Evidence for fluid and melt generation in response to an asthenospheric upwelling beneath the Hangai Dome, Mongolia

• Published in: Earth and planetary science letters Vol. 487; pp. 201 - 209
• Main Authors: Comeau, Matthew J., Käufl, Johannes S., Becken, Michael, Kuvshinov, Alexey, Grayver, Alexander V., Kamm, Jochen, Demberel, Sodnomsambuu, Sukhbaatar, Usnikh, Batmagnai, Erdenechimeg
• Format: Journal Article
• Language: English
• Published: Elsevier B.V 01.04.2018
• Subjects: electrical resistivity; Hangai; intraplate volcanism; magnetotellurics; Mongolia; partial melt; Mongolia; magnetotellurics; Hangai; electrical resistivity; intraplate volcanism; partial melt
• ISSN: 0012-821X; 1385-013X
• DOI: 10.1016/j.epsl.2018.02.007

The Hangai Dome, Mongolia, is an unusual high-elevation, intra-continental plateau characterized by dispersed, low-volume, intraplate volcanism. Its subsurface structure and its origin remains unexplained, due in part to a lack of high-resolution geophysical data. Magnetotelluric data along a ∼610 km profile crossing the Hangai Dome were used to generate electrical resistivity models of the crust and upper mantle. The crust is found to be unexpectedly heterogeneous. The upper crust is highly resistive but contains several features interpreted as ancient fluid pathways and fault zones, including the South Hangai fault system and ophiolite belt that is revealed to be a major crustal boundary. South of the Hangai Dome a clear transition in crustal properties is observed which reflects the rheological differences across accreted terranes. The lower crust contains discrete zones of low-resistivity material that indicate the presence of fluids and a weakened lower crust. The upper mantle contains a large low-resistivity zone that is consistent with the presence of partial melt within an asthenospheric upwelling, believed to be driving intraplate volcanism and supporting uplift. •A ∼610 km long electrical resistivity model across the Hangai Dome is presented.•The observed South Hangai fault system shows a clear transition across terranes.•Lower-crustal low-resistivity indicates the presence of fluid and a weakened layer.•A large, low-resistivity zone detected in the upper mantle requires partial melt.•Uplift and volcanism attributed to partial melting in an asthenospheric upwelling.