Geomagnetic Paleointensity of the Early Earth [2.45 Ga] as recorded in Karelia [Russia] and the Superior Province [Canada]

University Of Rochester, Rochester NY

Investigators

Abstract

Tarduno 0125253 Geomagnetic paleointensity data from Proterozoic and Archean rocks can provide insight into the origin and early history of the Earth's magnetic field. This interval is of particular interest because it may mark the time of growth of the solid inner core. However, paleointensity measurements are difficult because of alteration induced during standard (Thellier) laboratory heating procedures. The investigators have developed an approach to measure paleointensity using single plagioclase crystals that has potential for studying the early geodynamo. Plagioclase crystals, which contain nanometer-sized magnetic inclusions, are less susceptible to experimental alteration than many bulk-rock samples. Preliminary rock magnetic and Thellier analyses of plagioclase crystals separated from 2.45 billion-year-old mafic dikes from Karelia (Russia), provide the basis for this work. They propose field and laboratory programs to obtain time-averaged paleointensity data based on single plagioclase crystals from Proterozoic and Archean dikes of Karelia and the Superior Province (Canada). These data will be used to test hypotheses concerning the early geomagnetic field, including whether a stepwise increase in paleointensity occurred related to inner core growth, and whether the early field had large octupole components. This work includes support for a postdoctoral researcher, a graduate student, and several undergraduate students.