Department of Earth SciencesWestern Science

NSERC USRA Summer Projects are Available

December 14, 2012

If you are a current Western undergraduate student with a cumulative average over 80% and are interested in any of the projects below, we encourage you to apply by getting in touch with the professors listed.

A new electron microprobe is arriving in the department this spring. Electron microprobe analysis is a technique where the compositions of minerals and other solid phases are determined non-destructively at a scale as small as approximately 100 nanometers. This equipment is also used to generate elemental maps. The USRA position will involve calibrating analyses of a variety of minerals and elements as well as analyzing mineral deposit and planetary materials.

The oldest known pieces of our planet are crystals of the mineral “zircon” dated to 4.4 billion years. These zircons contain other records of the conditions on the early Earth, such as evidence of giant meteorite impact events, at the time of the origin of life and continents, and are therefore of great interest. One project involves examining a new sample of early Earth zircons, at least as old as 3.8 billion years, recently discovered by my group in an ancient crustal terrain in the Canadian Arctic. The successful NSERC USRA student will learn how to explore the chemical and structural record of this zircon population for evidence of ancient impacts while gaining experience in optical and electron microscopy techniques in the nationally unique ZAPLab facility. Similar projects on meteorite samples are also available. For more information contact ZAPLab director Des Moser (desmond.moser@uwo.ca).

This project involves searching hydroacoustic records for wave signatures associated with large bolides (fireballs) and understanding better the seismic efficiency of impacts on land and sea. The goal of the project is to isolate one or more bolide signatures from a suite of 11 hydroacoustic stations worldwide and identify signals from meteorites impacting the ocean surface and/or airwaves from fireball explosions coupled to the ocean. The project will involve signal analysis using MATLAB and some interpretation of wave propagation in the ocean. Additionally, a detailed literature search related to seismo-acoustic and seismo-hydroacoustic coupling will be performed with respect to efficiency of seismic and hydroacoustic impacts.

Impact cratering is one of the most fundamental geological processes in the Solar System. Impact events generate pressures and temperatures that can vaporize, melt, shock metamorphose, and/or deform a substantial volume of the target. Understanding and quantifying these effects is critical for the interpretation of the primary information about a planetary body recorded in an extraterrestrial sample. All meteorites are shocked to some degree but understanding the pre-impact record is often difficult; new mineral phases and polymorphs can be formed, and rocks can be completely melted. This work will focus on the study of samples from several impact craters, as well as meteorites from the University of Western Ontario Meteorite Collection. Samples will be studied using a variety of analytical techniques. Depending on the interests of the student, fieldwork is possible.

Minerals subjected to stress, such as by tectonic forces during regional metamorphism or shock metamorphism during meteorite impact, exhibit deformation by inhomogeneous or plastic strain (e.g. bending).  Inhomogeneous or plastic strain can produce two effects in 2-dimensional X-ray diffraction patterns: (1) increasing mosaic spread as seen by streaking in the chi dimension, and (2) inherent strain, as seen by line broadening of the X-ray diffraction peak in the 2theta dimension.  The Bruker D8 Discover micro X-ray diffractometer, with a two-dimensional general area diffraction detector system (GADDS), can be used to make in situ observations of both mosaic spread (FWHM along chi) and inherent strain (peak FWHM along 2theta) in minerals and calibrate these parameters as a function of degree of strain/shock experienced by the specimen.

The NSERC USRA student will observe strain in selected minerals in terrestrial rocks and meteorites, using optical microscopy and microXRD, as well as running calibration experiments by applying a controlled amount of strain to samples (measured via strain gauge) using a purpose-built strain jig, and correlating this to mosaicity (streak length) as observed by microXRD. Time permitting, the student will complement these data with observations from SEM/EBSD imaging of selected samples.

The emergence of X-ray microdiffraction (mXRD) has expanded the capabilities of XRD, allowing non-destructive XRD analysis of polished sections, probe mounts, rock slabs, or whole meteorites, with little sample preparation required.  The 100-300 mm beam spot size of the X-ray beam allows grain-by-grain correlation of crystal structure to other microanalytical parameters on the microscopic scale (e.g. crystal structure can be correlated to mineral chemistry as found by the electron microprobe). Furthermore, the surface can be mineralogically mapped, and orientational information is preserved, giving mXRD new potential to study mineral associations and strain.

