Spring 2010 Colloquia

January 11 First day of classes, no colloquium

January 18 Martin Luther King Day, no colloquium

January 25 Seth Young, Geological Sciences, Indiana University Title: The Late Ordovician Greenhouse to Icehouse Transition: Isotopic evidence for fluctuations in silicate weathering, carbon cycling, and pCO2.

January 27 GeoSci-Physics Colloquium: H. J. Melosh, Purdue University. Title: Our Catastrophic Solar System:  Impacts and the Latest Revolution in Earth Science

February 1 Owen Award Ceremony: Wayne Bundy Title: Intellectual Adventures Provoked by Geoscience.

February 4 Environmental Science/Geoscience Seminar Series. Chen Zhu, Fullbright Scholar and Associate Professor of Geological Sciences and Public and Environmental Affairs. Title: CO2-water-rock interaction in geological carbon sequestration.

Abstract: Geological storage of carbon dioxide (CO2) is one of the most promising options for mitigating global warming. The storage is accomplished by deep underground injection into geological formations. How much CO2 can be stored in an aquifer? What will happen to CO2, the native brine, and the host rocks? Where does the CO2 go? To answer these questions, we need to understand how CO2, water, and rock interact with each other. To assess how fast these interactions take place (chemical kinetics), we need to wrestle with one of the fundamental challenges in geochemistry. It has been known for a long time that the laboratory measured dissolution rates of feldspars—the most abundant minerals in the Earth’s Crust—are two to five orders of magnitude faster than rates estimated from field studies. Because host and cap rocks for sequestration typically have 20% of feldspars, such a large discrepancy presents an obstacle for quantitatively evaluating CO2-water-rock interaction as well as many other geological and environmental processes. To resolve this long standing controversy, we have conducted field studies and a series of lab experiments. The field and lab data confirm our new hypothesis that considering slow precipitation of secondary minerals can partly resolve the apparent discrepancy. The presentation will report basic research findings toward establishing a scientific basis for geological carbon sequestration and also numerical simulations of CO2 migration and fate in the Mt. Simon Sandstone found 6000 feet below parts of Indiana and in the Utisira sandstone at Sleipner, Norway.

Short Biography: Chen Zhu is currently an Associate Professor of Geological Sciences and Public and Environmental Affairs at Indiana University, and a Fulbright Scholar. He received his Ph.D. from the Johns Hopkins University, and was the 2006 recipient of the John Hem Award from the National Ground Water Association. He is the first author of the book "Environmental Applications of Geochemical Modeling" published by Cambridge University Press, and an Associate Editor for Geochimica et Cosmochimica Acta since 2005 and Journal of Contaminant Hydrology since 2002.

February 8 Andy Knoll, Harvard University. Title: Physiology as conceptual glue in historical geobiology.

February 9 Patten Foundation Lecture Title: Life on a Young Planet (see also his book with the same title)

February 11 Patten Foundation Lecture Title: Meridiani, Opportunity, and the Search for Life on Mars.

February 15 Maria Mastalerz, Indiana Geological Survey. Title: Coalbed methane and shale gas; Insights from the Illinois Basin.

February 22 Hiroshi Ohmoto, Pennsylvania State University. Title: Life and environment on the early Earth.

March 1 Matt Saltzman, Ohio State University. Title: A Pulse of atmospheric oxygen during the Late Cambrian

March 8 Gary Pavlis, Indiana University Department of Geological Sciences. Title: Three-Dimensional wavefield imaging of data from the US Array: New constraints on the geometry of the Farallon Slab

March 15 Spring Break, no colloquium

March 22 Michael Bostock, Tudor Lecture. Michael Bostock, University of British Columbia. Title: Fate of water in the Cascadia Forearc Unveiled by Teleseismic Imaging.

Abstract The past decade has witnessed the deployment of large numbers of broadband seismometers along the Cascadia forearc. A high density of sampling has permitted the mapping of subduction zone structure along and across strike using scattered teleseismic body waves. Forearc structural signatures across profiles sampling central Oregon, Puget Sound, and Vancouver Island are remarkably similar.

A ~5 km thick, dipping low-velocity zone (LVZ) extending to depths of >50 km is inferred here to represent subducting oceanic crust of the Juan de Fuca plate. Estimates of Poisson’s ratio within the shallow LVZ are extremely high, between 0.35 and 0.4, and cannot be attributed to lithology. Rather, they are interpreted to manifest near-lithostatic, pore-fluid pressures generated through metamorphic dehydration reactions within the oceanic crust.

Accordingly, the plate interface must represent an impermeable boundary at these depths. Farther down dip, the signature of the LVZ fades as its upper, followed by lower, boundaries become seismically indistinguishable from ambient mantle. Thermo-petrological models predict that metabasalt undergo a final transformation to nominally anhydrous eclogite at these depths, consistent with the seismic observation.

Immediately above the LVZ, within the mantle wedge, there is a significant velocity reduction that is sufficient to erase the seismic contrast that typically marks the transition from mantle wedge to continental crust. This feature is inferred to be due to the combined presence of antigorite and free water (at elevated pore pressure)resulting from eclogitization, consistent with thermo-petrological models.

A number of other geophysical (seismic reflection, gravity, magnetics) observations lend support to the serpentinization interpretation and demonstrate its continuity along strike. Both serpentinization and eclogitization involve large (10%-20%) changes in volume that are likely accommodated through fracturing, thereby promoting a dramatic increase in permeability across the plate interface near the mangle wedge corner. This location coincides with hypocentral locations of non-volcanic tremor and, given the oft-inferred association of tremor fluids, we propose that changes in plate interface permeability may play a key role in tremor generation.

March 29 Christine Shriner, Department of Geological Sciences. Title: A Geologic Method for the Explanation of Cultural Change and its Nature: Unraveling Archaeological Problems using Provenance and Processing.

April 5 Liese van Zee, Astronomy Department Indiana University. Title: Chemical Enrichment of Gas-Rich Galaxies in the Local Volume

April 12 Jay Ague, Yale University. Title: Mountain Building: Where's the Heat?

April 19 Tom Johnson, University of Illinois. Title: Cr isotopes and the fate of hexavalent Cr contamination in the environment

April 26: No Colloquium