivotal for the formation of the Earth’s oceans, atmosphere and climate system, creating and supporting an environment favourable for the emergence and diversification of life. By tracing the migration of volatiles between these reservoirs we can elucidate the origin of the Earth’s volatiles, the formation age of the Earth’s major geochemical reservoirs, how these reservoirs have evolved / interacted through time and whether any have remained isolated throughout geological history. The application of volatile-based studies to ancient reservoirs is key to constraining physical, biological and geochemical processes which have occurred throughout Earth’s history. This session welcomes contributions which address these issues using analytical, experimental and theoretical studies of volatiles within ancient Earth reservoirs, particularly those which include innovative and cross disciplinary applications to document the evolution of the early Earth and all applicable reservoirs.

Theme 04: Earth's Mantle and Core

04b: Sulphur and Chalcophile Element Behavior in Magmatic Processes

Convenors: Kate Kiseeva, Bernard Wood

According to the Goldschmidt classification 18 metals and nonmetals (S, Cu, Zn, Ga, Ge, As, Se, Ag, Cd, In, Sn, Sb, Te, Hg, Tl, Pb, Bi,Po) have profound affinities for sulphur and sulphides. Therefore, although sulphides are generally of low abundance in igneous rocks, the geochemical behavior of many economically important elements and other nominally siderophile elements (PGE for example) is generally considered to be intimately related to the abundance of sulphur in the system of interest. Recent improvements in the spatial resolution of analytical instruments (LA-ICPMS, for example) have revealed that many of these elements dissolve to high concentrations in silicate minerals in addition to sulphides. Therefore the behavior of nominally chalcophile elements at high temperatures is subject to revision and may be, in many cases more complex than previously believed. The aim of this session is the presentation of new analytical data and experimental results on (nominally) chalcophile element behavior in high temperature systems and to address the distributions of sulphur and chalcophile elements between mantle core and crust.

04d: Thermodynamics and Diffusion Kinetics within the Core and Mantle: A Session in Honor of Jibamitra Ganguly and Surendra Saxena

Convenors: Elias Bloch, Yingwei Fei

Keynote: Bernard Wood (University of Oxford)

Processes occurring deep within the Earth have fascinated both Jibamitra Ganguly and Surendra Saxena since beginning their careers as petrologists nearly half a century ago. Although experimental work has been a benchmark of Jibamitra and Surendra’s work, they have always recognized the importance of integrating experimental studies with data from geological materials, as well as with geophysical and geodynamic models and observations. This session is intended to highlight recent advances in our understanding of processes occurring in the mantle and core, primarily through the lens of thermodynamics and diffusion kinetics; however, both Jibamitra and Surendra have made contributions to a wide range of topics in Earth and Planetary Science, and we welcome submissions focused on meteorites and the Earth’s crust, as well as advances in multicomponent diffusion, geothermobarometry and thermochronology. We particularly encourage studies that utilize a combination of experimental or kinetic data with geochemical data from natural samples or geophysical observations.

04h: Deep Carbon

Convenors: Jung-Fu Lin, Craig Manning, Hélène BUREAU, Daniele Pinti

Keynote: Pierre Cartigny (IPGP France)

Carbon is one of the most abundant elements in the universe that can exist in many forms in the deep Earth and other planetary interiors. Its existence in fluids, as a volatile in magmas, in subducting slabs and the mantle, and as a candidate light element in Earth’s core influence the physics and chemistry of planetary interiors. The storage and cycling of deep carbon in Earth and other planetary bodies depend on the structure and stability of carbon-bearing minerals and melts at high pressure and temperature. Recent advances are providing new insights into novel physics and chemistry of native carbon phases, carbonate minerals, ices, clathrates, carbides, and phases containing trace carbon. As exceptional deep carbon minerals, diamonds provide key information about carbon in Earth’s interior: their study helps to trace fluids/melts, to determine their evolution deep inside the planet, and their origin. Together with their inclusions they provide key information about the deep carbon cycle over geological time, but also about the mineralogy of deep reservoirs. The significance of their stable isotopes signature and the significance of their inclusions are crucial questions to answer in order to understand the origin and on the cycling of carbon throughout the Earth. We welcome all petrological, mineralogical, geochemical, experimental, and theoretical contributions on carbon-bearing phases at extreme environments.

