Research Interests
My research draws on the magnetic behavior and crystal orientation of minerals to understand questions about Earth processes operating on global, tectonic, outcrop, and nanometer scales. In order to connect observations made at small scales to processes occurring on larger scales, my research incorporates a strong multi-disciplinary approach including rock magnetism, mineral texture studies (EBSD), scanning force microscopy (AFM, MFM), paleomagnetism, electron microscopy (TEM, SEM, electron holography), fieldwork, and numerical modeling.
Some of the projects I am involved with are: the mineralogic origin of iron oxide inclusions in silicate minerals and their recordings of the Earth's magnetic field, measurements of geomagnetic paleointensity, the origin of exsolution structures in minerals, the effect of preferred mineral orientation on bulk rock properties (such as magnetic remanence, susceptibility, and seismic anisotropy), and finally, climate records as chronicled by magnetic minerals in speleothems. The first of these projects is briefly described below.
The remanent magnetizations preserved within Precambrian rocks are the only available record of geodynamo behavior during early Earth history. Careful studies of the mineralogy that hold these recordings are required in order to address questions about the strength of the Precambrian Earth's magnetic field, the convective behavior of the liquid core, and potentially, the formation of the solid inner core. Silicate-hosted magnetic inclusions in minerals such as pyroxene, plagioclase, and hornblende are ideal for addressing such questions because they accurately record information about the Earth's magnetic field and are protected from subsequent alteration by their silicate hosts. My colleagues and I use magnetic imaging techniques such as magnetic force microscopy and electron holography to understand how nanometer scale mineral structures within these magnetic inclusions effect their remanence properties. In some inclusions, we have found that intraoxide exsolution produces a tessellated pattern of magnetite blocks in an ulvöspinel matrix. This mineral unmixing, combined with the inclusions' elongated shape, produces directionally dependent (or anisotropic) magnetic properties within single silicate crystals. Much of my current research aims at understanding this anisotropy so that single silicate crystals can be used to reveal the magnetic field behavior of the early Earth.
I encourage prospective students and postdocs with interests and backgrounds in geology, mineralogy, petrology, tectonics, sedimentology, material sciences, and physics to consider working with me and others at the Institute for Rock Magnetism.
In addition to magnetism and mineralogy, I have active interests in paleobiology and the study of mass extinctions.
Professional Society Memberships
- American Geophysical Union
- Geological Society of America
- Mineralogical Society of America
- Mineralogical Society of Great Britain and Ireland
Selected Publications
- Feinberg, J.M.,Wenk, H.-R., Scott, G.R., and Renne, P.R. 2006, Preferred orientation and anisotropy of seismic and magnetic properties in gabbronorites from the Bushveld layered intrusion: Tectonophysics, 420, 345-356.
- Rennei, P.R., Feinberg, J.M., Waters, M.R., Arroyo-Cabrales, J., Ochoa-Castillo, P., Perez-Campa, M., and Knight, K.B. (2005) Age of the Xalnene ash, Central Mexico, and archeological implications: Nature, 438, doi:10.1038/nature04425.
- Feinberg, J.M., Scott, G.R., Renne, P.R., and Wenk, H.-R., 2005, Exsolved Magnetite Inclusions in Silicates: Features Determining Their Remanence Behavior: Geology, 33 (6), p. 513-516.
- Twitchett, R.J., Feinberg, J.M., O'Connor, D.D., Alvarez, W., and McCollum, L., 2005, Early Triassic Ophiuroids: their Paleoecology, Taphonomy and Distribution: Palaios, 20, p. 213-223.
- Feinberg, J.M., Wenk, H.-R., Renne, P.R., Scott, G.R., 2004. Epitaxial relationships of silicate-hosted magnetite determined using electron backscatter diffraction (EBSD) technique. American Mineralogist, 89, p. 462-466.
- Renne, P.R., Scott, G.R., Glen, J.M.G., and Feinberg, J.M. (2002) Oriented inclusions of magnetite in clinopyroxene: Source of stable remanent magnetization in gabbros of the Messum Complex, Namibia. Geochemistry, Geophysics, Geosystems, 3(12), 1079, doi: 10.10229/2002GC000319.
Recent Research Support
- 2007-2009: Startup funds from the Department of Geology and Geophysics and IT College, University of Minnesota
- 2005-2008: NERC: Silicate Hosted Magnetic Inclusions as Paleomagnetic Recorders
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