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Decompression melting driving intraplate volcanism in Australia: Evidence from magnetotelluric sounding
Author(s) -
Aivazpourporgou Sahereh,
Thiel Stephan,
Hayman Patrick C.,
Moresi Louis N.,
Heinson Graham
Publication year - 2015
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 - 10.1002/2014gl060088
Subject(s) - geology , lithosphere , asthenosphere , mantle (geology) , low velocity zone , intraplate earthquake , geophysics , mantle plume , geochemistry , petrology , seismology , tectonics
A long‐period magnetotelluric (MT) survey, with 39 sites covering an area of 270 by 150 km, has identified melt within the thinned lithosphere of Pleistocene‐Holocene Newer Volcanics Province (NVP) in southeast Australia, which has been variously attributed to mantle plume activity or edge‐driven mantle convection. Two‐dimensional inversions from the MT array imaged a low‐resistivity anomaly (10–30 Ω m) beneath the NVP at ~40–80 km depth, which is consistent with the presence of ~1.5–4% partial melt in the lithosphere, but inconsistent with elevated iron content, metasomatism products or a hot spot. The conductive zone is located within thin juvenile oceanic mantle lithosphere, which was accreted onto thicker Proterozoic continental mantle lithosphere. We propose that the NVP owes its origin to decompression melting within the asthenosphere, promoted by lithospheric thickness variations in conjunction with rapid shear, where asthenospheric material is drawn by shear flow at a “step” at the base of the lithosphere.