Location: Palais des congrès, Montreal, Canada
Web: http://www.vmgoldschmidt.org/2012/index.htm
Includes the following sessions:
4b: The occurrence, genesis and evolution of alkaline magmas
Convenors: Glenn Gaetani (ggaetani@whoi.edu), Philip Kyle (kyle@nmt.edu), Kenneth Sims (ksims7@uwyo.edu), Erin Writer (ephilli8@uwyo.edu)
Alkaline volcanism occurs in oceanic and continental intraplate and rift settings and more rarely along convergent margins. In this session we will examine the similarities and differences in the occurrence, genesis and magmatic evolution of alkaline magmas from geochemical, petrologic and geophysical perspectives. We encourage contributions that involve a range of different approaches to understanding alkaline magmas including field studies, experiments, geochemical and isotopic measurements, and numerical modeling.
4c: Large volcanic plumbing systems in intraplate settings
Convenors: Massimo D’Antonio (masdanto@unina.it), Roberto Moretti (roberto.moretti@unina2.it), Ivan Savov (earis@leeds.ac.uk)
Relevant areas of intraplate volcanism on Earth, such as the Main Ethiopian Rift in East Africa and Hawaii islands in Pacific Ocean, are fed by large plumbing systems. This session aims at bringing together experts working on large volcanic plumbing systems in a variety of intraplate settings, both marine and continental, using multi-disciplinary approaches. Contributions from petrologists, fluid geochemists and geophysicists that focus on active and fossil volcanoes located at sea as well as on land in intraplate settings, are welcomed. Approaches ranging from geochemical characterization of magmatic processes, including partial melting of mantle in several P-T-fluid conditions, fluid transfer and fluxing at variable depth in the lithosphere, and magma-fluid interaction, to variable imaging techniques aimed at reconstructing geometry and architecture of large plumbing systems are encouraged.
Keynote speaker: Leonid Danyushvkyi (University of Tasmania)
4e: Mid-ocean ridge processes: melting and melt extraction in a heterogeneous mantle
Convenors: Michael Bizimis (mbizimis@geol.sc.edu), Andreas Stracke (stracke.andreas@uni-muenster.de), Richard Katz (richard.katz@earth.ox.ac.uk)
The composition of mid ocean ridge basalts (MORB) and abyssal peridotites retain a time-integrated record of melting and melt extraction from a heterogeneous upper mantle. How are the different enriched and depleted components arranged in the mantle? What are their length scales and extent of heterogeneity? Under what conditions do they melt and how do the partial melts subsequently travel, react and modify the mantle lithosphere en route to the surface? These remain major, open questions of Mid-ocean Ridge processes. We invite contributions from field, petrological, geochemical geophysical and modeling studies that explore the above questions, especially from the perspective of the mantle sample.
Keynote speaker: Henry Dick (Woods Hole Oceanographic Institute)
4f: Roles of lithospheric, depleted, and enriched mantle sources in the genesis of large Ni-Cu-PGE deposits
Convenors: James Mungall (mungall@geology.utoronto.ca), Edward Ripley (ripley@indiana.edu)
Major Ni-Cu-PGE deposits owe their origins to large-scale melting events in the upper mantle, most commonly in continental intraplate or marginal settings. Possible contributing sources of the parental magmas include depleted upper mantle, enriched OIB-type mantle possibly incorporating recycled ancient crust, and reactivated ancient subcratonic lithosphere. This session invites contributions on controversial issues related to the fertility of intraplate magmas parental to Ni-Cu-PGE deposits, such as mantle source composition, and the origins, physical distribution and geometry of the various mantle reservoirs implicated in their genesis.
Keynote speaker: Nicholas Arndt (University of Grenoble)
4g: Geochronology and geochemistry of large igneous provinces
Convenors: Paul Sylvester (psylvester@mun.ca), Richard Ernst (richard.ernst@ernstgeosciences.com), Mike Hamilton (mahamilton@utoronto.ca), Wouter Bleeker (wouter.bleeker@nrcan.gc.ca)
Large igneous provinces (LIPs) are the result of large volume magmatic events emplaced over short time scales, found through all of the geologic record. Recent advances in U-Pb geochronology of baddeleyite by TIMS, SIMS and LA-ICPMS have allowed many more mafic LIP events to be dated precisely. The new ages are used for correlations between LIP units on now dispersed terrane fragments, providing constraints on reconstructions of supercontinents. Precise age data also allow geochemical comparisons between different LIP events, leading to a better understanding of variations in their mantle sources and melting processes. This session aims to highlight the analytical developments of U-Pb geochronology of baddeleyite and the application of high-precision age data for LIPs to paleo-continental reconstructions, mantle geochemistry, mantle dynamics and plumes, the intrusive and extrusive architecture of LIPs, global environmental catastrophes and biological mass extinctions, and the genesis and distribution of ore deposits and hydrocarbons within LIP systems.