The NSERC USRA student will examine the mineralogy of a variety of meteorites (chondrites and achondrites) using the Bruker D8 mXRD, From mXRD data, the student will identify mineral phases from their crystal structures, using the International Centre for Diffraction Data (ICDD) database, and measure unit cell parameters and strain-related mosaicity for selected minerals. Time permitting, the student will complement these data with observations from optical petrography and SEM/EBSD imaging of selected samples.

The behaviour of seismic waves in the Earth’s mantle suggests that it is an anisotropic medium. This anisotropy has been proposed to originate from alignment of anisotropic minerals in the mantle, such as olivine and pyroxene, along preferred axes. We can not sample the mantle directly, but kimberlites bring with them samples of the Earth’s mantle in the form of xenoliths of peridotitic mantle (olivine) and eclogitic material (clinopyroxene). Mantle xenoliths can be examined in situ by micro X-ray diffraction (mXRD), to look for lattice preferred orientation (LPO) in the phenocryst mineral population. These samples may also preserve inhomogeneous strain, from igneous or metamorphic processes. This can be measured via the degree of ‘streaking’ of X-ray spots, and may correlate with LPO.

The NSERC USRA student will examine the mineralogy of a variety of mantle xenoliths from kimberlite pipes in NWT, Canada, using the Bruker D8 mXRD. They will identify mineral phases from their crystal structures, using the International Centre for Diffraction Data (ICDD) database, and will analyse them for LPO and strain-related mosaicity. Time permitting, the student will complement these data with observations from optical petrography and SEM/EBSD imaging of selected samples.

Planetary materials found in the impact crater or from the meteorite samples are considered to be subjected to different extent of shock impact.  The shocked materials are also regarded as quench products of its parent body that contains many different mineral phases.  In this study, it aims to use Raman spectroscopy to investigate the important mineral phases found in the meteorite at temperature from 300 to 1000 K.  The unique function of Raman spectroscopy allows the mineral phases to be examined in situ at high temperatures.  Both optical and spectroscopic information can be collected at the same time.  Furthermore, spectroscopic data can be used to evaluate the stable and metastable phase during and after shock events.

One curious aspect of some Pleistocene megafauna (mammoths, horses) is their strong tendency to be enriched in nitrogen-15 relative to the typical ratio of 15N/14N found in herbivores, except during the latest Pleistocene.  Several hypotheses have been offered to explain this unusual result, including climate-related dynamics in the ‘Mammoth Steppe’ ecosystem, physiological behaviours causing nitrogen recycling within the bodies of these large animals, and coprophagy.  We will test the hypothesis that these megafauna consumed 15N-enriched plants that thrived in their habitat – as a consequence of aridity, dung fertilization and related processes in this now extinct soil-plant-animal ecosystem.  The hypothesis will be explored through study of modern elephant and cattle pastures, and then extended to a suitable Pleistocene site where analysis of paleobotanical materials located in context with mammoth and horse remains is possible.  We will also explore possible reasons for the sudden lowering of nitrogen-15 concentrations in the tissues of these megafauna at the end of the Pleistocene, testing in particular the idea that this dramatic change arose from fundamental modifications to nitrogen cycling in the soil-plant system because of a major shift in climate.

The student will participate in field work, and be responsible for sample characterization, stable isotopic analysis, preliminary interpretation of the data collected, and preparation of a report summarizing the results.

This project is part of the CFI-CRC funded ‘Back to the Future’ climate change in the America’s initiative.

Glacial meltwater escaping from Lake Agassiz, other proglacial lakes, and/or the Laurentide Ice Sheet has been strongly implicated in triggering the global Younger Dryas cold spell between ~13,000 and 11,500 cal years BP.  Key questions remain concerning the pathway(s) travelled by this glacial meltwater on its way to the Atlantic Ocean – with northwestern routes (via the McKenzie River Valley to the Arctic Ocean), northeastern routes (via Hudson’s Bay) and eastern routes (through the Great Lakes) all gaining favour at one time or another.  We will use the stable isotopic compositions of flora and shelly fauna (oxygen- and carbon-isotope compositions of carbonate, carbon- and nitrogen-isotope compositions of organic matter) to evaluate the eastern route hypothesis.  We will calibrate the meltwater signal by analysis of climate proxies preserved sediments from cores taken from Georgian Bay.