04i: Reactions in Earth's Carbon Cycle from the Surface to the Center

Convenors: Jie Li, Simon Redfern, Peter Szatmari

Carbon is continually transported from the mantle to the surface by volcanism as well as along deep crustal faults; it is returned to the sub-lithospheric mantle by subduction. Massive eruptions carrying CO2 increase chemical weathering and carbonate deposition by biogenic and abiogenic processes. Increased CO2 flux into the shallow lithosphere shifts serpentinization to producing hydrocarbons creating favorable conditions for the origin of life on Earth and potentially other bodies of the solar system. What are the key reactions that govern the transformation and movement of carbon in Earth? And what criteria should be used to select as crucial a handful of abiotic and biotic reactions out of myriad chemical processes involving carbon in different host phases, variable valence states, under a wide range of pressure and temperature conditions, and over a vast span of spatial and temporal scales? How can these key reactions be used to advance our understanding of the quantities, movements, forms, and origins of Earth’s carbon? We welcome here 1) new geological, geochemical and geophysical observations on and below the Earth’s surface, particularly in sedimentary basins adjacent to large igneous provinces and kimberlite pipes; 2) experimental and theoretical investigations of chemical reactions that influence the Earth's deep carbon cycle; and 3) integrative and synthesis studies that weave existing disparate discoveries into a coherent structure and offer new insights into the role of carbon in Earth's dynamics and evolution.

Theme 05: Crust to Mantle - Mantle to Crust

05a: MORB Petrogenesis: From Mantle Partial Melting to Fractional Crystallization

Convenors: Marine Paquet, Daniele Brunelli

Keynote: Yan Liang (Brown University)

Mid-Ocean Ridge Basalts are the most abundant lavas on Earth, and are the derived products of melts from mantle partial melting. There is growing body of evidence for heterogeneous sources contributing to MORB chemical composition and driving the degree and depth of partial melting along with mantle Tp and spreading rate. Primary melts experience then mixing and aggregation, melt/rock interactions from the melting region to lithospheric mantle and crust, and progressive fractional crystallization. Understanding the energy and chemical constraints on these processes is key to reconstruct age, composition and lithological heterogeneity of the Earth’s upper mantle. This session is intended to gather contributions that address all aspects of MORB petrogenesis. Submission of studies, including geochemistry and petrology, thermodynamic and chemical modelling, and integrated field observations and geophysics are encouraged.

05b: New Advances in Active Subduction Zones

Convenors: Julia Ribeiro, Yoshi Tamura, Catherine Chauvel, Serge Lallemand

Keynote: Ozamu Ishizuka (JAMSTEC)

Active subduction zones are natural laboratories to further investigate subduction processes, and they have been the renewed locus of intense dredging and drilling, and geochemical and geophysical research over the past few years. To one step forward, here we seek to further explore subduction processes, which include the deep element cycle, the origin and the pathways of slab fluids, the redox state of the mantle, petrogenesis of subduction zone magmas, slab melting, and the thermal state of the slab. This session seeks to integrate petrographic observations, geochemistry, geophysics and numerical modelling to advance our current knowledge about subduction zones. We also welcome new studies about recent marine expeditions.

05d: The Geochemistry of Hotspots and Intraplate Magmas: Mantle Sources, Metasomatism, Magmatic Processes and Xenolith Cargoes

Convenors: Andrea Giuliani, Matthew Jackson

Keynote: Sonja Aulbach (Geothe University, Frankfurt)

