AGU Fall Meeting 2008

2008 AGU Fall Meeting
15–19 December 2008
San Francisco, California, USA
http://www.agu.org/meetings/fm08/

The Fall Meeting is expected to draw a crowd of over 15,000 geophysicists from around the world. The Fall Meeting provides an opportunity for researchers, teachers, students, and consultants to present and review the latest issues affecting the Earth, the planets, and their environments in space. This meeting will cover topics in all areas of Earth and space sciences.

Sessions of interest to InterRidge Members:
B11: Developing Integrated Models for Mid-ocean Ridge Processes at the Ridge 2000 East Pacific Rise Integrated Study Site
Conveners: Daniel J. Fornari, Maya Tolstoy
The East Pacific Rise at 8°-11°N is one of the best studied segments of the mid-ocean ridge (MOR) in the world, and has been a focus site (Integrated Study Site - ISS) of the Ridge 2000 (R2K) Program since 2001. In particular, monitoring and repeat visits to the hydrothermal vent sites in the 9° 46’-50’N area have led to a sophisticated temporal and spatial understanding of this area. It is the only known ridge site where a full volcanic cycle has been studied with eruptions occurring in 1991-2 and 2005-6. In additional to being volcanically active, there is well-documented temporal and spatial variability in fluid chemistry, biological community development, vent fluid temperature responses and patterns of microseismicity. As such it is an ideal site at which to study the linkages between different aspects of the MOR system, and specifically to understand causal processes associated with the input of energy from the mantle that drives the hydrothermal system and associated biological communities and microbial populations that are supported by it. With more than 15 years of multidisciplinary studies, and 5 years of focused R2K ISS studies at this site, integrated conceptual and numerical models that describe the processes operating at this fast spreading ridge are being developed. This session will focus on EPR ISS data integration and modeling efforts. Results from recent field data that will soon be available for integration are also welcome with an emphasis on how these data will be most useful in addressing the underlying processes critical to understanding the integrated MOR system.

B15: Life in the Deep Subsurface: A Decade of Peeking at the Unseen Majority
Conveners: Peter Girguis, Beth Orcutt, Mitchell Schulte
Ten years ago, back-of-the-envelope calculations suggested that an “unseen majority” of microbial life existed in the deep subsurface of terrestrial and marine environments, a hypothesis that has significant ramifications for our understanding of energy flow and elemental cycling on Earth. In this session, we aim to bring together researchers in geo- and biosciences to discuss what we have learned in the intervening decade about life in the deep biosphere. We hope to address the following topics: What is the extent and activity of life in the deep biosphere? Which microbes comprise the deep biosphere, and how do they acquire energy for life? What are the limits for life in the deep subsurface? How important is lithoautotrophy in this habitat? In the marine subsurface, what role does microbial life have in the exchange of elements between the ocean and the crust? We also hope to highlight recent technological advances that have allowed us to access the deep biosphere.

B32: Linking Geochemistry, Geology, and Microbiology in Hydrothermal Systems
Conveners: Cristina Takacs-Vesbach and W.C. Pat Shanks
Hydrothermal features require truly interdisciplinary research approaches to understand linkages among the geochemistry, geology, and microbiology of these unique systems. This session will host presentations that are focused on collaborative investigations of terrestrial and marine hydrothermal features around the world with the goal of understanding the factors that drive geochemistry and community composition. We are especially interested in studies that synthesize large, diverse datasets that relate ecologic, molecular, and geochemical data.