Keynote speaker: Kevin Chamberlain (University of Wyoming)
4h: Geochemical and isotopic insights into large volume silicic eruptions and supereruptions
Convenors: Ilya Bindeman (bindeman@uoregon.edu), Erwan Martin (erwan.martin@upmc.fr)
Recent decade has increased awareness of the origin of large volume magmatism, volcano-plutonic connections, and influence of large volume volcanic eruptions on climate. The session will bring together talks dealing with the origin of large volume silicic magmas, mechanisms of their eruption, and influence of volcanic ash on the environments. The emphasis will be placed on novel geochemical and isotopic approaches, but contributions who deal with numerical modeling of caldera forming eruptions, field studies of large calderas, the role of meteoric hydrothermal system in thermal and material balance in large calderas, or atmospheric of ash and SO2 gas are welcomed.
4j: New views of mantle heterogeneity from oceanic basalts
Convenors: Aaron Pietruszka (apietruszka@geology.sdsu.edu), Dominique Weis (dweis@eos.ubc.ca)
The chemical and isotopic diversity of young basalts from oceanic islands, seamounts and plateaus record evidence of the compositional heterogeneity of the Earth’s mantle. The goal of this session is to highlight recent studies on the nature and origin of mantle heterogeneity at all length scales and over a range of depths. We welcome contributions that use elemental and/or isotopic measurements of oceanic basalts (and their minerals and melt inclusions) and/or geochemical modeling to see through the filter of the melting process to the underlying compositional heterogeneity of the mantle. Integrated contributions, with geophysical and/or geodynamical perspectives, are also encouraged.
5a: What zircons tell us about crustal evolution
Convenors: Ian Campbell (ian.campbell@anu.edu.au), Tony Kemp (tony.kemp@jcu.edu.au), Ming Li (liming19820426@163.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.
5b: Evolution and differentiation of the continental crust: a celebration of the contributions by Michael Brown
Convenors: Julia Baldwin (julie.baldwin@umontana.edu), Christine Siddoway (csiddoway@coloradocollege.edu), Richard White (rwhite@uni-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)
5d: Recycling of continental crust into the mantle: evidence and observations from ocean margins, the crust and the mantle, modern and ancient
Convenors: David Scholl (dscholl@usgs.gov), Kent Condie (kcondie@nmt.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:
Keynote speakers: Suzanne Kay (Cornell University), Robert Woodbury (Cornell Universi ty), Charles Stern (University of Colorado)
5e: Extraction of crust from the mantle through time: from the Archean to the present
Convenors: Othmar Müntener (othmar.muntener@unil.ch), Oliver Jagoutz (jagoutz@mit.edu), Jean Bedard (jeanh.bedard@nrcan.gc.ca), Steve Parman (stephen_parman@brown.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.
5g: Formation, evolution, and destruction of cratons
Convenors: Cin-Ty Lee (ctlee@rice.edu), Steven Shirey (shirey@dtm.ciw.edu), Albrecht Hofmann (albrecht.hofmann@mpic.de)
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 cratons today is reasonably well understood, a number of outstanding questions related to their formation, evolution and survival are important: By what processes and in what settings do these highly refractory lithospheric keels form? 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 ltihospere? We invite contributions bearing on all aspects of these questions.
Keynote speaker: Roberta Rudnick (University of Maryland)
7d: Records of climate change from terrestrial archives: palaeosols and loess
Convenors: Mohammed Rafi G. Sayyed (mrgsayyed@yahoo.com), Martine Gerard (martine.gerard@impmc.upmc.fr)
The driving forces of evolution of Earth’s climate, from cold snowball Earth to warm greenhouse state, can be revealed and quantified by palaeoclimate studies. Nowadays fragile global environmental conditions demand urgent improving of the understanding of paleoclimates to better predict climate change. The physical, chemical and biological composition of ancient soils or more polygenetic buried soils hold great potential as proxies for regional palaeoclimate and palaeoatmospheric circulation patterns as well as palaeoatmospheric pCO2 variations for intervals of Earth’s history characterized by extreme and abrupt environmental perturbations. More understanding of the mechanisms that influence biogeochemical data preservation in the proxies is needed to avoid biases of interpretation. Once these issues are addressed, the geochemistry of palaeosols can provide both qualitative and semi-quantitative information about the changing redox state of the atmosphere since the Precambrian times. Palaeosol-loess sequences also have a great potential for the evolution of climate throughout Earth’s history as they have preserved detailed climatic records of stepwise terrestrial climate change. We invite contributions that investigate various biogeochemical proxies of the evolution of the climate system from Precambrian to Holocene as well as on extreme events (e.g. LIPs related to catastrophic global climate impacts and mass extinctions events).
Keynote speaker: Alexander Makeev (Moscow State University)