Understanding the composition of the Earth’s interior away from convergent margins is fundamental to constrain the long-term lithosphere recycling as well as the survival of early-formed reservoirs in the modern mantle. Tracing the composition of the deep Earth, including the recycling of surface components, requires investigation of mantle-derived magmas and the xenoliths they entrain during ascent. Partial melting processes in intraplate settings generate a variety of magma compositions, which testifies to the heterogeneous nature of the Earth’s mantle and the complex processes affecting magmas during ascent and emplacement (melt differentiation, mixing, assimilation, degassing, etc). Therefore, the volcanic products observed at the surface commonly require complex – and often model-dependant – deconvolution of the contributions from these processes, to unravel the source signature. This session invites contributions that explore the geochemistry and petrology of hotspot lavas and mantle xenoliths at both oceanic and continental settings. We welcome studies which aim at providing insights into the lithological and geochemical (including stable and radiogenic isotope) composition of mantle sources that are sampled by, and the processes that operate on, intraplate volcanics. We particularly invite research that explores the geochemistry of bulk lavas, melt inclusions, single phases or xenoliths from intraplate volcanic settings including ocean island basalts (OIBs), petit spots, monogenetic basaltic fields, kimberlites and related rocks.

05e: Lithosphere Evolution during Subduction and Collision

Convenors: Yildirim Dilek, Jing-Sui Yang, Suzanne O'Reilly, Georges Ceuleneer

Keynote: Cin-Ty Lee (Rice University)

The compositions and fabrics of crustal and mantle rocks record the history of large-scale tectonic and magmatic events that have shaped Earth’s evolution. We aim to bring together perspectives from mineralogy, petrology, geochemistry, microstructure analysis, geophysics, and numerical modelling to: • constrain the mantle source and generation of oceanic lithosphere • track changes in mantle processes, composition, and heterogeneities through time • probe the nature of subduction, ancient to recent • examine the role of subduction and collision in lithospheric evolution and in shaping Earth’s crust • reveal the structure and geophysical properties of domains in collision zones • understand the range of implications from these topics, including those on the global Carbon cycle, mantle convection models, timescales of recycling processes, and the role and nature of fluid phases and melt-rock interactions throughout the mantle. Observations from exposed ophiolites and mantle terranes, from mantle xenoliths, and samples from active settings (e.g., from IODP drilling), provide many constraints. Recent analysis of ophiolites supports multiple episodes of melt extraction and migration in their genesis, and two-way deep recycling of crustal and mantle material during the formation of oceanic lithosphere. Studies of exposed mantle terranes probe ancient and modern subduction zones, shedding light on mantle fluid pathways, mantle modification due to magmatism, scale and distribution of mantle heterogeneities, and deep deformation styles. We encourage the synergistic use of the such observations with geophysical and geodynamical data, including contrasts in seismic velocity, attenuation, and anisotropy, magnetotelluric responses to water and melts, and dynamic modelling.

05g: Evolution, Distribution and Recycling of Volatiles in the Mantle of Earth and Other Planetary Bodies

Convenors: Kristina Walowski, Rosie Jones, David Hilton, Yuji Sano, Sami Mikhail, Davide Novella

Keynote: Vincenzo Stagno (Sapienza University of Rome, Italy)

Volatile elements are typically enriched in the atmospheres of terrestrial planets. However, recent advances demonstrate that volatile elements (e.g., H, C, N, S, halogens, noble gases) may be residing in the mantle to a significant degree, and that they impact a number of petrological and geophysical processes in the mantle in a way that is disproportionate to their abundance. Volatiles can induce distinct effects on mineral phase transitions, melting temperatures, oxidation states, trace element mobility, isotope fractionation, mechanical properties, and conductivity; processes which have a combined impact on global scale phenomenon, from mantle convection to plate tectonics. In addition, minor volatile species, such as the noble gases and their isotopes, provide vital geochemical tracers of these processes, with the potential to reveal causes of compositional heterogeneity within the mantle and the structure of the deep Earth. Critical questions to be addressed include, for example, the origin and characteristics of the volatile inventory of the terrestrial planets (including Earth), the solid Earth volatile degassing/regassing balance through time, and rates and mechanisms of volatile exchange between different terrestrial reservoirs. This session welcomes contributions on geochemical, geophysical, astronomical, petrological, mineralogical, experimental, and modeling investigations that aim to understand the role, distribution and geochemical evolution of volatiles in the terrestrial mantle and in other planetary bodies.

