In this talk, I will present geochemical and petrologic evidence for the origin of basalts in the Northern Cascade Arc of British Columbia and Washington. As one of the hottest subduction zones in the world, Northern Cascadia presents some important implications for our understanding of arc magmatism. Throughout most of the Cascades, basalts are calc-alkaline and show the typical compositional features associated with arc basalts globally. In the Northern Cascades, however, basalts display minimal input from the subducting slab. Northern Cascades basalts are also alkalic, a characteristic more commonly associated with an intraplate setting. Could these features reflect the particularly hot conditions in Northern Cascadia?

Here, most subducted water is predicted to be released from the slab long before reaching the arc axis, meaning that a pronounced slab signature may not be imparted to the basalts. However, new geochemical data indicate that the Northern Cascades has an isotopically distinct, more enriched mantle source than the rest of the Cascade Arc. Furthermore, Northern Cascades basalts were generated at significantly higher pressures than basalts in the rest of the arc. There may be a tear in the subducting plate that promotes upwelling of deep, fertile mantle, which undergoes decompression melting to produce the unusual Northern Cascades magmas.

Emily Mullen

Postdoctoral Research Fellow

Pacific Centre for Isotopic & Geochemical Research

Department of Earth & Ocean Sciences

University of British Columbia

Pure silica glass under hydrostatic pressure in the elastic regime shows an anomalous behavior called the elastic anomaly. When silica is compressed above the elastic limit (≈ 9GPa), a permanent densification of silica is observed.

We have compared the behovior of pure silica glass under pressure to those of the NS3/Albite join and extended these compositions into the peralumimous domain in order to directly correlate microscopic atomic structural modifications with macroscopic physical properties under pressure. These glasses were studied in the short range order by solid Nuclear Magnetic Resonance (NMR) and X-ray Absorption Near Edge Structure (XANES). The intermediate range order was studied by Raman spectroscopy and long range order with Brillouin spectroscopy.

The different elastic and plastic bevaviors of silicate glasses will be presented in this talk and an interpretation will be given in term of different structural modifications depending on the glass composition.

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