Research Overview
My research interests in mineralogy range from field studies through experimental investigations of mineral crystal chemistry, structures and stability to quantum mechanical descriptions of bonding and reactions in mineral structures. My long-term research goal is an understanding of the relationship between the paragenesis of low-temperature minerals and their crystal structures, with applications to problems of environmental importance.
Complicated assemblages of fine-grained low-temperature minerals challenge our understanding of mineralogy, both chemically and geologically. Crystal structures of minerals in complex geochemical environments should be related to the occurrences and distribution of the minerals. The discipline of Mineralogy has much to offer the Earth Sciences in this area: an understanding of the relationship between the paragenetic sequences of minerals and their corresponding crystal structures may be realized, and is crucial to understanding complex mineral occurrences. It is only very recently that the introduction of synchrotron radiation and CCD-based detectors to mineralogy has made it possible to solve the structures of crystals with effective volume < (20 mm)3. Detailed knowledge of the structural relationships of fine-grained low-temperature minerals is now attainable, and will revolutionize understanding and applications of low-temperature mineralogy.
Much of my current research is focused on understanding the occurrence, chemistry, and structural relationships of uranyl (U6+) minerals. It is only recently that the extraordinarily complex nature of uranyl mineral structures has become apparent, with my discoveries of topologies with repeats in excess of 50 Å, and pentavalent uranium in mineral structures. The structural complexity of uranyl minerals is a tremendous challenge to our understanding of low-temperature mineralogy. More than 180 uranyl minerals are known, and are the key to understanding the genesis of uranium ore deposits. They are also of significant environmental concern: they form due to the weathering of uranium mine and mill tailings, where soils are contaminated with actinides, and are the main products of alteration of spent nuclear fuel in a geological repository that is oxidizing and moist, such as the proposed repository at Yucca Mountain. It is therefore regrettable that the structures remain unknown for ~2/3 of the ~180 species. The uranyl phases that form under repository conditions will impact upon the release rates of the radionuclides from the spent fuel because they may incorporate many of the radionuclides into their structures. Much of my research is therefore focused on the mechanisms and likelihood of incorporation of radionuclides into the structures of uranyl minerals, as well as their ion-exchange properties.
2003-2005 Environmental Management Science Program, U.S. Department of Energy: sole PI: Quantifying and Predicting Reactive Transport of Uranium in Waste Plumes: Are Colloids and Nanoparticles Importance? $75,000.
2002-2007 Environmental Molecular Science Institute, National Science Foundation. Co-PI (together with Fein and Maurice). Actinides and Heavy Metals in the Environment – The Formation, Stability, and Impact of Nano- and Micro-Particles. $5,500,000.
2003-2004 Pacific Northwest National Laboratory. PI. Subsurface Chemistry in Hanford’s Tank Farms. $80,000.
2002-2005 Environmental Management Science Program, U.S. Department of Energy: sole PI: Phosphate Barriers for Immobilization of Uranium Plumes. $270,000.
2000-2004 Environmental Management Science Program, U.S. Department of Energy: sole PI: Direct Investigations of the Immobilization of Radionuclides in the Alteration Products of Spent Nuclear Fuel. $871,000.
2002-2003 National Science Foundation – NATO: sole PI: Crystal Structure Analysis of Uranyl Selenites and New (Rare) Minerals Using CCD-based X-ray Area Detector. $42,600.
2001-2002 University of Notre Dame Equipment Restoration Fund: Co-PI (together with McGinn and Varma): Acquisition of an Electron Microprobe. $200,000.
2001-2002 North Atlantic Treaty Organization: Coordinating PI: Collaborative Linkage Grant: Investigations of Incorporation of Toxic Metals and Radionuclides into Structures of Secondary Minerals. 528,000 Belgium Francs (approx. $17,000).
2001-2003 Georgia Pacific Corporation: Co-PI (together with Irvine): Investigations of the occurrences of natural dioxins. $225,000.
1999-2001 National Science Foundation: Co-PI (together with Blackburn and McGinn): Acquisition of a Travelling Solvent Floating Zone Furnace for Research and Education. $131,500.
1999-2001 REU Supplement, National Science Foundation: sole PI: Investigations of the Crystal Chemistry of Pb Uranyl Oxide Hydrate Minerals Using a CCD-based X-Ray Area Detector. $6125
1999-2001 National Science Foundation – NATO: sole PI: CCD X-Ray Detectors Applied to Mineral Structure Analysis. $49,800
1999-2001 National Science Foundation: sole PI: Investigations of the Crystal Chemistry of Pb Uranyl Oxide Hydrate Minerals Using a CCD-based X-Ray Area Detector. $92,000
1997-2000 Environmental Management Science Program, sole U.S. Department of Energy: PI: Direct Investigations of the Immobilization of Radionuclides in the Alteration Products of Spent Nuclear Fuel. $632,487.
1997 Capitalization, University of Notre Dame. $300,000