Theme 08: Nano to Microscale Processes in Geochemistry

08i: Geochemical Processes in Confined Media

Convenors: Diane REBISCOUL, David Cole, Dag Kristian Dysthe, Nicholas M Harrison, Alejandro FERNANDEZ-MARTINEZ

Keynote: Rosa Maria Espinosa-Marzal (University of Illinois)

Geochemical processes in pore networks down to the nanoscale control geofluid accumulation, transport and extraction, which is of great interest to various fields such as reservoir engineering, environmental sciences, and nuclear waste management. Processes such as sorption, precipitation, dissolution or diffusion occurring in nanoconfinement differ significantly from that of bulk materials. Nanoporosity impacts permeability and reactivity, and plays major roles in many geological systems including clay minerals and clay rocks, nanoporous mineral phases and alteration layers. However, the determination of thermodynamic and kinetic properties in these systems still poses significant technical and intellectual challenges. Predictive modelling of, for instance, dissolution kinetics or phase transformations requires a multi-length and multi-time scale approach. Quantum mechanical descriptions of water-surface interactions, the mesoscale structuring of the water and the macroscale mass transport within the material must be coupled from time scales reaching from a femtosecond to a second. This is essential as parameterising kinetic equations using information from measurements on dilute media fails to capture the influence of the nanoconfinement which include the altered dynamics of the structured water and the influence of modified solvation equilibria for ions which adsorb to pore surfaces and set up strong electrostatic fields. This session will be focused on the recent advances in the experimental characterization and multiscale modelling studies of processes that determine the geochemical and thermophysical properties of confined solutions. Studies addressing geochemical processes such as sorption, precipitation and dissolution occurring in confined media are welcome.

Theme 10: Chemistry of Ocean (Past Present and Future)

10d: Seafloor Hydrothermal Processes on Modern and Ancient Earth: Implications for Life, Elemental Budgets, and Oxidation States of the Lithosphere-Hydrosphere-Atmosphere System

Convenors: Benjamin Tutolo, Drew Syverson, Nicholas Pester

Keynote: Laurence Coogan (University of Victoria)

Seafloor hydrothermal systems have profoundly influenced the chemical composition and redox state of Earth’s lithosphere-hydrosphere-atmosphere system throughout Earth history. However, their very nature within the oceanic crust drastically limits the temporal extent of direct geologic observations of their existence. Thus, attempts to correlate seafloor hydrothermal processes with biological evolution, global elemental budgets, and global redox states throughout Earth history generally require multi-disciplinary projects that integrate studies of modern analogues, extrapolations of the geologic record, novel laboratory experiments, and numerical models of these systems. In this session, we intend to develop a forum for presenting and integrating these various sets of observations in order to focus the community’s efforts on answering key questions regarding chemical budgets and oxidation states on modern and ancient Earth. In particular, we invite contributions focusing on seafloor measurements of modern hydrothermal systems; studies of recovered oceanic drill core, obducted oceanic crust, or proxy records in ancient rocks; experimental exploration of seafloor (bio)geochemical interactions; and integrative numerical models that expand the spatiotemporal scales of these field and experimental observations. Specific focuses could include the role of igneous oceanic crust alteration processes in the geologic carbon cycle, the contribution of submarine volcanism to the oxidation state of the early Earth, changes in ocean chemistry associated with the relative balance of continental weathering and seafloor hydrothermal fluxes, and the relation between these factors and tempos and milestones of biological evolution.

10j: Bio-Geochemical Processes Across the Sediment-Water Interface: Key Tools, New Sites and Recent Advances

Convenors: William Homoky, Edouard Metzger, Kazumasa Oguri, Howard Scher, Eric Viollier, Mustafa Yucel

Keynote: Nils Risgaard-Petersen (Aarhus University)

Aquatic sediments are both a component and archive of climate and environmental change, with utility for production of energy and mineral resources, and a niche for a large microbial carbon reservoir with high turnover rates. In the wake of warming deep waters, acidifying oceans and deoxygenating seas or estuaries, the biogeochemical response of the sediment-water interface depends on competitive processes that can only be simplistically predicted at the moment. Improving our knowledge base on biogeochemistry of marine and freshwater sediments and proper transfer of this knowledge to numerical modeling efforts is required to accurately predict aquatic system response to environmental changes. This session aims to provide a multidisciplinary forum for the latest breakthroughs in sediment biogeochemistry. We invite contributions on benthic biogeochemical dynamics in oceans, coastal and inland waters. Advances using a broad range of approaches including process rate experiments, geochemical gradients and flux measurements, microsensor profiling and imaging techniques, major and trace elements isotopic compositions, shallow and deep microbiology, bioturbation and reactive transport modeling are all welcome. In particular we welcome any novel bio-geochemical insights from the water- and/or sediment-column that challenge traditional views about the sedimentary response to, impact on, or record of environmental change. 

