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Magnetotelluric imaging of upper crustal partial melt at Tendaho graben in Afar, Ethiopia
Author(s) -
Didana Yohannes Lemma,
Thiel Stephan,
Heinson Graham
Publication year - 2014
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 - 10.1002/2014gl060000
Subject(s) - geology , magnetotellurics , graben , crust , geothermal gradient , petrology , partial melting , magma chamber , borehole , magma , geochemistry , seismology , geophysics , volcano , electrical resistivity and conductivity , tectonics , paleontology , electrical engineering , engineering
We report on a recent magnetotelluric (MT) survey across the Manda Hararo magmatic segment (MHMS) within the Tendaho graben in the Afar Depression in northeastern Ethiopia. Twenty‐two broadband MT sites with ∼1 km station spacing were deployed along a profile with the recorded data covering a period range from 0.003 s to 1000 s. A two‐dimensional (2‐D) resistivity model reveals an upper crustal fracture zone (fault) and partial melt with resistivity of 1–10 Ω m at a depth of >1 km. The partial melt has a maximum horizontal width of 15 km and extends to a depth of 15 km within the Afar Stratoid Series basalts. We estimate a melt fraction of about 13 % based on geochemical and borehole data, and bulk resistivity from the 2‐D MT inversion model. The interpreted upper crustal partial melt may have been formed by either a magma intrusion from mantle sources or a large volume of continental crust that has been fluxed by a small amount of mantle melt and heat. Within the MHMS and Tendaho graben, a magma intrusion is a plausible explanation for the upper crustal conductor. The inferred presence of a conductive fracture zone or fault with hydrothermal fluid and shallow heat sourcing magma reservoir also makes the Tendaho graben a promising prospect for the development of conventional hydrothermal geothermal energy.