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Theme 5

Evolution of the Continental Crust: Formation, Tectonics and Orogeny

Shan Gao, China University,
Tracy Rushmer, Australia,

Co-hosted sessions

SESSIONS

5a. What zircons tell us about crustal evolution

Co-convenors:
Ian Campbell (Australian National University) - Ian.Campbellanu.edu.au
Tony Kemp (James Cook University, Australia) - Tony.Kempjcu.edu.au
Ming Li (Wuhan, China) - liming19820426163.com

Advances in laser ICP-MS, laser ICP-MS multicollectors and ion probes make it possible to date zircons by the U/Pb method, and analyze them for Hf and/or O isotopes as well as for trace elements. These techniques have been applied to zircons of igneous and metamorphic rocks, and to detrital zircons collected from sedimentary rocks and river sands. The data provide new insights into the timing of formation of primitive continental crust, when it differentiated to form the magmas from which zircon crystallizes and whether these events were continuous or episodic. We invite contributions that highlight any aspect of the use of zircon and related accessory phases in the study of evolution of the continental crust.

Keynote speaker:
Martin Whitehouse (Swedish Museum of Natural History), martin.whitehousenrm.se

5b. Evolution and differentiation of the continental crust: A celebration of the contributions by Michael Brown

Co-convenors:
Julia Baldwin (University of Montana) - julie.baldwinumontana.edu; jbaldwinmso.umt.edu
Christine Siddoway (Colorado College) - csiddowaycoloradocollege.edu
Richard White (Universität Mainz, Germany) - rwhiteuni-mainz.de

This session is a tribute to Mike Brown, University of Maryland, for his contributions to our understanding of crustal melting, melt extraction and transport through the crust, the effect of melt generation on crustal rheology and changes in style of metamorphism through Earth history. We invite contributions related to the broad topic of the evolution and differentiation of the continental crust. We particularly invite contributions from field and experimental petrology, structural geology, and isotope geochemistry that address the fundamental processes of crustal anatexis, melt segregation, intracrustal differentiation during orogenesis, P-T-t-d histories of HP/HT metamorphic belts and associated melting processes, and the causes of, sources of heat, and partial melting processes under extreme metamorphic conditions.

Keynote speaker:
Roger Powell (University of Melbourne) - RPearthsciences.unimelb.edu.au

5c. From chondrite to a differentiated Earth: The formation of primitive silicate reservoirs, their fate and evolution through Earth’s early times.

Co-convenors:
Jonathan O'Neil (Université Blaise Pascal, France) - J.ONeilopgc.univ-bpclermont.fr
Mathieu Touboul (University of Maryland) - mtouboulumd.edu

The silicate portion of the Earth has differentiated shortly after its formation. However, the exact nature, the composition and the interaction between these reservoirs through time is still poorly understood. Are we missing an early enriched reservoir? How did the first crust formed? Did a magma ocean formed? What was the fate of these early reservoirs and how long did they survived? These silicates reservoirs may also have been affected by early events perhaps unique to the primitive Earth such as the Late Heavy Bombardment and the late-veneer. We invite contributions related to the formation early silicate reservoirs (crust/mantle) and early geological processes that have affected their composition and evolution through time.

Keynote speaker:
Richard W. Carlson (Carnegie Institution of Washington), rcarlsonciw.edu
Invited speaker:
Matthew G. Jackson (Boston University), jacksonmbu.edu

5d. Recycling of continental crust into the mantle: evidence and observations from ocean margins, the crust and the mantle, modern and ancient.

(co-hosted by Themes 5 and 6)

Co-convenors:
David W. Scholl (U.S. Geological Survey, Menlo Park) - dschollusgs.gov
Kent Condie (New Mexico Tech) - kcondienmt.edu

Partial melting of the mantle is the fundamental process that makes continental crust. But tectonic processes subsequently return or recycle crustal material into the mantle and in doing so helped shaped the rock architecture, zircon-age chronology, and bulk composition of existing continental crust. The purpose and intent of this session is to provide a whole-system, across-time forum for papers and posters to present geological, geophysical, and geochemical observations and evidence about tectonic processes that recycle crustal material to the mantle:

1. At modern and ancient subduction zones,
2. By delamination or foundering of underplated or orogenically depressed crust, and
3. Over deep time implied by mantle geochemical signatures and signals.

Keynote speakers:
Suzanne M. Kay (Cornell University), smk16cornell.edu
Robert Woodbury Kay (Cornell University), rwk6cornell.edu
Charles R. Stern (University of Colorado), Charles.Sterncolorado.edu

5e. Extraction of crust from the mantle through time: from the Archean to the present

(co-hosted by Themes 5, 3 and 6)

Co-convenors:
Othmar Müntener (Université de Lausanne) - Othmar.Muntenerunil.ch
Oliver Jagoutz (MIT) - jagoutzmit.edu
Jean Bedard (Geological Survey of Canada-Québec) - JeanH.BedardRNCan-NRCan.gc.ca
Steve Parman (Brown University) - Stephen_Parmanbrown.edu

While there is consensus on the basic mechanisms how continental crust grows during post Archean times, there is controversy how the early crust on Earth was formed. Is plate tectonics the dominant process or are alternative models such as catalytic delamination more compatible with the thermal evolution of the Early Earth? What is the role of water and other volatiles on the early Earth? Are the Archean 'building blocks' that are preserved representative of the Early crust? We invite contributions using a variety of approaches such as field observations, geochronologic and isotopic studies, petrology and modeling approaches and geophysical constraints to address these problems.