Theme 14: Geobiology of the Past (Mass Extinction, Fossils, Origin of Life)

14h: Geobiology in the Time of Big Data

Convenors: Shaunna Morrison, Daniel Hummer

As the amount of data related to geobiology grows exponentially, it becomes increasingly important to find new ways to analyze and integrate diverse types of data to answer large-scale questions. We propose a session that examines these Big Data questions in the context of geobiology. Talks will address Earth’s surface oxidation state and formation, mineral ecology, metabolism evolution, the use of proteomics and mineral data to constrain electron receptors for early life, the interpretation and prediction of planetary composition, mineralogy, petrology through advanced data analytics; and investigation of aspects of the co-evolution of the geosphere and biosphere, delving into the origins of life, paleobiology, and evolution.

Theme 15: Geobiology of the Modern

15b: Hydrothermal Biogeochemistry and Geobiology

Convenors: Christopher German, Wolfgang Bach, Costantino Vetriani, Donato Giovannelli

Keynote: Ken Takai (JAMSTEC)

Hydrothermal systems are increasingly recognized to involve biological, particularly microbial, aspects to their geochemical cycles – whether in the case of subseafloor water-rock interactions or in terms of the fate of their export products released into the overlying water column. Both the depth of hydrothermal systems and their geologic setting can play an important role in the nature of the systems that arise and their impact on the oceans - up to and including the photic zone. In the limit, such systems can also provide new insights to the origins of life on Earth and the potential for life-hosting habitats on other Ocean Worlds. This session will seek to bring together researchers interested in sharing their newest findings from a wide range of seafloor hydrothermal settings, from understudied shallow hydrothermal vents and other previously under-represented settings - ranging from the ultra-slow spreading Arctic ridges to subduction-related venting in the SW Pacific and from intra-plate volcanic hotspots to tectonically controlled fracturing of the ocean crust. We welcome contributions on the biogeochemistry and geobiology of hydrothermal systems throughout Earth’s oceans, as well as comparative studies ranging from continental geothermal studies to putative submarine venting beyond Earth.

15h: Biogeochemistry in the Deep Ocean and Subsurface: Contributions of the Deep Biosphere to Earth Systems

Convenors: Fumio Inagaki, Kai-Uwe Hinrichs, Chuanlun Zhang, Brian Hedlund, Fengping Wang, Stefan Sievert, Karen Lloyd, Benedicte Menez

Keynote: Victoria Orphan (Caltech)

The deep ocean and subseafloor biosphere is vast and diverse, harboring many uncultured clades of microorganisms. Energy and nutrients are supplied primarily by transformations of biologically and/or abiotically produced organic matter and the redox chemistry of water-rock interactions. Recent technological breakthroughs in biogeochemistry, geomicrobiology and molecular biology, as well as in obtaining pristine samples from the hadal zone of the ocean and the deep-subsurface biosphere enable us to address essential questions about microbial community composition, biogeochemical contribution, and limits to microbial ecosystems in the deep ocean and subseafloor biosphere. In this session, we would like to highlight studies broadly focusing on the triangular relationship between microbiology, geochemistry, and geophysics in (but not limited to) diverse oceanic and subseafloor biosphere settings. Given the slow pace of deep life activity and the associated challenges for detecting biosignatures in the most extreme sections of the Earth's microbial ecosystems, we also encourage submissions addressing the exploration of biomarkers.

