This award provides $1,396,115 in continued NSF support over 36 months to operate the Institute for Rock Magnetism (IRM) which supports in-depth pure and applied research on rock, sediment and mineral magnetic properties. Funds provide for: PI and associate director summer salary support; a helium reliquification system to recover expensive liquid He; salary support for a Facility manager and staff scientists; travel support for the Visiting Fellows program and advisory committee meetings; support for consumables (e.g., liquid He, liquid Nitrogen and gases) and replacement parts; and publishing and mailing costs for the IRM quarterly newsletter. The IRM has been funded by the Instrumentation and Facilities Program (IF) in the Division of Earth Sciences for the last twenty years to support, develop and operate a world-class, international multi-user facility for studies in rock magnetism and paleomagnetism. IRM's goals include: 1) providing service to the community to foster a deeper understanding of the complex physical mechanisms that govern the magnetic behavior (under varying conditions of temperature, time, stress, and ambient magnetic field) of fine-particle assemblages including natural nanoparticles of iron oxides, hydroxides and sulfides; 2) providing the geoscience research community with access to a full suite of sensitive instrumentation for these detailed studies; 3) maintaining the facility instrumentation and computer network; 4) providing visiting scholars with the support necessary to use the facilities effectively, including technical, educational, and logistical components of support; 5) adapting methods and techniques from physics and materials science, as well as developing new methods, for using magnetic measurement data to characterize complex natural samples and to address questions of specific interest to geoscientists; and; 6) serving as a catalyst in widening and improving the applications of magnetic analysis in geological and biological studies, by holding workshops and conferences, and by maintaining active (and separately funded) research programs in those areas; and 7) .providing research-related news and information to the geoscience community and related disciplines through a web site, online database and quarterly newsletters. Continued facility support will provide and enhance research infrastructure for the geoscience community. IRM maintains and provides access to a set of advanced instruments for magnetic research that is unique in the Earth sciences, and fosters interdisciplinary collaboration by organizing biannual topical conferences and occasional training workshops. Undergraduates from UM, local colleges, and from around the country receive support through numerous programs including NSF-REU program and mentorship of IRM-resident graduate students, post-docs, faculty and staff. A new Summer School for Rock Magnetism will be started targeted at graduate and advanced undergraduates in the geosciences. IRM organizes interdisciplinary workshops, publishes information and articles for non-specialist audiences in our quarterly newsletter and on our web site, and maintains a public database of experimental results on well-characterized synthetic and natural magnetic materials.
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Magnetic iron-bearing minerals occur naturally in trace amounts in virtually all of the rocks and sediments that make up the crust of the Earth, as well as those of the Moon, meteorites and other extraterrestrial bodies. As is the case with manufactured magnetic recording media, these natural materials store information in the orientation, strength, spatial patterns, and stability of their collective magnetizations. This information can be recovered and investigated through careful measurements on sensitive magnetometers, providing a unique source of data on the evolution of the Earth’s core and of the planetary magnetic field that it produces, as well as on the history of magnetic fields elsewhere in the solar system. Natural magnetic recordings also yield important evidence concerning the thermal, chemical and mechanical processes involved in the acquisition of magnetic ‘memory’ and in some cases its overprinting by later processes. Further, measurements using applied magnetic fields, controlled temperatures and other experimental variables provide rapid and sensitive characterization of the compositions, particle-size distributions, and other material properties of the iron-bearing minerals in natural materials, and these properties can be used to infer the conditions under which the materials formed and the processes that have subsequently acted on them. The Institute for Rock Magnetism (IRM) is a national facility that provides advanced instrumentation for magnetic measurements to researchers in geoscience and related fields including planetary science, environmental science, biophysics, archeology, materials science and engineering. IRM operations are overseen by faculty members of the Department of Earth Sciences at the University of Minnesota, in collaboration with a seven-member Review and Advisory Committee (RAC) comprised of external experts in relevant fields of research, A three-person professional staff maintains the instruments and related laboratory hardware and software infrastructure, and assists visiting researchers in designing experiments, making measurements, and processing and analyzing data. During the four-year grant period, sixty seven Visiting Fellowships were awarded to researchers whose proposals were approved by the RAC. These usually involve ten days of intensive lab work. Over 100 additional visiting scientists used the facility during the same period for shorter stays to get important data for their research projects. Education and training are integrated with research through a summer school and though a student research program, in which visiting graduate students learn to incorporate magnetic measurement techniques into their own research projects with extensive interaction and assistance from IRM faculty and staff. Here are two examples of specific research areas, out of the many investigated at the IRM by Visiting Fellows during the grant period: 1. Identification of source areas for obsidian flakes associated with archeological sites. Volcanic glass is an excellent material for making stone tools, and was widely exploited by prehistoric peoples. Linking discovered artifacts with specific geographic source areas makes it possible to determine how far they were transported and thus to infer something about population mobility and trade in these societies. Trace-element geochemistry is often effective at defining source regions but is commonly unable to pinpoint individual volcanic flows as specific artifact sources. Visiting scientists made detailed magnetic measurements of 250 obsidian samples from 25 sampling locations in the Gutansar volcanic complex in Armenia, and found that magnetic properties could not only distinguish obsidian flows that are geochemically identical but could also identify different quarries within a flow. The integration of magnetic measurements into such studies is thus helping to provide a more complete picture of Palaeolithic human activities. 2. Recognition of high-pressure shock features caused by meteorite impacts in terrestrial and extraterrestrial rocks. The Earth, like the Moon and other bodies of the inner solar system, has been subjected to a long history of bombardment by comets and asteroids, at infrequent intervals but with large effects. Unlike the Moon and other bodies, the Earth has a tectonically-active surface and an atmosphere that drives weathering and sedimentation, all of which obscure the record of impact cratering. Reconstructing the history of major impacts on the Earth’s surface therefore relies heavily on forensic evidence of shocked materials, calibrated by studies on nuclear test sites, geologically-recent impacts (e.g., Barringer crater), and smaller-scale laboratory shock experiments. These show diagnostic deformation features in the crystal structures of minerals, including magnetic iron-bearing minerals. Such features can be detected and quantified through sensitive magnetic measurements under varying controlled conditions of temperature and applied field. Visiting scientists have studied samples from drill holes into the Chesapeake Bay structure, formed by an impact 35 million years ago but only discovered in 1983. Their measurements showed distinctive changes in the properties of both magnetite (an iron oxide mineral) and pyrrhotite (an iron sulfide) related to changes in crystal composition and structure produced by the high transient pressures.
