Dr. Roberta L. Flemming

Mineralogy

Associate Professor
Office: BGS 0172
Phone: (519) 661-2111 x.83143
Fax: (519) 661-3198
Email: rflemmin@uwo.ca

Research Interests

Professor Roberta Flemming and her research group study a variety of mineralogical and geological problems using a combination of crystallography, mineral chemistry and spectroscopy. Observations made from synthetic minerals produced at high temperatures and pressures in the laboratory, and from natural minerals obtained in the field, are used to understand changes in mineral structure, chemistry, cation distribution, solid-solubility, and phase transition behaviour, in response to changes in pressure, temperature, and composition (P-T-X), for application to a variety of geological problems. Flemming employs a variety of techniques, including X-ray diffraction and microdiffraction, Rietveld refinement of diffraction data, electron probe microanalysis (EPMA), and a variety of spectroscopic techniques, including solid-state nuclear magnetic resonance (NMR). Flemming’s current research objectives are outlined below:

1. Fundamental understanding and quantification of mineral behavior as a function of pressure (P), temperature (T) and composition (X) by synthesizing minerals at various P-T-X, and studying their crystal structure (X-ray diffraction/Rietveld refinement), crystal chemistry (EPMA), and cation order-disorder (NMR spectroscopy, e.g. ²⁹Si, ²⁷Al, ¹⁷O).
2. Systematic investigation of Kimberlite Indicator Minerals (KIM) (e.g. garnet, chromite, Cr-diopside). Variation in unit cell parameters (µXRD) is correlated to geochemical data (EPMA), on a grain-by-grain basis, with the aim of developing µXRD as a tool for diamond exploration. Inclusions and strain in minerals give additional clues to origin.
3. Systematic mineralogical investigation of meteorites. In situ µXRD provides rapid mineral ID, for meteorite classification. A growing database of unit cell parameters for meteorite minerals will be correlated to geochemical information, which may ultimately be correlated to planetary origin. Rietveld refinement of powder XRD data provides modal mineral analysis, and enables crystal structural study of selected phases.
4. Development of micro X-ray diffraction (µXRD) as a tool for geologists. µXRD provides a unique opportunity to correlate crystal structural information with other microanalytical data on the microscopic scale (50-500 µm) not previously available. In situ examination of minerals preserves orientational information. Anticipated projects include development of µXRD-related exsolution geothermometry (e.g. two pyroxenes), and quantification of strain-related mosaicity in minerals in meteorites, impact structures, and other rocks, with an aim toward development of a µXRD strain index.

Selected Publications

Flemming, R.L. (2007) Micro X-ray Diffraction (µXRD): A versatile technique for characterization of Earth and planetary materials. Canadian Journal of Earth Sciences, In press.

Courses Taught

Undergraduate courses (currently taught):
Earth Sciences 2206a: Mineral Systems, Crystallography and Optics
Earth Sciences 2212b: Genesis of Meteorites & Planetary Materials
Earth Sciences 3310b: Structure and Chemistry of Minerals and Materials

Undergraduate courses (previously taught):
Environmental Science 300F: Great Lakes Pollution (2001, 2002)
Earth Sciences 3341b: Environmental Geochemistry (2003)

Graduate Courses:
Geology/Geophysics 9580a/9680a: Graduate Seminar
Geology 9516b: Advanced Mineralogy and Crystallography (offered even years, winter)
Geology 9549a: Special Topics in Mineralogy (2005)

Students

1. Fundamental understanding and quantification of mineral behavior as a function of pressure (P), temperature (T) and composition (X).
   Guangrong Ning – Synthetic cpx-garnet mixtures: Information from Rietveld refinement of X-ray diffraction data.
   
   Available project - Cation ordering and entropy in pyroxene group minerals.
2. Systematic investigation of Kimberlite Indicator Minerals (KIM) with the aim of developing µXRD as a tool for diamond exploration.
   Ben Harwood – A comparison of the crystal structure and major element chemistry of kimberlitic garnets and ilmenites.
   
   Available projects include investigation of crystal structural – crystal chemical correlations in other KIM minerals such as Cr-diopside and chromite.
3. Systematic mineralogical investigation of meteorites by In situ µXRD and powder XRD.
   Matt Izawa – correlation between modal mineralogy as determined by powder XRD/Rietveld refinement and Diffuse Reflectance IR spectra, for Tagish Lake Carbonaceous chondrite and enstatite chondrites.
   
   Available projects include:
   
   • Systematic mineralogical study of a wide variety of meteorites including a progression of 4 Vesta meteorites: howardites, eucrites, diogenites and dunites.
   • Systematic examination of minerals forming during fusion crust formation.
   • Systematic determination of Unit cell parameters for major minerals in meteorites (e.g. clinopyroxene and olivine). Unit cell parameters will be correlated to mineral chemistry, and potentially correlated to planetary origin.
4. Development of micro X-ray diffraction (µXRD) as a tool for geologists.
   
   Available projects include:
   • Quantification of strain-related mosaicity in minerals in meteorites, impact structures, and other rocks, with an aim toward development of a µXRD strain index and calibration using existing strain indices.
   • Development of µXRD for exsolution geothermometry. (e.g. two pyroxenes). GADDS image provides simultaneous unit cell information for both phases, as well as their T-dependent orientational relationship.

• Faculty
• Administrative Staff
• Research Staff & Postdoctoral Fellows
• Graduate Students