15i: Microbial Biomineralization: Mechanisms, Impacts and Applications

Convenors: Aude Picard, Julie Cosmidis, Maria Dittrich, Maria Romero Gonzalez, Estelle Couradeau, Irina Bundeleva

Microorganisms have been shaping the geochemical environments of the Earth for the past 3.8 Ga. Their ability to precipitate solid phases from aqueous species in a variety of environments has led to the deposition of mineral deposits of various sizes in the rock record and in modern environments. The breadth of this session encompasses the formation, geochemical impact, preservation and potential applications of all microbial biominerals. We therefore invite contributions from field, experimental and theoretical studies pinpointing the mechanisms of induced and controlled biomineralization by prokaryotic and unicellular eukaryotic organisms themselves as well as the role of the organic compounds they produce especially the extracellular polymeric substances (EPS). We highly encourage interdisciplinary studies addressing the impact of biominerals – carbonates, phosphates, silicates, sulfides and oxides – on biogeochemical cycles (e.g. Fe, Mn, Ca, P, S, Si, C), the interactions between minerals and cellular or extracellular organic compounds, the role of biominerals in the preservation of organic matter, and the potential industrial and bioremediation applications of biominerals.

Theme 17: Paleoclimate

17f: Constraints on Past Carbon Cycle Dynamics and pCO2

Convenors: David Naafs, Sarah Greene, Peter Barry, Sandra Kirtland Turner

Keynote: Heiko Pälike (University of Bremen)

The various components and feedbacks of the global carbon cycle play a fundamental role in regulating Earth’s climate system on many timescales. The geological record offers an ideal opportunity to test and expand our understanding of the key processes, feedbacks, and radiative forcing potential that exceed human timescales. Palaeoreconstructions often rely on empirical observation of the modern carbon cycle to provide constraints on the magnitude and make up of carbon reservoirs and fluxes. This session aims to bring together researchers using a wide range of techniques (observations, proxies and/or model simulations) to investigate past atmospheric carbon trajectories, controlling sources/sinks, feedbacks, and rates of change in the global carbon cycle. We also invite those researchers who measure modern carbon fluxes to understand records of the past (volcanologists, atmospheric geochemists, wetland ecologists, etc). Submissions interrogating the behavior of carbon reservoirs (e.g., atmosphere, aquatic, sedimentary, mantle, crust) during carbon cycle perturbations over a variety of timescales are encouraged.

Theme 19: Energy Resources for Society

19a: Hydrogen Generation, Mobility and Reactivity in the Earth’s Crust: From Mantle to Surface Degassing

Convenors: Laurent Truche, Michel Pichavant

Keynote: Frieder Klein (whoi)

Hydrogen (H2) is an important volatile component in the lithosphere, but it remains one of the most poorly quantified molecules on the Earth. To better understand the H2 behavior in the crust we need to better constrain its sources, flux and reactivity. The currently available measurements in natural samples (atmosphere; modern hydrothermal systems, gases in seismically active zones, boreholes, ore mines, fluid inclusions and gases absorbed by rocks) indicate that some geological fluids are very rich in H2. Hydrogen, despite its stability, is involved in a wide range a redox reactions and may affect the geochemical cycles of numerous multivalence elements. Microbial ecosystems can be sustained by H2 producing water-rock interaction in the Earth’s subsurface and at deep hydrothermal submarine vents. Natural hydrogen sources and hydrogen geological storage are also envisioned as key components of a low fossil fuel economy. This session welcome contribution on H2 producing fluid-rock interactions over a wide range of T-P (e.g. serpentinization, radiolysis, mechanoradical), rate and mechanisms of H2 induced redox reactions (e.g. abiotic hydrocarbon formation, subsurface microbial life), and physico-chemical process that may impact H2 mobility in the crust (e.g. sorption, diffusion, solubility and vapor-liquid equilibrium). The proposed session will bring together field measurements, laboratory experiments and computer simulations to build our understanding of the mechanisms and physico-chemical factors that control H2 behavior in the crust.

