S19: The crust-mantle system in the Hadean and Early Archean

Conveners:	M. Whitehouse	(martin.whitehouse@nrm.se)
	R. Frei	(robertf@geol.ku.dk)
Keynote:	Vickie Bennett	(ANU, Australia)

This symposium seeks contributions using theoretical as well as direct observations from the rock record that shed light on the evolution of crust-mantle system in the young Earth. The topics include, but are not limited to the genesis of the most ancient rocks and minerals, processes that led to the formation and modification of the first continental crust, evolution of the early mantle, early tectonic styles, the beginning of plate tectonic processes and the oldest sedimentary cycles.

S20: The early atmosphere and hydrosphere

Conveners:	H. Strauss	(hstrauss@uni-muenster.de)
	J. Farquhar	(jfarquha@essic.umd.edu)
Keynote:	David Catling	(Bristol, UK)

This session will explore how geochemical observations and analytical approaches can be used to reconstruct the evolution of Earthís early atmosphere and hydrosphere. The stable isotope fractionation of carbon, nitrogen, sulfur and hydrogen play a vital role in our understanding of the flux of volatiles from the mantle to the atmosphere and hydrosphere. Water and the atmospheric gases played an important role in the origin of life. Weathering processes on the Earthís surface were influenced by the composition of atmosphere and in turn may have modified its chemical characteristics over time. We welcome contributions that address these issues by studying the geological record and through modeling.

S21: Chemical geodynamics in the Hadean and Archean

Conveners:	K. Mezger	(klaush@nwz.uni-muenster.de)
	A. Polat	(polat@uwindsor.ca)
Keynote:	John Percival	(Ottawa, Canada)

In general, the geochemical characteristics of modern volcanic rocks from different tectonic settings are distinct in terms of isotope and trace element systematics. Can we assume that similar, uniformitarian, geochemical behavior also prevailed in the Hadean and Archean? What were the tectonic and geochemical parameters that led to different magmatic suites in Earthís early history compared to the more recent past? How important were processes and parameters like source composition, residual mineralogy, partial melting, and hybridization? Can we understand the early chemical geodynamics without using a non-uniformitarian approach? We welcome contributions that use isotope, major and trace element systematics of rocks or geochemical modeling to address key issues in the petrogenesis of the oldest rocks and reservoirs on Earth.

S22: Earth's first billion years - This symposium is dedicated to Bob Zartman

Conveners:	S. Bowring	(sbowring@mit.edu)
	G.J. Wasserburg	(gjw@gps.caltech.edu)
Keynote:	Alex Halliday	(University of Oxford, UK)

This symposium is directed toward a review of early Earth evolution from its connection to the protosolar nebula to differentiation and development of internal structure. In particular, emphasis will be given to the isotopic and chemical indicators of major differentiation processes, the formation and destruction or the early crust and the transition to the "mature" state of the planet. Contributions are sought that discuss evidence for preservation of very ancient reservoirs in the Earth's interior, the ages and characteristics of Earth's oldest rocks and connections to Lunar evolution.

The following symposium is relevant for Theme 4 and for Theme 9. Full details are given in Symposium 51.

S51: Early evolution of life and bio/hydro/atmosphere

Conveners:	Jochen Brocks	(jochen.brocks@anu.edu.au)
	Emmanuelle Javaux	(EJ.Javaux@ulg.ac.be)