Open AccessA Model of Crustal Conductive Structure In the Canadian Cordillera
Author(s) -
Majorowicz Jacek A.,
Gough D. Ian
Publication year - 1994
Publication title -
geophysical journal international
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.302
H-Index - 168
eISSN - 1365-246X
pISSN - 0956-540X
DOI - 10.1111/j.1365-246x.1994.tb03934.x
Subject(s) - geology , magnetotellurics , crust , seismology , subduction , mantle (geology) , pluton , geophysics , electrical conductor , block (permutation group theory) , tectonics , submarine pipeline , electrical resistivity and conductivity , geotechnical engineering , physics , geometry , mathematics , quantum mechanics , electrical engineering , engineering
SUMMARY Results from magnetotelluric soundings in the frequency range 0.016–160 Hz are used to model conductive structure in the upper and middle crust along a section across strike of the Canadian Cordillera, a region of continental accretion associated with three successive subductions over the last 200 Ma. 2‐D finite‐difference modelling is applied to secure a first‐order fit to observed phase and apparent resistivity pseudosections in two polarizations, with the electric field along geological strike (E‐polarization) and across strike (B‐polarization). the fit to observed fields, and its limitations, are shown in detail by comparing calculated and observed pseudosections. the misfits are instructive and are to be expected where 2‐D modelling is fitted to 3‐D structure in the Earth. the model nevertheless indicates two major resistive and three major conductive blocks in the upper and middle crust. the larger resistive block probably represents granitoid plutons of the Coast Plutonic Belt, which are shown to continue beneath the adjoining Intermontane Belt. the three conductive blocks are believed to result from saline water in fractures. the block under the Coast Plutonic Belt may draw its water from the currently active subduction offshore, whereas the block in line with the Fraser Fault may draw its water from the atmosphere and the block under the Omineca Belt from a global‐scale upcurrent in the mantle.