T05: Magmatic, Tectonic, and Hydrothermal Interactions at (Ultra-) Slow Spreading Mid-Ocean Ridges
Conveners: Eric Hellebrand, Johan Lissenberg, Javier Escartin, Gretchen Frueh-Green
Recent multidisciplinary studies on slow and ultraslow mid-ocean ridges have revealed a number of unpredicted but fundamental observations that are now gradually being integrated in crustal accretion models. These observations include scales of geochemical-petrological heterogeneities in the MORB mantle, mechanisms of (reactive) melt transport to and within the crust, varying conditions and degrees of hydrothermal alteration, the role of (deep) hydrothermal circulation on deformation styles and the importance of detachment faulting for crustal accretion and hydrothermal processes. The interaction between temporally and spatially variable melt supply on one side, and the seawater-enhanced conductive cooling on the other is extremely diverse. This is manifested by a large spectrum of morphotectonic seafloor features and ultimately produces a complex, non-layered oceanic crust that is geophysically challenging to image. This session aims at bringing together high- and low-temperature petrologists and geochemists, structural geologists and geophysicists to discuss recent findings that contribute to improving our understanding of crustal accretion, deformation and alteration at (ultra)slow-spreading mid-ocean ridges. We also welcome contributions from the fast-spreading ridge, ophiolite and passive margins communities that address similar or contrasting processes leading to heterogeneities in crustal architecture and alteration.

V07: Abyssal Mantle: Origin and Surface Exposure Processes of Ultramafic Rocks
Conveners: Akihisa Motoki and Susanna Sichel
This session will focus on (1) the origin and evolution of the abyssal mantle based on major elements, trace elements, and isotopes; (2) the processes by which abyssal mantle is exposed at amagmatic spreading ridges; and (3) the tectonic evolution of megamullions and associated processes of serpentinization.

V16: Oceanic Spreading Centers and Volcanic Rift Systems: Tracking Fluxes and the Interplay Between Processes from Mantle to Microbe
Conveners: Robert Dunn, Peter Girguis, and William Seyfried
Recent years have been a watershed for research on oceanic and onshore rift systems. Current studies are now providing the first data that characterize and quantify the relationship between mantle melting, geochemical circulation, and biological diversity and activity both within and upon the seafloor. It has become increasingly apparent that oceanic spreading centers and associated hydrothermal vent systems are deeply complex, comprising several interconnected mass, fluid, thermal, and biological exchanges as energy fluxes from the mantle, through the crust, and into the overlying oceans. Mantle melting and volcanism along the spreading axis greatly enhances chemical exchange between the crust and the overlying seawater, nourishing chemosynthetic biological communities. These communities provide keys for exploring the evolution of life on Earth, as they thrive in conditions that may have harbored the first organisms on Earth.
Furthermore, recent studies of onshore rift systems in areas such as Iceland and Afar provide new insights into the distribution of melts within a spreading rift and relations between magma supply and surface tectonics. Assessment of the similarities/differences in host rock chemistry and geothermally-supported ecosystems between onshore and mid-ocean rifts may provide new avenues to explore controls on diversity and survival mechanisms.
This interdisciplinary session aims to highlight recent results, to include a range of scientific approaches, and to explore the full scope of processes involved in rifting, hydrothermal venting, and development/evolution of geothermal biologic communities. We encourage submissions that cover all regions of the global mid-ocean ridge system and correlative subaerial rift systems. The goal is for session reports on magmatic, volcanic, hydrothermal/geochemical and microbiological processes to prompt discussion that can refine current models of rifting, volcanism, and hydrothermal systems.

V25: New Insights on the Formation and Evolution of Fast-Spreading Ocean Crust from IODP Site 1256, Pito and Hess Deeps, and Active Ridges
Conveners: Damon Teagle, Kathryn Gillis, John Maclennan, Jeffrey Karson
Oceanic crust covers in excess of 60% of our planet. Half of that crust formed at fast spreading ridges. To understand the magmatic processes that generate this crust, and the hydrothermal circulation that cools it, we require contributions from an array of disciplines. Marine geophysical investigations have found that the internal structure of crust formed at fast-spreading rates is relatively uniform. Studies of lava eruption and diking events have refined understanding of episodicity in magmatic accretion of the crust. Knowledge of geological structure of the crust is required for testing theoretical models of crustal accretion of fast-spreading crust. Laboratory studies of spatially constrained samples are key to estimating the attendant fluxes of mass and heat. This session will focus on, but is not limited to, recent studies of fast spread ocean crust exposed in tectonic windows at Hess Deep and Pito Deep and recovered by deep drilling at Site 1256. We welcome all relevant geological, tectonic, geophysical, theoretical, hydrothermal, biological, and geochemical studies of the ocean crust formed at fast spreading rates.