Working with already-collected lake sediment cores plus participation in May-August 2013 sampling of modern shelly fauna, the students will be responsible for the isolation, identification and stable isotopic analysis of the various faunal and floral materials found in the cores and collected in the field, preliminary interpretation of the data collected, and preparation of a report summarizing the results.

This project is part of the CFI-CRC funded ‘Back to the Future’ climate change in the America’s initiative.

Late Pleistocene and Holocene sediments of the Great Lakes Basin contain many proxies for climate change in this region over the last ~15,000 cal years BP.  As a companion to ongoing stable isotopic studies of sediments from Lakes Superior, Michigan, Huron, Ontario and Erie, we will examine similar proxies for climate change contained in sediments from a small sinkhole lake (Barry Lake) located near Peterborough, Ontario, and a small pond (Carolinian Pond) contained in Pinery Provincial Park, Lake Huron, Ontario. Our focus will be on sediments recording climate changes spanning the warming period known as the Holocene Hypsithermal, the later cooling known as the Holocene Neoglacial interval, and the climate patterns over the last 500 years, including warming over the last ~100 years.

Working with already-collected gravity sediment cores from Barry Lake, and through participation in May-June 2013 sediment coring expeditions to the Carolinian Pond and similar water bodies, the student will be responsible for the isolation, identification and stable isotopic analysis of the various faunal and floral materials found in the cores, preliminary interpretation of the data collected, and preparation of a report summarizing the results.

This project is part of the CFI-CRC funded ‘Back to the Future’ climate change in the America’s initiative.

Explore several new meteorites with Dr. McCausland, Western’s Curator of meteorites using non-destructive techniques such as X-ray Computed Tomography 3D imaging and related techniques as well as by microscopic examination of rock thin sections. This work is anticipated to result in the submission of official descriptive reports for several new meteorites, and can lead to further scientific study of interesting discoveries where warranted. Experience with introductory mineralogy is helpful, but not required.

Before arriving on Earth as meteorites, small rocks in orbit around the sun were exposed to energetic galactic cosmic rays, which left small damage tracks in meteoritic minerals such as olivine, pyroxene, feldspar and apatite. The cosmic ray exposure history for any meteorite can be read from the cosmic ray track record, which decreases with greater depth, providing essential information on the size of the object before it arrived on Earth. This work involves joining the Western’s Curator of meteorites and other researchers in the Meteor Physics group in the etch preparation and measuring of the cosmic ray tracks in minerals, and in helping to develop more automated, digital techniques for collecting the track data. Research on specific meteorites separate from other researchers is planned, leading to reports on their cosmic ray exposure and on methods development. A background in introductory mineralogy and/or introductory physics is useful but not required.

Many fragments of a very primitive, unusual early Solar System meteorite arrived in January, 2000 on the frozen surface of Tagish Lake, northern British Columbia. A large number of specimens from the search that year are now present in Western’s meteorite collection. These Tagish Lake meteorite samples require further careful description and followup study of some unusual features –the project is to assist Dr. McCausland, Western’s Curator of meteorites in this descriptive work and to explore the interesting discoveries in this group of samples, leading to a report of the key features of the Tagish Lake collection and possibly their scientific implications. Experience with introductory mineralogy is helpful, but not required.

The permanent magnetic record in rocks such as limestone and red shale can act like a frozen compass to record the ancient direction to the north pole at the time when the rock formed. This work uses samples from Western Newfoundland to estimate the ancient location of North America with respect to the Earth’s polar regions at ~490 million years ago, by laboratory measurements of sample stepwise demagnetization to reveal the ancient magnetic direction. A possible development of this work with Dr. McCausland is to conduct new sampling of similar-aged rocks. Note that this work will require two to three weeks’ residency in Windsor, Ontario during the summer, to work at the excellent Paleomagnetic Laboratory, University of Windsor. All other work is based at Western.

Students interested in gaining practical experience in a research setting applied to Economic Geology are required to help with various current projects sponsored by mineral exploration companies. You will be given the opportunity to apply your skills in all aspects of the research program. Individual students will be matched to projects based on interest and skill level but may include: mineral exploration, field mapping, geochemical analysis, and environmental remediation. Some experience in a research or lab environment is desirable but not required. Some fieldwork in northern Ontario may be required. Students interested in an industry-sponsored honours thesis project are especially encouraged to apply.

Students interested in a USRA in stratigraphy & sedimentology are welcome to contact Dr. Plint for information.