Keynote speakers:
Blair Schoene (Princeton University), bschoeneprinceton.edu
Tony I.S. Kemp (University of Western Australia), steffen.hagemannuwa.edu.au

5f. Characterizing mid- to lower-crustal flow related to orogenic processes

(co-hosted by themes 5 and 6)

Co-convenors:
Félix Gervais (École Polytechnique de Montréal) - felix.gervaispolymtl.ca
Dan Gibson (Simon Fraser University, Vancouver) - hdgibsonsfu.ca
Laurent Godin (Queen’s University, Kingston, Canada) - godingeol.queensu.ca

Crustal flow within the mid- to lower crust is recognized as a fundamental orogenic process, and has far reaching implications when attempting to reconstruct the development of an orogen. Traditionally, fieldwork combined with structural geology and conventional thermobarometry have been the main tools applied to investigate the flow of rocks in the deep interior of orogenic belts. More recently, the integration of traditional approaches with analytical tools of ever growing sophistication has opened new avenues to unravel the complex processes of crustal flow. Significant insight has been gained from variety of disciplines and techniques, including metamorphic isochemical phase diagram modeling, geophysics, thermochronology, diffusion modeling, analogue and finite element modeling. In this session, we are looking for a variety of contributions ranging from traditional fieldwork to simulation modeling that will bring us a step closer to understanding the many intricacies of crustal flow related to orogenesis.

Keynote speaker:
Clare Warren (The Open University, Milton Keynes, UK), c.warrenopen.ac.uk

5g. Formation, evolution, and destruction of cratons and their lithospheric roots

Co-convenors:
Albrecht Hofmann (Max Planck Institute for Chemistry) - albrecht.hofmannmpic.de
Cin-Ty Lee (Rice University, Houston) - ctleerice.edu
Chuan-Zhou Liu (Chinese Academy of Sciences, Beijing) - chzliunmail.iggcas.ac.cn
Aleksandar Mišković (University of British Columbia, Canada) - amiskoviceos.ubc.ca
D. Graham Pearson (University of Alberta) - gdpearsonualberta.ca
Steven Shirey (Carnegie Institution of Washington) - shireydtm.ciw.edu

Cratons are strong (“kratos”), seismically inactive ancient regions of the continents that are passive participants in plate tectonics. The apparent strength of cratons is due, in part, to the presence of a thick, refractory mantle keel. While the composition and structure of thick lithospheric roots beneath cratons today is reasonably well understood, their presence raises outstanding questions. How did cratonic lithospheres form and how were they preserved through geological time? Are certain time periods or geologic processes conducive to craton formation? What properties of the mantle keels or the overlying crust control the strength of cratons? What is the relationship, if any between the keels and the overlying continental crust? What is the cause of late granite blooms that are common in many Archean cratons? By what processes might cratons be destroyed or reworked and how often does this happen? What is the history of metasomatism, and/or access of fluid to the lithosphere? While cratons contain both ancient crust and mantle keels, recent evidence suggests that the temporal relationship between the two is variable, depending on location, and can be complex. While chemical buoyancy and high residual viscosity that are needed to stabilise cratons, there are competing models regarding the exact mechanisms of craton formation, their compositional variability, and evolution. Moreover, the conventional view that cratons are inert lithospheric domains has been repeatedly challenged and signs of craton modification and destruction are now widely recognised. This session seeks to highlight recent advances in our understanding of the formation, preservation and disintegration of cratonic roots and their overlying crust, emphasising the application of: a) petrology, geochemistry and geochronology applied to mantle xenoliths, diamonds, melts and fluids sampled by kimberlitic and related magmas, b) laboratory experiments constraining physio-chemical properties of cratonic mantle, and c) geophysical observations and geodynamic models of craton structure and dynamics.

Keynote speaker:
Roberta Rudnick (University of Maryland) - rudnickumd.edu
Invited speakers:
Dmitri Ionov (Université Jean Monnet, Saint-Étienne, France), dmitri.ionovuniv-st-etienne.fr
Peter Kelemen (Columbia University, NY, USA), peterkldeo.columbia.edu
Terence Blackburn (Massachusetts Institute of Technology), terrenceMIT.edu
Yigang Xu (Guangzhou Institute of Geochemistry, China), yigangxugig.ac.cn

Co-hosted sessions:

Please note that for abstract submission purposes, the following sessions and their respective descriptions appear in their primary Theme assignments (numbers in red or before the title).

4g.- Geochronology and geochemistry of large igneous provinces

Co-convenors: Paul Sylvester/Memorial University, Richard Ernst/Ernst Geosciences, Mike Hamilton/Toronto and Wouter Bleeker/GSC
(co-hosted by Themes 4 and 5)

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