19c: Abiotic Production of Light Hydrocarbons from CO2: Geochemical Process and CO2 Valorization

Convenors: Isabelle Martinez, Thomas McCollom

Methane, carboxylic acids and other energetically interesting light hydrocarbons (HC’s) are observed in a variety of natural environments such as serpentinized ultramafic rocks, deep marine black and white hydrothermal smoker vents, alkaline igneous rock complexes and metamorphic rocks. They are often associated with CO2 - H2 aqueous fluids and have thus been tentatively interpreted as products of the abiotic CO2 reduction. Carbon oxide transformation into HC is actually achieved at the industrial scale using the Fischer-Tropsch process which refers to the catalytic reaction developed in industry to convert gaseous CO into CH4 in the presence of H2. The analogy between industrial and Fischer-Tropsch type (FTT) natural process raises many interesting scientific questions, e.g., liquid vs gaseous reaction medium, presence of mineral catalysts and CO2 reduction pathways. Answers to these questions may have, in turn, long-term implications for the Energy Transition through the definition of new CO2 valorization and HC’s synthesis routes. This session welcomes contributions on abiotic production of organic molecules during fluid-rock interactions. This session basically aims at exchanging results and ideas on the hydrogenation reactions of CO2 including the characterization of relevant natural systems (chemistry, isotopes, mineralogy), laboratory experiments and potential industrial perspectives regarding in particular the use of natural catalysts.

Theme 20: Geo-omics Meets Organic Geochemistry

20e: Mining Terrestrial Subsurface Life: New Insights in Old Strata

Convenors: Kelly Wrighton , Zarath Summers

The terrestrial biosphere is a relatively under-sampled ecosystem and represents a new opportunity for studying biodiversity and biogeochemical cycling. Diverse physiochemical conditions in subsurface habitats often require unique adaptations for life to persist, including mechanisms for tolerance of salinity, pressure, and limited light and organic carbon substrates. Understanding the biota present in the terrestrial biosphere and their interactions with each other and the environment is critical to subsurface resource management. This knowledge is necessary as humans increasingly exploit the subsurface through hydrocarbon, mining, and carbon dioxide sequestration activities. This session will highlight current geobiological investigations in natural and managed terrestrial subsurface environments. We intend to showcase the range of methodologies used to probe terrestrial subsurface organisms and their biogeochemistry, including but not limited to isotope geochemistry, lipid analysis, spectroscopy, as well as microbial diversity, cultivation, and genomics.

Theme 21: Innovation in Geochemical Methods

21g: Halogen Isotopes as Geochemical Tracers in Rocks, Sediments, Ground and Surface Waters on Earth and within the Solar System

Convenors: Hans Eggenkamp, Masaaki Musashi

Keynote: Max Coleman (NASA Jet Propulsion Lab, Caltech)

Isotopes of halogens, especially chlorine, have been paid attention to not only as geochemical tracers of fluid flow during subduction processes at continental margins but also as signatures in aquifers that are essential to the occurrence of the life anywhere in the universe. Due to the fact that halogens (Cl, Br, I) in solution are normally present as conservative ions they are commonly used as tracers in all kind of aqueous fluids, rain-, pore-, ground- and formation waters, lakes, rivers and oceans. Isotopes of the halogens, both stable (δ37Cl, δ81Br) and radiogenic (36Cl, 129I) add an important layer of extra information beyond just the concentration data. Stable isotopes can for example be used as tracers for processes such as fluid flow, mixing, diffusion, dissolution/evaporation, ion-exchange, ion filtration and organic/inorganic reactions. Stable chlorine isotopes have even be measured, in-situ, on Mars. Radiogenic isotopes are important tracers to determine the age of groundwater (36Cl, t½= 301000y) or as tracer of man-produced nuclear fission (129I, t½=15.7Ma). Still the number of laboratories working with these isotopes is relatively limited. The reason for this is not very clear but may be related to either time consuming analytical procedures of the still not well understood processes that are responsible for their isotope distribution and fractionation. This session aims at bringing together both stable isotope and radiogenic isotope scientists in order to discuss new and improved analytical methods, new experimental data that will improve our understanding of these isotope systems and measurements of natural samples that show the usability of halogen isotopes as tracers. Further we hope that this session will improve contacts between the stable and radiogenic halogen isotope communities in order to improve their mutual understanding and hopefully to develop collaborative research projects.

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