S23: Deep Earth mineralogy

Conveners:	R. Boehler	(boe@mpch-mainz.mpg.de)
	Dan Frost	(Dan.Frost@Uni-Bayreuth.de)
Keynote:	Renata Wentzcovitch	(University of Minnesota)

The physical and chemical properties of the D'' layer at the core-mantle boundary govern heat transfer between the core and mantle, which ultimately drives mantle convection. In addition, any chemical reaction between the outer core and D" may influence the chemical evolution of the mantle. This symposium will focus on recent advances in the study of phase behavior, density, melting, and chemical partitioning of deep-earth minerals relevant to the lowermost mantle and metal-alloys relevant to the outer core. Of particular and continuing interest is the origin of the D'' layer and related questions of the role of thermal gradients, the post-perovskite phase, partial melting, and core-mantle reactions.

S24: Hidden reservoirs in the mantle: Required, desired, or superfluous?

Conveners:	Maud Boyet	(maud.boyet@univ-st-etienne.fr)
	Nicolas Coltice	(nicolas.coltice@univ-lyon1.fr)
Keynotes:	Chris Ballentine	(Oxford, UK)
	Sebastian Rost	(Leeds, UK)

How well do we understand the Earth? Our intuition typically guides us to reject hypothesis that invoke ìhidden reservoirs" in the Earth. That wisdom, however, contrasts with developments over the last decade in which several models have been put forth documenting evidence for the existence of complementary reservoirs in stealth, untapped layers deep in the earth. Justifications for these layers come from many studies (He, Hf, Sr, Nd and Pb isotopes, Nb, Ta element ratios and abundances, radioactive elements, etc) which have led to different physical models for their depth, volume and formational conditions. This symposium will bring together a diversity of players and the evidence in an attempt to sort out the need, existence, consequences and co-habitability of these many skeletons in our deep Earth closet.

S25: Mantle processes and properties on multiple scales: Observation, experiment, modeling

Conveners:	Gerd Steinle-Neumann	(G.Steinle-Neumann@uni-bayreuth.de)
	Taras Gerya	(taras.gerya@erdw.ethz.ch)
	Chris Ballentine	(chris.ballentine@manchester.ac.uk)
	Paul Tackley	(paul.tackley@erdw.ethz.ch)
Keynotes:	Steve Parman	(Durham, UK) Houtermans Medal, 2007 EAG
	Jeannot Trampert	(Utrecht)

In recent years laboratory experiments and computer modeling on the one hand and geophysical and geochemical observations on the other have crucially contributed to our understanding of Earth's mantle composition, structure and dynamics. Further progress will clearly depend on cross-disciplinary efforts combining approaches from different fields. Therefore the goal of our session is to bring together experimentalists, modelers and "observers" in order to discuss most recent developments concerning mantle processes and to point out directions where different methods can complement each other.

S26: Earth's energy Equation - Radioactive elements and heat flow in the core and mantle

Conveners:	John Lassiter	(lassiter1@mail.utexas.edu)
	Stephane Labrosse	(Stephane.Labrosse@ens-lyon.fr)
Keynote:	Bruce Buffett	(University of Chicago)

The dynamics and evolution of Earth's interior are fundamentally controlled by the production and transport of heat. Conventional models posit surface heat loss of ~44 TW with half of this supported by the decay of radioactive elements, none of which are sited in the Earth's core. Such models have been recently challenged from many perspectives, including total energy output, distribution of elements in the mantle (e.g., D'' hot layers), inner core crystallization and age of the inner core. This symposium aims at integrating recent advances in experimental petrology, heat flow modeling, energetics of the geodynamo and mantle convection, compositional modeling of the core-mantle system, and particle physics to gain a better understanding of the thermal evolution of the Earth.

S27: A decade of Hf isotope research ­ What have we learned?

Conveners:	Janne Blichert-Toft	(Janne.Blichert-Toft@ens-lyon.fr)
	Francis Albarède	(albarede@ens-lyon.fr)?
Keynote:	Jon Patchett	(University of Arizona)?

The advent of ICP-MS methods has led to enormous growth in the application of Hf isotopes to mantle geochemistry and geochronology, because new experimental methods have made this isotope system accessible to many workers who had previously considered this system too challenging to become involved. Nevertheless, questions have persisted, for example whether Hf isotopes might yield sufficiently similar geochemical information as Nd isotopes and might therefore be considered redundant. However, there now exists a rather large body of Hf isotope data, so that their impact on mantle geochemistry, mantle geodynamics and evolution, crustal growth, geochronology, meteorites and planetary sciences can be assessed. This has also produced new controversies regarding the half life of ¹⁷⁶Lu, the bulk-Earth Hf isotopic composition, the interpretation of decoupled Hf and Nd isotope data, and the possible existence of a hidden reservoir in the mantle. This symposium will review the advances made in the past several years in addition to inviting contributions at the current forefront of this research.

