Electrical conductivity of the earth's crust and upper mantle

A review of progress in modelling of induced geoelectric and geomagnetic fields with special regard to induced currents

“…We restrict ourselves therefore to a summary of regional conductivity studies of relevance to modelling GIC within Europe and North America. However we note that studies reported in Schwarz (1990) provide valuable detail for regions such as New Zealand, South Africa, Australia, and Japan.…”

“…We summarise major recent discoveries and provide, for the reader, references to the major papers. We concentrate on papers published in the last ten years or so and therefore refer the reader to the reviews of Schwarz, 1990, andHjelt, 1988, for the status of the scientific literature prior to this time.…”

Role of sulfur and carbon in the electrical conductivity of the middle crust

“…Magnetotelluric and deep geomagnetic sounding reveal that Earth's continental crest contains zones of high electrical conductivity [e.g., Haak and Hutton, 1986;Hjelt, 1988;Schwarz, 1990]. These highly conducting layers have stimulated a controversial discussion concerning their origin.…”

Combined transient electromagnetic and magnetotelluric study of the southern Kenya rift valley

“…In addition, the top of the reflective and conductive middle crust is often coincident with the bottom of the zone of earthquake activity (Gough, 1986). This suggests that the transition from the upper resistive to the middle conductive crust correlates in general with the brittle to ductile transition in rock rheology (Bailey, 1990), and this is also believed to occur around 400°C (Schwarz, 1990).…”

“…Two of the main origins of deep graphite are (Schwarz, 1990;Jodicke, 1992;Hyndman et al, 1993): (i) organic material Introduction rocks. In a conductive rift environment the presence of graphite is not usually invoked as a source of low resistivities, since a continuous supply of deep fluids is expected and also there appears to be a strong correlation with temperature which is not expected for graphite .…”