V32: Hydrology of Marine Hydrothermal Systems
Conveners: Dim Coumou, Philipp Weis, Thomas Driesner, Robert Lowell
The subsurface hydrology of marine hydrothermal systems (mid-ocean ridges, submarine arc volcanoes etc.) is still poorly understood. In particular, the causes for the temporal and spatial variability as measured on active black smokers as well as submarine arc systems are subject of an active debate. Hydrologic tracer tests are technically challenging and expensive to perform, numerical simulations of these sysems have been difficult to conduct due to the non-linearities in fluid properties and phase behavior, and studies on fossil examples usually reveal a time-integrated result, for example in the form of rock alterations. Recent improvements in simulation techniques now allow physically rigorous scenario testing studies, including the simulation of complex phase separation processes as well as high resolution representation of fluid flow in two and three dimensions. We invite contributions from measurement campaigns on active systems, studies on fluid-rock interaction in fossil systems, geophysical constraints on flow physics, and numerical simulation to facilitate a multidisciplinary view on the hydrology of these systems and to identify of the most relevant scenarios for further studies.

V42: Geochemical Heterogeneities in OIB and MORB Sources: Implications for Melting Processes and Mantle Dynamics
Conveners: Christoph Beier, Simon Turner, Craig O'Neill, Paul Asimow, Cin-Ty Lee, and Vincent Salters
It is a given that the mantle sources of mid-ocean ridge and intraplate oceanic volcanoes are heterogeneous on multiple scales, principally as a result of recycling of lithospheric material, though other mechanisms may be significant. Such heterogeneity can be seen rather directly using trace element and volatile species concentrations and in stable and radiogenic isotope ratios. Heterogeneity of sources in major elements is more challenging to describe in detail because of strong modifications by and feedback with melting and fractionation processes. It has been shown that various Ocean Islands and Mid-Ocean Ridges have small scale trace element and radiogenic isotope heterogeneities and also exhibit relatively large variations in their melting dynamics as inferred from U-Th-Ra-Pa disequilibria in young samples; sampling opportunities make ocean island localities best for studying temporal variations, whereas mid-ocean ridges are better suited for studies of spatial variations across a wide range of scales, from individual melt inclusions to interoceanic comparisons. Although geochemical studies have provided clear evidence for such recycled components (including volatiles) in the mantle, the details of how these affect or perhaps even control melting rates and processes remain unclear. How do isotopic heterogeneities at various scales correlate with major element variations and physical parameters such as potential temperature, crustal thickness, seismic velocity, etc.? It is necessary to approach the issue of melting and mantle heterogeneity from both geodynamical and geochemical perspectives. The aim of this session is to explore empirical evidence and conceptual models for the impact of geochemical heterogeneities on mantle melting in both Ocean Island Basalts and Mid-Ocean Ridge Basalts. We welcome contributions from the fields of trace element and isotope geochemistry as well as geophysical and numerical modelling incorporating the impact of mantle heterogeneity on mantle melting.

Workshop on Communicating Your Science to the Public
Sunday, 14 December 2008, 8:30AM - 4:00PM
A Free Workshop at the Fall Meeting
Learn from journalists, public information officers, and others how to convey research findings and their significance to the public both clearly and simply.
http://www.agu.org/meetings/fm08/index.php/Workshop/HomePage

VentDB database kickoff meeting, 16 December 2008
VentDB is a database for geochemical data of seafloor hydrothermal springs that is now under development with funds from the U.S. NSF. A lunch meeting is organized at the upcoming AGU Fall Meeting to provide all interested researchers with an overview of the project, and to establish a working group to guide the incorporation of data into the database.
When: Tuesday, December 16, 2008; 12-1:30 pm
Where: TBA (in a hotel close to the Moscone Center, San Francisco)
Lunch will be provided.
To register, please contact Kerstin Lehnert at [email protected]

Contact Information:
AGU Meetings Department
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Washington DC 20009 USA
Phone: +1 202 462 6900
N. America: (800) 966-2481
E-mail: [email protected] (Subject: 2008 Fall Meeting)