S28: Siderophile and chalcophile trace elements in the earth's mantle

Conveners:	Christian Ballhaus	(chrisb@nwz.uni-muenster.de)
	Gerhard Bruegmann	(bruegman@mpch-mainz.mpg.de)
	Werner Ertel	(ertel@min.uni-muenchen.de)
	Thomas Meisel	(Thomas.Meisel@mu-leoben.at)
Keynote:	Jean-Pierre Lorand	(Natural History Museum, Paris)
	Rich Walker	(University of Maryland, USA)

Highly siderophile and chalcophile elements are sensitive tracers for mantle-core equilibrium and partial melting processes in the earth's mantle. In the present-day upper mantle, these elements are to a large extent stored in sulfide; hence their behavior is inextricably linked to the chemical and physical behavior of sulfide phases. The session invites contributions to all aspects of siderophile and chalcophile elemental and isotopic geochemistry in mantle rocks and basalt melts, as well as to experimental phase relations in sulfide-silicate-metal systems relevant to mantle geochemistry and core formation.

S29: Magmatic phenocrysts and their inclusions as probes of mantle composition and melting

Convener:	Leonid Danyushevsky	(L.Dan@utas.edu.au)
Keynote:	Alexander Sobolev	(asobolev@mpch-mainz.mpg.de)

What is the composition of convecting mantle? What are the origin and scales of mantle heterogeneities? How can we assess melting processes in the mantle? Early magmatic phenocrysts constitute a rich store of information about primary (or at least parental) melts and their source rocks in the mantle. This information can be unlocked by microanalyses of the phenocrysts themselves, as well the melt and fluid inclusions. In contrast, the information content of erupted bulk melts is often severely compromised by magma-chamber and ñconduit processes. This symposium will review the state of the art of research, and present new data, ideas and models, and in-situ analytical techniques on early phenocrysts and their melt and fluid inclusions from the entire range of geodynamic settings. In addition, we invite complementary contributions on mantle mineralogy and inclusions.

S30: Melt formation and segregation in basalt source regions

Convener:	Marc Hirschmann	(Marc.M.Hirschmann-1@umn.edu)
	Yan Liang	(yan_liang@brown.edu)
Keynote:	Greg Yaxley	(ANU)

The generation and segregation of melt in the upper mantle is a fundamental, but only partially understood, process. Melting and melt segregation involve interacting physical-chemical processes over a wide range of length scales and multiple lithological units. Although there are now extensive studies investigating partial melting of spinel peridotite, there are fewer studies documenting partial melt compositions of garnet peridotite or the compositions of partial melts formed in the presence of key volatiles. Recent thinking about possible source rocks of basaltic melts has prompted new experimental studies of processes involving partial melting of eclogite and pyroxenite, and of melting associated with hybridization between peridotite and vein lithologies. At the same time, geochemical studies of lavas and mantle rocks continue to provide new constraints on possible mantle lithologies and processes in basalt source regions. Finally, thermodynamic and physical models of partial melting, melt-rock interaction, and melt segregation are being developed and improved. In this symposium, we will explore current progress as well as future directions of experimental, theoretical, and field-based studies on partial melting, melt migration, and melt-rock interaction involving various lithologies in the mantle.

S31: Hotspots and LIPs: Plumes or shallow-mantle sources

Conveners:	Dominique Weis	(dweis@eos.ubc.ca)
	Cinzia Farnetani	(cinzia@ipgp.jussieu.fr)
Keynotes:	Francis Albarède	(École Normale Supérieure, Lyon)
	Don DePaolo	(University of California, Berkeley)

The origin of hotspots and large igneous processes appears to be as controversial as ever. Points of disagreement extend beyond the current plume debate to questions of the petrological nature of the source rocks (peridotite, eclogite, pyroxenite, and their hybrids), the source of geochemical enrichment (metasomatism, recycling of crust), and the "fixity" of hotspots. This symposium will bring together geochemists, petrologists and geophysicists to debate the issues.

The following symposium is also relevant to the "Earth's mantle ", but emphasizes new analytical developments: For full description see Symposium S05.

S05: Rare gases in geochemistry

Conveners:	Bernard Marty	(bmarty@crpg.cnrs-nancy.fr)
	Chris Ballentine	(chris.ballentine@manchester.ac.uk)
Keynote:	David Hilton	(La Jolla)