The seismic structure, distribution of normal-sense shear zones, and peak pressures of Ottawan (~1090-1020 Ma) metamorphism in the hinterland of the Grenville Orogen collectively define a crustal-scale horst and graben architecture inferred to have resulted from collapse of a former orogenic plateau. Domal-shaped horsts are large core complexes 100 km or more across that expose Ottawan, high-grade mid crust (peak P-T conditions ~1000 ± 100 MPa, 850-900 °C) with sub-horizontal gneissic foliations. Basinal-shaped grabens are underlain by the remnants of an orogenic lid in which sub-vertical, pre-Ottawan foliations are preserved and peak Ottawan P-T conditions were ≤ 400 MPa, 500 °C. Intervening crust, with peak Ottawan pressures between ~1000 and 400 MPa, exhibits steep foliations and is under-represented at the erosion surface.

Timing of Ottawan metamorphism exhibits a progression from granulite-facies in the orogenic mid crust at ~1090-1050 Ma, through amphibolite-facies in the upper crust at ~1050-1020 Ma, to heating to ≤ 500 °C in the uppermost crust surrounding the orogenic lid at ~1020-980 Ma. This temporal and spatial sequence is inferred to result from conductive heat transfer as hot mid crust was exhumed against successively higher crustal levels during collapse. The age data imply collapse lasted for ≥ 50 Ma, comparable to the duration of Ottawan thickening, and that it overlapped with important crustal thickening at the orogen margin during the ~1000-980 Ma Rigolet phase.

In addition to normal-sense displacement on major shear zones separating the core complexes and orogenic lid, the structural signal of collapse in the migmatitic mid crust includes orogen-normal stretching lineations defined by retrograde mineral assemblages, and evidence for pervasive vertical thinning (flattening), which resulted in a component of orogen-parallel stretching. Collapse thus involved gravity-driven horizontal extension of the ductile mid crust, which in turn led to wholesale boudinage of the overlying brittle upper crust, with core-complex formation initiated by rise of ductile mid crust into boudin necks.

In contrast to the mid crust, approximately coeval fabrics and structures in the under-represented ductile upper crust are steep to upright and record vertical thickening driven by sub-horizontal plate tectonic traction forces. Coeval vertical thinning / horizontal spreading of the weak mid crust driven by gravity, and vertical thickening / horizontal shortening of the stronger upper crust driven by traction forces, implies that deformation in the two levels was decoupled, strain was triaxial at both crustal levels, and that collapse was a fundamentally 3-D process. An important conclusion from these observations is that orogenic collapse cannot be realistically modelled in a 2-D, plane-strain framework.

That collapse also affected igneous and hydrothermal processes is indicated by the temporal and spatial association of normal-sense shear zones at the margins of several core complexes with leucogranite emplacement, and with fenetization (alkali metasomatism) and the formation of IO(CG) deposits.

In summary, viewing the seismic, structural, metamorphic and igneous features of the Grenville Orogen through the prism of orogenic collapse yields a profoundly revised image of its architecture and appears to provide a coherent context for its tectonic evolution.

All welcome

The talk has three components. First I look at the technical and cultural challenges of addressing the invention, innovation and deployment of energy and carbon management systems at a scale suitable for addressing the pressing CO2 emissions changes of our age. Specifically I look at the role, challenges and opportunities faced by Canada's university research community in leading key components of the response. Secondly I review briefly how Carbon Management Canada -an NCE funding research at most all Canadian universities, is working with the Universities to support research from the basic and fundamental  through invention and innovation  to  deployed technology, looking at both technical and the equally important social issues of change.In the final half of the talk, I talk about two areas my research group is involved in which we have a energy/ carbon emissions reduction focus.

All welcome.

The NASA Johnson Space Center Astromaterials Acquisition and Curation Office has the unique responsibility to curate NASA's extraterrestrial samples - from past and forthcoming missions - into the indefinite future. Presently curation includes documentation, preservation, preparation, and distribution of samples from the Moon, asteroids, comets, the solar wind, and the planet Mars. Each of these sample sets has a unique history and comes from a unique environment. The curation laboratories and procedures developed over forty years have proven both necessary and sufficient to serve the evolving needs of a worldwide research community. A new generation of sample return missions is being planned and proposed
to destinations across the solar system. Curation must evolve to meet the increased challenges of these new samples.

Dr. John Hanchar

Professor, Department of Earth Sciences, Memorial University

Title: "Assembly of an igneous intrusive complex: An example from Adamello, Italy"

GSC Calgary and Past President, Geological Association of Canada (GAC)

Title: TBA

Associate Professor, Department of Geological Sciences, Case Western Reserve University

Title: "Chemical evolution of the outer core: Insights from high-pressure experiments"

Professor of Geophysics, Department of Geological Sciences, University of Michigan

Title: "A dynamical view of volcanism and seismogenesis in subduction zones"

Assistant Professor and CRC Chair, Department of Chemistry, University of Toronto

Title: "Sources, Sinks, and Chemical Transformations of Atmospheric Reactive Nitrogen"

Assistant Professor, Department of Geosciences, SUNY Stony Brook

Title: "Silicic Magmatism on the Moon: Insights from the Diviner Lunar Radiometer"

Assistant Professor, Earth & Planetary Sciences, McGill University

Title: TBA

Dean, Faculty of Geosciences, Utrecht University

Title: "About geology and sustainability: is the past really a key to the future?"

Free and open to the public; students are encouraged to attend

Refreshments at 11:45; talk at noon

Talk abstract:

About geology and sustainability: is the past really a key to the future?

Due to growth of the human population, our earth is rapidly approaching the limits of its carrying capacity. Biodiversity is affected beyond (rapid) repair, resources like fossil fuels and metals are becoming scarce. In this perspective, geology is a key discipline. Obviously, deep understanding of System Earth is needed to better define the precise nature of some of the threats we face. For instance, studying the past might provide insight in future threats like global warming. Secondly, we need geological knowledge to better exploit the resources we need, although it is clear that we soon might need alternatives for many of the traditional ones. And finally, given the knowledge regarding earth materials, geologists might be able to contribute to finding such new resources based on carefully planned research in the domain of Earth Materials.

In giving a brief overview of the research work done in the Earth Sciences Department at Utrecht University, some examples will be presented and briefly discussed, ranging from the dangerous lowering of the fresh water table on many continents, to Eocene warming events and how solar activity naturally triggers release of enormous amounts of methane, and to  CO₂ capture and storage as a way to fight the global green house effect.

VP Exploration, Barron Energy Corporation

Title:  "The Recognition and Exploitation of Fracture Systems in a Carbonate Reservoir”

Free and open to the public; students are encouraged to attend

Pizza served after the talk

Abstract 

 Introduced about twenty years ago as a tool for  marine geochemistry, lithium isotopes have benefited from recent technical innovations to move closer to the forefront of the geochemical toolbox for many aspects of solid Earth research. This talk will focus on the state of understanding of this stable isotope system in the mantle and crust, including major breakthroughs and outstanding problems.

 Everyone Welcome