The Nature of the Mid-Archean Geomagnetic Field

University Of Rochester, Rochester NY

Investigators

Abstract

Paleomagnetic and paleointensity data of late Archean/early Proterozoic age (approximately 2.7 to 2.5 million years old) show many of the hallmarks of the geomagnetic field of the last 200 million years. Our picture of the field prior to this time, however, is unclear because even the best-preserved rocks have likely seen prolonged low-grade metamorphic conditions. A new CO2 laser/superconducting quantum interference device (SQUID) magnetometer approach affords the opportunity to analyze for the first time paleomagnetic and paleointensity signatures of single, oriented silicate grains. These grains contain minute magnetic inclusions that should preserve original magnetizations. A joint laboratory and field plan will be pursued, focused on the analysis of Archean plutonic rocks of the Kaapvaal Craton (southern Africa). The definition of the nature of the Archean geomagnetic field will be of interest to a broad range of scientists studying the early Earth and inner core, as well as those involved in numerical and experimental simulations of planetary dynamos. The work will contribute to scientific infrastructure, through the development of the CO2 laser/SQUID magnetometer system, and to education. Undergraduate and graduate students will be involved in the full range of activities associated with the project, including field studies, equipment development and laboratory analyses.