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Compaction‐Driven Fluid Localization as an Explanation for Lower Crustal Electrical Conductors in an Intracontinental Setting
Author(s) -
Comeau Matthew J.,
Becken Michael,
Connolly James A. D.,
Grayver Alexander V.,
Kuvshinov Alexey V.
Publication year - 2020
Publication title -
geophysical research letters
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.007
H-Index - 273
eISSN - 1944-8007
pISSN - 0094-8276
DOI - 10.1029/2020gl088455
Subject(s) - geology , magnetotellurics , electrical resistivity and conductivity , compaction , crust , anisotropy , tectonics , petrology , geophysics , deformation (meteorology) , fluid dynamics , seismology , geomorphology , mechanics , oceanography , physics , quantum mechanics , electrical engineering , engineering
Abstract We present electrical resistivity models, derived from magnetotelluric data, of the crust beneath the Bulnay region, Mongolia. They reveal that the lower crust contains a pattern of discrete zones (width of ~25 km) of low resistivity (<30 Ωm). Such features may be an effect of unaccounted‐for electrical anisotropy. However, when anisotropy is considered in the modeling, the features remain. We investigate an alternative explanation, based on a conceptual model of fluid localization and stagnation by thermally activated compaction, and demonstrate it is compatible with the observed low‐resistivity zones. The model explains the location, shape, and size of the zones, with plausible values of the activation energy for lower crustal creep (270–360 kJ/mol), and a viscous compaction length on the order of 10 km. The results imply tectonic deformation and compaction processes, rather than lithological‐structural heterogeneity, control the regional lower crustal fluid flow.