Conductivity structure of the lithosphere-asthenosphere boundary beneath the eastern North American margin
Evans, Rob L.
Elsenbeck, James R.
MetadataShow full item record
KeywordLithosphere-asthensphere boundary (LAB); Magnetotelluric (MT); 2-D MT inversion; Conductivity structure; Kimberlite intrusion; Shear-driven deformation
Tectonic plate motion and mantle dynamics processes are heavily influenced by the characteristics of the lithosphere-asthenosphere boundary (LAB), yet this boundary remains enigmatic regarding its properties and geometry. The processes involved in rifting at passive margins result in substantial alteration of the lithosphere through the transition from continental to oceanic lithologies. Here we employ marine magnetotelluric (MT) data acquired along a ∼135 km long profile, offshore Martha's Vineyard, New England, USA, to image the electrical conductivity structure beneath the New England continental margin for the first time. We invert the data using two different MT 2-D inversion algorithms and present a series of models that are obtained using three different parameterizations: fully unconstrained, unconstrained with an imposed LAB discontinuity and a priori constrained lithosphere resistivity. This suite of models infers variability in the depth of the LAB, with an average depth of 115 km at the eastern North America passive margin. Models robustly detect a ∼350 Ωm lithospheric anomalous conductivity zone (LACZ) that extends vertically through the entire lithosphere. Our preferred conductivity model is consistent with regional P-to-S receiver function data, shear-wave velocity, gravity anomalies, and prominent geological features. We propose that the LACZ is indicative of paleolithospheric thinning, either resulting from kimberlite intrusions associated with rifting and the New England Great Meteor hot spot track, or from shear-driven localized deformation related to rifting.
Author Posting. © American Geophysical Union, 2017. 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 18 (2017): 676–696, doi:10.1002/2016GC006667.
Suggested CitationGeochemistry, Geophysics, Geosystems 18 (2017): 676–696
Showing items related by title, author, creator and subject.
Water in cratonic lithosphere : calibrating laboratory-determined models of electrical conductivity of mantle minerals using geophysical and petrological observations Jones, Alan G.; Fullea, Javier; Evans, Rob L.; Muller, Mark R. (American Geophysical Union, 2012-06-14)Measurements of electrical conductivity of “slightly damp” mantle minerals from different laboratories are inconsistent, requiring geophysicists to make choices between them when interpreting their electrical observations. ...
Velocity-conductivity relations for cratonic lithosphere and their application : example of Southern Africa Jones, Alan G.; Fishwick, Stewart; Evans, Rob L.; Muller, Mark R.; Fullea, Javier (John Wiley & Sons, 2013-04-05)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 ...
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 ...