Velocity-conductivity relations for cratonic lithosphere and their application : example of Southern Africa
Jones, Alan G.
Evans, Rob L.
Muller, Mark R.
MetadataShow full item record
Seismic velocity is a function of bulk vibrational properties of the media, whereas electrical resistivity is most often a function of transport properties of an interconnected minor phase. In the absence of a minor conducting phase then the two should be inter-relatable primarily due to their sensitivity to temperature variation. We develop expressions between shear wave velocity and resistivity for varying temperature, composition, and water content based on knowledge from two kimberlite fields: Jagersfontein (Kaapvaal Craton) and Gibeon (Rehoboth Terrane). We test the expressions through comparison between a new high-resolution regional seismic model, derived from surface wave inversion of earthquake data from Africa and the surrounding regions, and a new electrical image from magnetotelluric (MT) data recorded in SAMTEX (Southern African Magnetotelluric Experiment). The data-defined robust linear regression between the two is found to be statistically identical to the laboratory-defined expression for 40 wt ppm water in olivine. Cluster analysis defines five clusters that are all geographically distinct and tectonically relate to (i) fast, cold, and variably wet Kaapvaal Craton, (ii) fast and wet central Botswana, (iii) slow, warm, and wet Rehoboth Terrane, (iv) moderately fast, cold, and very dry southernmost Angola Craton, and (v) slow, warm, and somewhat dry Damara Belt. From the linear regression expression and the MT image we obtain predicted seismic velocity at 100 km and compare it with that from seismic observations. The differences between the two demonstrate that the linear relationship between Vs and resistivity is appropriate for over 80% of Southern Africa. Finally, using the regressions for varying water content, we infer water content in olivine across Southern Africa.
Author Posting. © American Geophysical Union, 2013. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Geochemistry, Geophysics, Geosystems 14 (2013): 806–827, doi:10.1002/ggge.20075.
Showing items related by title, author, creator and subject.
Velocity–conductivity relationships for mantle mineral assemblages in Archean cratonic lithosphere based on a review of laboratory data and Hashin–Shtrikman extremal bounds Jones, Alan G.; Evans, Rob L.; Eaton, David W. (2008-08-12)Can mineral physics and mixing theories explain field observations of seismic velocity and electrical conductivity, and is there an advantage to combining seismological and electromagnetic techniques? These two questions ...
Lithospheric structure of an Archean craton and adjacent mobile belt revealed from 2-D and 3-D inversion of magnetotelluric data : example from southern Congo craton in northern Namibia Khoza, T. David; Jones, Alan G.; Muller, Mark R.; Evans, Rob L.; Miensopust, Marion P.; Webb, Susan J. (John Wiley & Sons, 2013-08-09)Archean cratons, and the stitching Proterozoic orogenic belts on their flanks, form an integral part of the Southern Africa tectonic landscape. Of these, virtually nothing is known of the position and thickness of the ...
Late Archean to Early Proterozoic lithospheric mantle beneath the western North China craton: Sr–Nd–Os isotopes of peridotite xenoliths from Yangyuan and Fansi Xu, Yi-Gang; Blusztajn, Jerzy S.; Ma, Jin-Long; Suzuki, Katsuhiko; Liu, J.-F.; Hart, Stanley R. (2007-02-02)Sr-Nd-Os isotopic analyses are presented for peridotite xenoliths from Tertiary alkali basalts in Yangyuan and Fansi with the aim of identifying and characterizing the relics of ancient lithospheric mantle that survived ...